Diversity techniques for mobile wireless radio systems

Diversity Dictionary

ldquothe presence of a wide range of variation Including everyonerdquo

AJALAJ Assistant Professor ndashDept of ECE

Federal Institute of Science And Technology (FISAT) TM MAIL ec2reachgmailcom

Cultural Dimensions

PERSONAL

CORPORATE

ETHNIC

GENERATIONAL

RELIGIOUS

CLASS

GENDER

REGIONAL

NATIONAL

PROFESSIONAL EDUCATIONAL

UNITY IN DIVERSITY

What is Diversity

bull Diversity may refer to Multiculturalism the ideology of including people of diverse

cultural and religious backgrounds Diversity (politics) the political and social policy of

encouraging tolerance for people of different backgrounds Diversity (business) the business tactic which encourages

diversity to better serve a heterogeneous customer base Diversity training the process of educating employees

students or volunteers to function in a diverse environment Biodiversity the variation of life forms within a given

ecosystem Diversity scheme a method for improving the reliability of a

message signal by using multiple communications channels

DIVERSITY as far as mobile

wireless radio systems are

concerned

Common assumption

bull Common assumption

signals that scatter off of different objects fade independently

How when diversity is created

bull Diversity is created when these signals are separated in the receiver

Examples

RAKE receiver - - separates paths by delay [PATH DIVERSITY]

Multi beam antenna - - separates paths by angle [ANGLE DIVERSITY]

change the relative phases of the multi pathsignals

bull Examplesbull 1048672Identical antennas slightly different locations[SPACE DIVERSITY]bull 1048672Same signal received on different RF carriers[FREQUENCY DIVERSITY] Required carrier

separation depends inversely on delay spread

Another way to create diversity

Still other ways to generate diversity

bull Dual polarized antennas [POLARIZATION DIVERSITY]

Introduction

bull Fading

Signal fluctuations caused by multipath propagation and shadowing effects

bull Diversity

Receiving the same information bearing signal over 2 or more fading channels

Introduction (contrsquod)

bull SpaceTransmission using multiple transmitreceive antennas

bull FrequencyTransmission using multiple frequency channels separated by at least the coherence bandwidth

bull Time Transmission using multiple time slots separated by at least the coherence time

Spatial diversity

bull Single-input single-output (SISO) channel

No spatial diversitybull Single-input multiple-output (SIMO) channel

Receive diversitybull Multiple-input single-output (MISO) channel

Transmit diversity bull Multiple-input multiple-output (MIMO) channel

Combined transmit and receive diversity

The following classes of diversity schemes can be identified

1Space diversity 2Polarization diversity 3Frequency diversity 4Time diversity 5Angle or direction diversity

1] Space diversity

bull The signal is transferred over several different propagation paths

bull In the case of wired transmission this can be achieved by transmitting via multiple wires

bull In the case of wireless transmission it can be achieved by antenna diversity using multiple transmitter antennas (transmit diversity) andor multiple receiving antennas (reception diversity)

bull In the latter case a diversity combining technique is applied before further signal processing takes place

2] Polarization diversity

bull Polarization diversity Multiple versions of a signal are transmitted and received via antennas with different polarization

bull A diversity combining technique is applied on the receiver side

POLARIZER

3] Frequency diversity

bull Frequency diversity The signal is transferred using several frequency channels or spread over a wide spectrum that is affected by frequency-selective fading

bull Middle-late 20th century microwave radio relay lines often used several regular wideband radio channels and one protection channel for automatic use by any faded channel Later examples include OFDM modulation in combination with subcarrier interleaving and

forward error correction Spread spectrum for example frequency hopping or DS-CDMA

4] Time diversity

bull Time diversity Multiple versions of the same signal are transmitted at different time instants

Terrestrial microwave radio system with two antenna arrays configured for space-diversity

Diversity Combining

bull Once you have created two or morediversity channels what do you do with them

Spatial diversity (contrsquod)

bullMaximum ratio combining (MRC)

h1

h2

h1

h2

yx

Combining schemes

bullSelection combining (SC)

h1

h2

yx

MonitorSNR

Selectbranch

Switch-and-stay combining (SSC) Switch-and-examine combining (SEC)

h1

h2

x

ComparatorChannelestimator

switchingthreshold

bullSwitched diversity

No trade off to

Without excessively increasing

bull 1 transmitting powerbull 2 Co-channel reuse distance

bull One of the most effective technique to solve this issue is diversity reception technique

What are all the needs of diversity techniques

bull 1No of signal transmission pathsbull 2A circuit to combine the received signal or

select one of them

CONCEPTS OF DIVERSITY BRANCH AND SIGNAL PATH

(a) Branch Construction method using frequency diversity

(b) Branch Construction method using Time diversity

COMBINING AND SWITCHNING METHODS

COMBINING AND SWITCHNINGMETHODS

FOR COHERENT DETECTION

FOR NON - COHERENT DETECTION

FOR COHERENT DETECTION

bull There is no difference whether the combining is carried out in the pre detection or in the post detection stage

FOR NON-COHERENT DETECTION

bull There is a difference in performance exists between whether pre detection amp post detection combining methods

(a) Maximal ratio combining (MRC)

bull MRC is the best performance improvement compared with the other methods

bull However the trade off is It requires 1 cophasing 2 weighting 3summing circuitsResulting in most complicated implementationComplexity performance

(b) Equal Gain Combining (EGC)

EGCbull EGC is similar to MRC except the weighting

circuits are omittedbull The performance improvement obtained by

equal gain combiner is slightly inferior to that of a MRC since the interference and noise corrupted signal combined with high quality signals

For VHF UHF and microwave wireless radio applications

bull Both MRC and EGC methods are unsuitablebull Compared with MRC EGC methods the

selection method is more suitable for mobile radio applications because of its simple implementation

(c) Selection or Switching Combining

bull The diversity branch having the highest signal level (or) lowest Pe is selected

bull Also in addition stable operation is easily achieved even in the fast multipath fading environments

bull But the performance improvement obtained by the selection method is still only slightly inferior to that of MRC method

Disadvantage of Selection or Switching

bull Combining The continuous monitoring of the signals requires the same no of receivers as the no of diversity branches

bull This redundancy can be alleviated by the use of switching or scanning receiver

SWITCHNINGMETHODS

FIXED THERSHOLD VARIABLE THERSHOLD

(a) Switching Methods with Fixed threshold

bull The switching from one branch to the other occurs when the signal level falls below a threshold value

bull The threshold value is fixedbull However this threshold value is not

necessarily the best over the entire service area

FIXED THERSHOLD

(b) Switching Methods with Variable threshold

bull Here the threshold value is adjusted dynamically as the vehicle moves

bull It includes the feedback using Estimationbull But it may introduce the envelope and phase

transients that will reduce the performance improvement

VARIABLE THERSHOLD

Conclusions

bull The diversity is used to provide the receiver with several replicas of the same signal

bull Diversity techniques are used to improve the performance of the radio channel without any increase in the transmitted power

bull As higher as the received signal replicas are decorrelated as much as the diversity gain

Thank you for you attention

• No trade off to
• What are all the needs of diversity techniques
• CONCEPTS OF DIVERSITY BRANCH AND SIGNAL PATH
• (a) Branch Construction method using frequency diversity
• (b) Branch Construction method using Time diversity
• COMBINING AND SWITCHNING METHODS
• Slide 29
• FOR COHERENT DETECTION
• (a) Maximal ratio combining (MRC)
• Slide 32
• (b) Equal Gain Combining (EGC)
• EGC
• For VHF UHF and microwave wireless radio applications
• (c) Selection or Switching Combining
• Slide 37
• Disadvantage of Selection or Switching
• Slide 39
• (a) Switching Methods with Fixed threshold
• Slide 41
• (b) Switching Methods with Variable threshold
• Slide 43

Cultural Dimensions

PERSONAL

CORPORATE

ETHNIC

GENERATIONAL

RELIGIOUS

CLASS

GENDER

REGIONAL

NATIONAL

PROFESSIONAL EDUCATIONAL

UNITY IN DIVERSITY

What is Diversity

bull Diversity may refer to Multiculturalism the ideology of including people of diverse

cultural and religious backgrounds Diversity (politics) the political and social policy of

encouraging tolerance for people of different backgrounds Diversity (business) the business tactic which encourages

diversity to better serve a heterogeneous customer base Diversity training the process of educating employees

students or volunteers to function in a diverse environment Biodiversity the variation of life forms within a given

ecosystem Diversity scheme a method for improving the reliability of a

message signal by using multiple communications channels

DIVERSITY as far as mobile

wireless radio systems are

concerned

Common assumption

bull Common assumption

signals that scatter off of different objects fade independently

How when diversity is created

bull Diversity is created when these signals are separated in the receiver

Examples

RAKE receiver - - separates paths by delay [PATH DIVERSITY]

Multi beam antenna - - separates paths by angle [ANGLE DIVERSITY]

change the relative phases of the multi pathsignals

bull Examplesbull 1048672Identical antennas slightly different locations[SPACE DIVERSITY]bull 1048672Same signal received on different RF carriers[FREQUENCY DIVERSITY] Required carrier

separation depends inversely on delay spread

Another way to create diversity

Still other ways to generate diversity

bull Dual polarized antennas [POLARIZATION DIVERSITY]

Introduction

bull Fading

Signal fluctuations caused by multipath propagation and shadowing effects

bull Diversity

Receiving the same information bearing signal over 2 or more fading channels

Introduction (contrsquod)

bull SpaceTransmission using multiple transmitreceive antennas

bull FrequencyTransmission using multiple frequency channels separated by at least the coherence bandwidth

bull Time Transmission using multiple time slots separated by at least the coherence time

Spatial diversity

bull Single-input single-output (SISO) channel

No spatial diversitybull Single-input multiple-output (SIMO) channel

Receive diversitybull Multiple-input single-output (MISO) channel

Transmit diversity bull Multiple-input multiple-output (MIMO) channel

Combined transmit and receive diversity

The following classes of diversity schemes can be identified

1Space diversity 2Polarization diversity 3Frequency diversity 4Time diversity 5Angle or direction diversity

1] Space diversity

bull The signal is transferred over several different propagation paths

bull In the case of wired transmission this can be achieved by transmitting via multiple wires

bull In the case of wireless transmission it can be achieved by antenna diversity using multiple transmitter antennas (transmit diversity) andor multiple receiving antennas (reception diversity)

bull In the latter case a diversity combining technique is applied before further signal processing takes place

2] Polarization diversity

bull Polarization diversity Multiple versions of a signal are transmitted and received via antennas with different polarization

bull A diversity combining technique is applied on the receiver side

POLARIZER

3] Frequency diversity

bull Frequency diversity The signal is transferred using several frequency channels or spread over a wide spectrum that is affected by frequency-selective fading

bull Middle-late 20th century microwave radio relay lines often used several regular wideband radio channels and one protection channel for automatic use by any faded channel Later examples include OFDM modulation in combination with subcarrier interleaving and

forward error correction Spread spectrum for example frequency hopping or DS-CDMA

4] Time diversity

bull Time diversity Multiple versions of the same signal are transmitted at different time instants

Terrestrial microwave radio system with two antenna arrays configured for space-diversity

Diversity Combining

bull Once you have created two or morediversity channels what do you do with them

Spatial diversity (contrsquod)

bullMaximum ratio combining (MRC)

h1

h2

h1

h2

yx

Combining schemes

bullSelection combining (SC)

h1

h2

yx

MonitorSNR

Selectbranch

Switch-and-stay combining (SSC) Switch-and-examine combining (SEC)

h1

h2

x

ComparatorChannelestimator

switchingthreshold

bullSwitched diversity

No trade off to

Without excessively increasing

bull 1 transmitting powerbull 2 Co-channel reuse distance

bull One of the most effective technique to solve this issue is diversity reception technique

What are all the needs of diversity techniques

bull 1No of signal transmission pathsbull 2A circuit to combine the received signal or

select one of them

CONCEPTS OF DIVERSITY BRANCH AND SIGNAL PATH

(a) Branch Construction method using frequency diversity

(b) Branch Construction method using Time diversity

COMBINING AND SWITCHNING METHODS

COMBINING AND SWITCHNINGMETHODS

FOR COHERENT DETECTION

FOR NON - COHERENT DETECTION

FOR COHERENT DETECTION

bull There is no difference whether the combining is carried out in the pre detection or in the post detection stage

FOR NON-COHERENT DETECTION

bull There is a difference in performance exists between whether pre detection amp post detection combining methods

(a) Maximal ratio combining (MRC)

bull MRC is the best performance improvement compared with the other methods

bull However the trade off is It requires 1 cophasing 2 weighting 3summing circuitsResulting in most complicated implementationComplexity performance

(b) Equal Gain Combining (EGC)

EGCbull EGC is similar to MRC except the weighting

circuits are omittedbull The performance improvement obtained by

equal gain combiner is slightly inferior to that of a MRC since the interference and noise corrupted signal combined with high quality signals

For VHF UHF and microwave wireless radio applications

bull Both MRC and EGC methods are unsuitablebull Compared with MRC EGC methods the

selection method is more suitable for mobile radio applications because of its simple implementation

(c) Selection or Switching Combining

bull The diversity branch having the highest signal level (or) lowest Pe is selected

bull Also in addition stable operation is easily achieved even in the fast multipath fading environments

bull But the performance improvement obtained by the selection method is still only slightly inferior to that of MRC method

Disadvantage of Selection or Switching

bull Combining The continuous monitoring of the signals requires the same no of receivers as the no of diversity branches

bull This redundancy can be alleviated by the use of switching or scanning receiver

SWITCHNINGMETHODS

FIXED THERSHOLD VARIABLE THERSHOLD

(a) Switching Methods with Fixed threshold

bull The switching from one branch to the other occurs when the signal level falls below a threshold value

bull The threshold value is fixedbull However this threshold value is not

necessarily the best over the entire service area

FIXED THERSHOLD

(b) Switching Methods with Variable threshold

bull Here the threshold value is adjusted dynamically as the vehicle moves

bull It includes the feedback using Estimationbull But it may introduce the envelope and phase

transients that will reduce the performance improvement

VARIABLE THERSHOLD

Conclusions

bull The diversity is used to provide the receiver with several replicas of the same signal

bull Diversity techniques are used to improve the performance of the radio channel without any increase in the transmitted power

bull As higher as the received signal replicas are decorrelated as much as the diversity gain

Thank you for you attention

• No trade off to
• What are all the needs of diversity techniques
• CONCEPTS OF DIVERSITY BRANCH AND SIGNAL PATH
• (a) Branch Construction method using frequency diversity
• (b) Branch Construction method using Time diversity
• COMBINING AND SWITCHNING METHODS
• Slide 29
• FOR COHERENT DETECTION
• (a) Maximal ratio combining (MRC)
• Slide 32
• (b) Equal Gain Combining (EGC)
• EGC
• For VHF UHF and microwave wireless radio applications
• (c) Selection or Switching Combining
• Slide 37
• Disadvantage of Selection or Switching
• Slide 39
• (a) Switching Methods with Fixed threshold
• Slide 41
• (b) Switching Methods with Variable threshold
• Slide 43

What is Diversity

bull Diversity may refer to Multiculturalism the ideology of including people of diverse

cultural and religious backgrounds Diversity (politics) the political and social policy of

encouraging tolerance for people of different backgrounds Diversity (business) the business tactic which encourages

diversity to better serve a heterogeneous customer base Diversity training the process of educating employees

students or volunteers to function in a diverse environment Biodiversity the variation of life forms within a given

ecosystem Diversity scheme a method for improving the reliability of a

message signal by using multiple communications channels

DIVERSITY as far as mobile

wireless radio systems are

concerned

Common assumption

bull Common assumption

signals that scatter off of different objects fade independently

How when diversity is created

bull Diversity is created when these signals are separated in the receiver

Examples

RAKE receiver - - separates paths by delay [PATH DIVERSITY]

Multi beam antenna - - separates paths by angle [ANGLE DIVERSITY]

change the relative phases of the multi pathsignals

bull Examplesbull 1048672Identical antennas slightly different locations[SPACE DIVERSITY]bull 1048672Same signal received on different RF carriers[FREQUENCY DIVERSITY] Required carrier

separation depends inversely on delay spread

Another way to create diversity

Still other ways to generate diversity

bull Dual polarized antennas [POLARIZATION DIVERSITY]

Introduction

bull Fading

Signal fluctuations caused by multipath propagation and shadowing effects

bull Diversity

Receiving the same information bearing signal over 2 or more fading channels

Introduction (contrsquod)

bull SpaceTransmission using multiple transmitreceive antennas

bull FrequencyTransmission using multiple frequency channels separated by at least the coherence bandwidth

bull Time Transmission using multiple time slots separated by at least the coherence time

Spatial diversity

bull Single-input single-output (SISO) channel

No spatial diversitybull Single-input multiple-output (SIMO) channel

Receive diversitybull Multiple-input single-output (MISO) channel

Transmit diversity bull Multiple-input multiple-output (MIMO) channel

Combined transmit and receive diversity

The following classes of diversity schemes can be identified

1Space diversity 2Polarization diversity 3Frequency diversity 4Time diversity 5Angle or direction diversity

1] Space diversity

bull The signal is transferred over several different propagation paths

bull In the case of wired transmission this can be achieved by transmitting via multiple wires

bull In the case of wireless transmission it can be achieved by antenna diversity using multiple transmitter antennas (transmit diversity) andor multiple receiving antennas (reception diversity)

bull In the latter case a diversity combining technique is applied before further signal processing takes place

2] Polarization diversity

bull Polarization diversity Multiple versions of a signal are transmitted and received via antennas with different polarization

bull A diversity combining technique is applied on the receiver side

POLARIZER

3] Frequency diversity

bull Frequency diversity The signal is transferred using several frequency channels or spread over a wide spectrum that is affected by frequency-selective fading

bull Middle-late 20th century microwave radio relay lines often used several regular wideband radio channels and one protection channel for automatic use by any faded channel Later examples include OFDM modulation in combination with subcarrier interleaving and

forward error correction Spread spectrum for example frequency hopping or DS-CDMA

4] Time diversity

bull Time diversity Multiple versions of the same signal are transmitted at different time instants

Terrestrial microwave radio system with two antenna arrays configured for space-diversity

Diversity Combining

bull Once you have created two or morediversity channels what do you do with them

Spatial diversity (contrsquod)

bullMaximum ratio combining (MRC)

h1

h2

h1

h2

yx

Combining schemes

bullSelection combining (SC)

h1

h2

yx

MonitorSNR

Selectbranch

Switch-and-stay combining (SSC) Switch-and-examine combining (SEC)

h1

h2

x

ComparatorChannelestimator

switchingthreshold

bullSwitched diversity

No trade off to

Without excessively increasing

bull 1 transmitting powerbull 2 Co-channel reuse distance

bull One of the most effective technique to solve this issue is diversity reception technique

What are all the needs of diversity techniques

bull 1No of signal transmission pathsbull 2A circuit to combine the received signal or

select one of them

CONCEPTS OF DIVERSITY BRANCH AND SIGNAL PATH

(a) Branch Construction method using frequency diversity

(b) Branch Construction method using Time diversity

COMBINING AND SWITCHNING METHODS

COMBINING AND SWITCHNINGMETHODS

FOR COHERENT DETECTION

FOR NON - COHERENT DETECTION

FOR COHERENT DETECTION

bull There is no difference whether the combining is carried out in the pre detection or in the post detection stage

FOR NON-COHERENT DETECTION

bull There is a difference in performance exists between whether pre detection amp post detection combining methods

(a) Maximal ratio combining (MRC)

bull MRC is the best performance improvement compared with the other methods

bull However the trade off is It requires 1 cophasing 2 weighting 3summing circuitsResulting in most complicated implementationComplexity performance

(b) Equal Gain Combining (EGC)

EGCbull EGC is similar to MRC except the weighting

circuits are omittedbull The performance improvement obtained by

equal gain combiner is slightly inferior to that of a MRC since the interference and noise corrupted signal combined with high quality signals

For VHF UHF and microwave wireless radio applications

bull Both MRC and EGC methods are unsuitablebull Compared with MRC EGC methods the

selection method is more suitable for mobile radio applications because of its simple implementation

(c) Selection or Switching Combining

bull The diversity branch having the highest signal level (or) lowest Pe is selected

bull Also in addition stable operation is easily achieved even in the fast multipath fading environments

bull But the performance improvement obtained by the selection method is still only slightly inferior to that of MRC method

Disadvantage of Selection or Switching

bull Combining The continuous monitoring of the signals requires the same no of receivers as the no of diversity branches

bull This redundancy can be alleviated by the use of switching or scanning receiver

SWITCHNINGMETHODS

FIXED THERSHOLD VARIABLE THERSHOLD

(a) Switching Methods with Fixed threshold

bull The switching from one branch to the other occurs when the signal level falls below a threshold value

bull The threshold value is fixedbull However this threshold value is not

necessarily the best over the entire service area

FIXED THERSHOLD

(b) Switching Methods with Variable threshold

bull Here the threshold value is adjusted dynamically as the vehicle moves

bull It includes the feedback using Estimationbull But it may introduce the envelope and phase

transients that will reduce the performance improvement

VARIABLE THERSHOLD

Conclusions

bull The diversity is used to provide the receiver with several replicas of the same signal

bull Diversity techniques are used to improve the performance of the radio channel without any increase in the transmitted power

bull As higher as the received signal replicas are decorrelated as much as the diversity gain

Thank you for you attention

• No trade off to
• What are all the needs of diversity techniques
• CONCEPTS OF DIVERSITY BRANCH AND SIGNAL PATH
• (a) Branch Construction method using frequency diversity
• (b) Branch Construction method using Time diversity
• COMBINING AND SWITCHNING METHODS
• Slide 29
• FOR COHERENT DETECTION
• (a) Maximal ratio combining (MRC)
• Slide 32
• (b) Equal Gain Combining (EGC)
• EGC
• For VHF UHF and microwave wireless radio applications
• (c) Selection or Switching Combining
• Slide 37
• Disadvantage of Selection or Switching
• Slide 39
• (a) Switching Methods with Fixed threshold
• Slide 41
• (b) Switching Methods with Variable threshold
• Slide 43

DIVERSITY as far as mobile

wireless radio systems are

concerned

Common assumption

bull Common assumption

signals that scatter off of different objects fade independently

How when diversity is created

bull Diversity is created when these signals are separated in the receiver

Examples

RAKE receiver - - separates paths by delay [PATH DIVERSITY]

Multi beam antenna - - separates paths by angle [ANGLE DIVERSITY]

change the relative phases of the multi pathsignals

bull Examplesbull 1048672Identical antennas slightly different locations[SPACE DIVERSITY]bull 1048672Same signal received on different RF carriers[FREQUENCY DIVERSITY] Required carrier

separation depends inversely on delay spread

Another way to create diversity

Still other ways to generate diversity

bull Dual polarized antennas [POLARIZATION DIVERSITY]

Introduction

bull Fading

Signal fluctuations caused by multipath propagation and shadowing effects

bull Diversity

Receiving the same information bearing signal over 2 or more fading channels

Introduction (contrsquod)

bull SpaceTransmission using multiple transmitreceive antennas

bull FrequencyTransmission using multiple frequency channels separated by at least the coherence bandwidth

bull Time Transmission using multiple time slots separated by at least the coherence time

Spatial diversity

bull Single-input single-output (SISO) channel

No spatial diversitybull Single-input multiple-output (SIMO) channel

Receive diversitybull Multiple-input single-output (MISO) channel

Transmit diversity bull Multiple-input multiple-output (MIMO) channel

Combined transmit and receive diversity

The following classes of diversity schemes can be identified

1Space diversity 2Polarization diversity 3Frequency diversity 4Time diversity 5Angle or direction diversity

1] Space diversity

bull The signal is transferred over several different propagation paths

bull In the case of wired transmission this can be achieved by transmitting via multiple wires

bull In the case of wireless transmission it can be achieved by antenna diversity using multiple transmitter antennas (transmit diversity) andor multiple receiving antennas (reception diversity)

bull In the latter case a diversity combining technique is applied before further signal processing takes place

2] Polarization diversity

bull Polarization diversity Multiple versions of a signal are transmitted and received via antennas with different polarization

bull A diversity combining technique is applied on the receiver side

POLARIZER

3] Frequency diversity

bull Frequency diversity The signal is transferred using several frequency channels or spread over a wide spectrum that is affected by frequency-selective fading

bull Middle-late 20th century microwave radio relay lines often used several regular wideband radio channels and one protection channel for automatic use by any faded channel Later examples include OFDM modulation in combination with subcarrier interleaving and

forward error correction Spread spectrum for example frequency hopping or DS-CDMA

4] Time diversity

bull Time diversity Multiple versions of the same signal are transmitted at different time instants

Terrestrial microwave radio system with two antenna arrays configured for space-diversity

Diversity Combining

bull Once you have created two or morediversity channels what do you do with them

Spatial diversity (contrsquod)

bullMaximum ratio combining (MRC)

h1

h2

h1

h2

yx

Combining schemes

bullSelection combining (SC)

h1

h2

yx

MonitorSNR

Selectbranch

Switch-and-stay combining (SSC) Switch-and-examine combining (SEC)

h1

h2

x

ComparatorChannelestimator

switchingthreshold

bullSwitched diversity

No trade off to

Without excessively increasing

bull 1 transmitting powerbull 2 Co-channel reuse distance

bull One of the most effective technique to solve this issue is diversity reception technique

What are all the needs of diversity techniques

bull 1No of signal transmission pathsbull 2A circuit to combine the received signal or

select one of them

CONCEPTS OF DIVERSITY BRANCH AND SIGNAL PATH

(a) Branch Construction method using frequency diversity

(b) Branch Construction method using Time diversity

COMBINING AND SWITCHNING METHODS

COMBINING AND SWITCHNINGMETHODS

FOR COHERENT DETECTION

FOR NON - COHERENT DETECTION

FOR COHERENT DETECTION

bull There is no difference whether the combining is carried out in the pre detection or in the post detection stage

FOR NON-COHERENT DETECTION

bull There is a difference in performance exists between whether pre detection amp post detection combining methods

(a) Maximal ratio combining (MRC)

bull MRC is the best performance improvement compared with the other methods

bull However the trade off is It requires 1 cophasing 2 weighting 3summing circuitsResulting in most complicated implementationComplexity performance

(b) Equal Gain Combining (EGC)

EGCbull EGC is similar to MRC except the weighting

circuits are omittedbull The performance improvement obtained by

equal gain combiner is slightly inferior to that of a MRC since the interference and noise corrupted signal combined with high quality signals

For VHF UHF and microwave wireless radio applications

bull Both MRC and EGC methods are unsuitablebull Compared with MRC EGC methods the

selection method is more suitable for mobile radio applications because of its simple implementation

(c) Selection or Switching Combining

bull The diversity branch having the highest signal level (or) lowest Pe is selected

bull Also in addition stable operation is easily achieved even in the fast multipath fading environments

bull But the performance improvement obtained by the selection method is still only slightly inferior to that of MRC method

Disadvantage of Selection or Switching

bull Combining The continuous monitoring of the signals requires the same no of receivers as the no of diversity branches

bull This redundancy can be alleviated by the use of switching or scanning receiver

SWITCHNINGMETHODS

FIXED THERSHOLD VARIABLE THERSHOLD

(a) Switching Methods with Fixed threshold

bull The switching from one branch to the other occurs when the signal level falls below a threshold value

bull The threshold value is fixedbull However this threshold value is not

necessarily the best over the entire service area

FIXED THERSHOLD

(b) Switching Methods with Variable threshold

bull Here the threshold value is adjusted dynamically as the vehicle moves

bull It includes the feedback using Estimationbull But it may introduce the envelope and phase

transients that will reduce the performance improvement

VARIABLE THERSHOLD

Conclusions

bull The diversity is used to provide the receiver with several replicas of the same signal

bull Diversity techniques are used to improve the performance of the radio channel without any increase in the transmitted power

bull As higher as the received signal replicas are decorrelated as much as the diversity gain

Thank you for you attention

• No trade off to
• What are all the needs of diversity techniques
• CONCEPTS OF DIVERSITY BRANCH AND SIGNAL PATH
• (a) Branch Construction method using frequency diversity
• (b) Branch Construction method using Time diversity
• COMBINING AND SWITCHNING METHODS
• Slide 29
• FOR COHERENT DETECTION
• (a) Maximal ratio combining (MRC)
• Slide 32
• (b) Equal Gain Combining (EGC)
• EGC
• For VHF UHF and microwave wireless radio applications
• (c) Selection or Switching Combining
• Slide 37
• Disadvantage of Selection or Switching
• Slide 39
• (a) Switching Methods with Fixed threshold
• Slide 41
• (b) Switching Methods with Variable threshold
• Slide 43

Common assumption

bull Common assumption

signals that scatter off of different objects fade independently

How when diversity is created

bull Diversity is created when these signals are separated in the receiver

Examples

RAKE receiver - - separates paths by delay [PATH DIVERSITY]

Multi beam antenna - - separates paths by angle [ANGLE DIVERSITY]

change the relative phases of the multi pathsignals

bull Examplesbull 1048672Identical antennas slightly different locations[SPACE DIVERSITY]bull 1048672Same signal received on different RF carriers[FREQUENCY DIVERSITY] Required carrier

separation depends inversely on delay spread

Another way to create diversity

Still other ways to generate diversity

bull Dual polarized antennas [POLARIZATION DIVERSITY]

Introduction

bull Fading

Signal fluctuations caused by multipath propagation and shadowing effects

bull Diversity

Receiving the same information bearing signal over 2 or more fading channels

Introduction (contrsquod)

bull SpaceTransmission using multiple transmitreceive antennas

bull FrequencyTransmission using multiple frequency channels separated by at least the coherence bandwidth

bull Time Transmission using multiple time slots separated by at least the coherence time

Spatial diversity

bull Single-input single-output (SISO) channel

No spatial diversitybull Single-input multiple-output (SIMO) channel

Receive diversitybull Multiple-input single-output (MISO) channel

Transmit diversity bull Multiple-input multiple-output (MIMO) channel

Combined transmit and receive diversity

The following classes of diversity schemes can be identified

1Space diversity 2Polarization diversity 3Frequency diversity 4Time diversity 5Angle or direction diversity

1] Space diversity

bull The signal is transferred over several different propagation paths

bull In the case of wired transmission this can be achieved by transmitting via multiple wires

bull In the case of wireless transmission it can be achieved by antenna diversity using multiple transmitter antennas (transmit diversity) andor multiple receiving antennas (reception diversity)

bull In the latter case a diversity combining technique is applied before further signal processing takes place

2] Polarization diversity

bull Polarization diversity Multiple versions of a signal are transmitted and received via antennas with different polarization

bull A diversity combining technique is applied on the receiver side

POLARIZER

3] Frequency diversity

bull Frequency diversity The signal is transferred using several frequency channels or spread over a wide spectrum that is affected by frequency-selective fading

bull Middle-late 20th century microwave radio relay lines often used several regular wideband radio channels and one protection channel for automatic use by any faded channel Later examples include OFDM modulation in combination with subcarrier interleaving and

forward error correction Spread spectrum for example frequency hopping or DS-CDMA

4] Time diversity

bull Time diversity Multiple versions of the same signal are transmitted at different time instants

Terrestrial microwave radio system with two antenna arrays configured for space-diversity

Diversity Combining

bull Once you have created two or morediversity channels what do you do with them

Spatial diversity (contrsquod)

bullMaximum ratio combining (MRC)

h1

h2

h1

h2

yx

Combining schemes

bullSelection combining (SC)

h1

h2

yx

MonitorSNR

Selectbranch

Switch-and-stay combining (SSC) Switch-and-examine combining (SEC)

h1

h2

x

ComparatorChannelestimator

switchingthreshold

bullSwitched diversity

No trade off to

Without excessively increasing

bull 1 transmitting powerbull 2 Co-channel reuse distance

bull One of the most effective technique to solve this issue is diversity reception technique

What are all the needs of diversity techniques

bull 1No of signal transmission pathsbull 2A circuit to combine the received signal or

select one of them

CONCEPTS OF DIVERSITY BRANCH AND SIGNAL PATH

(a) Branch Construction method using frequency diversity

(b) Branch Construction method using Time diversity

COMBINING AND SWITCHNING METHODS

COMBINING AND SWITCHNINGMETHODS

FOR COHERENT DETECTION

FOR NON - COHERENT DETECTION

FOR COHERENT DETECTION

bull There is no difference whether the combining is carried out in the pre detection or in the post detection stage

FOR NON-COHERENT DETECTION

bull There is a difference in performance exists between whether pre detection amp post detection combining methods

(a) Maximal ratio combining (MRC)

bull MRC is the best performance improvement compared with the other methods

bull However the trade off is It requires 1 cophasing 2 weighting 3summing circuitsResulting in most complicated implementationComplexity performance

(b) Equal Gain Combining (EGC)

EGCbull EGC is similar to MRC except the weighting

circuits are omittedbull The performance improvement obtained by

equal gain combiner is slightly inferior to that of a MRC since the interference and noise corrupted signal combined with high quality signals

For VHF UHF and microwave wireless radio applications

bull Both MRC and EGC methods are unsuitablebull Compared with MRC EGC methods the

selection method is more suitable for mobile radio applications because of its simple implementation

(c) Selection or Switching Combining

bull The diversity branch having the highest signal level (or) lowest Pe is selected

bull Also in addition stable operation is easily achieved even in the fast multipath fading environments

bull But the performance improvement obtained by the selection method is still only slightly inferior to that of MRC method

Disadvantage of Selection or Switching

bull Combining The continuous monitoring of the signals requires the same no of receivers as the no of diversity branches

bull This redundancy can be alleviated by the use of switching or scanning receiver

SWITCHNINGMETHODS

FIXED THERSHOLD VARIABLE THERSHOLD

(a) Switching Methods with Fixed threshold

bull The switching from one branch to the other occurs when the signal level falls below a threshold value

bull The threshold value is fixedbull However this threshold value is not

necessarily the best over the entire service area

FIXED THERSHOLD

(b) Switching Methods with Variable threshold

bull Here the threshold value is adjusted dynamically as the vehicle moves

bull It includes the feedback using Estimationbull But it may introduce the envelope and phase

transients that will reduce the performance improvement

VARIABLE THERSHOLD

Conclusions

bull The diversity is used to provide the receiver with several replicas of the same signal

bull Diversity techniques are used to improve the performance of the radio channel without any increase in the transmitted power

bull As higher as the received signal replicas are decorrelated as much as the diversity gain

Thank you for you attention

• No trade off to
• What are all the needs of diversity techniques
• CONCEPTS OF DIVERSITY BRANCH AND SIGNAL PATH
• (a) Branch Construction method using frequency diversity
• (b) Branch Construction method using Time diversity
• COMBINING AND SWITCHNING METHODS
• Slide 29
• FOR COHERENT DETECTION
• (a) Maximal ratio combining (MRC)
• Slide 32
• (b) Equal Gain Combining (EGC)
• EGC
• For VHF UHF and microwave wireless radio applications
• (c) Selection or Switching Combining
• Slide 37
• Disadvantage of Selection or Switching
• Slide 39
• (a) Switching Methods with Fixed threshold
• Slide 41
• (b) Switching Methods with Variable threshold
• Slide 43

How when diversity is created

bull Diversity is created when these signals are separated in the receiver

Examples

RAKE receiver - - separates paths by delay [PATH DIVERSITY]

Multi beam antenna - - separates paths by angle [ANGLE DIVERSITY]

change the relative phases of the multi pathsignals

bull Examplesbull 1048672Identical antennas slightly different locations[SPACE DIVERSITY]bull 1048672Same signal received on different RF carriers[FREQUENCY DIVERSITY] Required carrier

separation depends inversely on delay spread

Another way to create diversity

Still other ways to generate diversity

bull Dual polarized antennas [POLARIZATION DIVERSITY]

Introduction

bull Fading

Signal fluctuations caused by multipath propagation and shadowing effects

bull Diversity

Receiving the same information bearing signal over 2 or more fading channels

Introduction (contrsquod)

bull SpaceTransmission using multiple transmitreceive antennas

bull FrequencyTransmission using multiple frequency channels separated by at least the coherence bandwidth

bull Time Transmission using multiple time slots separated by at least the coherence time

Spatial diversity

bull Single-input single-output (SISO) channel

No spatial diversitybull Single-input multiple-output (SIMO) channel

Receive diversitybull Multiple-input single-output (MISO) channel

Transmit diversity bull Multiple-input multiple-output (MIMO) channel

Combined transmit and receive diversity

The following classes of diversity schemes can be identified

1Space diversity 2Polarization diversity 3Frequency diversity 4Time diversity 5Angle or direction diversity

1] Space diversity

bull The signal is transferred over several different propagation paths

bull In the case of wired transmission this can be achieved by transmitting via multiple wires

bull In the case of wireless transmission it can be achieved by antenna diversity using multiple transmitter antennas (transmit diversity) andor multiple receiving antennas (reception diversity)

bull In the latter case a diversity combining technique is applied before further signal processing takes place

2] Polarization diversity

bull Polarization diversity Multiple versions of a signal are transmitted and received via antennas with different polarization

bull A diversity combining technique is applied on the receiver side

POLARIZER

3] Frequency diversity

bull Frequency diversity The signal is transferred using several frequency channels or spread over a wide spectrum that is affected by frequency-selective fading

bull Middle-late 20th century microwave radio relay lines often used several regular wideband radio channels and one protection channel for automatic use by any faded channel Later examples include OFDM modulation in combination with subcarrier interleaving and

forward error correction Spread spectrum for example frequency hopping or DS-CDMA

4] Time diversity

bull Time diversity Multiple versions of the same signal are transmitted at different time instants

Terrestrial microwave radio system with two antenna arrays configured for space-diversity

Diversity Combining

bull Once you have created two or morediversity channels what do you do with them

Spatial diversity (contrsquod)

bullMaximum ratio combining (MRC)

h1

h2

h1

h2

yx

Combining schemes

bullSelection combining (SC)

h1

h2

yx

MonitorSNR

Selectbranch

Switch-and-stay combining (SSC) Switch-and-examine combining (SEC)

h1

h2

x

ComparatorChannelestimator

switchingthreshold

bullSwitched diversity

No trade off to

Without excessively increasing

bull 1 transmitting powerbull 2 Co-channel reuse distance

bull One of the most effective technique to solve this issue is diversity reception technique

What are all the needs of diversity techniques

bull 1No of signal transmission pathsbull 2A circuit to combine the received signal or

select one of them

CONCEPTS OF DIVERSITY BRANCH AND SIGNAL PATH

(a) Branch Construction method using frequency diversity

(b) Branch Construction method using Time diversity

COMBINING AND SWITCHNING METHODS

COMBINING AND SWITCHNINGMETHODS

FOR COHERENT DETECTION

FOR NON - COHERENT DETECTION

FOR COHERENT DETECTION

bull There is no difference whether the combining is carried out in the pre detection or in the post detection stage

FOR NON-COHERENT DETECTION

bull There is a difference in performance exists between whether pre detection amp post detection combining methods

(a) Maximal ratio combining (MRC)

bull MRC is the best performance improvement compared with the other methods

bull However the trade off is It requires 1 cophasing 2 weighting 3summing circuitsResulting in most complicated implementationComplexity performance

(b) Equal Gain Combining (EGC)

EGCbull EGC is similar to MRC except the weighting

circuits are omittedbull The performance improvement obtained by

equal gain combiner is slightly inferior to that of a MRC since the interference and noise corrupted signal combined with high quality signals

For VHF UHF and microwave wireless radio applications

bull Both MRC and EGC methods are unsuitablebull Compared with MRC EGC methods the

selection method is more suitable for mobile radio applications because of its simple implementation

(c) Selection or Switching Combining

bull The diversity branch having the highest signal level (or) lowest Pe is selected

bull Also in addition stable operation is easily achieved even in the fast multipath fading environments

bull But the performance improvement obtained by the selection method is still only slightly inferior to that of MRC method

Disadvantage of Selection or Switching

bull Combining The continuous monitoring of the signals requires the same no of receivers as the no of diversity branches

bull This redundancy can be alleviated by the use of switching or scanning receiver

SWITCHNINGMETHODS

FIXED THERSHOLD VARIABLE THERSHOLD

(a) Switching Methods with Fixed threshold

bull The switching from one branch to the other occurs when the signal level falls below a threshold value

bull The threshold value is fixedbull However this threshold value is not

necessarily the best over the entire service area

FIXED THERSHOLD

(b) Switching Methods with Variable threshold

bull Here the threshold value is adjusted dynamically as the vehicle moves

bull It includes the feedback using Estimationbull But it may introduce the envelope and phase

transients that will reduce the performance improvement

VARIABLE THERSHOLD

Conclusions

bull The diversity is used to provide the receiver with several replicas of the same signal

bull Diversity techniques are used to improve the performance of the radio channel without any increase in the transmitted power

bull As higher as the received signal replicas are decorrelated as much as the diversity gain

Thank you for you attention

• No trade off to
• What are all the needs of diversity techniques
• CONCEPTS OF DIVERSITY BRANCH AND SIGNAL PATH
• (a) Branch Construction method using frequency diversity
• (b) Branch Construction method using Time diversity
• COMBINING AND SWITCHNING METHODS
• Slide 29
• FOR COHERENT DETECTION
• (a) Maximal ratio combining (MRC)
• Slide 32
• (b) Equal Gain Combining (EGC)
• EGC
• For VHF UHF and microwave wireless radio applications
• (c) Selection or Switching Combining
• Slide 37
• Disadvantage of Selection or Switching
• Slide 39
• (a) Switching Methods with Fixed threshold
• Slide 41
• (b) Switching Methods with Variable threshold
• Slide 43

change the relative phases of the multi pathsignals

bull Examplesbull 1048672Identical antennas slightly different locations[SPACE DIVERSITY]bull 1048672Same signal received on different RF carriers[FREQUENCY DIVERSITY] Required carrier

separation depends inversely on delay spread

Another way to create diversity

Still other ways to generate diversity

bull Dual polarized antennas [POLARIZATION DIVERSITY]

Introduction

bull Fading

Signal fluctuations caused by multipath propagation and shadowing effects

bull Diversity

Receiving the same information bearing signal over 2 or more fading channels

Introduction (contrsquod)

bull SpaceTransmission using multiple transmitreceive antennas

bull FrequencyTransmission using multiple frequency channels separated by at least the coherence bandwidth

bull Time Transmission using multiple time slots separated by at least the coherence time

Spatial diversity

bull Single-input single-output (SISO) channel

No spatial diversitybull Single-input multiple-output (SIMO) channel

Receive diversitybull Multiple-input single-output (MISO) channel

Transmit diversity bull Multiple-input multiple-output (MIMO) channel

Combined transmit and receive diversity

The following classes of diversity schemes can be identified

1Space diversity 2Polarization diversity 3Frequency diversity 4Time diversity 5Angle or direction diversity

1] Space diversity

bull The signal is transferred over several different propagation paths

bull In the case of wired transmission this can be achieved by transmitting via multiple wires

bull In the case of wireless transmission it can be achieved by antenna diversity using multiple transmitter antennas (transmit diversity) andor multiple receiving antennas (reception diversity)

bull In the latter case a diversity combining technique is applied before further signal processing takes place

2] Polarization diversity

bull Polarization diversity Multiple versions of a signal are transmitted and received via antennas with different polarization

bull A diversity combining technique is applied on the receiver side

POLARIZER

3] Frequency diversity

bull Frequency diversity The signal is transferred using several frequency channels or spread over a wide spectrum that is affected by frequency-selective fading

bull Middle-late 20th century microwave radio relay lines often used several regular wideband radio channels and one protection channel for automatic use by any faded channel Later examples include OFDM modulation in combination with subcarrier interleaving and

forward error correction Spread spectrum for example frequency hopping or DS-CDMA

4] Time diversity

bull Time diversity Multiple versions of the same signal are transmitted at different time instants

Terrestrial microwave radio system with two antenna arrays configured for space-diversity

Diversity Combining

bull Once you have created two or morediversity channels what do you do with them

Spatial diversity (contrsquod)

bullMaximum ratio combining (MRC)

h1

h2

h1

h2

yx

Combining schemes

bullSelection combining (SC)

h1

h2

yx

MonitorSNR

Selectbranch

Switch-and-stay combining (SSC) Switch-and-examine combining (SEC)

h1

h2

x

ComparatorChannelestimator

switchingthreshold

bullSwitched diversity

No trade off to

Without excessively increasing

bull 1 transmitting powerbull 2 Co-channel reuse distance

bull One of the most effective technique to solve this issue is diversity reception technique

What are all the needs of diversity techniques

bull 1No of signal transmission pathsbull 2A circuit to combine the received signal or

select one of them

CONCEPTS OF DIVERSITY BRANCH AND SIGNAL PATH

(a) Branch Construction method using frequency diversity

(b) Branch Construction method using Time diversity

COMBINING AND SWITCHNING METHODS

COMBINING AND SWITCHNINGMETHODS

FOR COHERENT DETECTION

FOR NON - COHERENT DETECTION

FOR COHERENT DETECTION

bull There is no difference whether the combining is carried out in the pre detection or in the post detection stage

FOR NON-COHERENT DETECTION

bull There is a difference in performance exists between whether pre detection amp post detection combining methods

(a) Maximal ratio combining (MRC)

bull MRC is the best performance improvement compared with the other methods

bull However the trade off is It requires 1 cophasing 2 weighting 3summing circuitsResulting in most complicated implementationComplexity performance

(b) Equal Gain Combining (EGC)

EGCbull EGC is similar to MRC except the weighting

circuits are omittedbull The performance improvement obtained by

equal gain combiner is slightly inferior to that of a MRC since the interference and noise corrupted signal combined with high quality signals

For VHF UHF and microwave wireless radio applications

bull Both MRC and EGC methods are unsuitablebull Compared with MRC EGC methods the

selection method is more suitable for mobile radio applications because of its simple implementation

(c) Selection or Switching Combining

bull The diversity branch having the highest signal level (or) lowest Pe is selected

bull Also in addition stable operation is easily achieved even in the fast multipath fading environments

bull But the performance improvement obtained by the selection method is still only slightly inferior to that of MRC method

Disadvantage of Selection or Switching

bull Combining The continuous monitoring of the signals requires the same no of receivers as the no of diversity branches

bull This redundancy can be alleviated by the use of switching or scanning receiver

SWITCHNINGMETHODS

FIXED THERSHOLD VARIABLE THERSHOLD

(a) Switching Methods with Fixed threshold

bull The switching from one branch to the other occurs when the signal level falls below a threshold value

bull The threshold value is fixedbull However this threshold value is not

necessarily the best over the entire service area

FIXED THERSHOLD

(b) Switching Methods with Variable threshold

bull Here the threshold value is adjusted dynamically as the vehicle moves

bull It includes the feedback using Estimationbull But it may introduce the envelope and phase

transients that will reduce the performance improvement

VARIABLE THERSHOLD

Conclusions

bull The diversity is used to provide the receiver with several replicas of the same signal

bull Diversity techniques are used to improve the performance of the radio channel without any increase in the transmitted power

bull As higher as the received signal replicas are decorrelated as much as the diversity gain

Thank you for you attention

• No trade off to
• What are all the needs of diversity techniques
• CONCEPTS OF DIVERSITY BRANCH AND SIGNAL PATH
• (a) Branch Construction method using frequency diversity
• (b) Branch Construction method using Time diversity
• COMBINING AND SWITCHNING METHODS
• Slide 29
• FOR COHERENT DETECTION
• (a) Maximal ratio combining (MRC)
• Slide 32
• (b) Equal Gain Combining (EGC)
• EGC
• For VHF UHF and microwave wireless radio applications
• (c) Selection or Switching Combining
• Slide 37
• Disadvantage of Selection or Switching
• Slide 39
• (a) Switching Methods with Fixed threshold
• Slide 41
• (b) Switching Methods with Variable threshold
• Slide 43

Still other ways to generate diversity

bull Dual polarized antennas [POLARIZATION DIVERSITY]

Introduction

bull Fading

Signal fluctuations caused by multipath propagation and shadowing effects

bull Diversity

Receiving the same information bearing signal over 2 or more fading channels

Introduction (contrsquod)

bull SpaceTransmission using multiple transmitreceive antennas

bull FrequencyTransmission using multiple frequency channels separated by at least the coherence bandwidth

bull Time Transmission using multiple time slots separated by at least the coherence time

Spatial diversity

bull Single-input single-output (SISO) channel

No spatial diversitybull Single-input multiple-output (SIMO) channel

Receive diversitybull Multiple-input single-output (MISO) channel

Transmit diversity bull Multiple-input multiple-output (MIMO) channel

Combined transmit and receive diversity

The following classes of diversity schemes can be identified

1Space diversity 2Polarization diversity 3Frequency diversity 4Time diversity 5Angle or direction diversity

1] Space diversity

bull The signal is transferred over several different propagation paths

bull In the case of wired transmission this can be achieved by transmitting via multiple wires

bull In the case of wireless transmission it can be achieved by antenna diversity using multiple transmitter antennas (transmit diversity) andor multiple receiving antennas (reception diversity)

bull In the latter case a diversity combining technique is applied before further signal processing takes place

2] Polarization diversity

bull Polarization diversity Multiple versions of a signal are transmitted and received via antennas with different polarization

bull A diversity combining technique is applied on the receiver side

POLARIZER

3] Frequency diversity

bull Frequency diversity The signal is transferred using several frequency channels or spread over a wide spectrum that is affected by frequency-selective fading

bull Middle-late 20th century microwave radio relay lines often used several regular wideband radio channels and one protection channel for automatic use by any faded channel Later examples include OFDM modulation in combination with subcarrier interleaving and

forward error correction Spread spectrum for example frequency hopping or DS-CDMA

4] Time diversity

bull Time diversity Multiple versions of the same signal are transmitted at different time instants

Terrestrial microwave radio system with two antenna arrays configured for space-diversity

Diversity Combining

bull Once you have created two or morediversity channels what do you do with them

Spatial diversity (contrsquod)

bullMaximum ratio combining (MRC)

h1

h2

h1

h2

yx

Combining schemes

bullSelection combining (SC)

h1

h2

yx

MonitorSNR

Selectbranch

Switch-and-stay combining (SSC) Switch-and-examine combining (SEC)

h1

h2

x

ComparatorChannelestimator

switchingthreshold

bullSwitched diversity

No trade off to

Without excessively increasing

bull 1 transmitting powerbull 2 Co-channel reuse distance

bull One of the most effective technique to solve this issue is diversity reception technique

What are all the needs of diversity techniques

bull 1No of signal transmission pathsbull 2A circuit to combine the received signal or

select one of them

CONCEPTS OF DIVERSITY BRANCH AND SIGNAL PATH

(a) Branch Construction method using frequency diversity

(b) Branch Construction method using Time diversity

COMBINING AND SWITCHNING METHODS

COMBINING AND SWITCHNINGMETHODS

FOR COHERENT DETECTION

FOR NON - COHERENT DETECTION

FOR COHERENT DETECTION

bull There is no difference whether the combining is carried out in the pre detection or in the post detection stage

FOR NON-COHERENT DETECTION

bull There is a difference in performance exists between whether pre detection amp post detection combining methods

(a) Maximal ratio combining (MRC)

bull MRC is the best performance improvement compared with the other methods

bull However the trade off is It requires 1 cophasing 2 weighting 3summing circuitsResulting in most complicated implementationComplexity performance

(b) Equal Gain Combining (EGC)

EGCbull EGC is similar to MRC except the weighting

circuits are omittedbull The performance improvement obtained by

equal gain combiner is slightly inferior to that of a MRC since the interference and noise corrupted signal combined with high quality signals

For VHF UHF and microwave wireless radio applications

bull Both MRC and EGC methods are unsuitablebull Compared with MRC EGC methods the

selection method is more suitable for mobile radio applications because of its simple implementation

(c) Selection or Switching Combining

bull The diversity branch having the highest signal level (or) lowest Pe is selected

bull Also in addition stable operation is easily achieved even in the fast multipath fading environments

bull But the performance improvement obtained by the selection method is still only slightly inferior to that of MRC method

Disadvantage of Selection or Switching

bull Combining The continuous monitoring of the signals requires the same no of receivers as the no of diversity branches

bull This redundancy can be alleviated by the use of switching or scanning receiver

SWITCHNINGMETHODS

FIXED THERSHOLD VARIABLE THERSHOLD

(a) Switching Methods with Fixed threshold

bull The switching from one branch to the other occurs when the signal level falls below a threshold value

bull The threshold value is fixedbull However this threshold value is not

necessarily the best over the entire service area

FIXED THERSHOLD

(b) Switching Methods with Variable threshold

bull Here the threshold value is adjusted dynamically as the vehicle moves

bull It includes the feedback using Estimationbull But it may introduce the envelope and phase

transients that will reduce the performance improvement

VARIABLE THERSHOLD

Conclusions

bull The diversity is used to provide the receiver with several replicas of the same signal

bull Diversity techniques are used to improve the performance of the radio channel without any increase in the transmitted power

bull As higher as the received signal replicas are decorrelated as much as the diversity gain

Thank you for you attention

• No trade off to
• What are all the needs of diversity techniques
• CONCEPTS OF DIVERSITY BRANCH AND SIGNAL PATH
• (a) Branch Construction method using frequency diversity
• (b) Branch Construction method using Time diversity
• COMBINING AND SWITCHNING METHODS
• Slide 29
• FOR COHERENT DETECTION
• (a) Maximal ratio combining (MRC)
• Slide 32
• (b) Equal Gain Combining (EGC)
• EGC
• For VHF UHF and microwave wireless radio applications
• (c) Selection or Switching Combining
• Slide 37
• Disadvantage of Selection or Switching
• Slide 39
• (a) Switching Methods with Fixed threshold
• Slide 41
• (b) Switching Methods with Variable threshold
• Slide 43

Introduction

bull Fading

Signal fluctuations caused by multipath propagation and shadowing effects

bull Diversity

Receiving the same information bearing signal over 2 or more fading channels

Introduction (contrsquod)

bull SpaceTransmission using multiple transmitreceive antennas

bull FrequencyTransmission using multiple frequency channels separated by at least the coherence bandwidth

bull Time Transmission using multiple time slots separated by at least the coherence time

Spatial diversity

bull Single-input single-output (SISO) channel

No spatial diversitybull Single-input multiple-output (SIMO) channel

Receive diversitybull Multiple-input single-output (MISO) channel

Transmit diversity bull Multiple-input multiple-output (MIMO) channel

Combined transmit and receive diversity

The following classes of diversity schemes can be identified

1Space diversity 2Polarization diversity 3Frequency diversity 4Time diversity 5Angle or direction diversity

1] Space diversity

bull The signal is transferred over several different propagation paths

bull In the case of wired transmission this can be achieved by transmitting via multiple wires

bull In the case of wireless transmission it can be achieved by antenna diversity using multiple transmitter antennas (transmit diversity) andor multiple receiving antennas (reception diversity)

bull In the latter case a diversity combining technique is applied before further signal processing takes place

2] Polarization diversity

bull Polarization diversity Multiple versions of a signal are transmitted and received via antennas with different polarization

bull A diversity combining technique is applied on the receiver side

POLARIZER

3] Frequency diversity

bull Frequency diversity The signal is transferred using several frequency channels or spread over a wide spectrum that is affected by frequency-selective fading

bull Middle-late 20th century microwave radio relay lines often used several regular wideband radio channels and one protection channel for automatic use by any faded channel Later examples include OFDM modulation in combination with subcarrier interleaving and

forward error correction Spread spectrum for example frequency hopping or DS-CDMA

4] Time diversity

bull Time diversity Multiple versions of the same signal are transmitted at different time instants

Terrestrial microwave radio system with two antenna arrays configured for space-diversity

Diversity Combining

bull Once you have created two or morediversity channels what do you do with them

Spatial diversity (contrsquod)

bullMaximum ratio combining (MRC)

h1

h2

h1

h2

yx

Combining schemes

bullSelection combining (SC)

h1

h2

yx

MonitorSNR

Selectbranch

Switch-and-stay combining (SSC) Switch-and-examine combining (SEC)

h1

h2

x

ComparatorChannelestimator

switchingthreshold

bullSwitched diversity

No trade off to

Without excessively increasing

bull 1 transmitting powerbull 2 Co-channel reuse distance

bull One of the most effective technique to solve this issue is diversity reception technique

What are all the needs of diversity techniques

bull 1No of signal transmission pathsbull 2A circuit to combine the received signal or

select one of them

CONCEPTS OF DIVERSITY BRANCH AND SIGNAL PATH

(a) Branch Construction method using frequency diversity

(b) Branch Construction method using Time diversity

COMBINING AND SWITCHNING METHODS

COMBINING AND SWITCHNINGMETHODS

FOR COHERENT DETECTION

FOR NON - COHERENT DETECTION

FOR COHERENT DETECTION

bull There is no difference whether the combining is carried out in the pre detection or in the post detection stage

FOR NON-COHERENT DETECTION

bull There is a difference in performance exists between whether pre detection amp post detection combining methods

(a) Maximal ratio combining (MRC)

bull MRC is the best performance improvement compared with the other methods

bull However the trade off is It requires 1 cophasing 2 weighting 3summing circuitsResulting in most complicated implementationComplexity performance

(b) Equal Gain Combining (EGC)

EGCbull EGC is similar to MRC except the weighting

circuits are omittedbull The performance improvement obtained by

equal gain combiner is slightly inferior to that of a MRC since the interference and noise corrupted signal combined with high quality signals

For VHF UHF and microwave wireless radio applications

bull Both MRC and EGC methods are unsuitablebull Compared with MRC EGC methods the

selection method is more suitable for mobile radio applications because of its simple implementation

(c) Selection or Switching Combining

bull The diversity branch having the highest signal level (or) lowest Pe is selected

bull Also in addition stable operation is easily achieved even in the fast multipath fading environments

bull But the performance improvement obtained by the selection method is still only slightly inferior to that of MRC method

Disadvantage of Selection or Switching

bull Combining The continuous monitoring of the signals requires the same no of receivers as the no of diversity branches

bull This redundancy can be alleviated by the use of switching or scanning receiver

SWITCHNINGMETHODS

FIXED THERSHOLD VARIABLE THERSHOLD

(a) Switching Methods with Fixed threshold

bull The switching from one branch to the other occurs when the signal level falls below a threshold value

bull The threshold value is fixedbull However this threshold value is not

necessarily the best over the entire service area

FIXED THERSHOLD

(b) Switching Methods with Variable threshold

bull Here the threshold value is adjusted dynamically as the vehicle moves

bull It includes the feedback using Estimationbull But it may introduce the envelope and phase

transients that will reduce the performance improvement

VARIABLE THERSHOLD

Conclusions

bull The diversity is used to provide the receiver with several replicas of the same signal

bull Diversity techniques are used to improve the performance of the radio channel without any increase in the transmitted power

bull As higher as the received signal replicas are decorrelated as much as the diversity gain

Thank you for you attention

• No trade off to
• What are all the needs of diversity techniques
• CONCEPTS OF DIVERSITY BRANCH AND SIGNAL PATH
• (a) Branch Construction method using frequency diversity
• (b) Branch Construction method using Time diversity
• COMBINING AND SWITCHNING METHODS
• Slide 29
• FOR COHERENT DETECTION
• (a) Maximal ratio combining (MRC)
• Slide 32
• (b) Equal Gain Combining (EGC)
• EGC
• For VHF UHF and microwave wireless radio applications
• (c) Selection or Switching Combining
• Slide 37
• Disadvantage of Selection or Switching
• Slide 39
• (a) Switching Methods with Fixed threshold
• Slide 41
• (b) Switching Methods with Variable threshold
• Slide 43

Introduction (contrsquod)

bull SpaceTransmission using multiple transmitreceive antennas

bull FrequencyTransmission using multiple frequency channels separated by at least the coherence bandwidth

bull Time Transmission using multiple time slots separated by at least the coherence time

Spatial diversity

bull Single-input single-output (SISO) channel

No spatial diversitybull Single-input multiple-output (SIMO) channel

Receive diversitybull Multiple-input single-output (MISO) channel

Transmit diversity bull Multiple-input multiple-output (MIMO) channel

Combined transmit and receive diversity

The following classes of diversity schemes can be identified

1Space diversity 2Polarization diversity 3Frequency diversity 4Time diversity 5Angle or direction diversity

1] Space diversity

bull The signal is transferred over several different propagation paths

bull In the case of wired transmission this can be achieved by transmitting via multiple wires

bull In the case of wireless transmission it can be achieved by antenna diversity using multiple transmitter antennas (transmit diversity) andor multiple receiving antennas (reception diversity)

bull In the latter case a diversity combining technique is applied before further signal processing takes place

2] Polarization diversity

bull Polarization diversity Multiple versions of a signal are transmitted and received via antennas with different polarization

bull A diversity combining technique is applied on the receiver side

POLARIZER

3] Frequency diversity

bull Frequency diversity The signal is transferred using several frequency channels or spread over a wide spectrum that is affected by frequency-selective fading

bull Middle-late 20th century microwave radio relay lines often used several regular wideband radio channels and one protection channel for automatic use by any faded channel Later examples include OFDM modulation in combination with subcarrier interleaving and

forward error correction Spread spectrum for example frequency hopping or DS-CDMA

4] Time diversity

bull Time diversity Multiple versions of the same signal are transmitted at different time instants

Terrestrial microwave radio system with two antenna arrays configured for space-diversity

Diversity Combining

bull Once you have created two or morediversity channels what do you do with them

Spatial diversity (contrsquod)

bullMaximum ratio combining (MRC)

h1

h2

h1

h2

yx

Combining schemes

bullSelection combining (SC)

h1

h2

yx

MonitorSNR

Selectbranch

Switch-and-stay combining (SSC) Switch-and-examine combining (SEC)

h1

h2

x

ComparatorChannelestimator

switchingthreshold

bullSwitched diversity

No trade off to

Without excessively increasing

bull 1 transmitting powerbull 2 Co-channel reuse distance

bull One of the most effective technique to solve this issue is diversity reception technique

What are all the needs of diversity techniques

bull 1No of signal transmission pathsbull 2A circuit to combine the received signal or

select one of them

CONCEPTS OF DIVERSITY BRANCH AND SIGNAL PATH

(a) Branch Construction method using frequency diversity

(b) Branch Construction method using Time diversity

COMBINING AND SWITCHNING METHODS

COMBINING AND SWITCHNINGMETHODS

FOR COHERENT DETECTION

FOR NON - COHERENT DETECTION

FOR COHERENT DETECTION

bull There is no difference whether the combining is carried out in the pre detection or in the post detection stage

FOR NON-COHERENT DETECTION

bull There is a difference in performance exists between whether pre detection amp post detection combining methods

(a) Maximal ratio combining (MRC)

bull MRC is the best performance improvement compared with the other methods

bull However the trade off is It requires 1 cophasing 2 weighting 3summing circuitsResulting in most complicated implementationComplexity performance

(b) Equal Gain Combining (EGC)

EGCbull EGC is similar to MRC except the weighting

circuits are omittedbull The performance improvement obtained by

equal gain combiner is slightly inferior to that of a MRC since the interference and noise corrupted signal combined with high quality signals

For VHF UHF and microwave wireless radio applications

bull Both MRC and EGC methods are unsuitablebull Compared with MRC EGC methods the

selection method is more suitable for mobile radio applications because of its simple implementation

(c) Selection or Switching Combining

bull The diversity branch having the highest signal level (or) lowest Pe is selected

bull Also in addition stable operation is easily achieved even in the fast multipath fading environments

bull But the performance improvement obtained by the selection method is still only slightly inferior to that of MRC method

Disadvantage of Selection or Switching

bull Combining The continuous monitoring of the signals requires the same no of receivers as the no of diversity branches

bull This redundancy can be alleviated by the use of switching or scanning receiver

SWITCHNINGMETHODS

FIXED THERSHOLD VARIABLE THERSHOLD

(a) Switching Methods with Fixed threshold

bull The switching from one branch to the other occurs when the signal level falls below a threshold value

bull The threshold value is fixedbull However this threshold value is not

necessarily the best over the entire service area

FIXED THERSHOLD

(b) Switching Methods with Variable threshold

bull Here the threshold value is adjusted dynamically as the vehicle moves

bull It includes the feedback using Estimationbull But it may introduce the envelope and phase

transients that will reduce the performance improvement

VARIABLE THERSHOLD

Conclusions

bull The diversity is used to provide the receiver with several replicas of the same signal

bull Diversity techniques are used to improve the performance of the radio channel without any increase in the transmitted power

bull As higher as the received signal replicas are decorrelated as much as the diversity gain

Thank you for you attention

• No trade off to
• What are all the needs of diversity techniques
• CONCEPTS OF DIVERSITY BRANCH AND SIGNAL PATH
• (a) Branch Construction method using frequency diversity
• (b) Branch Construction method using Time diversity
• COMBINING AND SWITCHNING METHODS
• Slide 29
• FOR COHERENT DETECTION
• (a) Maximal ratio combining (MRC)
• Slide 32
• (b) Equal Gain Combining (EGC)
• EGC
• For VHF UHF and microwave wireless radio applications
• (c) Selection or Switching Combining
• Slide 37
• Disadvantage of Selection or Switching
• Slide 39
• (a) Switching Methods with Fixed threshold
• Slide 41
• (b) Switching Methods with Variable threshold
• Slide 43

Spatial diversity

bull Single-input single-output (SISO) channel

No spatial diversitybull Single-input multiple-output (SIMO) channel

Receive diversitybull Multiple-input single-output (MISO) channel

Transmit diversity bull Multiple-input multiple-output (MIMO) channel

Combined transmit and receive diversity

The following classes of diversity schemes can be identified

1Space diversity 2Polarization diversity 3Frequency diversity 4Time diversity 5Angle or direction diversity

1] Space diversity

bull The signal is transferred over several different propagation paths

bull In the case of wired transmission this can be achieved by transmitting via multiple wires

bull In the case of wireless transmission it can be achieved by antenna diversity using multiple transmitter antennas (transmit diversity) andor multiple receiving antennas (reception diversity)

bull In the latter case a diversity combining technique is applied before further signal processing takes place

2] Polarization diversity

bull Polarization diversity Multiple versions of a signal are transmitted and received via antennas with different polarization

bull A diversity combining technique is applied on the receiver side

POLARIZER

3] Frequency diversity

bull Frequency diversity The signal is transferred using several frequency channels or spread over a wide spectrum that is affected by frequency-selective fading

bull Middle-late 20th century microwave radio relay lines often used several regular wideband radio channels and one protection channel for automatic use by any faded channel Later examples include OFDM modulation in combination with subcarrier interleaving and

forward error correction Spread spectrum for example frequency hopping or DS-CDMA

4] Time diversity

bull Time diversity Multiple versions of the same signal are transmitted at different time instants

Terrestrial microwave radio system with two antenna arrays configured for space-diversity

Diversity Combining

bull Once you have created two or morediversity channels what do you do with them

Spatial diversity (contrsquod)

bullMaximum ratio combining (MRC)

h1

h2

h1

h2

yx

Combining schemes

bullSelection combining (SC)

h1

h2

yx

MonitorSNR

Selectbranch

Switch-and-stay combining (SSC) Switch-and-examine combining (SEC)

h1

h2

x

ComparatorChannelestimator

switchingthreshold

bullSwitched diversity

No trade off to

Without excessively increasing

bull 1 transmitting powerbull 2 Co-channel reuse distance

bull One of the most effective technique to solve this issue is diversity reception technique

What are all the needs of diversity techniques

bull 1No of signal transmission pathsbull 2A circuit to combine the received signal or

select one of them

CONCEPTS OF DIVERSITY BRANCH AND SIGNAL PATH

(a) Branch Construction method using frequency diversity

(b) Branch Construction method using Time diversity

COMBINING AND SWITCHNING METHODS

COMBINING AND SWITCHNINGMETHODS

FOR COHERENT DETECTION

FOR NON - COHERENT DETECTION

FOR COHERENT DETECTION

bull There is no difference whether the combining is carried out in the pre detection or in the post detection stage

FOR NON-COHERENT DETECTION

bull There is a difference in performance exists between whether pre detection amp post detection combining methods

(a) Maximal ratio combining (MRC)

bull MRC is the best performance improvement compared with the other methods

bull However the trade off is It requires 1 cophasing 2 weighting 3summing circuitsResulting in most complicated implementationComplexity performance

(b) Equal Gain Combining (EGC)

EGCbull EGC is similar to MRC except the weighting

circuits are omittedbull The performance improvement obtained by

equal gain combiner is slightly inferior to that of a MRC since the interference and noise corrupted signal combined with high quality signals

For VHF UHF and microwave wireless radio applications

bull Both MRC and EGC methods are unsuitablebull Compared with MRC EGC methods the

selection method is more suitable for mobile radio applications because of its simple implementation

(c) Selection or Switching Combining

bull The diversity branch having the highest signal level (or) lowest Pe is selected

bull Also in addition stable operation is easily achieved even in the fast multipath fading environments

bull But the performance improvement obtained by the selection method is still only slightly inferior to that of MRC method

Disadvantage of Selection or Switching

bull Combining The continuous monitoring of the signals requires the same no of receivers as the no of diversity branches

bull This redundancy can be alleviated by the use of switching or scanning receiver

SWITCHNINGMETHODS

FIXED THERSHOLD VARIABLE THERSHOLD

(a) Switching Methods with Fixed threshold

bull The switching from one branch to the other occurs when the signal level falls below a threshold value

bull The threshold value is fixedbull However this threshold value is not

necessarily the best over the entire service area

FIXED THERSHOLD

(b) Switching Methods with Variable threshold

bull Here the threshold value is adjusted dynamically as the vehicle moves

bull It includes the feedback using Estimationbull But it may introduce the envelope and phase

transients that will reduce the performance improvement

VARIABLE THERSHOLD

Conclusions

bull The diversity is used to provide the receiver with several replicas of the same signal

bull Diversity techniques are used to improve the performance of the radio channel without any increase in the transmitted power

bull As higher as the received signal replicas are decorrelated as much as the diversity gain

Thank you for you attention

• No trade off to
• What are all the needs of diversity techniques
• CONCEPTS OF DIVERSITY BRANCH AND SIGNAL PATH
• (a) Branch Construction method using frequency diversity
• (b) Branch Construction method using Time diversity
• COMBINING AND SWITCHNING METHODS
• Slide 29
• FOR COHERENT DETECTION
• (a) Maximal ratio combining (MRC)
• Slide 32
• (b) Equal Gain Combining (EGC)
• EGC
• For VHF UHF and microwave wireless radio applications
• (c) Selection or Switching Combining
• Slide 37
• Disadvantage of Selection or Switching
• Slide 39
• (a) Switching Methods with Fixed threshold
• Slide 41
• (b) Switching Methods with Variable threshold
• Slide 43

The following classes of diversity schemes can be identified

1Space diversity 2Polarization diversity 3Frequency diversity 4Time diversity 5Angle or direction diversity

1] Space diversity

bull The signal is transferred over several different propagation paths

bull In the case of wired transmission this can be achieved by transmitting via multiple wires

bull In the case of wireless transmission it can be achieved by antenna diversity using multiple transmitter antennas (transmit diversity) andor multiple receiving antennas (reception diversity)

bull In the latter case a diversity combining technique is applied before further signal processing takes place

2] Polarization diversity

bull Polarization diversity Multiple versions of a signal are transmitted and received via antennas with different polarization

bull A diversity combining technique is applied on the receiver side

POLARIZER

3] Frequency diversity

bull Frequency diversity The signal is transferred using several frequency channels or spread over a wide spectrum that is affected by frequency-selective fading

bull Middle-late 20th century microwave radio relay lines often used several regular wideband radio channels and one protection channel for automatic use by any faded channel Later examples include OFDM modulation in combination with subcarrier interleaving and

forward error correction Spread spectrum for example frequency hopping or DS-CDMA

4] Time diversity

bull Time diversity Multiple versions of the same signal are transmitted at different time instants

Terrestrial microwave radio system with two antenna arrays configured for space-diversity

Diversity Combining

bull Once you have created two or morediversity channels what do you do with them

Spatial diversity (contrsquod)

bullMaximum ratio combining (MRC)

h1

h2

h1

h2

yx

Combining schemes

bullSelection combining (SC)

h1

h2

yx

MonitorSNR

Selectbranch

Switch-and-stay combining (SSC) Switch-and-examine combining (SEC)

h1

h2

x

ComparatorChannelestimator

switchingthreshold

bullSwitched diversity

No trade off to

Without excessively increasing

bull 1 transmitting powerbull 2 Co-channel reuse distance

bull One of the most effective technique to solve this issue is diversity reception technique

What are all the needs of diversity techniques

bull 1No of signal transmission pathsbull 2A circuit to combine the received signal or

select one of them

CONCEPTS OF DIVERSITY BRANCH AND SIGNAL PATH

(a) Branch Construction method using frequency diversity

(b) Branch Construction method using Time diversity

COMBINING AND SWITCHNING METHODS

COMBINING AND SWITCHNINGMETHODS

FOR COHERENT DETECTION

FOR NON - COHERENT DETECTION

FOR COHERENT DETECTION

bull There is no difference whether the combining is carried out in the pre detection or in the post detection stage

FOR NON-COHERENT DETECTION

bull There is a difference in performance exists between whether pre detection amp post detection combining methods

(a) Maximal ratio combining (MRC)

bull MRC is the best performance improvement compared with the other methods

bull However the trade off is It requires 1 cophasing 2 weighting 3summing circuitsResulting in most complicated implementationComplexity performance

(b) Equal Gain Combining (EGC)

EGCbull EGC is similar to MRC except the weighting

circuits are omittedbull The performance improvement obtained by

equal gain combiner is slightly inferior to that of a MRC since the interference and noise corrupted signal combined with high quality signals

For VHF UHF and microwave wireless radio applications

bull Both MRC and EGC methods are unsuitablebull Compared with MRC EGC methods the

selection method is more suitable for mobile radio applications because of its simple implementation

(c) Selection or Switching Combining

bull The diversity branch having the highest signal level (or) lowest Pe is selected

bull Also in addition stable operation is easily achieved even in the fast multipath fading environments

bull But the performance improvement obtained by the selection method is still only slightly inferior to that of MRC method

Disadvantage of Selection or Switching

bull Combining The continuous monitoring of the signals requires the same no of receivers as the no of diversity branches

bull This redundancy can be alleviated by the use of switching or scanning receiver

SWITCHNINGMETHODS

FIXED THERSHOLD VARIABLE THERSHOLD

(a) Switching Methods with Fixed threshold

bull The switching from one branch to the other occurs when the signal level falls below a threshold value

bull The threshold value is fixedbull However this threshold value is not

necessarily the best over the entire service area

FIXED THERSHOLD

(b) Switching Methods with Variable threshold

bull Here the threshold value is adjusted dynamically as the vehicle moves

bull It includes the feedback using Estimationbull But it may introduce the envelope and phase

transients that will reduce the performance improvement

VARIABLE THERSHOLD

Conclusions

bull The diversity is used to provide the receiver with several replicas of the same signal

bull Diversity techniques are used to improve the performance of the radio channel without any increase in the transmitted power

bull As higher as the received signal replicas are decorrelated as much as the diversity gain

Thank you for you attention

• No trade off to
• What are all the needs of diversity techniques
• CONCEPTS OF DIVERSITY BRANCH AND SIGNAL PATH
• (a) Branch Construction method using frequency diversity
• (b) Branch Construction method using Time diversity
• COMBINING AND SWITCHNING METHODS
• Slide 29
• FOR COHERENT DETECTION
• (a) Maximal ratio combining (MRC)
• Slide 32
• (b) Equal Gain Combining (EGC)
• EGC
• For VHF UHF and microwave wireless radio applications
• (c) Selection or Switching Combining
• Slide 37
• Disadvantage of Selection or Switching
• Slide 39
• (a) Switching Methods with Fixed threshold
• Slide 41
• (b) Switching Methods with Variable threshold
• Slide 43

1] Space diversity

bull The signal is transferred over several different propagation paths

bull In the case of wired transmission this can be achieved by transmitting via multiple wires

bull In the case of wireless transmission it can be achieved by antenna diversity using multiple transmitter antennas (transmit diversity) andor multiple receiving antennas (reception diversity)

bull In the latter case a diversity combining technique is applied before further signal processing takes place

2] Polarization diversity

bull Polarization diversity Multiple versions of a signal are transmitted and received via antennas with different polarization

bull A diversity combining technique is applied on the receiver side

POLARIZER

3] Frequency diversity

bull Frequency diversity The signal is transferred using several frequency channels or spread over a wide spectrum that is affected by frequency-selective fading

bull Middle-late 20th century microwave radio relay lines often used several regular wideband radio channels and one protection channel for automatic use by any faded channel Later examples include OFDM modulation in combination with subcarrier interleaving and

forward error correction Spread spectrum for example frequency hopping or DS-CDMA

4] Time diversity

bull Time diversity Multiple versions of the same signal are transmitted at different time instants

Terrestrial microwave radio system with two antenna arrays configured for space-diversity

Diversity Combining

bull Once you have created two or morediversity channels what do you do with them

Spatial diversity (contrsquod)

bullMaximum ratio combining (MRC)

h1

h2

h1

h2

yx

Combining schemes

bullSelection combining (SC)

h1

h2

yx

MonitorSNR

Selectbranch

Switch-and-stay combining (SSC) Switch-and-examine combining (SEC)

h1

h2

x

ComparatorChannelestimator

switchingthreshold

bullSwitched diversity

No trade off to

Without excessively increasing

bull 1 transmitting powerbull 2 Co-channel reuse distance

bull One of the most effective technique to solve this issue is diversity reception technique

What are all the needs of diversity techniques

bull 1No of signal transmission pathsbull 2A circuit to combine the received signal or

select one of them

CONCEPTS OF DIVERSITY BRANCH AND SIGNAL PATH

(a) Branch Construction method using frequency diversity

(b) Branch Construction method using Time diversity

COMBINING AND SWITCHNING METHODS

COMBINING AND SWITCHNINGMETHODS

FOR COHERENT DETECTION

FOR NON - COHERENT DETECTION

FOR COHERENT DETECTION

bull There is no difference whether the combining is carried out in the pre detection or in the post detection stage

FOR NON-COHERENT DETECTION

bull There is a difference in performance exists between whether pre detection amp post detection combining methods

(a) Maximal ratio combining (MRC)

bull MRC is the best performance improvement compared with the other methods

bull However the trade off is It requires 1 cophasing 2 weighting 3summing circuitsResulting in most complicated implementationComplexity performance

(b) Equal Gain Combining (EGC)

EGCbull EGC is similar to MRC except the weighting

circuits are omittedbull The performance improvement obtained by

equal gain combiner is slightly inferior to that of a MRC since the interference and noise corrupted signal combined with high quality signals

For VHF UHF and microwave wireless radio applications

bull Both MRC and EGC methods are unsuitablebull Compared with MRC EGC methods the

selection method is more suitable for mobile radio applications because of its simple implementation

(c) Selection or Switching Combining

bull The diversity branch having the highest signal level (or) lowest Pe is selected

bull Also in addition stable operation is easily achieved even in the fast multipath fading environments

bull But the performance improvement obtained by the selection method is still only slightly inferior to that of MRC method

Disadvantage of Selection or Switching

bull Combining The continuous monitoring of the signals requires the same no of receivers as the no of diversity branches

bull This redundancy can be alleviated by the use of switching or scanning receiver

SWITCHNINGMETHODS

FIXED THERSHOLD VARIABLE THERSHOLD

(a) Switching Methods with Fixed threshold

bull The switching from one branch to the other occurs when the signal level falls below a threshold value

bull The threshold value is fixedbull However this threshold value is not

necessarily the best over the entire service area

FIXED THERSHOLD

(b) Switching Methods with Variable threshold

bull Here the threshold value is adjusted dynamically as the vehicle moves

bull It includes the feedback using Estimationbull But it may introduce the envelope and phase

transients that will reduce the performance improvement

VARIABLE THERSHOLD

Conclusions

bull The diversity is used to provide the receiver with several replicas of the same signal

bull Diversity techniques are used to improve the performance of the radio channel without any increase in the transmitted power

bull As higher as the received signal replicas are decorrelated as much as the diversity gain

Thank you for you attention

• No trade off to
• What are all the needs of diversity techniques
• CONCEPTS OF DIVERSITY BRANCH AND SIGNAL PATH
• (a) Branch Construction method using frequency diversity
• (b) Branch Construction method using Time diversity
• COMBINING AND SWITCHNING METHODS
• Slide 29
• FOR COHERENT DETECTION
• (a) Maximal ratio combining (MRC)
• Slide 32
• (b) Equal Gain Combining (EGC)
• EGC
• For VHF UHF and microwave wireless radio applications
• (c) Selection or Switching Combining
• Slide 37
• Disadvantage of Selection or Switching
• Slide 39
• (a) Switching Methods with Fixed threshold
• Slide 41
• (b) Switching Methods with Variable threshold
• Slide 43

2] Polarization diversity

bull Polarization diversity Multiple versions of a signal are transmitted and received via antennas with different polarization

bull A diversity combining technique is applied on the receiver side

POLARIZER

3] Frequency diversity

bull Frequency diversity The signal is transferred using several frequency channels or spread over a wide spectrum that is affected by frequency-selective fading

bull Middle-late 20th century microwave radio relay lines often used several regular wideband radio channels and one protection channel for automatic use by any faded channel Later examples include OFDM modulation in combination with subcarrier interleaving and

forward error correction Spread spectrum for example frequency hopping or DS-CDMA

4] Time diversity

bull Time diversity Multiple versions of the same signal are transmitted at different time instants

Terrestrial microwave radio system with two antenna arrays configured for space-diversity

Diversity Combining

bull Once you have created two or morediversity channels what do you do with them

Spatial diversity (contrsquod)

bullMaximum ratio combining (MRC)

h1

h2

h1

h2

yx

Combining schemes

bullSelection combining (SC)

h1

h2

yx

MonitorSNR

Selectbranch

Switch-and-stay combining (SSC) Switch-and-examine combining (SEC)

h1

h2

x

ComparatorChannelestimator

switchingthreshold

bullSwitched diversity

No trade off to

Without excessively increasing

bull 1 transmitting powerbull 2 Co-channel reuse distance

bull One of the most effective technique to solve this issue is diversity reception technique

What are all the needs of diversity techniques

bull 1No of signal transmission pathsbull 2A circuit to combine the received signal or

select one of them

CONCEPTS OF DIVERSITY BRANCH AND SIGNAL PATH

(a) Branch Construction method using frequency diversity

(b) Branch Construction method using Time diversity

COMBINING AND SWITCHNING METHODS

COMBINING AND SWITCHNINGMETHODS

FOR COHERENT DETECTION

FOR NON - COHERENT DETECTION

FOR COHERENT DETECTION

bull There is no difference whether the combining is carried out in the pre detection or in the post detection stage

FOR NON-COHERENT DETECTION

bull There is a difference in performance exists between whether pre detection amp post detection combining methods

(a) Maximal ratio combining (MRC)

bull MRC is the best performance improvement compared with the other methods

bull However the trade off is It requires 1 cophasing 2 weighting 3summing circuitsResulting in most complicated implementationComplexity performance

(b) Equal Gain Combining (EGC)

EGCbull EGC is similar to MRC except the weighting

circuits are omittedbull The performance improvement obtained by

equal gain combiner is slightly inferior to that of a MRC since the interference and noise corrupted signal combined with high quality signals

For VHF UHF and microwave wireless radio applications

bull Both MRC and EGC methods are unsuitablebull Compared with MRC EGC methods the

selection method is more suitable for mobile radio applications because of its simple implementation

(c) Selection or Switching Combining

bull The diversity branch having the highest signal level (or) lowest Pe is selected

bull Also in addition stable operation is easily achieved even in the fast multipath fading environments

bull But the performance improvement obtained by the selection method is still only slightly inferior to that of MRC method

Disadvantage of Selection or Switching

bull Combining The continuous monitoring of the signals requires the same no of receivers as the no of diversity branches

bull This redundancy can be alleviated by the use of switching or scanning receiver

SWITCHNINGMETHODS

FIXED THERSHOLD VARIABLE THERSHOLD

(a) Switching Methods with Fixed threshold

bull The switching from one branch to the other occurs when the signal level falls below a threshold value

bull The threshold value is fixedbull However this threshold value is not

necessarily the best over the entire service area

FIXED THERSHOLD

(b) Switching Methods with Variable threshold

bull Here the threshold value is adjusted dynamically as the vehicle moves

bull It includes the feedback using Estimationbull But it may introduce the envelope and phase

transients that will reduce the performance improvement

VARIABLE THERSHOLD

Conclusions

bull The diversity is used to provide the receiver with several replicas of the same signal

bull Diversity techniques are used to improve the performance of the radio channel without any increase in the transmitted power

bull As higher as the received signal replicas are decorrelated as much as the diversity gain

Thank you for you attention

• No trade off to
• What are all the needs of diversity techniques
• CONCEPTS OF DIVERSITY BRANCH AND SIGNAL PATH
• (a) Branch Construction method using frequency diversity
• (b) Branch Construction method using Time diversity
• COMBINING AND SWITCHNING METHODS
• Slide 29
• FOR COHERENT DETECTION
• (a) Maximal ratio combining (MRC)
• Slide 32
• (b) Equal Gain Combining (EGC)
• EGC
• For VHF UHF and microwave wireless radio applications
• (c) Selection or Switching Combining
• Slide 37
• Disadvantage of Selection or Switching
• Slide 39
• (a) Switching Methods with Fixed threshold
• Slide 41
• (b) Switching Methods with Variable threshold
• Slide 43

POLARIZER

3] Frequency diversity

bull Frequency diversity The signal is transferred using several frequency channels or spread over a wide spectrum that is affected by frequency-selective fading

bull Middle-late 20th century microwave radio relay lines often used several regular wideband radio channels and one protection channel for automatic use by any faded channel Later examples include OFDM modulation in combination with subcarrier interleaving and

forward error correction Spread spectrum for example frequency hopping or DS-CDMA

4] Time diversity

bull Time diversity Multiple versions of the same signal are transmitted at different time instants

Terrestrial microwave radio system with two antenna arrays configured for space-diversity

Diversity Combining

bull Once you have created two or morediversity channels what do you do with them

Spatial diversity (contrsquod)

bullMaximum ratio combining (MRC)

h1

h2

h1

h2

yx

Combining schemes

bullSelection combining (SC)

h1

h2

yx

MonitorSNR

Selectbranch

Switch-and-stay combining (SSC) Switch-and-examine combining (SEC)

h1

h2

x

ComparatorChannelestimator

switchingthreshold

bullSwitched diversity

No trade off to

Without excessively increasing

bull 1 transmitting powerbull 2 Co-channel reuse distance

bull One of the most effective technique to solve this issue is diversity reception technique

What are all the needs of diversity techniques

bull 1No of signal transmission pathsbull 2A circuit to combine the received signal or

select one of them

CONCEPTS OF DIVERSITY BRANCH AND SIGNAL PATH

(a) Branch Construction method using frequency diversity

(b) Branch Construction method using Time diversity

COMBINING AND SWITCHNING METHODS

COMBINING AND SWITCHNINGMETHODS

FOR COHERENT DETECTION

FOR NON - COHERENT DETECTION

FOR COHERENT DETECTION

bull There is no difference whether the combining is carried out in the pre detection or in the post detection stage

FOR NON-COHERENT DETECTION

bull There is a difference in performance exists between whether pre detection amp post detection combining methods

(a) Maximal ratio combining (MRC)

bull MRC is the best performance improvement compared with the other methods

bull However the trade off is It requires 1 cophasing 2 weighting 3summing circuitsResulting in most complicated implementationComplexity performance

(b) Equal Gain Combining (EGC)

EGCbull EGC is similar to MRC except the weighting

circuits are omittedbull The performance improvement obtained by

equal gain combiner is slightly inferior to that of a MRC since the interference and noise corrupted signal combined with high quality signals

For VHF UHF and microwave wireless radio applications

bull Both MRC and EGC methods are unsuitablebull Compared with MRC EGC methods the

selection method is more suitable for mobile radio applications because of its simple implementation

(c) Selection or Switching Combining

bull The diversity branch having the highest signal level (or) lowest Pe is selected

bull Also in addition stable operation is easily achieved even in the fast multipath fading environments

bull But the performance improvement obtained by the selection method is still only slightly inferior to that of MRC method

Disadvantage of Selection or Switching

bull Combining The continuous monitoring of the signals requires the same no of receivers as the no of diversity branches

bull This redundancy can be alleviated by the use of switching or scanning receiver

SWITCHNINGMETHODS

FIXED THERSHOLD VARIABLE THERSHOLD

(a) Switching Methods with Fixed threshold

bull The switching from one branch to the other occurs when the signal level falls below a threshold value

bull The threshold value is fixedbull However this threshold value is not

necessarily the best over the entire service area

FIXED THERSHOLD

(b) Switching Methods with Variable threshold

bull Here the threshold value is adjusted dynamically as the vehicle moves

bull It includes the feedback using Estimationbull But it may introduce the envelope and phase

transients that will reduce the performance improvement

VARIABLE THERSHOLD

Conclusions

bull The diversity is used to provide the receiver with several replicas of the same signal

bull Diversity techniques are used to improve the performance of the radio channel without any increase in the transmitted power

bull As higher as the received signal replicas are decorrelated as much as the diversity gain

Thank you for you attention

• No trade off to
• What are all the needs of diversity techniques
• CONCEPTS OF DIVERSITY BRANCH AND SIGNAL PATH
• (a) Branch Construction method using frequency diversity
• (b) Branch Construction method using Time diversity
• COMBINING AND SWITCHNING METHODS
• Slide 29
• FOR COHERENT DETECTION
• (a) Maximal ratio combining (MRC)
• Slide 32
• (b) Equal Gain Combining (EGC)
• EGC
• For VHF UHF and microwave wireless radio applications
• (c) Selection or Switching Combining
• Slide 37
• Disadvantage of Selection or Switching
• Slide 39
• (a) Switching Methods with Fixed threshold
• Slide 41
• (b) Switching Methods with Variable threshold
• Slide 43

3] Frequency diversity

bull Frequency diversity The signal is transferred using several frequency channels or spread over a wide spectrum that is affected by frequency-selective fading

bull Middle-late 20th century microwave radio relay lines often used several regular wideband radio channels and one protection channel for automatic use by any faded channel Later examples include OFDM modulation in combination with subcarrier interleaving and

forward error correction Spread spectrum for example frequency hopping or DS-CDMA

4] Time diversity

bull Time diversity Multiple versions of the same signal are transmitted at different time instants

Terrestrial microwave radio system with two antenna arrays configured for space-diversity

Diversity Combining

bull Once you have created two or morediversity channels what do you do with them

Spatial diversity (contrsquod)

bullMaximum ratio combining (MRC)

h1

h2

h1

h2

yx

Combining schemes

bullSelection combining (SC)

h1

h2

yx

MonitorSNR

Selectbranch

Switch-and-stay combining (SSC) Switch-and-examine combining (SEC)

h1

h2

x

ComparatorChannelestimator

switchingthreshold

bullSwitched diversity

No trade off to

Without excessively increasing

bull 1 transmitting powerbull 2 Co-channel reuse distance

bull One of the most effective technique to solve this issue is diversity reception technique

What are all the needs of diversity techniques

bull 1No of signal transmission pathsbull 2A circuit to combine the received signal or

select one of them

CONCEPTS OF DIVERSITY BRANCH AND SIGNAL PATH

(a) Branch Construction method using frequency diversity

(b) Branch Construction method using Time diversity

COMBINING AND SWITCHNING METHODS

COMBINING AND SWITCHNINGMETHODS

FOR COHERENT DETECTION

FOR NON - COHERENT DETECTION

FOR COHERENT DETECTION

bull There is no difference whether the combining is carried out in the pre detection or in the post detection stage

FOR NON-COHERENT DETECTION

bull There is a difference in performance exists between whether pre detection amp post detection combining methods

(a) Maximal ratio combining (MRC)

bull MRC is the best performance improvement compared with the other methods

bull However the trade off is It requires 1 cophasing 2 weighting 3summing circuitsResulting in most complicated implementationComplexity performance

(b) Equal Gain Combining (EGC)

EGCbull EGC is similar to MRC except the weighting

circuits are omittedbull The performance improvement obtained by

equal gain combiner is slightly inferior to that of a MRC since the interference and noise corrupted signal combined with high quality signals

For VHF UHF and microwave wireless radio applications

bull Both MRC and EGC methods are unsuitablebull Compared with MRC EGC methods the

selection method is more suitable for mobile radio applications because of its simple implementation

(c) Selection or Switching Combining

bull The diversity branch having the highest signal level (or) lowest Pe is selected

bull Also in addition stable operation is easily achieved even in the fast multipath fading environments

bull But the performance improvement obtained by the selection method is still only slightly inferior to that of MRC method

Disadvantage of Selection or Switching

bull Combining The continuous monitoring of the signals requires the same no of receivers as the no of diversity branches

bull This redundancy can be alleviated by the use of switching or scanning receiver

SWITCHNINGMETHODS

FIXED THERSHOLD VARIABLE THERSHOLD

(a) Switching Methods with Fixed threshold

bull The switching from one branch to the other occurs when the signal level falls below a threshold value

bull The threshold value is fixedbull However this threshold value is not

necessarily the best over the entire service area

FIXED THERSHOLD

(b) Switching Methods with Variable threshold

bull Here the threshold value is adjusted dynamically as the vehicle moves

bull It includes the feedback using Estimationbull But it may introduce the envelope and phase

transients that will reduce the performance improvement

VARIABLE THERSHOLD

Conclusions

bull The diversity is used to provide the receiver with several replicas of the same signal

bull Diversity techniques are used to improve the performance of the radio channel without any increase in the transmitted power

bull As higher as the received signal replicas are decorrelated as much as the diversity gain

Thank you for you attention

• No trade off to
• What are all the needs of diversity techniques
• CONCEPTS OF DIVERSITY BRANCH AND SIGNAL PATH
• (a) Branch Construction method using frequency diversity
• (b) Branch Construction method using Time diversity
• COMBINING AND SWITCHNING METHODS
• Slide 29
• FOR COHERENT DETECTION
• (a) Maximal ratio combining (MRC)
• Slide 32
• (b) Equal Gain Combining (EGC)
• EGC
• For VHF UHF and microwave wireless radio applications
• (c) Selection or Switching Combining
• Slide 37
• Disadvantage of Selection or Switching
• Slide 39
• (a) Switching Methods with Fixed threshold
• Slide 41
• (b) Switching Methods with Variable threshold
• Slide 43

4] Time diversity

bull Time diversity Multiple versions of the same signal are transmitted at different time instants

Terrestrial microwave radio system with two antenna arrays configured for space-diversity

Diversity Combining

bull Once you have created two or morediversity channels what do you do with them

Spatial diversity (contrsquod)

bullMaximum ratio combining (MRC)

h1

h2

h1

h2

yx

Combining schemes

bullSelection combining (SC)

h1

h2

yx

MonitorSNR

Selectbranch

Switch-and-stay combining (SSC) Switch-and-examine combining (SEC)

h1

h2

x

ComparatorChannelestimator

switchingthreshold

bullSwitched diversity

No trade off to

Without excessively increasing

bull 1 transmitting powerbull 2 Co-channel reuse distance

bull One of the most effective technique to solve this issue is diversity reception technique

What are all the needs of diversity techniques

bull 1No of signal transmission pathsbull 2A circuit to combine the received signal or

select one of them

CONCEPTS OF DIVERSITY BRANCH AND SIGNAL PATH

(a) Branch Construction method using frequency diversity

(b) Branch Construction method using Time diversity

COMBINING AND SWITCHNING METHODS

COMBINING AND SWITCHNINGMETHODS

FOR COHERENT DETECTION

FOR NON - COHERENT DETECTION

FOR COHERENT DETECTION

bull There is no difference whether the combining is carried out in the pre detection or in the post detection stage

FOR NON-COHERENT DETECTION

bull There is a difference in performance exists between whether pre detection amp post detection combining methods

(a) Maximal ratio combining (MRC)

bull MRC is the best performance improvement compared with the other methods

bull However the trade off is It requires 1 cophasing 2 weighting 3summing circuitsResulting in most complicated implementationComplexity performance

(b) Equal Gain Combining (EGC)

EGCbull EGC is similar to MRC except the weighting

circuits are omittedbull The performance improvement obtained by

equal gain combiner is slightly inferior to that of a MRC since the interference and noise corrupted signal combined with high quality signals

For VHF UHF and microwave wireless radio applications

bull Both MRC and EGC methods are unsuitablebull Compared with MRC EGC methods the

selection method is more suitable for mobile radio applications because of its simple implementation

(c) Selection or Switching Combining

bull The diversity branch having the highest signal level (or) lowest Pe is selected

bull Also in addition stable operation is easily achieved even in the fast multipath fading environments

bull But the performance improvement obtained by the selection method is still only slightly inferior to that of MRC method

Disadvantage of Selection or Switching

bull Combining The continuous monitoring of the signals requires the same no of receivers as the no of diversity branches

bull This redundancy can be alleviated by the use of switching or scanning receiver

SWITCHNINGMETHODS

FIXED THERSHOLD VARIABLE THERSHOLD

(a) Switching Methods with Fixed threshold

bull The switching from one branch to the other occurs when the signal level falls below a threshold value

bull The threshold value is fixedbull However this threshold value is not

necessarily the best over the entire service area

FIXED THERSHOLD

(b) Switching Methods with Variable threshold

bull Here the threshold value is adjusted dynamically as the vehicle moves

bull It includes the feedback using Estimationbull But it may introduce the envelope and phase

transients that will reduce the performance improvement

VARIABLE THERSHOLD

Conclusions

bull The diversity is used to provide the receiver with several replicas of the same signal

bull Diversity techniques are used to improve the performance of the radio channel without any increase in the transmitted power

bull As higher as the received signal replicas are decorrelated as much as the diversity gain

Thank you for you attention

• No trade off to
• What are all the needs of diversity techniques
• CONCEPTS OF DIVERSITY BRANCH AND SIGNAL PATH
• (a) Branch Construction method using frequency diversity
• (b) Branch Construction method using Time diversity
• COMBINING AND SWITCHNING METHODS
• Slide 29
• FOR COHERENT DETECTION
• (a) Maximal ratio combining (MRC)
• Slide 32
• (b) Equal Gain Combining (EGC)
• EGC
• For VHF UHF and microwave wireless radio applications
• (c) Selection or Switching Combining
• Slide 37
• Disadvantage of Selection or Switching
• Slide 39
• (a) Switching Methods with Fixed threshold
• Slide 41
• (b) Switching Methods with Variable threshold
• Slide 43

Terrestrial microwave radio system with two antenna arrays configured for space-diversity

Diversity Combining

bull Once you have created two or morediversity channels what do you do with them

Spatial diversity (contrsquod)

bullMaximum ratio combining (MRC)

h1

h2

h1

h2

yx

Combining schemes

bullSelection combining (SC)

h1

h2

yx

MonitorSNR

Selectbranch

Switch-and-stay combining (SSC) Switch-and-examine combining (SEC)

h1

h2

x

ComparatorChannelestimator

switchingthreshold

bullSwitched diversity

No trade off to

Without excessively increasing

bull 1 transmitting powerbull 2 Co-channel reuse distance

bull One of the most effective technique to solve this issue is diversity reception technique

What are all the needs of diversity techniques

bull 1No of signal transmission pathsbull 2A circuit to combine the received signal or

select one of them

CONCEPTS OF DIVERSITY BRANCH AND SIGNAL PATH

(a) Branch Construction method using frequency diversity

(b) Branch Construction method using Time diversity

COMBINING AND SWITCHNING METHODS

COMBINING AND SWITCHNINGMETHODS

FOR COHERENT DETECTION

FOR NON - COHERENT DETECTION

FOR COHERENT DETECTION

bull There is no difference whether the combining is carried out in the pre detection or in the post detection stage

FOR NON-COHERENT DETECTION

bull There is a difference in performance exists between whether pre detection amp post detection combining methods

(a) Maximal ratio combining (MRC)

bull MRC is the best performance improvement compared with the other methods

bull However the trade off is It requires 1 cophasing 2 weighting 3summing circuitsResulting in most complicated implementationComplexity performance

(b) Equal Gain Combining (EGC)

EGCbull EGC is similar to MRC except the weighting

circuits are omittedbull The performance improvement obtained by

equal gain combiner is slightly inferior to that of a MRC since the interference and noise corrupted signal combined with high quality signals

For VHF UHF and microwave wireless radio applications

bull Both MRC and EGC methods are unsuitablebull Compared with MRC EGC methods the

selection method is more suitable for mobile radio applications because of its simple implementation

(c) Selection or Switching Combining

bull The diversity branch having the highest signal level (or) lowest Pe is selected

bull Also in addition stable operation is easily achieved even in the fast multipath fading environments

bull But the performance improvement obtained by the selection method is still only slightly inferior to that of MRC method

Disadvantage of Selection or Switching

bull Combining The continuous monitoring of the signals requires the same no of receivers as the no of diversity branches

bull This redundancy can be alleviated by the use of switching or scanning receiver

SWITCHNINGMETHODS

FIXED THERSHOLD VARIABLE THERSHOLD

(a) Switching Methods with Fixed threshold

bull The switching from one branch to the other occurs when the signal level falls below a threshold value

bull The threshold value is fixedbull However this threshold value is not

necessarily the best over the entire service area

FIXED THERSHOLD

(b) Switching Methods with Variable threshold

bull Here the threshold value is adjusted dynamically as the vehicle moves

bull It includes the feedback using Estimationbull But it may introduce the envelope and phase

transients that will reduce the performance improvement

VARIABLE THERSHOLD

Conclusions

bull The diversity is used to provide the receiver with several replicas of the same signal

bull Diversity techniques are used to improve the performance of the radio channel without any increase in the transmitted power

bull As higher as the received signal replicas are decorrelated as much as the diversity gain

Thank you for you attention

• No trade off to
• What are all the needs of diversity techniques
• CONCEPTS OF DIVERSITY BRANCH AND SIGNAL PATH
• (a) Branch Construction method using frequency diversity
• (b) Branch Construction method using Time diversity
• COMBINING AND SWITCHNING METHODS
• Slide 29
• FOR COHERENT DETECTION
• (a) Maximal ratio combining (MRC)
• Slide 32
• (b) Equal Gain Combining (EGC)
• EGC
• For VHF UHF and microwave wireless radio applications
• (c) Selection or Switching Combining
• Slide 37
• Disadvantage of Selection or Switching
• Slide 39
• (a) Switching Methods with Fixed threshold
• Slide 41
• (b) Switching Methods with Variable threshold
• Slide 43

Diversity Combining

bull Once you have created two or morediversity channels what do you do with them

Spatial diversity (contrsquod)

bullMaximum ratio combining (MRC)

h1

h2

h1

h2

yx

Combining schemes

bullSelection combining (SC)

h1

h2

yx

MonitorSNR

Selectbranch

Switch-and-stay combining (SSC) Switch-and-examine combining (SEC)

h1

h2

x

ComparatorChannelestimator

switchingthreshold

bullSwitched diversity

No trade off to

Without excessively increasing

bull 1 transmitting powerbull 2 Co-channel reuse distance

bull One of the most effective technique to solve this issue is diversity reception technique

What are all the needs of diversity techniques

bull 1No of signal transmission pathsbull 2A circuit to combine the received signal or

select one of them

CONCEPTS OF DIVERSITY BRANCH AND SIGNAL PATH

(a) Branch Construction method using frequency diversity

(b) Branch Construction method using Time diversity

COMBINING AND SWITCHNING METHODS

COMBINING AND SWITCHNINGMETHODS

FOR COHERENT DETECTION

FOR NON - COHERENT DETECTION

FOR COHERENT DETECTION

bull There is no difference whether the combining is carried out in the pre detection or in the post detection stage

FOR NON-COHERENT DETECTION

bull There is a difference in performance exists between whether pre detection amp post detection combining methods

(a) Maximal ratio combining (MRC)

bull MRC is the best performance improvement compared with the other methods

bull However the trade off is It requires 1 cophasing 2 weighting 3summing circuitsResulting in most complicated implementationComplexity performance

(b) Equal Gain Combining (EGC)

EGCbull EGC is similar to MRC except the weighting

circuits are omittedbull The performance improvement obtained by

equal gain combiner is slightly inferior to that of a MRC since the interference and noise corrupted signal combined with high quality signals

For VHF UHF and microwave wireless radio applications

bull Both MRC and EGC methods are unsuitablebull Compared with MRC EGC methods the

selection method is more suitable for mobile radio applications because of its simple implementation

(c) Selection or Switching Combining

bull The diversity branch having the highest signal level (or) lowest Pe is selected

bull Also in addition stable operation is easily achieved even in the fast multipath fading environments

bull But the performance improvement obtained by the selection method is still only slightly inferior to that of MRC method

Disadvantage of Selection or Switching

bull Combining The continuous monitoring of the signals requires the same no of receivers as the no of diversity branches

bull This redundancy can be alleviated by the use of switching or scanning receiver

SWITCHNINGMETHODS

FIXED THERSHOLD VARIABLE THERSHOLD

(a) Switching Methods with Fixed threshold

bull The switching from one branch to the other occurs when the signal level falls below a threshold value

bull The threshold value is fixedbull However this threshold value is not

necessarily the best over the entire service area

FIXED THERSHOLD

(b) Switching Methods with Variable threshold

bull Here the threshold value is adjusted dynamically as the vehicle moves

bull It includes the feedback using Estimationbull But it may introduce the envelope and phase

transients that will reduce the performance improvement

VARIABLE THERSHOLD

Conclusions

bull The diversity is used to provide the receiver with several replicas of the same signal

bull Diversity techniques are used to improve the performance of the radio channel without any increase in the transmitted power

bull As higher as the received signal replicas are decorrelated as much as the diversity gain

Thank you for you attention

• No trade off to
• What are all the needs of diversity techniques
• CONCEPTS OF DIVERSITY BRANCH AND SIGNAL PATH
• (a) Branch Construction method using frequency diversity
• (b) Branch Construction method using Time diversity
• COMBINING AND SWITCHNING METHODS
• Slide 29
• FOR COHERENT DETECTION
• (a) Maximal ratio combining (MRC)
• Slide 32
• (b) Equal Gain Combining (EGC)
• EGC
• For VHF UHF and microwave wireless radio applications
• (c) Selection or Switching Combining
• Slide 37
• Disadvantage of Selection or Switching
• Slide 39
• (a) Switching Methods with Fixed threshold
• Slide 41
• (b) Switching Methods with Variable threshold
• Slide 43

Spatial diversity (contrsquod)

bullMaximum ratio combining (MRC)

h1

h2

h1

h2

yx

Combining schemes

bullSelection combining (SC)

h1

h2

yx

MonitorSNR

Selectbranch

Switch-and-stay combining (SSC) Switch-and-examine combining (SEC)

h1

h2

x

ComparatorChannelestimator

switchingthreshold

bullSwitched diversity

No trade off to

Without excessively increasing

bull 1 transmitting powerbull 2 Co-channel reuse distance

bull One of the most effective technique to solve this issue is diversity reception technique

What are all the needs of diversity techniques

bull 1No of signal transmission pathsbull 2A circuit to combine the received signal or

select one of them

CONCEPTS OF DIVERSITY BRANCH AND SIGNAL PATH

(a) Branch Construction method using frequency diversity

(b) Branch Construction method using Time diversity

COMBINING AND SWITCHNING METHODS

COMBINING AND SWITCHNINGMETHODS

FOR COHERENT DETECTION

FOR NON - COHERENT DETECTION

FOR COHERENT DETECTION

bull There is no difference whether the combining is carried out in the pre detection or in the post detection stage

FOR NON-COHERENT DETECTION

bull There is a difference in performance exists between whether pre detection amp post detection combining methods

(a) Maximal ratio combining (MRC)

bull MRC is the best performance improvement compared with the other methods

bull However the trade off is It requires 1 cophasing 2 weighting 3summing circuitsResulting in most complicated implementationComplexity performance

(b) Equal Gain Combining (EGC)

EGCbull EGC is similar to MRC except the weighting

circuits are omittedbull The performance improvement obtained by

equal gain combiner is slightly inferior to that of a MRC since the interference and noise corrupted signal combined with high quality signals

For VHF UHF and microwave wireless radio applications

bull Both MRC and EGC methods are unsuitablebull Compared with MRC EGC methods the

selection method is more suitable for mobile radio applications because of its simple implementation

(c) Selection or Switching Combining

bull The diversity branch having the highest signal level (or) lowest Pe is selected

bull Also in addition stable operation is easily achieved even in the fast multipath fading environments

bull But the performance improvement obtained by the selection method is still only slightly inferior to that of MRC method

Disadvantage of Selection or Switching

bull Combining The continuous monitoring of the signals requires the same no of receivers as the no of diversity branches

bull This redundancy can be alleviated by the use of switching or scanning receiver

SWITCHNINGMETHODS

FIXED THERSHOLD VARIABLE THERSHOLD

(a) Switching Methods with Fixed threshold

bull The switching from one branch to the other occurs when the signal level falls below a threshold value

bull The threshold value is fixedbull However this threshold value is not

necessarily the best over the entire service area

FIXED THERSHOLD

(b) Switching Methods with Variable threshold

bull Here the threshold value is adjusted dynamically as the vehicle moves

bull It includes the feedback using Estimationbull But it may introduce the envelope and phase

transients that will reduce the performance improvement

VARIABLE THERSHOLD

Conclusions

bull The diversity is used to provide the receiver with several replicas of the same signal

bull Diversity techniques are used to improve the performance of the radio channel without any increase in the transmitted power

bull As higher as the received signal replicas are decorrelated as much as the diversity gain

Thank you for you attention

• No trade off to
• What are all the needs of diversity techniques
• CONCEPTS OF DIVERSITY BRANCH AND SIGNAL PATH
• (a) Branch Construction method using frequency diversity
• (b) Branch Construction method using Time diversity
• COMBINING AND SWITCHNING METHODS
• Slide 29
• FOR COHERENT DETECTION
• (a) Maximal ratio combining (MRC)
• Slide 32
• (b) Equal Gain Combining (EGC)
• EGC
• For VHF UHF and microwave wireless radio applications
• (c) Selection or Switching Combining
• Slide 37
• Disadvantage of Selection or Switching
• Slide 39
• (a) Switching Methods with Fixed threshold
• Slide 41
• (b) Switching Methods with Variable threshold
• Slide 43

Combining schemes

bullSelection combining (SC)

h1

h2

yx

MonitorSNR

Selectbranch

Switch-and-stay combining (SSC) Switch-and-examine combining (SEC)

h1

h2

x

ComparatorChannelestimator

switchingthreshold

bullSwitched diversity

No trade off to

Without excessively increasing

bull 1 transmitting powerbull 2 Co-channel reuse distance

bull One of the most effective technique to solve this issue is diversity reception technique

What are all the needs of diversity techniques

bull 1No of signal transmission pathsbull 2A circuit to combine the received signal or

select one of them

CONCEPTS OF DIVERSITY BRANCH AND SIGNAL PATH

(a) Branch Construction method using frequency diversity

(b) Branch Construction method using Time diversity

COMBINING AND SWITCHNING METHODS

COMBINING AND SWITCHNINGMETHODS

FOR COHERENT DETECTION

FOR NON - COHERENT DETECTION

FOR COHERENT DETECTION

bull There is no difference whether the combining is carried out in the pre detection or in the post detection stage

FOR NON-COHERENT DETECTION

bull There is a difference in performance exists between whether pre detection amp post detection combining methods

(a) Maximal ratio combining (MRC)

bull MRC is the best performance improvement compared with the other methods

bull However the trade off is It requires 1 cophasing 2 weighting 3summing circuitsResulting in most complicated implementationComplexity performance

(b) Equal Gain Combining (EGC)

EGCbull EGC is similar to MRC except the weighting

circuits are omittedbull The performance improvement obtained by

equal gain combiner is slightly inferior to that of a MRC since the interference and noise corrupted signal combined with high quality signals

For VHF UHF and microwave wireless radio applications

bull Both MRC and EGC methods are unsuitablebull Compared with MRC EGC methods the

selection method is more suitable for mobile radio applications because of its simple implementation

(c) Selection or Switching Combining

bull The diversity branch having the highest signal level (or) lowest Pe is selected

bull Also in addition stable operation is easily achieved even in the fast multipath fading environments

bull But the performance improvement obtained by the selection method is still only slightly inferior to that of MRC method

Disadvantage of Selection or Switching

bull Combining The continuous monitoring of the signals requires the same no of receivers as the no of diversity branches

bull This redundancy can be alleviated by the use of switching or scanning receiver

SWITCHNINGMETHODS

FIXED THERSHOLD VARIABLE THERSHOLD

(a) Switching Methods with Fixed threshold

bull The switching from one branch to the other occurs when the signal level falls below a threshold value

bull The threshold value is fixedbull However this threshold value is not

necessarily the best over the entire service area

FIXED THERSHOLD

(b) Switching Methods with Variable threshold

bull Here the threshold value is adjusted dynamically as the vehicle moves

bull It includes the feedback using Estimationbull But it may introduce the envelope and phase

transients that will reduce the performance improvement

VARIABLE THERSHOLD

Conclusions

bull The diversity is used to provide the receiver with several replicas of the same signal

bull Diversity techniques are used to improve the performance of the radio channel without any increase in the transmitted power

bull As higher as the received signal replicas are decorrelated as much as the diversity gain

Thank you for you attention

• No trade off to
• What are all the needs of diversity techniques
• CONCEPTS OF DIVERSITY BRANCH AND SIGNAL PATH
• (a) Branch Construction method using frequency diversity
• (b) Branch Construction method using Time diversity
• COMBINING AND SWITCHNING METHODS
• Slide 29
• FOR COHERENT DETECTION
• (a) Maximal ratio combining (MRC)
• Slide 32
• (b) Equal Gain Combining (EGC)
• EGC
• For VHF UHF and microwave wireless radio applications
• (c) Selection or Switching Combining
• Slide 37
• Disadvantage of Selection or Switching
• Slide 39
• (a) Switching Methods with Fixed threshold
• Slide 41
• (b) Switching Methods with Variable threshold
• Slide 43

Switch-and-stay combining (SSC) Switch-and-examine combining (SEC)

h1

h2

x

ComparatorChannelestimator

switchingthreshold

bullSwitched diversity

No trade off to

Without excessively increasing

bull 1 transmitting powerbull 2 Co-channel reuse distance

bull One of the most effective technique to solve this issue is diversity reception technique

What are all the needs of diversity techniques

bull 1No of signal transmission pathsbull 2A circuit to combine the received signal or

select one of them

CONCEPTS OF DIVERSITY BRANCH AND SIGNAL PATH

(a) Branch Construction method using frequency diversity

(b) Branch Construction method using Time diversity

COMBINING AND SWITCHNING METHODS

COMBINING AND SWITCHNINGMETHODS

FOR COHERENT DETECTION

FOR NON - COHERENT DETECTION

FOR COHERENT DETECTION

bull There is no difference whether the combining is carried out in the pre detection or in the post detection stage

FOR NON-COHERENT DETECTION

bull There is a difference in performance exists between whether pre detection amp post detection combining methods

(a) Maximal ratio combining (MRC)

bull MRC is the best performance improvement compared with the other methods

bull However the trade off is It requires 1 cophasing 2 weighting 3summing circuitsResulting in most complicated implementationComplexity performance

(b) Equal Gain Combining (EGC)

EGCbull EGC is similar to MRC except the weighting

circuits are omittedbull The performance improvement obtained by

equal gain combiner is slightly inferior to that of a MRC since the interference and noise corrupted signal combined with high quality signals

For VHF UHF and microwave wireless radio applications

bull Both MRC and EGC methods are unsuitablebull Compared with MRC EGC methods the

selection method is more suitable for mobile radio applications because of its simple implementation

(c) Selection or Switching Combining

bull The diversity branch having the highest signal level (or) lowest Pe is selected

bull Also in addition stable operation is easily achieved even in the fast multipath fading environments

bull But the performance improvement obtained by the selection method is still only slightly inferior to that of MRC method

Disadvantage of Selection or Switching

bull Combining The continuous monitoring of the signals requires the same no of receivers as the no of diversity branches

bull This redundancy can be alleviated by the use of switching or scanning receiver

SWITCHNINGMETHODS

FIXED THERSHOLD VARIABLE THERSHOLD

(a) Switching Methods with Fixed threshold

bull The switching from one branch to the other occurs when the signal level falls below a threshold value

bull The threshold value is fixedbull However this threshold value is not

necessarily the best over the entire service area

FIXED THERSHOLD

(b) Switching Methods with Variable threshold

bull Here the threshold value is adjusted dynamically as the vehicle moves

bull It includes the feedback using Estimationbull But it may introduce the envelope and phase

transients that will reduce the performance improvement

VARIABLE THERSHOLD

Conclusions

bull The diversity is used to provide the receiver with several replicas of the same signal

bull Diversity techniques are used to improve the performance of the radio channel without any increase in the transmitted power

bull As higher as the received signal replicas are decorrelated as much as the diversity gain

Thank you for you attention

• No trade off to
• What are all the needs of diversity techniques
• CONCEPTS OF DIVERSITY BRANCH AND SIGNAL PATH
• (a) Branch Construction method using frequency diversity
• (b) Branch Construction method using Time diversity
• COMBINING AND SWITCHNING METHODS
• Slide 29
• FOR COHERENT DETECTION
• (a) Maximal ratio combining (MRC)
• Slide 32
• (b) Equal Gain Combining (EGC)
• EGC
• For VHF UHF and microwave wireless radio applications
• (c) Selection or Switching Combining
• Slide 37
• Disadvantage of Selection or Switching
• Slide 39
• (a) Switching Methods with Fixed threshold
• Slide 41
• (b) Switching Methods with Variable threshold
• Slide 43

No trade off to

Without excessively increasing

bull 1 transmitting powerbull 2 Co-channel reuse distance

bull One of the most effective technique to solve this issue is diversity reception technique

What are all the needs of diversity techniques

bull 1No of signal transmission pathsbull 2A circuit to combine the received signal or

select one of them

CONCEPTS OF DIVERSITY BRANCH AND SIGNAL PATH

(a) Branch Construction method using frequency diversity

(b) Branch Construction method using Time diversity

COMBINING AND SWITCHNING METHODS

COMBINING AND SWITCHNINGMETHODS

FOR COHERENT DETECTION

FOR NON - COHERENT DETECTION

FOR COHERENT DETECTION

bull There is no difference whether the combining is carried out in the pre detection or in the post detection stage

FOR NON-COHERENT DETECTION

bull There is a difference in performance exists between whether pre detection amp post detection combining methods

(a) Maximal ratio combining (MRC)

bull MRC is the best performance improvement compared with the other methods

bull However the trade off is It requires 1 cophasing 2 weighting 3summing circuitsResulting in most complicated implementationComplexity performance

(b) Equal Gain Combining (EGC)

EGCbull EGC is similar to MRC except the weighting

circuits are omittedbull The performance improvement obtained by

equal gain combiner is slightly inferior to that of a MRC since the interference and noise corrupted signal combined with high quality signals

For VHF UHF and microwave wireless radio applications

bull Both MRC and EGC methods are unsuitablebull Compared with MRC EGC methods the

selection method is more suitable for mobile radio applications because of its simple implementation

(c) Selection or Switching Combining

bull The diversity branch having the highest signal level (or) lowest Pe is selected

bull Also in addition stable operation is easily achieved even in the fast multipath fading environments

bull But the performance improvement obtained by the selection method is still only slightly inferior to that of MRC method

Disadvantage of Selection or Switching

bull Combining The continuous monitoring of the signals requires the same no of receivers as the no of diversity branches

bull This redundancy can be alleviated by the use of switching or scanning receiver

SWITCHNINGMETHODS

FIXED THERSHOLD VARIABLE THERSHOLD

(a) Switching Methods with Fixed threshold

bull The switching from one branch to the other occurs when the signal level falls below a threshold value

bull The threshold value is fixedbull However this threshold value is not

necessarily the best over the entire service area

FIXED THERSHOLD

(b) Switching Methods with Variable threshold

bull Here the threshold value is adjusted dynamically as the vehicle moves

bull It includes the feedback using Estimationbull But it may introduce the envelope and phase

transients that will reduce the performance improvement

VARIABLE THERSHOLD

Conclusions

bull The diversity is used to provide the receiver with several replicas of the same signal

bull Diversity techniques are used to improve the performance of the radio channel without any increase in the transmitted power

bull As higher as the received signal replicas are decorrelated as much as the diversity gain

Thank you for you attention

• No trade off to
• What are all the needs of diversity techniques
• CONCEPTS OF DIVERSITY BRANCH AND SIGNAL PATH
• (a) Branch Construction method using frequency diversity
• (b) Branch Construction method using Time diversity
• COMBINING AND SWITCHNING METHODS
• Slide 29
• FOR COHERENT DETECTION
• (a) Maximal ratio combining (MRC)
• Slide 32
• (b) Equal Gain Combining (EGC)
• EGC
• For VHF UHF and microwave wireless radio applications
• (c) Selection or Switching Combining
• Slide 37
• Disadvantage of Selection or Switching
• Slide 39
• (a) Switching Methods with Fixed threshold
• Slide 41
• (b) Switching Methods with Variable threshold
• Slide 43

What are all the needs of diversity techniques

bull 1No of signal transmission pathsbull 2A circuit to combine the received signal or

select one of them

CONCEPTS OF DIVERSITY BRANCH AND SIGNAL PATH

(a) Branch Construction method using frequency diversity

(b) Branch Construction method using Time diversity

COMBINING AND SWITCHNING METHODS

COMBINING AND SWITCHNINGMETHODS

FOR COHERENT DETECTION

FOR NON - COHERENT DETECTION

FOR COHERENT DETECTION

bull There is no difference whether the combining is carried out in the pre detection or in the post detection stage

FOR NON-COHERENT DETECTION

bull There is a difference in performance exists between whether pre detection amp post detection combining methods

(a) Maximal ratio combining (MRC)

bull MRC is the best performance improvement compared with the other methods

bull However the trade off is It requires 1 cophasing 2 weighting 3summing circuitsResulting in most complicated implementationComplexity performance

(b) Equal Gain Combining (EGC)

EGCbull EGC is similar to MRC except the weighting

circuits are omittedbull The performance improvement obtained by

equal gain combiner is slightly inferior to that of a MRC since the interference and noise corrupted signal combined with high quality signals

For VHF UHF and microwave wireless radio applications

bull Both MRC and EGC methods are unsuitablebull Compared with MRC EGC methods the

selection method is more suitable for mobile radio applications because of its simple implementation

(c) Selection or Switching Combining

bull The diversity branch having the highest signal level (or) lowest Pe is selected

bull Also in addition stable operation is easily achieved even in the fast multipath fading environments

bull But the performance improvement obtained by the selection method is still only slightly inferior to that of MRC method

Disadvantage of Selection or Switching

bull Combining The continuous monitoring of the signals requires the same no of receivers as the no of diversity branches

bull This redundancy can be alleviated by the use of switching or scanning receiver

SWITCHNINGMETHODS

FIXED THERSHOLD VARIABLE THERSHOLD

(a) Switching Methods with Fixed threshold

bull The switching from one branch to the other occurs when the signal level falls below a threshold value

bull The threshold value is fixedbull However this threshold value is not

necessarily the best over the entire service area

FIXED THERSHOLD

(b) Switching Methods with Variable threshold

bull Here the threshold value is adjusted dynamically as the vehicle moves

bull It includes the feedback using Estimationbull But it may introduce the envelope and phase

transients that will reduce the performance improvement

VARIABLE THERSHOLD

Conclusions

bull The diversity is used to provide the receiver with several replicas of the same signal

bull Diversity techniques are used to improve the performance of the radio channel without any increase in the transmitted power

bull As higher as the received signal replicas are decorrelated as much as the diversity gain

Thank you for you attention

• No trade off to
• What are all the needs of diversity techniques
• CONCEPTS OF DIVERSITY BRANCH AND SIGNAL PATH
• (a) Branch Construction method using frequency diversity
• (b) Branch Construction method using Time diversity
• COMBINING AND SWITCHNING METHODS
• Slide 29
• FOR COHERENT DETECTION
• (a) Maximal ratio combining (MRC)
• Slide 32
• (b) Equal Gain Combining (EGC)
• EGC
• For VHF UHF and microwave wireless radio applications
• (c) Selection or Switching Combining
• Slide 37
• Disadvantage of Selection or Switching
• Slide 39
• (a) Switching Methods with Fixed threshold
• Slide 41
• (b) Switching Methods with Variable threshold
• Slide 43

CONCEPTS OF DIVERSITY BRANCH AND SIGNAL PATH

(a) Branch Construction method using frequency diversity

(b) Branch Construction method using Time diversity

COMBINING AND SWITCHNING METHODS

COMBINING AND SWITCHNINGMETHODS

FOR COHERENT DETECTION

FOR NON - COHERENT DETECTION

FOR COHERENT DETECTION

bull There is no difference whether the combining is carried out in the pre detection or in the post detection stage

FOR NON-COHERENT DETECTION

bull There is a difference in performance exists between whether pre detection amp post detection combining methods

(a) Maximal ratio combining (MRC)

bull MRC is the best performance improvement compared with the other methods

bull However the trade off is It requires 1 cophasing 2 weighting 3summing circuitsResulting in most complicated implementationComplexity performance

(b) Equal Gain Combining (EGC)

EGCbull EGC is similar to MRC except the weighting

circuits are omittedbull The performance improvement obtained by

equal gain combiner is slightly inferior to that of a MRC since the interference and noise corrupted signal combined with high quality signals

For VHF UHF and microwave wireless radio applications

bull Both MRC and EGC methods are unsuitablebull Compared with MRC EGC methods the

selection method is more suitable for mobile radio applications because of its simple implementation

(c) Selection or Switching Combining

bull The diversity branch having the highest signal level (or) lowest Pe is selected

bull Also in addition stable operation is easily achieved even in the fast multipath fading environments

bull But the performance improvement obtained by the selection method is still only slightly inferior to that of MRC method

Disadvantage of Selection or Switching

bull Combining The continuous monitoring of the signals requires the same no of receivers as the no of diversity branches

bull This redundancy can be alleviated by the use of switching or scanning receiver

SWITCHNINGMETHODS

FIXED THERSHOLD VARIABLE THERSHOLD

(a) Switching Methods with Fixed threshold

bull The switching from one branch to the other occurs when the signal level falls below a threshold value

bull The threshold value is fixedbull However this threshold value is not

necessarily the best over the entire service area

FIXED THERSHOLD

(b) Switching Methods with Variable threshold

bull Here the threshold value is adjusted dynamically as the vehicle moves

bull It includes the feedback using Estimationbull But it may introduce the envelope and phase

transients that will reduce the performance improvement

VARIABLE THERSHOLD

Conclusions

bull The diversity is used to provide the receiver with several replicas of the same signal

bull Diversity techniques are used to improve the performance of the radio channel without any increase in the transmitted power

bull As higher as the received signal replicas are decorrelated as much as the diversity gain

Thank you for you attention

• No trade off to
• What are all the needs of diversity techniques
• CONCEPTS OF DIVERSITY BRANCH AND SIGNAL PATH
• (a) Branch Construction method using frequency diversity
• (b) Branch Construction method using Time diversity
• COMBINING AND SWITCHNING METHODS
• Slide 29
• FOR COHERENT DETECTION
• (a) Maximal ratio combining (MRC)
• Slide 32
• (b) Equal Gain Combining (EGC)
• EGC
• For VHF UHF and microwave wireless radio applications
• (c) Selection or Switching Combining
• Slide 37
• Disadvantage of Selection or Switching
• Slide 39
• (a) Switching Methods with Fixed threshold
• Slide 41
• (b) Switching Methods with Variable threshold
• Slide 43

(a) Branch Construction method using frequency diversity

(b) Branch Construction method using Time diversity

COMBINING AND SWITCHNING METHODS

COMBINING AND SWITCHNINGMETHODS

FOR COHERENT DETECTION

FOR NON - COHERENT DETECTION

FOR COHERENT DETECTION

bull There is no difference whether the combining is carried out in the pre detection or in the post detection stage

FOR NON-COHERENT DETECTION

bull There is a difference in performance exists between whether pre detection amp post detection combining methods

(a) Maximal ratio combining (MRC)

bull MRC is the best performance improvement compared with the other methods

bull However the trade off is It requires 1 cophasing 2 weighting 3summing circuitsResulting in most complicated implementationComplexity performance

(b) Equal Gain Combining (EGC)

EGCbull EGC is similar to MRC except the weighting

circuits are omittedbull The performance improvement obtained by

equal gain combiner is slightly inferior to that of a MRC since the interference and noise corrupted signal combined with high quality signals

For VHF UHF and microwave wireless radio applications

bull Both MRC and EGC methods are unsuitablebull Compared with MRC EGC methods the

selection method is more suitable for mobile radio applications because of its simple implementation

(c) Selection or Switching Combining

bull The diversity branch having the highest signal level (or) lowest Pe is selected

bull Also in addition stable operation is easily achieved even in the fast multipath fading environments

bull But the performance improvement obtained by the selection method is still only slightly inferior to that of MRC method

Disadvantage of Selection or Switching

bull Combining The continuous monitoring of the signals requires the same no of receivers as the no of diversity branches

bull This redundancy can be alleviated by the use of switching or scanning receiver

SWITCHNINGMETHODS

FIXED THERSHOLD VARIABLE THERSHOLD

(a) Switching Methods with Fixed threshold

bull The switching from one branch to the other occurs when the signal level falls below a threshold value

bull The threshold value is fixedbull However this threshold value is not

necessarily the best over the entire service area

FIXED THERSHOLD

(b) Switching Methods with Variable threshold

bull Here the threshold value is adjusted dynamically as the vehicle moves

bull It includes the feedback using Estimationbull But it may introduce the envelope and phase

transients that will reduce the performance improvement

VARIABLE THERSHOLD

Conclusions

bull The diversity is used to provide the receiver with several replicas of the same signal

bull Diversity techniques are used to improve the performance of the radio channel without any increase in the transmitted power

bull As higher as the received signal replicas are decorrelated as much as the diversity gain

Thank you for you attention

• No trade off to
• What are all the needs of diversity techniques
• CONCEPTS OF DIVERSITY BRANCH AND SIGNAL PATH
• (a) Branch Construction method using frequency diversity
• (b) Branch Construction method using Time diversity
• COMBINING AND SWITCHNING METHODS
• Slide 29
• FOR COHERENT DETECTION
• (a) Maximal ratio combining (MRC)
• Slide 32
• (b) Equal Gain Combining (EGC)
• EGC
• For VHF UHF and microwave wireless radio applications
• (c) Selection or Switching Combining
• Slide 37
• Disadvantage of Selection or Switching
• Slide 39
• (a) Switching Methods with Fixed threshold
• Slide 41
• (b) Switching Methods with Variable threshold
• Slide 43

(b) Branch Construction method using Time diversity

COMBINING AND SWITCHNING METHODS

COMBINING AND SWITCHNINGMETHODS

FOR COHERENT DETECTION

FOR NON - COHERENT DETECTION

FOR COHERENT DETECTION

bull There is no difference whether the combining is carried out in the pre detection or in the post detection stage

FOR NON-COHERENT DETECTION

bull There is a difference in performance exists between whether pre detection amp post detection combining methods

(a) Maximal ratio combining (MRC)

bull MRC is the best performance improvement compared with the other methods

bull However the trade off is It requires 1 cophasing 2 weighting 3summing circuitsResulting in most complicated implementationComplexity performance

(b) Equal Gain Combining (EGC)

EGCbull EGC is similar to MRC except the weighting

circuits are omittedbull The performance improvement obtained by

equal gain combiner is slightly inferior to that of a MRC since the interference and noise corrupted signal combined with high quality signals

For VHF UHF and microwave wireless radio applications

bull Both MRC and EGC methods are unsuitablebull Compared with MRC EGC methods the

selection method is more suitable for mobile radio applications because of its simple implementation

(c) Selection or Switching Combining

bull The diversity branch having the highest signal level (or) lowest Pe is selected

bull Also in addition stable operation is easily achieved even in the fast multipath fading environments

bull But the performance improvement obtained by the selection method is still only slightly inferior to that of MRC method

Disadvantage of Selection or Switching

bull Combining The continuous monitoring of the signals requires the same no of receivers as the no of diversity branches

bull This redundancy can be alleviated by the use of switching or scanning receiver

SWITCHNINGMETHODS

FIXED THERSHOLD VARIABLE THERSHOLD

(a) Switching Methods with Fixed threshold

bull The switching from one branch to the other occurs when the signal level falls below a threshold value

bull The threshold value is fixedbull However this threshold value is not

necessarily the best over the entire service area

FIXED THERSHOLD

(b) Switching Methods with Variable threshold

bull Here the threshold value is adjusted dynamically as the vehicle moves

bull It includes the feedback using Estimationbull But it may introduce the envelope and phase

transients that will reduce the performance improvement

VARIABLE THERSHOLD

Conclusions

bull The diversity is used to provide the receiver with several replicas of the same signal

bull Diversity techniques are used to improve the performance of the radio channel without any increase in the transmitted power

bull As higher as the received signal replicas are decorrelated as much as the diversity gain

Thank you for you attention

• No trade off to
• What are all the needs of diversity techniques
• CONCEPTS OF DIVERSITY BRANCH AND SIGNAL PATH
• (a) Branch Construction method using frequency diversity
• (b) Branch Construction method using Time diversity
• COMBINING AND SWITCHNING METHODS
• Slide 29
• FOR COHERENT DETECTION
• (a) Maximal ratio combining (MRC)
• Slide 32
• (b) Equal Gain Combining (EGC)
• EGC
• For VHF UHF and microwave wireless radio applications
• (c) Selection or Switching Combining
• Slide 37
• Disadvantage of Selection or Switching
• Slide 39
• (a) Switching Methods with Fixed threshold
• Slide 41
• (b) Switching Methods with Variable threshold
• Slide 43

COMBINING AND SWITCHNING METHODS

COMBINING AND SWITCHNINGMETHODS

FOR COHERENT DETECTION

FOR NON - COHERENT DETECTION

FOR COHERENT DETECTION

bull There is no difference whether the combining is carried out in the pre detection or in the post detection stage

FOR NON-COHERENT DETECTION

bull There is a difference in performance exists between whether pre detection amp post detection combining methods

(a) Maximal ratio combining (MRC)

bull MRC is the best performance improvement compared with the other methods

bull However the trade off is It requires 1 cophasing 2 weighting 3summing circuitsResulting in most complicated implementationComplexity performance

(b) Equal Gain Combining (EGC)

EGCbull EGC is similar to MRC except the weighting

circuits are omittedbull The performance improvement obtained by

equal gain combiner is slightly inferior to that of a MRC since the interference and noise corrupted signal combined with high quality signals

For VHF UHF and microwave wireless radio applications

bull Both MRC and EGC methods are unsuitablebull Compared with MRC EGC methods the

selection method is more suitable for mobile radio applications because of its simple implementation

(c) Selection or Switching Combining

bull The diversity branch having the highest signal level (or) lowest Pe is selected

bull Also in addition stable operation is easily achieved even in the fast multipath fading environments

bull But the performance improvement obtained by the selection method is still only slightly inferior to that of MRC method

Disadvantage of Selection or Switching

bull Combining The continuous monitoring of the signals requires the same no of receivers as the no of diversity branches

bull This redundancy can be alleviated by the use of switching or scanning receiver

SWITCHNINGMETHODS

FIXED THERSHOLD VARIABLE THERSHOLD

(a) Switching Methods with Fixed threshold

bull The switching from one branch to the other occurs when the signal level falls below a threshold value

bull The threshold value is fixedbull However this threshold value is not

necessarily the best over the entire service area

FIXED THERSHOLD

(b) Switching Methods with Variable threshold

bull Here the threshold value is adjusted dynamically as the vehicle moves

bull It includes the feedback using Estimationbull But it may introduce the envelope and phase

transients that will reduce the performance improvement

VARIABLE THERSHOLD

Conclusions

bull The diversity is used to provide the receiver with several replicas of the same signal

bull Diversity techniques are used to improve the performance of the radio channel without any increase in the transmitted power

bull As higher as the received signal replicas are decorrelated as much as the diversity gain

Thank you for you attention

• No trade off to
• What are all the needs of diversity techniques
• CONCEPTS OF DIVERSITY BRANCH AND SIGNAL PATH
• (a) Branch Construction method using frequency diversity
• (b) Branch Construction method using Time diversity
• COMBINING AND SWITCHNING METHODS
• Slide 29
• FOR COHERENT DETECTION
• (a) Maximal ratio combining (MRC)
• Slide 32
• (b) Equal Gain Combining (EGC)
• EGC
• For VHF UHF and microwave wireless radio applications
• (c) Selection or Switching Combining
• Slide 37
• Disadvantage of Selection or Switching
• Slide 39
• (a) Switching Methods with Fixed threshold
• Slide 41
• (b) Switching Methods with Variable threshold
• Slide 43

COMBINING AND SWITCHNINGMETHODS

FOR COHERENT DETECTION

FOR NON - COHERENT DETECTION

FOR COHERENT DETECTION

bull There is no difference whether the combining is carried out in the pre detection or in the post detection stage

FOR NON-COHERENT DETECTION

bull There is a difference in performance exists between whether pre detection amp post detection combining methods

(a) Maximal ratio combining (MRC)

bull MRC is the best performance improvement compared with the other methods

bull However the trade off is It requires 1 cophasing 2 weighting 3summing circuitsResulting in most complicated implementationComplexity performance

(b) Equal Gain Combining (EGC)

EGCbull EGC is similar to MRC except the weighting

circuits are omittedbull The performance improvement obtained by

equal gain combiner is slightly inferior to that of a MRC since the interference and noise corrupted signal combined with high quality signals

For VHF UHF and microwave wireless radio applications

bull Both MRC and EGC methods are unsuitablebull Compared with MRC EGC methods the

selection method is more suitable for mobile radio applications because of its simple implementation

(c) Selection or Switching Combining

bull The diversity branch having the highest signal level (or) lowest Pe is selected

bull Also in addition stable operation is easily achieved even in the fast multipath fading environments

bull But the performance improvement obtained by the selection method is still only slightly inferior to that of MRC method

Disadvantage of Selection or Switching

bull Combining The continuous monitoring of the signals requires the same no of receivers as the no of diversity branches

bull This redundancy can be alleviated by the use of switching or scanning receiver

SWITCHNINGMETHODS

FIXED THERSHOLD VARIABLE THERSHOLD

(a) Switching Methods with Fixed threshold

bull The switching from one branch to the other occurs when the signal level falls below a threshold value

bull The threshold value is fixedbull However this threshold value is not

necessarily the best over the entire service area

FIXED THERSHOLD

(b) Switching Methods with Variable threshold

bull Here the threshold value is adjusted dynamically as the vehicle moves

bull It includes the feedback using Estimationbull But it may introduce the envelope and phase

transients that will reduce the performance improvement

VARIABLE THERSHOLD

Conclusions

bull The diversity is used to provide the receiver with several replicas of the same signal

bull Diversity techniques are used to improve the performance of the radio channel without any increase in the transmitted power

bull As higher as the received signal replicas are decorrelated as much as the diversity gain

Thank you for you attention

• No trade off to
• What are all the needs of diversity techniques
• CONCEPTS OF DIVERSITY BRANCH AND SIGNAL PATH
• (a) Branch Construction method using frequency diversity
• (b) Branch Construction method using Time diversity
• COMBINING AND SWITCHNING METHODS
• Slide 29
• FOR COHERENT DETECTION
• (a) Maximal ratio combining (MRC)
• Slide 32
• (b) Equal Gain Combining (EGC)
• EGC
• For VHF UHF and microwave wireless radio applications
• (c) Selection or Switching Combining
• Slide 37
• Disadvantage of Selection or Switching
• Slide 39
• (a) Switching Methods with Fixed threshold
• Slide 41
• (b) Switching Methods with Variable threshold
• Slide 43

FOR COHERENT DETECTION

bull There is no difference whether the combining is carried out in the pre detection or in the post detection stage

FOR NON-COHERENT DETECTION

bull There is a difference in performance exists between whether pre detection amp post detection combining methods

(a) Maximal ratio combining (MRC)

bull MRC is the best performance improvement compared with the other methods

bull However the trade off is It requires 1 cophasing 2 weighting 3summing circuitsResulting in most complicated implementationComplexity performance

(b) Equal Gain Combining (EGC)

EGCbull EGC is similar to MRC except the weighting

circuits are omittedbull The performance improvement obtained by

equal gain combiner is slightly inferior to that of a MRC since the interference and noise corrupted signal combined with high quality signals

For VHF UHF and microwave wireless radio applications

bull Both MRC and EGC methods are unsuitablebull Compared with MRC EGC methods the

selection method is more suitable for mobile radio applications because of its simple implementation

(c) Selection or Switching Combining

bull The diversity branch having the highest signal level (or) lowest Pe is selected

bull Also in addition stable operation is easily achieved even in the fast multipath fading environments

bull But the performance improvement obtained by the selection method is still only slightly inferior to that of MRC method

Disadvantage of Selection or Switching

bull Combining The continuous monitoring of the signals requires the same no of receivers as the no of diversity branches

bull This redundancy can be alleviated by the use of switching or scanning receiver

SWITCHNINGMETHODS

FIXED THERSHOLD VARIABLE THERSHOLD

(a) Switching Methods with Fixed threshold

bull The switching from one branch to the other occurs when the signal level falls below a threshold value

bull The threshold value is fixedbull However this threshold value is not

necessarily the best over the entire service area

FIXED THERSHOLD

(b) Switching Methods with Variable threshold

bull Here the threshold value is adjusted dynamically as the vehicle moves

bull It includes the feedback using Estimationbull But it may introduce the envelope and phase

transients that will reduce the performance improvement

VARIABLE THERSHOLD

Conclusions

bull The diversity is used to provide the receiver with several replicas of the same signal

bull Diversity techniques are used to improve the performance of the radio channel without any increase in the transmitted power

bull As higher as the received signal replicas are decorrelated as much as the diversity gain

Thank you for you attention

• No trade off to
• What are all the needs of diversity techniques
• CONCEPTS OF DIVERSITY BRANCH AND SIGNAL PATH
• (a) Branch Construction method using frequency diversity
• (b) Branch Construction method using Time diversity
• COMBINING AND SWITCHNING METHODS
• Slide 29
• FOR COHERENT DETECTION
• (a) Maximal ratio combining (MRC)
• Slide 32
• (b) Equal Gain Combining (EGC)
• EGC
• For VHF UHF and microwave wireless radio applications
• (c) Selection or Switching Combining
• Slide 37
• Disadvantage of Selection or Switching
• Slide 39
• (a) Switching Methods with Fixed threshold
• Slide 41
• (b) Switching Methods with Variable threshold
• Slide 43

(a) Maximal ratio combining (MRC)

bull MRC is the best performance improvement compared with the other methods

bull However the trade off is It requires 1 cophasing 2 weighting 3summing circuitsResulting in most complicated implementationComplexity performance

(b) Equal Gain Combining (EGC)

EGCbull EGC is similar to MRC except the weighting

circuits are omittedbull The performance improvement obtained by

equal gain combiner is slightly inferior to that of a MRC since the interference and noise corrupted signal combined with high quality signals

For VHF UHF and microwave wireless radio applications

bull Both MRC and EGC methods are unsuitablebull Compared with MRC EGC methods the

selection method is more suitable for mobile radio applications because of its simple implementation

(c) Selection or Switching Combining

bull The diversity branch having the highest signal level (or) lowest Pe is selected

bull Also in addition stable operation is easily achieved even in the fast multipath fading environments

bull But the performance improvement obtained by the selection method is still only slightly inferior to that of MRC method

Disadvantage of Selection or Switching

bull Combining The continuous monitoring of the signals requires the same no of receivers as the no of diversity branches

bull This redundancy can be alleviated by the use of switching or scanning receiver

SWITCHNINGMETHODS

FIXED THERSHOLD VARIABLE THERSHOLD

(a) Switching Methods with Fixed threshold

bull The switching from one branch to the other occurs when the signal level falls below a threshold value

bull The threshold value is fixedbull However this threshold value is not

necessarily the best over the entire service area

FIXED THERSHOLD

(b) Switching Methods with Variable threshold

bull Here the threshold value is adjusted dynamically as the vehicle moves

bull It includes the feedback using Estimationbull But it may introduce the envelope and phase

transients that will reduce the performance improvement

VARIABLE THERSHOLD

Conclusions

bull The diversity is used to provide the receiver with several replicas of the same signal

bull Diversity techniques are used to improve the performance of the radio channel without any increase in the transmitted power

bull As higher as the received signal replicas are decorrelated as much as the diversity gain

Thank you for you attention

• No trade off to
• What are all the needs of diversity techniques
• CONCEPTS OF DIVERSITY BRANCH AND SIGNAL PATH
• (a) Branch Construction method using frequency diversity
• (b) Branch Construction method using Time diversity
• COMBINING AND SWITCHNING METHODS
• Slide 29
• FOR COHERENT DETECTION
• (a) Maximal ratio combining (MRC)
• Slide 32
• (b) Equal Gain Combining (EGC)
• EGC
• For VHF UHF and microwave wireless radio applications
• (c) Selection or Switching Combining
• Slide 37
• Disadvantage of Selection or Switching
• Slide 39
• (a) Switching Methods with Fixed threshold
• Slide 41
• (b) Switching Methods with Variable threshold
• Slide 43

bull MRC is the best performance improvement compared with the other methods

bull However the trade off is It requires 1 cophasing 2 weighting 3summing circuitsResulting in most complicated implementationComplexity performance

(b) Equal Gain Combining (EGC)

EGCbull EGC is similar to MRC except the weighting

circuits are omittedbull The performance improvement obtained by

equal gain combiner is slightly inferior to that of a MRC since the interference and noise corrupted signal combined with high quality signals

For VHF UHF and microwave wireless radio applications

bull Both MRC and EGC methods are unsuitablebull Compared with MRC EGC methods the

selection method is more suitable for mobile radio applications because of its simple implementation

(c) Selection or Switching Combining

bull The diversity branch having the highest signal level (or) lowest Pe is selected

bull Also in addition stable operation is easily achieved even in the fast multipath fading environments

bull But the performance improvement obtained by the selection method is still only slightly inferior to that of MRC method

Disadvantage of Selection or Switching

bull Combining The continuous monitoring of the signals requires the same no of receivers as the no of diversity branches

bull This redundancy can be alleviated by the use of switching or scanning receiver

SWITCHNINGMETHODS

FIXED THERSHOLD VARIABLE THERSHOLD

(a) Switching Methods with Fixed threshold

bull The switching from one branch to the other occurs when the signal level falls below a threshold value

bull The threshold value is fixedbull However this threshold value is not

necessarily the best over the entire service area

FIXED THERSHOLD

(b) Switching Methods with Variable threshold

bull Here the threshold value is adjusted dynamically as the vehicle moves

bull It includes the feedback using Estimationbull But it may introduce the envelope and phase

transients that will reduce the performance improvement

VARIABLE THERSHOLD

Conclusions

bull The diversity is used to provide the receiver with several replicas of the same signal

bull Diversity techniques are used to improve the performance of the radio channel without any increase in the transmitted power

bull As higher as the received signal replicas are decorrelated as much as the diversity gain

Thank you for you attention

• No trade off to
• What are all the needs of diversity techniques
• CONCEPTS OF DIVERSITY BRANCH AND SIGNAL PATH
• (a) Branch Construction method using frequency diversity
• (b) Branch Construction method using Time diversity
• COMBINING AND SWITCHNING METHODS
• Slide 29
• FOR COHERENT DETECTION
• (a) Maximal ratio combining (MRC)
• Slide 32
• (b) Equal Gain Combining (EGC)
• EGC
• For VHF UHF and microwave wireless radio applications
• (c) Selection or Switching Combining
• Slide 37
• Disadvantage of Selection or Switching
• Slide 39
• (a) Switching Methods with Fixed threshold
• Slide 41
• (b) Switching Methods with Variable threshold
• Slide 43

(b) Equal Gain Combining (EGC)

EGCbull EGC is similar to MRC except the weighting

circuits are omittedbull The performance improvement obtained by

equal gain combiner is slightly inferior to that of a MRC since the interference and noise corrupted signal combined with high quality signals

For VHF UHF and microwave wireless radio applications

bull Both MRC and EGC methods are unsuitablebull Compared with MRC EGC methods the

selection method is more suitable for mobile radio applications because of its simple implementation

(c) Selection or Switching Combining

bull The diversity branch having the highest signal level (or) lowest Pe is selected

bull Also in addition stable operation is easily achieved even in the fast multipath fading environments

bull But the performance improvement obtained by the selection method is still only slightly inferior to that of MRC method

Disadvantage of Selection or Switching

bull Combining The continuous monitoring of the signals requires the same no of receivers as the no of diversity branches

bull This redundancy can be alleviated by the use of switching or scanning receiver

SWITCHNINGMETHODS

FIXED THERSHOLD VARIABLE THERSHOLD

(a) Switching Methods with Fixed threshold

bull The switching from one branch to the other occurs when the signal level falls below a threshold value

bull The threshold value is fixedbull However this threshold value is not

necessarily the best over the entire service area

FIXED THERSHOLD

(b) Switching Methods with Variable threshold

bull Here the threshold value is adjusted dynamically as the vehicle moves

bull It includes the feedback using Estimationbull But it may introduce the envelope and phase

transients that will reduce the performance improvement

VARIABLE THERSHOLD

Conclusions

bull The diversity is used to provide the receiver with several replicas of the same signal

bull Diversity techniques are used to improve the performance of the radio channel without any increase in the transmitted power

bull As higher as the received signal replicas are decorrelated as much as the diversity gain

Thank you for you attention

• No trade off to
• What are all the needs of diversity techniques
• CONCEPTS OF DIVERSITY BRANCH AND SIGNAL PATH
• (a) Branch Construction method using frequency diversity
• (b) Branch Construction method using Time diversity
• COMBINING AND SWITCHNING METHODS
• Slide 29
• FOR COHERENT DETECTION
• (a) Maximal ratio combining (MRC)
• Slide 32
• (b) Equal Gain Combining (EGC)
• EGC
• For VHF UHF and microwave wireless radio applications
• (c) Selection or Switching Combining
• Slide 37
• Disadvantage of Selection or Switching
• Slide 39
• (a) Switching Methods with Fixed threshold
• Slide 41
• (b) Switching Methods with Variable threshold
• Slide 43

EGCbull EGC is similar to MRC except the weighting

circuits are omittedbull The performance improvement obtained by

equal gain combiner is slightly inferior to that of a MRC since the interference and noise corrupted signal combined with high quality signals

For VHF UHF and microwave wireless radio applications

bull Both MRC and EGC methods are unsuitablebull Compared with MRC EGC methods the

selection method is more suitable for mobile radio applications because of its simple implementation

(c) Selection or Switching Combining

bull The diversity branch having the highest signal level (or) lowest Pe is selected

bull Also in addition stable operation is easily achieved even in the fast multipath fading environments

bull But the performance improvement obtained by the selection method is still only slightly inferior to that of MRC method

Disadvantage of Selection or Switching

bull Combining The continuous monitoring of the signals requires the same no of receivers as the no of diversity branches

bull This redundancy can be alleviated by the use of switching or scanning receiver

SWITCHNINGMETHODS

FIXED THERSHOLD VARIABLE THERSHOLD

(a) Switching Methods with Fixed threshold

bull The switching from one branch to the other occurs when the signal level falls below a threshold value

bull The threshold value is fixedbull However this threshold value is not

necessarily the best over the entire service area

FIXED THERSHOLD

(b) Switching Methods with Variable threshold

bull Here the threshold value is adjusted dynamically as the vehicle moves

bull It includes the feedback using Estimationbull But it may introduce the envelope and phase

transients that will reduce the performance improvement

VARIABLE THERSHOLD

Conclusions

bull The diversity is used to provide the receiver with several replicas of the same signal

bull Diversity techniques are used to improve the performance of the radio channel without any increase in the transmitted power

bull As higher as the received signal replicas are decorrelated as much as the diversity gain

Thank you for you attention

• No trade off to
• What are all the needs of diversity techniques
• CONCEPTS OF DIVERSITY BRANCH AND SIGNAL PATH
• (a) Branch Construction method using frequency diversity
• (b) Branch Construction method using Time diversity
• COMBINING AND SWITCHNING METHODS
• Slide 29
• FOR COHERENT DETECTION
• (a) Maximal ratio combining (MRC)
• Slide 32
• (b) Equal Gain Combining (EGC)
• EGC
• For VHF UHF and microwave wireless radio applications
• (c) Selection or Switching Combining
• Slide 37
• Disadvantage of Selection or Switching
• Slide 39
• (a) Switching Methods with Fixed threshold
• Slide 41
• (b) Switching Methods with Variable threshold
• Slide 43

For VHF UHF and microwave wireless radio applications

bull Both MRC and EGC methods are unsuitablebull Compared with MRC EGC methods the

selection method is more suitable for mobile radio applications because of its simple implementation

(c) Selection or Switching Combining

bull The diversity branch having the highest signal level (or) lowest Pe is selected

bull Also in addition stable operation is easily achieved even in the fast multipath fading environments

bull But the performance improvement obtained by the selection method is still only slightly inferior to that of MRC method

Disadvantage of Selection or Switching

bull Combining The continuous monitoring of the signals requires the same no of receivers as the no of diversity branches

bull This redundancy can be alleviated by the use of switching or scanning receiver

SWITCHNINGMETHODS

FIXED THERSHOLD VARIABLE THERSHOLD

(a) Switching Methods with Fixed threshold

bull The switching from one branch to the other occurs when the signal level falls below a threshold value

bull The threshold value is fixedbull However this threshold value is not

necessarily the best over the entire service area

FIXED THERSHOLD

(b) Switching Methods with Variable threshold

bull Here the threshold value is adjusted dynamically as the vehicle moves

bull It includes the feedback using Estimationbull But it may introduce the envelope and phase

transients that will reduce the performance improvement

VARIABLE THERSHOLD

Conclusions

bull The diversity is used to provide the receiver with several replicas of the same signal

bull Diversity techniques are used to improve the performance of the radio channel without any increase in the transmitted power

bull As higher as the received signal replicas are decorrelated as much as the diversity gain

Thank you for you attention

• No trade off to
• What are all the needs of diversity techniques
• CONCEPTS OF DIVERSITY BRANCH AND SIGNAL PATH
• (a) Branch Construction method using frequency diversity
• (b) Branch Construction method using Time diversity
• COMBINING AND SWITCHNING METHODS
• Slide 29
• FOR COHERENT DETECTION
• (a) Maximal ratio combining (MRC)
• Slide 32
• (b) Equal Gain Combining (EGC)
• EGC
• For VHF UHF and microwave wireless radio applications
• (c) Selection or Switching Combining
• Slide 37
• Disadvantage of Selection or Switching
• Slide 39
• (a) Switching Methods with Fixed threshold
• Slide 41
• (b) Switching Methods with Variable threshold
• Slide 43

(c) Selection or Switching Combining

bull The diversity branch having the highest signal level (or) lowest Pe is selected

bull Also in addition stable operation is easily achieved even in the fast multipath fading environments

bull But the performance improvement obtained by the selection method is still only slightly inferior to that of MRC method

Disadvantage of Selection or Switching

bull Combining The continuous monitoring of the signals requires the same no of receivers as the no of diversity branches

bull This redundancy can be alleviated by the use of switching or scanning receiver

SWITCHNINGMETHODS

FIXED THERSHOLD VARIABLE THERSHOLD

(a) Switching Methods with Fixed threshold

bull The switching from one branch to the other occurs when the signal level falls below a threshold value

bull The threshold value is fixedbull However this threshold value is not

necessarily the best over the entire service area

FIXED THERSHOLD

(b) Switching Methods with Variable threshold

bull Here the threshold value is adjusted dynamically as the vehicle moves

bull It includes the feedback using Estimationbull But it may introduce the envelope and phase

transients that will reduce the performance improvement

VARIABLE THERSHOLD

Conclusions

bull The diversity is used to provide the receiver with several replicas of the same signal

bull Diversity techniques are used to improve the performance of the radio channel without any increase in the transmitted power

bull As higher as the received signal replicas are decorrelated as much as the diversity gain

Thank you for you attention

• No trade off to
• What are all the needs of diversity techniques
• CONCEPTS OF DIVERSITY BRANCH AND SIGNAL PATH
• (a) Branch Construction method using frequency diversity
• (b) Branch Construction method using Time diversity
• COMBINING AND SWITCHNING METHODS
• Slide 29
• FOR COHERENT DETECTION
• (a) Maximal ratio combining (MRC)
• Slide 32
• (b) Equal Gain Combining (EGC)
• EGC
• For VHF UHF and microwave wireless radio applications
• (c) Selection or Switching Combining
• Slide 37
• Disadvantage of Selection or Switching
• Slide 39
• (a) Switching Methods with Fixed threshold
• Slide 41
• (b) Switching Methods with Variable threshold
• Slide 43

bull The diversity branch having the highest signal level (or) lowest Pe is selected

bull Also in addition stable operation is easily achieved even in the fast multipath fading environments

bull But the performance improvement obtained by the selection method is still only slightly inferior to that of MRC method

Disadvantage of Selection or Switching

bull Combining The continuous monitoring of the signals requires the same no of receivers as the no of diversity branches

bull This redundancy can be alleviated by the use of switching or scanning receiver

SWITCHNINGMETHODS

FIXED THERSHOLD VARIABLE THERSHOLD

(a) Switching Methods with Fixed threshold

bull The switching from one branch to the other occurs when the signal level falls below a threshold value

bull The threshold value is fixedbull However this threshold value is not

necessarily the best over the entire service area

FIXED THERSHOLD

(b) Switching Methods with Variable threshold

bull Here the threshold value is adjusted dynamically as the vehicle moves

bull It includes the feedback using Estimationbull But it may introduce the envelope and phase

transients that will reduce the performance improvement

VARIABLE THERSHOLD

Conclusions

bull The diversity is used to provide the receiver with several replicas of the same signal

bull Diversity techniques are used to improve the performance of the radio channel without any increase in the transmitted power

bull As higher as the received signal replicas are decorrelated as much as the diversity gain

Thank you for you attention

• No trade off to
• What are all the needs of diversity techniques
• CONCEPTS OF DIVERSITY BRANCH AND SIGNAL PATH
• (a) Branch Construction method using frequency diversity
• (b) Branch Construction method using Time diversity
• COMBINING AND SWITCHNING METHODS
• Slide 29
• FOR COHERENT DETECTION
• (a) Maximal ratio combining (MRC)
• Slide 32
• (b) Equal Gain Combining (EGC)
• EGC
• For VHF UHF and microwave wireless radio applications
• (c) Selection or Switching Combining
• Slide 37
• Disadvantage of Selection or Switching
• Slide 39
• (a) Switching Methods with Fixed threshold
• Slide 41
• (b) Switching Methods with Variable threshold
• Slide 43

Disadvantage of Selection or Switching

bull Combining The continuous monitoring of the signals requires the same no of receivers as the no of diversity branches

bull This redundancy can be alleviated by the use of switching or scanning receiver

SWITCHNINGMETHODS

FIXED THERSHOLD VARIABLE THERSHOLD

(a) Switching Methods with Fixed threshold

bull The switching from one branch to the other occurs when the signal level falls below a threshold value

bull The threshold value is fixedbull However this threshold value is not

necessarily the best over the entire service area

FIXED THERSHOLD

(b) Switching Methods with Variable threshold

bull Here the threshold value is adjusted dynamically as the vehicle moves

bull It includes the feedback using Estimationbull But it may introduce the envelope and phase

transients that will reduce the performance improvement

VARIABLE THERSHOLD

Conclusions

bull The diversity is used to provide the receiver with several replicas of the same signal

bull Diversity techniques are used to improve the performance of the radio channel without any increase in the transmitted power

bull As higher as the received signal replicas are decorrelated as much as the diversity gain

Thank you for you attention

• No trade off to
• What are all the needs of diversity techniques
• CONCEPTS OF DIVERSITY BRANCH AND SIGNAL PATH
• (a) Branch Construction method using frequency diversity
• (b) Branch Construction method using Time diversity
• COMBINING AND SWITCHNING METHODS
• Slide 29
• FOR COHERENT DETECTION
• (a) Maximal ratio combining (MRC)
• Slide 32
• (b) Equal Gain Combining (EGC)
• EGC
• For VHF UHF and microwave wireless radio applications
• (c) Selection or Switching Combining
• Slide 37
• Disadvantage of Selection or Switching
• Slide 39
• (a) Switching Methods with Fixed threshold
• Slide 41
• (b) Switching Methods with Variable threshold
• Slide 43

SWITCHNINGMETHODS

FIXED THERSHOLD VARIABLE THERSHOLD

(a) Switching Methods with Fixed threshold

bull The switching from one branch to the other occurs when the signal level falls below a threshold value

bull The threshold value is fixedbull However this threshold value is not

necessarily the best over the entire service area

FIXED THERSHOLD

(b) Switching Methods with Variable threshold

bull Here the threshold value is adjusted dynamically as the vehicle moves

bull It includes the feedback using Estimationbull But it may introduce the envelope and phase

transients that will reduce the performance improvement

VARIABLE THERSHOLD

Conclusions

bull The diversity is used to provide the receiver with several replicas of the same signal

bull Diversity techniques are used to improve the performance of the radio channel without any increase in the transmitted power

bull As higher as the received signal replicas are decorrelated as much as the diversity gain

Thank you for you attention

• No trade off to
• What are all the needs of diversity techniques
• CONCEPTS OF DIVERSITY BRANCH AND SIGNAL PATH
• (a) Branch Construction method using frequency diversity
• (b) Branch Construction method using Time diversity
• COMBINING AND SWITCHNING METHODS
• Slide 29
• FOR COHERENT DETECTION
• (a) Maximal ratio combining (MRC)
• Slide 32
• (b) Equal Gain Combining (EGC)
• EGC
• For VHF UHF and microwave wireless radio applications
• (c) Selection or Switching Combining
• Slide 37
• Disadvantage of Selection or Switching
• Slide 39
• (a) Switching Methods with Fixed threshold
• Slide 41
• (b) Switching Methods with Variable threshold
• Slide 43

(a) Switching Methods with Fixed threshold

bull The switching from one branch to the other occurs when the signal level falls below a threshold value

bull The threshold value is fixedbull However this threshold value is not

necessarily the best over the entire service area

FIXED THERSHOLD

(b) Switching Methods with Variable threshold

bull Here the threshold value is adjusted dynamically as the vehicle moves

bull It includes the feedback using Estimationbull But it may introduce the envelope and phase

transients that will reduce the performance improvement

VARIABLE THERSHOLD

Conclusions

bull The diversity is used to provide the receiver with several replicas of the same signal

bull Diversity techniques are used to improve the performance of the radio channel without any increase in the transmitted power

bull As higher as the received signal replicas are decorrelated as much as the diversity gain

Thank you for you attention

• No trade off to
• What are all the needs of diversity techniques
• CONCEPTS OF DIVERSITY BRANCH AND SIGNAL PATH
• (a) Branch Construction method using frequency diversity
• (b) Branch Construction method using Time diversity
• COMBINING AND SWITCHNING METHODS
• Slide 29
• FOR COHERENT DETECTION
• (a) Maximal ratio combining (MRC)
• Slide 32
• (b) Equal Gain Combining (EGC)
• EGC
• For VHF UHF and microwave wireless radio applications
• (c) Selection or Switching Combining
• Slide 37
• Disadvantage of Selection or Switching
• Slide 39
• (a) Switching Methods with Fixed threshold
• Slide 41
• (b) Switching Methods with Variable threshold
• Slide 43

bull The switching from one branch to the other occurs when the signal level falls below a threshold value

bull The threshold value is fixedbull However this threshold value is not

necessarily the best over the entire service area

FIXED THERSHOLD

(b) Switching Methods with Variable threshold

bull Here the threshold value is adjusted dynamically as the vehicle moves

bull It includes the feedback using Estimationbull But it may introduce the envelope and phase

transients that will reduce the performance improvement

VARIABLE THERSHOLD

Conclusions

bull The diversity is used to provide the receiver with several replicas of the same signal

bull Diversity techniques are used to improve the performance of the radio channel without any increase in the transmitted power

bull As higher as the received signal replicas are decorrelated as much as the diversity gain

Thank you for you attention

• No trade off to
• What are all the needs of diversity techniques
• CONCEPTS OF DIVERSITY BRANCH AND SIGNAL PATH
• (a) Branch Construction method using frequency diversity
• (b) Branch Construction method using Time diversity
• COMBINING AND SWITCHNING METHODS
• Slide 29
• FOR COHERENT DETECTION
• (a) Maximal ratio combining (MRC)
• Slide 32
• (b) Equal Gain Combining (EGC)
• EGC
• For VHF UHF and microwave wireless radio applications
• (c) Selection or Switching Combining
• Slide 37
• Disadvantage of Selection or Switching
• Slide 39
• (a) Switching Methods with Fixed threshold
• Slide 41
• (b) Switching Methods with Variable threshold
• Slide 43

(b) Switching Methods with Variable threshold

bull Here the threshold value is adjusted dynamically as the vehicle moves

bull It includes the feedback using Estimationbull But it may introduce the envelope and phase

transients that will reduce the performance improvement

VARIABLE THERSHOLD

Conclusions

bull The diversity is used to provide the receiver with several replicas of the same signal

bull Diversity techniques are used to improve the performance of the radio channel without any increase in the transmitted power

bull As higher as the received signal replicas are decorrelated as much as the diversity gain

Thank you for you attention

• No trade off to
• What are all the needs of diversity techniques
• CONCEPTS OF DIVERSITY BRANCH AND SIGNAL PATH
• (a) Branch Construction method using frequency diversity
• (b) Branch Construction method using Time diversity
• COMBINING AND SWITCHNING METHODS
• Slide 29
• FOR COHERENT DETECTION
• (a) Maximal ratio combining (MRC)
• Slide 32
• (b) Equal Gain Combining (EGC)
• EGC
• For VHF UHF and microwave wireless radio applications
• (c) Selection or Switching Combining
• Slide 37
• Disadvantage of Selection or Switching
• Slide 39
• (a) Switching Methods with Fixed threshold
• Slide 41
• (b) Switching Methods with Variable threshold
• Slide 43

bull Here the threshold value is adjusted dynamically as the vehicle moves

bull It includes the feedback using Estimationbull But it may introduce the envelope and phase

transients that will reduce the performance improvement

VARIABLE THERSHOLD

Conclusions

bull The diversity is used to provide the receiver with several replicas of the same signal

bull Diversity techniques are used to improve the performance of the radio channel without any increase in the transmitted power

bull As higher as the received signal replicas are decorrelated as much as the diversity gain

Thank you for you attention

• No trade off to
• What are all the needs of diversity techniques
• CONCEPTS OF DIVERSITY BRANCH AND SIGNAL PATH
• (a) Branch Construction method using frequency diversity
• (b) Branch Construction method using Time diversity
• COMBINING AND SWITCHNING METHODS
• Slide 29
• FOR COHERENT DETECTION
• (a) Maximal ratio combining (MRC)
• Slide 32
• (b) Equal Gain Combining (EGC)
• EGC
• For VHF UHF and microwave wireless radio applications
• (c) Selection or Switching Combining
• Slide 37
• Disadvantage of Selection or Switching
• Slide 39
• (a) Switching Methods with Fixed threshold
• Slide 41
• (b) Switching Methods with Variable threshold
• Slide 43

Conclusions

bull The diversity is used to provide the receiver with several replicas of the same signal

bull Diversity techniques are used to improve the performance of the radio channel without any increase in the transmitted power

bull As higher as the received signal replicas are decorrelated as much as the diversity gain

Thank you for you attention

• No trade off to
• What are all the needs of diversity techniques
• CONCEPTS OF DIVERSITY BRANCH AND SIGNAL PATH
• (a) Branch Construction method using frequency diversity
• (b) Branch Construction method using Time diversity
• COMBINING AND SWITCHNING METHODS
• Slide 29
• FOR COHERENT DETECTION
• (a) Maximal ratio combining (MRC)
• Slide 32
• (b) Equal Gain Combining (EGC)
• EGC
• For VHF UHF and microwave wireless radio applications
• (c) Selection or Switching Combining
• Slide 37
• Disadvantage of Selection or Switching
• Slide 39
• (a) Switching Methods with Fixed threshold
• Slide 41
• (b) Switching Methods with Variable threshold
• Slide 43

Thank you for you attention

• No trade off to
• What are all the needs of diversity techniques
• CONCEPTS OF DIVERSITY BRANCH AND SIGNAL PATH
• (a) Branch Construction method using frequency diversity
• (b) Branch Construction method using Time diversity
• COMBINING AND SWITCHNING METHODS
• Slide 29
• FOR COHERENT DETECTION
• (a) Maximal ratio combining (MRC)
• Slide 32
• (b) Equal Gain Combining (EGC)
• EGC
• For VHF UHF and microwave wireless radio applications
• (c) Selection or Switching Combining
• Slide 37
• Disadvantage of Selection or Switching
• Slide 39
• (a) Switching Methods with Fixed threshold
• Slide 41
• (b) Switching Methods with Variable threshold
• Slide 43