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Purpose

Objectives

Expected Benefits

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An overview of diversity techniques.

How diversity technique can be utilized for performance

improvement.

Provide MATLAB computing to understand the

performance improvement using diversity technique.

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To acquire an update on the development of mobile phone technologies with potential for

supporting our own future carrier.

To learn about the present wireless communication condition in our country.

To demonstrate some latest technologies in communication field

How diversity techniques are used to improve the performance of the radio channel without

any increase in the transmitted power.

To evaluate the system performance degradation due to fading.

To undergo mathematical analysis and MATLAB simulation for analyzing the performance of

Raleigh fading channels.

To study Uniqueness of Mobile Radio Environment.

To overall basic knowledge about telecommunication.YuVa InnoVators

To know about the recent status of telecommunication sector

To work on the improvement of the communication services

Diversity is now being considered as one of the most

solution to mitigate the fading problem in wireless

communication.

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Communication signifies transmission, reception and

processing of information by electric means.

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An information source, presumably a person who creates a message.

The message, which is both sent by the information source and received by the destination.

A transmitter, a telephone instrument that captures an audio signal, converts it into an electronic signal, and amplifies it

for transmission through the telephone network.

A carrier or channel, which acts as a bridge between the transmitter and receiver. As the signal propagates through the

channel, it gets attenuated due to transmission loss and distorted due to various nonlinear effects and interference.

Channel can consist of a pair of wires, a coaxial cable or a radio link through free space

Noise, in the form of secondary signals that obscure or confuse the signal carried

Receiver It extracts the weakened and distorted signal from the channel, amplifies it and restores it to its original

form and then passes it into the message destination.

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OPTICAL COMMUNICATION SYSTEM

RADIO COMMUNICATION

POWER LINE COMMUNICATIONS SYSTEMS

DUPLEX COMMUNICATION SYSTEM

TACTICAL COMMUNICATIONS SYSTEM

WIRELESS COMMUNICATION

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The transfer of information over a distance without

the use of electrical conductors or "wires“

An electromagnetic signal is created, modulated,

amplified, and broadcast to one or more receivers that

can be fixed or mobile.

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Every wireless system must have the basics of a transmitter

(modulation), receiver (demodulation) and a channel

(frequency) to transmit the signal from a stationary or mobile

reference. YuVa InnoVators

A TYPICAL GSM BASE STATIONYuVa InnoVators

High Frequency (HF) 3-30 MHz (PRIME BAND)

Very High Frequency (VHF) 30-300 MHz (PRIME BAND)

Ultra High Frequency (UHF) 300-3000 MHz (PRIME BAND)

Super High Frequency (SHF) 3-30 GHz (INCREASING USE)

Extremely High Frequency (EHF) 30-300 GHz (PROSPECTIVE USE)

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SECURITY SYSTEMS

TELEVISION REMOTE CONTROL

CELLULAR TELEPHONY (PHONES AND MODEMS)

Wi–Fi

WIRELESS ENERGY TRANSFER

COMMUNICATIONS SATELLITEYuVa InnoVators

In telecommunications, modulation

is the process of conveying a

message signal inside another signal

that can be physically transmitted.

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The aim of digital modulation is to transfer a digital

bit stream over an analog passband channel

The aim of analog modulation is to transfer an analog

baseband (or lowpass) signal

The aim of pulse modulation methods is to transfer a

narrowband analog signal

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MODULATION

ANALOG MODULATION

AMPLITUDE MODULATION

FREQUENCY MODULATION

PHASE MODULATION

DIGITAL MODULATION

AMPLITUDE-SHIFT KEYING

FREQUENCY-SHIFT KEYING

PHASE-SHIFT KEYING

PULSE MODULATION

PULSE-AMPLITUDE MODULATION

PULSE-WIDTH MODULATION

PULSE-POSITION MODULATION

PULSE-CODE MODULATIONYuVa InnoVators

The modulation is applied continuously in response to the

analog information signal.

The amplitude of the carrier

signal is varied in accordance to the

instantaneous amplitude of the

modulating signal.

The frequency of the carrier

signal is varied in accordance to the

instantaneous frequency of the

modulating signal.

The phase shift of the carrier

signal is varied in accordance to the

instantaneous phase shift of the

modulating signal.

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An analog carrier signal is

modulated by a digital bit stream

Considered as digital-to-analog

conversionYuVa InnoVators

AMPLITUDE-SHIFT KEYING (ASK)

FREQUENCY-SHIFT KEYING (FSK)

PHASE-SHIFT KEYING (PSK)YuVa InnoVators

Pulse modulation schemes aim at transferring a narrowband analog

signal over an analog baseband channel as a two-level signal by

modulating a pulse wave.

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Essentially identical to coded OFDM (COFDM) and discrete

multi-tone modulation (DMT), is a frequency-division

multiplexing (FDM) scheme utilized as a digital multi-carrier

modulation method.

Orthogonal Frequency-Division Multiple Access (OFDMA)

is a multi-user version of the popular Orthogonal frequency-

division multiplexing (OFDM) digital modulation scheme.

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AN OFDM (A) MODULATOR AND (B) DEMODULATOR

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OFDM SIMULATION FLOWCHART

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Flexibility of deployment across various frequency bands with little needed

modification to the air interface.

Averaging interferences from neighboring cells, by using different basic carrier

permutations between users in different cells.

Interferences within the cell are averaged by using allocation with cyclic

permutations.

Enables orthogonality in the uplink by synchronizing users in time and frequency.

Enables Single Frequency Network coverage, where coverage problem exists and

gives excellent coverage.

Offers Frequency diversity by spreading the carriers all over the used spectrum.

Offers Time diversity by optional interleaving of carrier groups in time. YuVa InnoVators

FADING

INTERFERENCE

ERROR BURST

FREQUENCY REUSES

NOISE LEVEL IN CELLULAR FREQUENCY BAND

PATH LOSS YuVa InnoVators

The fading is deviation of the attenuation that a carrier-

modulated telecommunication signal experiences over certain

propagation media.

The fading may vary with time, geographical position and/or

radio frequency, and is often modeled as a random process.

In wireless systems, fading may either be due to multipath

propagation or due to shadowing from obstacles affecting the

wave propagation.YuVa InnoVators

1. Multipath Spread Tm

It tells us the maximum delay between paths of significant power in the channel

2. Coherence Bandwidth (Δ)c

Gives an idea of how far apart –in frequency- for signals to undergo different degrees of fading

3. Coherence Time (t)c

Gives a measure of the time duration over which the channel impulse response is essentially invariant (highly correlated)

4. Doppler Spread Bd

It gives the maximum range of Doppler shifts

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A MOBILE RADIO ENVIRONMENT (a) PROPAGATION LOSS(b) MULTIPATH FADING

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FAST FADING vs. SLOW FADING

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CO-CHANNEL INTERFERENCE

- Co-channel interference or CCI is crosstalk from two

different radio transmitters using the same frequency.

ADJACENT-CHANNEL INTERFERENCE

- Adjacent-channel interference or ACI is interference

caused by extraneous power from a signal in an adjacent

channel.

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The core concept of the cellular mobile radio system.

Users in different geographic locations may

simultaneously use the same frequency .

The frequency reuse concept can be used in the time

domain and the space domain.

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N-CELL REUSE PATTERNYuVa InnoVators

Tow-ray models for mobile radio environments

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TIME DIVERSITY

FREQUENCY DIVERSITY

SPACE DIVERSITY

SPATIAL DIVERSITY

PATTERN DIVERSITY

POLARIZATION DIVERSITY

MULTIUSER DIVERSITY

COOPERATIVE DIVERSITYYuVa InnoVators

Time Diversity is used in digital communication systems

to combat that the transmissions channel may suffer from

error bursts due to time-varying channel conditions.

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The signal is transferred using several frequency channels

or spread over a wide spectrum that is affected by

frequency-selective fading.

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Antenna diversity, also known as space diversity, is any one of

several wireless diversity schemes that use two or more

antennas to improve the quality and reliability of a wireless

link. Often, especially in urban and indoor environments, there

is not a clear line-of-sight (LOS) between transmitter and

receiver. Instead the signal is reflected along multiple paths

before finally being received

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Spatial diversity employs multiple antennas,

usually with the same characteristics, that are

physically separated from one another.

Depending upon the expected incidence of the

incoming signal, sometimes a space on the

order of a wavelength is sufficient.

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Pattern diversity consists of two or more co-located antennas with different radiation patterns.This type of diversity makes use of directiveantennas that are usually physically separated bysome (often short) distance.

Collectively they are capable of discriminating alarge portion of angle space and can provide ahigher gain versus a single omni directionalradiator.

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Multiple versions of a signal are transmitted and received via

antennas with different polarization.

LINEAR CIRCULAR ELLIPTICALYuVa InnoVators

Achieves antenna diversity gain by using the

cooperation of distributed antennas belonging to

each node.

Cooperative diversity is a cooperative multiple

antenna technique for improving or maximizing

total network channel capacities for any given set

of bandwidths .

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SELECTION COMBINING

SWITCHING COMBINING

EQUAL GAIN COMBINING

MAXIMAL-RATIO COMBININGYuVa InnoVators

Of the N received signals, the strongest signal is selected.

Any additional gain diminishes rapidly with the increasing number of

channels.

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• The receiver switches to another signal when current signal drops below apredefined threshold.

• This is a less efficient technique than selection combining.

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All the received signals are summed coherently.

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• The received signals are weighted with respect to their SNR

and then summed.

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Use of multiple antennas at both the transmitter and

receiver to improve quality (BER) or data rate

(bits/sec).

One of several forms of smart antenna technology.

Core scheme of MIMO: space-time coding (STC)

Two main functions of STC: diversity & multiplexingYuVa InnoVators

Spatial Diversity: Increased SNR Spatial Multiplexing: Increased rate

Receive and transmit diversity mitigates fading and significantly

improves link quality

Spatial multiplexing yields substantial increase in spectral

efficiencyYuVa InnoVators

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Diversity plays an important role in combating fading and co-channel

interference and avoiding error bursts. It is based on the fact that

individual channels experience different levels of fading and

interference. Multiple versions of the same signal may be transmitted

and/or received and combined in the receiver. Alternatively, a

redundant forward error correction code may be added and different

parts of the message transmitted over different channels. Diversity

techniques may exploit the multipath propagation, resulting in a

diversity gain, often measured in decibels.YuVa InnoVators

Comparison of the Performance of a wireless Communication System using Antenna Diversity

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SNR KNo. of receiving

antenna (Rx.)

BER-Floor for a Un-

coded System

40dB 0dB

2 10-5

3 10-7

4 10-8

5 10-10

6 10-12

The improvement of performance of a Wireless System using Multiple Antenna

(Diversity) System

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Comparison of Performance between one (L=1) and six receiving (L=6) Antenna of wireless Communication System using Maximum Ratio

Combining Diversity Method YuVa InnoVators

SNR KNo. of receiving

antenna (Rx.)

BER-Floor for the

System

50dB 0dB

1 10-5

6 10-22

Comparison of Performance between one (L=1) and six receiving (L=6) Antenna of wireless Communication System

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Comparison of Performance between one (L=1) and eight receiving (L=8) Antenna of wireless Communication System using Maximum

Ratio Combining Diversity Method YuVa InnoVators

Comparison of Performance between one (L=1) and eight receiving (L=8) Antenna of wireless Communication System

SNR KNo. of receiving

antenna (Rx.)

BER-Floor for the

System

60dB 0dB

1 10-4

8 10-34

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Comparison of Performance for different diversity schemes of a Wireless Communication System using Maximum Ratio Combining (MRC).

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Comparison of Performance for different diversity schemes of a Wireless Communication System.

SNR KNo. of receiving

antenna (Rx.)

BER-Floor for the

System

60dB 0dB

1 10-4

2 10-10

4 10-20

6 10-27

8 10-35

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The diversity is used to provide the receiver with several replicas of the samesignal. Diversity techniques are used to improve the performance of the radiochannel without any increase in the transmitted power. As higher as thereceived signal replicas are de correlated, as much as the diversity gain

Among different combining techniques MRC has the best performance andthe highest complexity, SC has the lowest performance and the leastcomplexity.

BER performance of a Multi-antenna system for both Coded and Un-codedsystem considering several number of Receiving Antenna. From the bothfigures it is noticed that there is remarkable improvement in the achievableprobability of bit error as number of receiving antenna increase. The BER ismeasured as 10-5 , 10-7 , 10-8 ,10-10 , and 10-12 for Receiving AntennaNumbers 2, 3, 4, 5 and 6 respectively. Also it is revealed that Bit-Error-Rate of a Multi-Antenna System is 10-23, 10-30 , 10-38 , 10-47 and 10-56

for Receiving Antenna Numbers 2, 3, 4, 5 and 6 respectively.YuVa InnoVators

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