網路多媒體研究所 1 WCDMA Technology Past, Present and Future Part II: CDMA Technology...
-
Upload
chloe-loreen-maxwell -
Category
Documents
-
view
227 -
download
8
Transcript of 網路多媒體研究所 1 WCDMA Technology Past, Present and Future Part II: CDMA Technology...
![Page 1: 網路多媒體研究所 1 WCDMA Technology Past, Present and Future Part II: CDMA Technology Overview.](https://reader036.fdocuments.net/reader036/viewer/2022062321/56649eb55503460f94bbe9e5/html5/thumbnails/1.jpg)
1 網路多媒體研究所網路多媒體研究所
WCDMA TechnologyWCDMA TechnologyPast, Present and FuturePast, Present and Future
Part II:CDMA Technology Overview
![Page 2: 網路多媒體研究所 1 WCDMA Technology Past, Present and Future Part II: CDMA Technology Overview.](https://reader036.fdocuments.net/reader036/viewer/2022062321/56649eb55503460f94bbe9e5/html5/thumbnails/2.jpg)
網路多媒體研究所網路多媒體研究所2
Part II: CDMA Technology Overview
• Introduction to Wireless Communication– Radio Channel Characteristic– Modulation– Basic Concepts to Mobile Communication
• CDMA Technology Overview– History of CDMA– Introduction to Spread Spectrum– Direct Sequence CDMA (DS-CDMA)– CDMA System Characteristic– Challenges in CDMA System Design
![Page 3: 網路多媒體研究所 1 WCDMA Technology Past, Present and Future Part II: CDMA Technology Overview.](https://reader036.fdocuments.net/reader036/viewer/2022062321/56649eb55503460f94bbe9e5/html5/thumbnails/3.jpg)
網路多媒體研究所網路多媒體研究所3
Typical Communication System
SourceSource
&ChannelEncoder
DigitalModulator
RF
RFDemodulator Equalization
Synchronization:Carrier and Timing
Source&ChannelDecoder
Sink
Antenna
Antenna
Radio Channel
![Page 4: 網路多媒體研究所 1 WCDMA Technology Past, Present and Future Part II: CDMA Technology Overview.](https://reader036.fdocuments.net/reader036/viewer/2022062321/56649eb55503460f94bbe9e5/html5/thumbnails/4.jpg)
網路多媒體研究所網路多媒體研究所4
Radio Channel Features
• Path Loss• Shadowing • Multipath Fading• Noise
![Page 5: 網路多媒體研究所 1 WCDMA Technology Past, Present and Future Part II: CDMA Technology Overview.](https://reader036.fdocuments.net/reader036/viewer/2022062321/56649eb55503460f94bbe9e5/html5/thumbnails/5.jpg)
網路多媒體研究所網路多媒體研究所5
What is Fading?
• Signals from different paths are received with different delays – due to reflections of buildings, trees, etc.
• Each path has different attenuation and time delay (phase delay)
• Sometimes the relative phase shifts align, so the signal received from different add constructively, but at other time they cancel each other.
• This is called Fading
![Page 6: 網路多媒體研究所 1 WCDMA Technology Past, Present and Future Part II: CDMA Technology Overview.](https://reader036.fdocuments.net/reader036/viewer/2022062321/56649eb55503460f94bbe9e5/html5/thumbnails/6.jpg)
網路多媒體研究所網路多媒體研究所6
Features of the Fading Component
• Path loss (Area-mean):– Hundreds or thousands of meters
– Reflection, diffraction, and scattering • Shadowing (Local-mean):
– A few tens or hundreds of meters– Caused by obstruction and motion
• Multipath fading (Short-term fast fading or small-scale fast fading):– Variation of the signal strength over a short distance on the
order of a few wavelengths or over short term duration on the order of seconds
– Due to multipath reflections of transmitted wave by local scatters, such as houses, buildings, etc, surrounding a MS
![Page 7: 網路多媒體研究所 1 WCDMA Technology Past, Present and Future Part II: CDMA Technology Overview.](https://reader036.fdocuments.net/reader036/viewer/2022062321/56649eb55503460f94bbe9e5/html5/thumbnails/7.jpg)
網路多媒體研究所網路多媒體研究所7
Received Signal Characteristics
• Received signal consists of many multipath components
• Amplitudes change slowly• Phases change rapidly
– Constructive and destructive addition of signal components
– Amplitude fading of received signal (both wideband and narrowband signals)
![Page 8: 網路多媒體研究所 1 WCDMA Technology Past, Present and Future Part II: CDMA Technology Overview.](https://reader036.fdocuments.net/reader036/viewer/2022062321/56649eb55503460f94bbe9e5/html5/thumbnails/8.jpg)
網路多媒體研究所網路多媒體研究所8
Typical Ways to Overcome Fading
• Diversity • Equalization• Forward error correcting codes and
interleaving• Increasing power• RAKE Receiver
![Page 9: 網路多媒體研究所 1 WCDMA Technology Past, Present and Future Part II: CDMA Technology Overview.](https://reader036.fdocuments.net/reader036/viewer/2022062321/56649eb55503460f94bbe9e5/html5/thumbnails/9.jpg)
網路多媒體研究所網路多媒體研究所9
Impact of Radio Channel on System Design (1/2)
Parameters System Design Considerations Path Loss System coverage
System capacity (propagation exponent)
Shadowing System coverage (need more power margin in the link budget)
System capacity
Delay Spread
(Coherent Bandwidth)
Number of resolvable paths (path diversity)
![Page 10: 網路多媒體研究所 1 WCDMA Technology Past, Present and Future Part II: CDMA Technology Overview.](https://reader036.fdocuments.net/reader036/viewer/2022062321/56649eb55503460f94bbe9e5/html5/thumbnails/10.jpg)
網路多媒體研究所網路多媒體研究所10
Impact of Radio Channel on System Design (2/2)
Parameters System Design Considerations
Doppler Spread
(Coherent Time)
Channel coding and interleaving Power control scheme Channel estimation
Fading Distribution Required Eb/Io System capacity and coverage
Power Delay Profile Path diversity Channel estimation Power control (SIR measurement)
![Page 11: 網路多媒體研究所 1 WCDMA Technology Past, Present and Future Part II: CDMA Technology Overview.](https://reader036.fdocuments.net/reader036/viewer/2022062321/56649eb55503460f94bbe9e5/html5/thumbnails/11.jpg)
網路多媒體研究所網路多媒體研究所11
Modulation
• Why Modulation ?– Different frequency band has different
radio characteristic, like fading, interference, thermal noise, etc…
– Convert information bits to waveform of digital signal with a carrier belong to certain frequency band
– Modulated signal could be easily transmitted and received than signal without modulating
![Page 12: 網路多媒體研究所 1 WCDMA Technology Past, Present and Future Part II: CDMA Technology Overview.](https://reader036.fdocuments.net/reader036/viewer/2022062321/56649eb55503460f94bbe9e5/html5/thumbnails/12.jpg)
網路多媒體研究所網路多媒體研究所12
Digital Modulation Techniques
• ASK (Amplitude Shift Keying)• PSK (Phase Shift Keying)• FSK (Frequency Shift Keying)• QAM (Quadrature Amplitude Modulatio
n)• Etc…
![Page 13: 網路多媒體研究所 1 WCDMA Technology Past, Present and Future Part II: CDMA Technology Overview.](https://reader036.fdocuments.net/reader036/viewer/2022062321/56649eb55503460f94bbe9e5/html5/thumbnails/13.jpg)
網路多媒體研究所網路多媒體研究所13
BPSK and QPSK
10
BPSKSignal Space
Diagram
11
10
QPSKSignal Space
Diagram
00
01
![Page 14: 網路多媒體研究所 1 WCDMA Technology Past, Present and Future Part II: CDMA Technology Overview.](https://reader036.fdocuments.net/reader036/viewer/2022062321/56649eb55503460f94bbe9e5/html5/thumbnails/14.jpg)
網路多媒體研究所網路多媒體研究所14
16-QAM and 64-QAM
16-QAMSignal Space
Diagram64-QAM
Signal SpaceDiagram
![Page 15: 網路多媒體研究所 1 WCDMA Technology Past, Present and Future Part II: CDMA Technology Overview.](https://reader036.fdocuments.net/reader036/viewer/2022062321/56649eb55503460f94bbe9e5/html5/thumbnails/15.jpg)
網路多媒體研究所網路多媒體研究所15
Modulation/Demodulation Block Diagram
Modulator
Demodulator
BasebandSignal
Antennacos(2π fct)Serial to
Parallel
sin(2π fct)
BasebandSignal
Antennacos(2π fct)
Parallel toSerial
sin(2π fct)
Integrationand dump
Integrationand dump
![Page 16: 網路多媒體研究所 1 WCDMA Technology Past, Present and Future Part II: CDMA Technology Overview.](https://reader036.fdocuments.net/reader036/viewer/2022062321/56649eb55503460f94bbe9e5/html5/thumbnails/16.jpg)
網路多媒體研究所網路多媒體研究所16
Cellular Concept
• Cell– Virtual Boundary of Radio
Coverage– Possible Issues
• Handover• Interference• Capacity
![Page 17: 網路多媒體研究所 1 WCDMA Technology Past, Present and Future Part II: CDMA Technology Overview.](https://reader036.fdocuments.net/reader036/viewer/2022062321/56649eb55503460f94bbe9e5/html5/thumbnails/17.jpg)
網路多媒體研究所網路多媒體研究所17
Multiple Access Concept
• Multiple Access is used to distinguish each user while using Radio Access Service
• Multiple Access– FDMA (Frequency Division Multiple
Access)– TDMA (Time Division Multiple Access)– CDMA (Code Division Multiple Access)
![Page 18: 網路多媒體研究所 1 WCDMA Technology Past, Present and Future Part II: CDMA Technology Overview.](https://reader036.fdocuments.net/reader036/viewer/2022062321/56649eb55503460f94bbe9e5/html5/thumbnails/18.jpg)
網路多媒體研究所網路多媒體研究所18
FDMA and TDMA
FDMAFDMA TDMATDMA
N
2
1
W
●●
●
Ts Time
Frequency
Ws
Ws
Ws
W ●●●
NTs Time
Frequency
N
Ts 2Ts
11 2 ●●●
![Page 19: 網路多媒體研究所 1 WCDMA Technology Past, Present and Future Part II: CDMA Technology Overview.](https://reader036.fdocuments.net/reader036/viewer/2022062321/56649eb55503460f94bbe9e5/html5/thumbnails/19.jpg)
網路多媒體研究所網路多媒體研究所19
CDMA
CDMACDMA
●●●
NCode N
Code 2
1Code 1
2
FrequencyTs
Code
●●●
N
1
2
Time
W
●●●
![Page 20: 網路多媒體研究所 1 WCDMA Technology Past, Present and Future Part II: CDMA Technology Overview.](https://reader036.fdocuments.net/reader036/viewer/2022062321/56649eb55503460f94bbe9e5/html5/thumbnails/20.jpg)
網路多媒體研究所網路多媒體研究所20
Duplex Concept
• Duplex is provided a two way Radio Access Service for each user– Uplink (reverse link)– Downlink (forward link)
• Duplex– TDD (Time Division Duplex)– FDD (Frequency Division Duplex)
![Page 21: 網路多媒體研究所 1 WCDMA Technology Past, Present and Future Part II: CDMA Technology Overview.](https://reader036.fdocuments.net/reader036/viewer/2022062321/56649eb55503460f94bbe9e5/html5/thumbnails/21.jpg)
網路多媒體研究所網路多媒體研究所21
FDD and TDD
FDDFDD TDDTDD
UPLINK
DOWNLINK
Ts Time
Frequency
Wdl
Wul
W ●●●
NTs Time
Frequency
Ts 2Ts
UPLINK
●●●
UPLINK
DOWNLINK
DOWNLINK
![Page 22: 網路多媒體研究所 1 WCDMA Technology Past, Present and Future Part II: CDMA Technology Overview.](https://reader036.fdocuments.net/reader036/viewer/2022062321/56649eb55503460f94bbe9e5/html5/thumbnails/22.jpg)
網路多媒體研究所網路多媒體研究所22
Handover
• When mobiles travel from cell to cell, changes of channels may occur and this action of changing channels is known as hand-over or hand-off.
• It is required that the call already established (or in progress) must not be interrupted
![Page 23: 網路多媒體研究所 1 WCDMA Technology Past, Present and Future Part II: CDMA Technology Overview.](https://reader036.fdocuments.net/reader036/viewer/2022062321/56649eb55503460f94bbe9e5/html5/thumbnails/23.jpg)
網路多媒體研究所網路多媒體研究所23
Hard Handover
![Page 24: 網路多媒體研究所 1 WCDMA Technology Past, Present and Future Part II: CDMA Technology Overview.](https://reader036.fdocuments.net/reader036/viewer/2022062321/56649eb55503460f94bbe9e5/html5/thumbnails/24.jpg)
網路多媒體研究所網路多媒體研究所24
Soft Handover
RNC
Cell 1
Cell 2
![Page 25: 網路多媒體研究所 1 WCDMA Technology Past, Present and Future Part II: CDMA Technology Overview.](https://reader036.fdocuments.net/reader036/viewer/2022062321/56649eb55503460f94bbe9e5/html5/thumbnails/25.jpg)
網路多媒體研究所網路多媒體研究所25
Softer Handover
![Page 26: 網路多媒體研究所 1 WCDMA Technology Past, Present and Future Part II: CDMA Technology Overview.](https://reader036.fdocuments.net/reader036/viewer/2022062321/56649eb55503460f94bbe9e5/html5/thumbnails/26.jpg)
網路多媒體研究所網路多媒體研究所26
Interference
• Inter Symbol Interference• Co-Channel Interference• Adjacent Channel Interference
![Page 27: 網路多媒體研究所 1 WCDMA Technology Past, Present and Future Part II: CDMA Technology Overview.](https://reader036.fdocuments.net/reader036/viewer/2022062321/56649eb55503460f94bbe9e5/html5/thumbnails/27.jpg)
網路多媒體研究所網路多媒體研究所27
Inter-Symbol Interference (ISI)
symbol
Inter-symbolinterference
Time
Amplitude
Amplitude
Time
Tx Signal
Rx Signal
![Page 28: 網路多媒體研究所 1 WCDMA Technology Past, Present and Future Part II: CDMA Technology Overview.](https://reader036.fdocuments.net/reader036/viewer/2022062321/56649eb55503460f94bbe9e5/html5/thumbnails/28.jpg)
網路多媒體研究所網路多媒體研究所28
Co-channel Interference (CCI) &
Adjacent Channel Interference (ACI)
fc fc‘
Channel Bandwidth Channel Bandwidth
fc = fc‘ fc fc
‘
Co-channelInterference
Adjacent ChannelInterference
Power
![Page 29: 網路多媒體研究所 1 WCDMA Technology Past, Present and Future Part II: CDMA Technology Overview.](https://reader036.fdocuments.net/reader036/viewer/2022062321/56649eb55503460f94bbe9e5/html5/thumbnails/29.jpg)
網路多媒體研究所網路多媒體研究所29
Illustration of Cellular Frequency Reuse Concept
• Reuse Efficiency = i2+ij+j2
![Page 30: 網路多媒體研究所 1 WCDMA Technology Past, Present and Future Part II: CDMA Technology Overview.](https://reader036.fdocuments.net/reader036/viewer/2022062321/56649eb55503460f94bbe9e5/html5/thumbnails/30.jpg)
網路多媒體研究所網路多媒體研究所30
Interference Contributions from Other Cells
• IS-95 Air Interface Standards
![Page 31: 網路多媒體研究所 1 WCDMA Technology Past, Present and Future Part II: CDMA Technology Overview.](https://reader036.fdocuments.net/reader036/viewer/2022062321/56649eb55503460f94bbe9e5/html5/thumbnails/31.jpg)
網路多媒體研究所網路多媒體研究所31
Part I: CDMA Technology Overview
• Introduction to Wireless Communication– Radio Channel Characteristic– Modulation– Basic Concepts to Mobile Communication
• CDMA Technology Overview– What is “CDMA”– History of CDMA– Introduction to Spread Spectrum– Direct Sequence CDMA (DS-CDMA)– Frequency Hopping CDMA (FH-CDMA)– CDMA System Characteristic– Challenges in CDMA System Design
![Page 32: 網路多媒體研究所 1 WCDMA Technology Past, Present and Future Part II: CDMA Technology Overview.](https://reader036.fdocuments.net/reader036/viewer/2022062321/56649eb55503460f94bbe9e5/html5/thumbnails/32.jpg)
網路多媒體研究所網路多媒體研究所32
CDMA Concept
CDMACDMA
●●●
NCode N
Code 2
1Code 1
2
FrequencyTs
Code
●●●
N
1
2
Time
W
●●●
![Page 33: 網路多媒體研究所 1 WCDMA Technology Past, Present and Future Part II: CDMA Technology Overview.](https://reader036.fdocuments.net/reader036/viewer/2022062321/56649eb55503460f94bbe9e5/html5/thumbnails/33.jpg)
網路多媒體研究所網路多媒體研究所33
What is CDMA?
• A multiple access technique using pseudo-random (PN) codes to spread the spectrum of each user signal.
• Signals are shared a common wide-band channel at the same time.
• Signals are distinguished from each other by using different PN codes.
• Receiver processes only the desired signal. All other user signals appear as interference (multiple-access interference) to the desired signal.
![Page 34: 網路多媒體研究所 1 WCDMA Technology Past, Present and Future Part II: CDMA Technology Overview.](https://reader036.fdocuments.net/reader036/viewer/2022062321/56649eb55503460f94bbe9e5/html5/thumbnails/34.jpg)
網路多媒體研究所網路多媒體研究所34
Pioneer CDMA Era
• 1949, Claude Shannon & Robert Pierce: basic idea of CDMA
• 1950, De Rosa-Rogoff: DSSS• 1956, Pierce & Green: RAKE receiver• 1961, Magnuski: Near-far problem• 1970s, Development for military & navig
ation systems
![Page 35: 網路多媒體研究所 1 WCDMA Technology Past, Present and Future Part II: CDMA Technology Overview.](https://reader036.fdocuments.net/reader036/viewer/2022062321/56649eb55503460f94bbe9e5/html5/thumbnails/35.jpg)
網路多媒體研究所網路多媒體研究所35
Narrowband CDMA Era
• 1978, Cooper & Nettleton: Cellular application of SS
• 1980s, Investigation of NB-CDMA for cellular application
• 1984, DS-CDMA & hybrid CDMA/FDMA proposal for GSM
• 1986, Verdu: Formulation of optimal multiuser detection
• 1993, IS-95 standard
![Page 36: 網路多媒體研究所 1 WCDMA Technology Past, Present and Future Part II: CDMA Technology Overview.](https://reader036.fdocuments.net/reader036/viewer/2022062321/56649eb55503460f94bbe9e5/html5/thumbnails/36.jpg)
網路多媒體研究所網路多媒體研究所36
Wideband CDMA Era
• 1995, WCDMA, CDMA2000• 2000, TD-SCDMA
![Page 37: 網路多媒體研究所 1 WCDMA Technology Past, Present and Future Part II: CDMA Technology Overview.](https://reader036.fdocuments.net/reader036/viewer/2022062321/56649eb55503460f94bbe9e5/html5/thumbnails/37.jpg)
網路多媒體研究所網路多媒體研究所37
I ntegrate and DumpUser 1 Data Detected Output
Spreading Code(User 1)
Despreading Code(User 1)
f
f
f
NarrowbandInterference
Other userInterference
Concept of Spread Spectrum
![Page 38: 網路多媒體研究所 1 WCDMA Technology Past, Present and Future Part II: CDMA Technology Overview.](https://reader036.fdocuments.net/reader036/viewer/2022062321/56649eb55503460f94bbe9e5/html5/thumbnails/38.jpg)
網路多媒體研究所網路多媒體研究所38
Definition of Spread Spectrum
• Spread spectrum is a mean of transmission in which the signal occupies a bandwidth in excess of the minimum necessary to send the information.
• Band spread is accomplished by means a code which is independent of the data, and a synchronized reception with the code at the receiver is used for despreading and subsequent data recovery.
![Page 39: 網路多媒體研究所 1 WCDMA Technology Past, Present and Future Part II: CDMA Technology Overview.](https://reader036.fdocuments.net/reader036/viewer/2022062321/56649eb55503460f94bbe9e5/html5/thumbnails/39.jpg)
網路多媒體研究所網路多媒體研究所39
Spread/Depread Spectrum• Spectrum After Spreading/Before Despreading
• Spectrum After Despreading/Before Spreading
frequency
… …BSS
BSS
BT frequency… …
![Page 40: 網路多媒體研究所 1 WCDMA Technology Past, Present and Future Part II: CDMA Technology Overview.](https://reader036.fdocuments.net/reader036/viewer/2022062321/56649eb55503460f94bbe9e5/html5/thumbnails/40.jpg)
網路多媒體研究所網路多媒體研究所40
Pseudorandom Codes
• The ideal spreading code would be an infinite sequence of equally likely random binary digits.
• In practice, periodic pseudorandom codes are used instead (PN codes).
• Specific PN codes include:– maximal-length code– Gold codes
![Page 41: 網路多媒體研究所 1 WCDMA Technology Past, Present and Future Part II: CDMA Technology Overview.](https://reader036.fdocuments.net/reader036/viewer/2022062321/56649eb55503460f94bbe9e5/html5/thumbnails/41.jpg)
網路多媒體研究所網路多媒體研究所41
Principle of S.S. (1/4)
1 -1 1 1 ...
1 1 -1 -1 -1 1 -1
1 1 -1 -1 -1 1 -1-1 -1 1 1 1 -1 11 1 -1 -1 -1 1 -11 1 -1 -1 -1 1 -1
......
1 1 -1 -1 -1 1 -1
積 分 器 7 -7 7 7 ...U ser 1 D a ta D etec ted O u tp u t
S p read in g C o d e(U ser 1 )
D esp read in g C o d e(U ser 1 )
![Page 42: 網路多媒體研究所 1 WCDMA Technology Past, Present and Future Part II: CDMA Technology Overview.](https://reader036.fdocuments.net/reader036/viewer/2022062321/56649eb55503460f94bbe9e5/html5/thumbnails/42.jpg)
網路多媒體研究所網路多媒體研究所42
-1 -1 -1 1 ...
1 -1 -1 -1 1 -1 1
-1 1 1 1 -1 1 -1-1 1 1 1 -1 1 -1-1 1 1 1 -1 1 -11 -1 -1 -1 1 -1 1
......
1 1 -1 -1 -1 1 -1
積 分 器 1 1 1 -1 ...U ser 2 D ata D etec ted O u tp u t
S p read in g C o d e(U ser 2 )
D esp read in g C o d e(U ser 1 )
Principle of S.S. (2/4)
![Page 43: 網路多媒體研究所 1 WCDMA Technology Past, Present and Future Part II: CDMA Technology Overview.](https://reader036.fdocuments.net/reader036/viewer/2022062321/56649eb55503460f94bbe9e5/html5/thumbnails/43.jpg)
網路多媒體研究所網路多媒體研究所43
1 -1 1 1 ...
1 1 -1 -1 -1 1 -1
0 2 0 0 -2 2 -2-2 0 2 2 0 0 00 2 0 0 -2 2 -22 0 -2 -2 0 0 0
......
1 1 -1 -1 -1 1 -1
積 分 器 8 -6 8 6 ...U ser 1 D ata D etec ted O u tp u t
S p read in g C o d e(U ser 1 )
D esp read in g C o d e(U ser 1 )
-1 -1 -1 1 ...
1 -1 -1 -1 1 -1 1S p read in g C o d e
(U ser 2 )
Principle of S.S. (3/4)
![Page 44: 網路多媒體研究所 1 WCDMA Technology Past, Present and Future Part II: CDMA Technology Overview.](https://reader036.fdocuments.net/reader036/viewer/2022062321/56649eb55503460f94bbe9e5/html5/thumbnails/44.jpg)
網路多媒體研究所網路多媒體研究所44
1 1 -1 -1 -1 1 -1 1 1 -1 -1 -1 1 -1
積 分 器U ser 1 D a ta D etec ted O u tp u t
S p read in g C o d e(U ser 1 )
D esp read in g C o d e(U ser 1 )
f
f
f
N arro w b an dIn te rfe ren ce
O th er u se rIn te rfe ren ce
Principle of S.S. (4/4)
![Page 45: 網路多媒體研究所 1 WCDMA Technology Past, Present and Future Part II: CDMA Technology Overview.](https://reader036.fdocuments.net/reader036/viewer/2022062321/56649eb55503460f94bbe9e5/html5/thumbnails/45.jpg)
網路多媒體研究所網路多媒體研究所45
Spreading/Despreading
Data
Spreading code
Spread signal= Data x code
Spreading code
Data = Spreadsignal x code
1
-1
1
-1
1
-1
1
-1
1
-1
Symbol
Chip
![Page 46: 網路多媒體研究所 1 WCDMA Technology Past, Present and Future Part II: CDMA Technology Overview.](https://reader036.fdocuments.net/reader036/viewer/2022062321/56649eb55503460f94bbe9e5/html5/thumbnails/46.jpg)
網路多媒體研究所網路多媒體研究所46
Block Diagram of a Typical S.S. System
Informationsource
Sourceencoder
{1,2,....,q}Encryptor
Channelencoder
Datamodulator
Spreadspectrummodulator
Poweramplification
(powerlimitation)
Informationsink
Sourcedecoder
DecryptorChanneldecoder
Datademodulator
Spreadspectrumdespreader
Receiverfrontend
Waveformchannel
(bandwidthlimitation)
Spreadingcode
generator
Timing andsynchronization
Discrete memoryless source
Noise
![Page 47: 網路多媒體研究所 1 WCDMA Technology Past, Present and Future Part II: CDMA Technology Overview.](https://reader036.fdocuments.net/reader036/viewer/2022062321/56649eb55503460f94bbe9e5/html5/thumbnails/47.jpg)
網路多媒體研究所網路多媒體研究所47
Advantages of Spread Spectrum
• Multiple access capability– Low cross-correlation of the code
• Protection against multipath interference– Frequency diversity
• Privacy– Only the user knows the spreading code
• (NB) Interference rejection– The code will spread the received interference
• Anti-jamming capability– The code will spread the received jamming
• Low probability of interception (LPI)– Low power spectrum density
![Page 48: 網路多媒體研究所 1 WCDMA Technology Past, Present and Future Part II: CDMA Technology Overview.](https://reader036.fdocuments.net/reader036/viewer/2022062321/56649eb55503460f94bbe9e5/html5/thumbnails/48.jpg)
網路多媒體研究所網路多媒體研究所48
Classification of CDMA
CDMA
Pure CDMA Hybrid CDMA
DS FH TH
Narrowband
Wideband
Fast FH
Slow FH
DS/FH DS/TH FH/TH DS/FH/TH TDMA/CDMA MC-CDMA
![Page 49: 網路多媒體研究所 1 WCDMA Technology Past, Present and Future Part II: CDMA Technology Overview.](https://reader036.fdocuments.net/reader036/viewer/2022062321/56649eb55503460f94bbe9e5/html5/thumbnails/49.jpg)
網路多媒體研究所網路多媒體研究所49
Time/Freq. Occupancy of DS, FH, and TH Signals
Freq
uenc
y
Time
Freq
uenc
y
Freq
uenc
y
Time Time
x
x
x
x x
x
DS FH TH
x
x
![Page 50: 網路多媒體研究所 1 WCDMA Technology Past, Present and Future Part II: CDMA Technology Overview.](https://reader036.fdocuments.net/reader036/viewer/2022062321/56649eb55503460f94bbe9e5/html5/thumbnails/50.jpg)
網路多媒體研究所網路多媒體研究所50
RAKE Receiver
![Page 51: 網路多媒體研究所 1 WCDMA Technology Past, Present and Future Part II: CDMA Technology Overview.](https://reader036.fdocuments.net/reader036/viewer/2022062321/56649eb55503460f94bbe9e5/html5/thumbnails/51.jpg)
網路多媒體研究所網路多媒體研究所51
Maximal Ratio Combining (MRC) in RAKE
• Radio channel consist of many multipaths• Each multipath change the amplitude and the phase of the transmitted signa
l• The data in QPSK signal is in phase• Energy splitted to many fingers detected by the mached filter• MRC corrects the phase with channel amplitude estimate
![Page 52: 網路多媒體研究所 1 WCDMA Technology Past, Present and Future Part II: CDMA Technology Overview.](https://reader036.fdocuments.net/reader036/viewer/2022062321/56649eb55503460f94bbe9e5/html5/thumbnails/52.jpg)
網路多媒體研究所網路多媒體研究所52
Challenges in CDMA System Design
• Soft Handover• Power Control
– Open loop– Closed loop (Inner and Outer loop)
• Code Design– Synchronization codes– Channelization codes– Scrambling codes
• Baseband Design– Synchronization (Frame/Slot/Symbol/Chip)– Searcher (find and maintain qualified paths)– AFC, AGC, and Clock Recovery– RAKE receiver (Channel estimation, RAKE fingers, and Maximal-ratio combini
ng)– Channel codec (convolutional codes, concatenated codes, turbo code
![Page 53: 網路多媒體研究所 1 WCDMA Technology Past, Present and Future Part II: CDMA Technology Overview.](https://reader036.fdocuments.net/reader036/viewer/2022062321/56649eb55503460f94bbe9e5/html5/thumbnails/53.jpg)
網路多媒體研究所網路多媒體研究所53
Conclusion:Features of S.S and CDMA
• Features of CDMA– High spectrum efficiency– Release from frequency management– Low mobile station transmit power– Soft-handover– Path Diversity (RAKE Fingers)– Security– Anti-jamming capability
• Features of Wideband Spreading– High and wide variety of data rates– Improvement of multipath resolution– Statistical multiplexing efficiency