CDMA System Basis
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Transcript CDMA System Basis
CDMA System Basis
ZTE 中兴 CDMA
Features of Wireless Telecomm
Individually
Bad propagation environment
Co-channel, Adjacent channel interference
and near-far effect.
Contradiction between limited frequency
resource and vast numbers of subscribers.
Complicated network and control
equipment are required.
ZTE 中兴 CDMA
Classification of Wireless
Telecomm
Classification
Mode
RF Operation
Class
Simplex, half-duplex, duplex
Signal
Analog, Digital
Modulation
FM, PM, AM
Multiple
Access
FDMA, TDMA, CDMA
ZTE 中兴 CDMA
ZTE 中兴 CDMA
Frequency Reuse
ZTE 中兴 CDMA
Evolution of Wireless Telecomm
1G
2G
3G
Analog
Digital
Digital
Voice
Voice & Data
AMPS
CDMA
Voice &
h i g h -s p ee d
Data
CDMA2000
TACS GSM/TDMA GPRS
1980’s
1992
1999
W_CDMA
2001 2003
ZTE 中兴 CDMA
Makeup of Wireless Telecomm
BSS
MS
BTS
MS
BTS
BTS
BSC
VLR
HLR
MSC
PSTN
MS
ISDN
BTS
BTS
BTS
MS
Um
Abis
BSC
A
MS: Mobile Station
BSS: Base Station
System
BTS: Base-station
Transceiver System
BSC: Base_Station
Controller
MSC:Mobile-service
Switching Center
VLR:Visiting Location
Register
HLR:Home Location
Register
PSTN:
ISDN:
MSC
ZTE 中兴 CDMA
Spectrum Spreading Technique
Theoretical Basis is Shanon equation
C=B*log2(1+S/N)
DSSS applied in CDMA
Used in military communication in 1950’s
and 1960’s
Qualcomm company successfully put it
into commercially cellular wireless
telecommunication by the end of 1980’s
ZTE 中兴 CDMA
Signal processing by DSSS
ZTE 中兴 CDMA
Features of CDMA System（1）
Large capacity
8~10 times of analog system
High-quality service
8Kb/s QCELP EQUALS 13Kb/s of GSM;
13Kb/s QCELP EQUALS 64kb/s of wireline
Soft handoff lowers call drop rate
RAKE receiving overcomes multi-path
fading
Good secrecy
ZTE 中兴 CDMA
Features of CDMA System （2）
Soft capacity
MS’s averaging transmission power is
lowered, decreasing radiation to human
body and environment . Be named as
“Green Handset”
Easy to realize dual-mode operation
System complexity increased
ZTE 中兴 CDMA
Key techniques of CDMA （1）
Diversity receiving
Time diversity——interleaving, error-detection
and correction
Frequency diversity——inherent feature of
wideband communication
Space diversity——multiple antenna receiving,
RAKE receiving, soft handoff
ZTE 中兴 CDMA
Key techniques of CDMA （2）
Precise power control
Open loop power control on reverse link
Closed loop power control on reverse link
Outer loop power control on reverse link
Power control on forward link
ZTE 中兴 CDMA
Key techniques of CDMA （3）
Rate variable codec (QCELP)
VOICE Detection (VOD)
Synchronization
Mobile assisted soft handoff
ZTE 中兴 CDMA
Key techniques of CDMA （4）
Blossoming & Wilting
Low Eb/No and high redundant error
correction encoding
Multiple access：long PN code, short PN
code and WALSH orthogonal code
ZTE 中兴 CDMA
Channel structure
Forward Channels
Piloting channel
Synchronizing channel
Paging channel
Traffic channel
Reverse Channels
Access channel
Traffic channel
ZTE 中兴 CDMA
CDMA Cell Sit e
Pilo t
Forw ard
Traf fic Channel
Sync
Forw ard Traf fic
Channel
Paging
Forward Traff ic
Channel
Walsh Code Assignment
0 -> Pilot
32 -> Sync
1-7 -> Paging(s)
rem. -> Fwd. Traffic
ZTE 中兴 CDMA
IS-95A Channel Modulation--Forward Link
Walsh
Functio n 0
Pilot
Channe l
(All 0’s)
A
Co de
Symbol
Sync
Channe l
Bits
1.2 kbps
Modulatio n
Symbol
Co nvolutio nal
Enco de r
2.4 ksps
r = 1/2, K = 9
Symbol
Repetitio n
4.8 ksps
Co de
Symbol
Paging
Channe l
Bits
9.6 kbps
4.8 kbps
Blo ck
Interle aver
Modulatio n
Symbol
Co nvolutio nal
Enco de r
19.2 ksps
r = 1/2, K = 9
9.6 ksps
Symbol
Repetitio n
19.2 ksps
Walsh
Functio n 32
Modulatio n
Symbol
A
4.8 ksps
Walsh
Functio n p
Modulatio n
Symbol
Blo ck
Interle aver
A
19.2 ksps
19.2 ksps
Long Co de
Mask for
Paging
Channe l p
Forw ard Traffic
Channe l co de
channe l
Informatio n
Bits for User m
w ith Rate Se t 1
(172, 80, 40, or
16 bits/frame )
8.6
4.0
2.0
0.8
Add Frame
Quality Indicators (12, 8, 0, or
kbps
0 bits/frame)
kbps
kbps
kbps
Add 8-bit
Enco de r Tail
per Frame
9.6
4.8
2.4
1.2
Long Co de
Ge ne rator
1.2288 Mcps
Co de
Symbol
Co nvolutio nal
Enco de r
kbps r = 1/2, K = 9 19.2 ksps
kbps
9.6 ksps
kbps
4.8 ksps
kbps
2.4 ksps
Pow er
Co ntrol
Bits
De cimator
Modulatio n
Symbol
Symbol
Repetitio n
19.2 ksps
Walsh
Functio n n
800 bps
Modulatio n
Symbol
MUX *
A
Blo ck
Interle aver 19.2 ksps
19.2 ksps
Long Co de
Mask for
Use r m
Long Co de
Ge ne rator
1.2288 Mcps
De cimator
800 Hz
De cimator
* Pow er contro l bits are not multiple xed in for suppe mental code channels of
the Forw ard Traffic Channels
ZTE 中兴 CDMA
Procedure of MS’s COMMUNICATION
Searching base station’s pilot channel
Demodulating synchronizing channel
MS requests on access channel
BS responds on paging channel
Traffic channel is assigned for
communication
ZTE 中兴 CDMA
Task Initialization
Start analog mode
End analog mode
MS idle changeover
when
NGHBR_CONFIG
is”011”
Power On
MS
Initial
Status
MS fully catches
System timing
MS idle
status
MS paged,
originating or
registering
Access channel
confirmation
System
access
status
End traffic channel
Indication of traffic
channel
Notes：not all are listed out
MS in traffic
Channel
status
ZTE 中兴 CDMA
ZXC10-BSS System structure-BSC
BSC: Base_Station Controller
BTS:
Base-station
Transceiver
System
NCM: Network Control Module
HIRS:
High-speed
Interconnect
Router Subsystem
CDSU: Channel/Digital Service Unit
TCM: Timing Control Module
SVM: Selector Vocoder Module
SVICM: Selector Vocoder Interface
Control Module
CPM: Call Process Module
OMC: Operation & Maintenance
Center
ZTE 中兴 CDMA
ZXC10-BSS System structure-BTS
Gps or
Glonass
TCM
TRx
HPA
RFE
RFIM
CHM
CHM
CHM
BTS
...
HIRS
CCM
BTM
BTS: Base-station Transceiver System
CHM: Channel Processing Module
CCM: Communication Control Module
HIRS: High-speed Interconnect
Subsystem
TCM: Timing Control Module
RFIM: RF Interface Module
TRx: Transceiver
HPA: High Power Amplifier
RFE: RF Front End
CDSU: Channel/Digital Service Unit
BTM: Base-station Test Module
BSC: Base-station Controller
Router
CDSU
ATM or E1
Other BTS
BSC
ZTE 中兴 CDMA
ZXC10_BSS System
Specification-BSC
Maximal BTS supported: 512
Vocoder：7200
Maximal Channels (including payoff and soft handoff):512 X 32 = 16384
Maximal traffic channels: 512 X 20 = 10240
Maximal subscribers: 102,500*
BTS side traffic：2,930 Erl*
BHCA：125,000*
Traffic：1.28BHCA/subscriber
ZTE 中兴 CDMA
ZXC-10 BSS-transition to 3G
IS95 A
Features:
IS95 B
Capacity
increased
Non-symmetrical
data service
provided
For:64Kb/s
Rev:14.4Kb/s
Backward
compatible with
95A
CDMA2000 1X
CDMA2000 3X
Capacity doubled Data service
(relative to 95A)
384Kb/s
2Mb/s(max)
Data service
144Kb/s
Backward
compatible with
307.2Kb/s(max)
95A/B/1X
Backward
compatible with
95A/B
ZTE 中兴 CDMA