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CDMA Technologies
for Cellular Phone System
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Contents
1. Introduction
2. Spread Spectrum Technology
3. DS-CDMA
4. Spreading Codes5. Features of CDMA
RAKE Receiver
Power Control
Frequency Allocation Soft Handoff
6. Conclusion
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Introduction:
Overview of Cellular systems
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Evolution of Cellular Systems
1st.Generation
(1980s)Analog
NMT CT0TACS CT1
AMPS
3rd. Generation
(2000s)2nd. Generation
(1990s)Digital
GSM DECT
DCS1800 CT2
PDC PHS
IS-54IS-95
IS-136
UP-PCS
IMT-2000
CDMA2000W-CDMA
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Major Operators of Cellular Phone Services
in Japan
Operator2G 3G
FrequencyRemarks for 3G handset
KDDI/au800 MHz(1.5GHz
For Tu-Ka)
800MHz
2GHz
CDMA2000 1xCDMA2000 1x EV-DO
backward compatibilitywith 2G (cdmaOne)
NTT DoCoMo800 MHz1.5GHz
2GHzW-CDMA singleW-CDMA/PDC Dual
vodaphone 1.5 GHz 2GHzW-CDMA singleW-CDMA/GSM Dual
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Japans Cellular Subscriber GrowthRecord
0
20
40
60
80
100
95 96 97 98 99 00 01 02 03 04 05
No.ofSubscribers(M
illion)
end December of Year
end Nov2005
89,679K
cdmaOne/CDMA2000 1x/
EV-DO21222K
PDC (TDMA)47,787K
W-CDMA20,670K
PDC
AnalogcdmaOne/CDMA2000 1x/EV-DO
W-CDMA
/Nov.
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Requirements for 3G mobile systems
High Capacity
Tolerance for interference
Privacy Tolerance for fading
Ability to various data rate
transmission Flexible QoS
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IMT-2000 systems approved by ITU-R
Popular
name
Access
method
Body of
Technical
Spec
production
IMT-DS IMT-MC IMT-TC IMT-SC IMT-FT
(Direct Sequence) (Multi Carrier) (Time Code) (Single Carrier) (Frequency Time)
W-CDMA CDMA2000
UTRA-TDD
UWC-136 DECT
CDMA-FDD CDMA-TDDCDMA-FDD TDMA-TDDTDMA-FDD
3GPP(FDD 3GPP2 3GPP(TDD)
CWTS
IS-136 DECT
ESTIESTI TIA
TTA
T1
CWTS
ARIB/TTC ARIB/TTC
CWTS
TTA
ESTI
TTA
T1
CWTS
TIA
Approved in 2000 as ITU-R M.1457
TD-CDMA
TD-SCDMA
Organization
Partners
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Duplex & Multiple Access Methods
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Duplex Methods of Radio Links
Mobile Station
Base Station
Forward link
Reverse link
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Frequency Division Duplex (FDD)
Forward link frequency and reverse link frequency is
different
In each link, signals are continuously transmitted in
parallel.
Mobile Station
Base Station
Forward link (F1)
Reverse link (F2)
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Time Division Duplex (TDD)
Forward link frequency and reverse link frequency is
the same.
In each link, signals are incontinuously transmitted
by turns just like a ping-pong.
Mobile Station
Base Station
Forward link (F1)
Reverse link (F1)
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Example of FDD systems
Transmitter
Receiver
BPF: Band Pass Filter
BPF
BPF
Transmitter
Receiver
BPF
BPF
F1
F2 F1
F2
Mobile Station Base Station
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Example of TDD Systems
Transmitter
Receiver
BPF: Band Pass Filter
BPF
Transmitter
Receiver
BPF
F1 F1
Mobile Station Base Station
Synchronous Switches
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Multiple Access Methods
Mobile Station
Base Station
Mobile StationMobile Station
Mobile Station
Forward linkReverse link
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FDMA Overview
A A
B B
C C
Time
f2
f1
f0
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TDMA Overview
C B A C B A C B A C B A
C
A
B
Time
f0
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What is CDMA ?
Sender Receiver
Code A
A
Code B
B
AB
AB
CB
C
A
Code A
AB
C
Time
BC
B
A
Base-band Spectrum Radio Spectrum
spread spectrum
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Summary of Multiple Access
FDMA
TDMA
CDMA
power
power
power
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Spread Spectrum Technology
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Spread Spectrum & Shannons Capacity Theorem
Capacity = Bandwidth x log2 (1 + SNR). more bandwidth and the better the signal to
noise ratio, the more bits per second you can
push through a channel
Capacity/Bandwidth = 1.44 x SNR.
If we can find a way of encoding our data into
a large signal bandwidth, then we can get
error free transmission under conditionswhere the noise is much more powerful than
the signal we are using.
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How to spread spectrum...
Direct Sequence (DS)
Modulation
(primary modulation)
user data
Spreading
(sec
ondary
mod
ulation)
Tx
Base-band
Frequency
Power
Density
Radio
Frequency
Power
Density
TIME
data rate
10110100
spreading sequence
(spreading code)
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EXOR Truth Table
INPUT
A B
OUTPUT
A XOR B
0 0 0
0 1 1
1 0 1
1 1 0
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Demodulating DS Signals (1/2)
If you know the correct spreading sequence (code) ,
Radio
Frequency
Power
Density
Accumulate for
one bit duration
Demodulated data
Base-band
Frequency
gatheringenergy !
spreading sequence(spreading code)
1011010010110100 10110100
received signal
TIME
0100101110110100 10110100
0 01
1111111100000000 00000000
0+0=0
1+0=1
0+1=11+1=0
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Demodulating DS Signals (2/2)
If you dont know the correct spreading sequence (code)
Base-band
Frequency
received signal
spreading sequence
(spreading code)
Accumulate for
one bit duration
Demodulated data
Radio
Frequency
Power
Density
1010101010101010 10101010
TIME
0100101110110100 10110100
No data can be detected
- --
1011010010110100 10110100
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Feature of SS
Privacy, Security
RadioFrequency
Power
Density
Power density of SS-signals would be lower than the noise density.
transmitted SS-signal
Noise
Power
Density
RadioFrequency
Noise
received signal de-
modulator
Base-bandFrequency
Power
DensityWith incorrect code
(or carrier frequency),SS-signal itselfcannot be detected.
Other system cannot recognize the existence ofcommunication, because of signal behind the noise.
With correct code(and carrier frequency),data can be detected.
Base-bandFrequency
Power
Density
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DS-CDMA
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Freq.Freq.
BPFDespreader
Code B
Freq.Freq.
BPFDespreader
Code A
DS-CDMA System Overview
(Forward link)
CDMA is a multiple spread spectrum.
Difference between each communication path is only the spreading code
Data B
Code B
BPF
Freq.Freq.
Data A
Code A
BPF
Freq.Freq.
MS-A
MS-B
BS
Data A
Data B
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Freq.Freq.
BPFDespreader
Code B
Freq.Freq.
BPFDespreader
Code A
DS-CDMA System Overview
(Reverse Link)
CDMA is a multiple spread spectrum.
Difference between each communication path is only the spreading code
Data B
Code B
BPF
Freq.Freq.
Data A
Code A
BPF
Freq.Freq.
MS-B
MS-A
BS
Data A
Data B
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Spreading Code
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Cross-Correlation
Cross-Correlation
between Code A and Code B = 6/16
Self-Correlation
for each code is 1.
one data bit duration
Spreading Code A
1 0 01 1 1 0 0 10 1 0 1 0 0 1
one data bit duration
Spreading Code A
1 0 01 1 1 0 0 10 1 0 1 0 0 1
Spreading Code A
1 0 01 1 1 0 0 10 1 0 1 0 0 1
0 0 00 0 0 0 0 00 0 0 0 0 0 0
Spreading Code B
1 0 01 1 0 0 1 11 0 0 1 0 1 1
0 0 00 0 1 0 1 01 1 0 0 0 1 0
0+0=0
1+0=1
0+1=1
1+1=0
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Preferable Codes
In order to minimize mutual interference in DS-CDMA , the spreading
codes with less cross-correlation should be chosen.
Synchronous DS-CDMA :Orthogonal Codes are appropriate. (Walsh code etc.)
Asynchronous DS-CDMA : Pseudo-random Noise (PN) codes / Maximum sequence Gold codes
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Three types of codes used in CDMA- 1/2
WALSH Codes- Walsh codes (64 bit long) originate
from orthogonal Walsh-Hadamard functions or
orthogonal Walsh-Hadamard matrices. The Walsh
codes offer an ideal orthogonal property if they are used
in a synchronous channel (e.g. the forward link or downlink in an IS-95A system), such that auto-
correlation of a code is one and cross-correlation
between any two codes is zero.
SHORT codes - In addition to the Walsh codes, the
CDMA standard also uses a short PN code, or simply
short code, which is a 16-bit short PN code used to
identify the different BSs and thus the cells where the
BSs are located
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LONG PN CODES- The Long Codes are 242 bits long andrun at 1.2288 Mb/s. It is used to both spread the signal andto encrypt it. A cyclically shifted version of the long code isgenerated by the cell phone during call setup. The shift iscalled the Long Code Mask and is unique to each phonecall. CDMA networks have a security protocol called CAVE
that requires a 64-bit authentication key, called A-key andthe unique ESN . The network uses both of these to createa random number that is then used to create a mask for the long code used to encrypt and spread each phonecall..
There is a Public long code and a Private long code. The
Public long code is used by the mobile to communicatewith the base during the call setup phase. The private longcode is one generated for each call then abandoned afterthe call is completed
Three types of codes used in CDMA- 2/2
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CDMA Reverse Link
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Offset-QPSK
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OQPSK
Taking four values of the phase (two bits) at atime to construct a QPSK symbol can allow thephase of the signal to jump by as much as 180rat a time. When the signal is low-pass filtered
(as is typical in a transmitter), these phase-shiftsresult in large amplitude fluctuations, anundesirable quality in communication systems.
Delaying the odd-bit data stream by a one-half-bit interval with respect to the even bit producesOQPSK modulation. This offset reduces therange of phase transitions to 0rand 90r,
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QPSK Vs OQPSK
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Synchronous DS-CDMA
Forward Link
(Down Link)
Synchronous Chip Timing
A
A
Signal for B Station(after de-spreading)
Less Interference for A station
Synchronous CDMA Systems realized in Point to Multi-point System.
e.g., Forward Link (Base Station to Mobile Station) in Mobile Phone.
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Asynchronous DS-CDMA
In asynchronous CDMA system, orthogonal codes produce badcross-correlation.
Reverse Link
(Up Link)
BA
Signal for B Station(after re-spreading)
Big Interference
from A station
Asynchronous Chip Timing
Signals from A and B areinterfering each other.
A
B
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Features of CDMA
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Mobile Propagation Environment
Multi-path Fading
The peaks and bottoms of received powerappear, in proportion to Doppler frequency.
Base Station (BS)Mobile Station (MS)
multi-path
propagationPath Delay
Power
path-2
path-2path-3
path-3
path-1
path-1
Time
Powe
r
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Fading in non-CDMA System
Path Delay
Power path-1
path-2
path-3
With low time-resolution, different signalpaths cannot be discriminated.
These signals sometimes strengthen, andsometimes cancel out each other,depending on their phase relation.
This is fading. In this case, signal quality is damaged
when signals cancel out each other.
In other words, signal quality is dominatedby the probability for detected power to beweaker than minimum required level.
Time
Power
Detected Power
In non-CDMA system, fading damages signal quality.
Required signal level
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Fading in CDMA System ...
As the CDMA system has high time-resolution,different path delay of CDMA signals can bediscriminated.
Energy from all paths can be summed by adjustingtheir phases and path delays.
This is a principle ofRAKE receiver.Path Delay
Power path-1
path-2
path-3
CDMAReceiver
CDMAReceiver
Synchro
nization
Ad
der
CODE Awith timing ofpath-1
Path Delay
Power path-1
Power
path-1
path-2
path-3
CODE Awith timing ofpath-2 Path Delay
Power
path-2
interference produced by path-2 and path-3
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Fading in CDMA System (continued)
In CDMA system, multi-path propagation improves
the signal quality by adopting RAKE receiver.
Time
Power
Detected Power
RAKEreceiver
Power
path-1
path-2
path-3
Detected power of CDMAsignal will be less fluctuated
by combining all energy
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Near-Far Problem
CODE B
CDMA
Transmitter
DATA B
CODE A
CDMA
ReceiverCODE A
CDMA
Transmitter
DATA A
P
Desired Signal Power = P/Lp-a
Interfered Signal Power = P/Lp-b/G
G: processing gain
Demodulated DATA
P
Lp-a
Lp-b
When user B is close to the receiver and user A is far
from the receiver, Lp-a could be much bigger than Lp-b.
In this case, desired signal power is smaller than the
interfered power.
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Power Control...
TimeDetecte
dPower
from A
from B
As the propagation losses between BS and MSs are different according toindividual communication distances, the received levels at the base stationare different from each other when all mobile stations transmit their signalsat the same power.
Moreover, the received level fluctuates quickly due to fading.
In order to maintain the strength of received signal level at BS, power control
technique must be employed in CDMA systems.
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Power Control (continued)
Open Loop Power Control Closed Loop Power Control
estimating pathloss
calculatingtransmission
power
transmitmeasuringreceived power
transmit receive
decidetransmission
power
transmit measuringreceived power
power controlcommand
about 1000 timesper second
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Effect of Power Control
TimeDetect
edPower
from MS Bfrom MS A
Effect of Power Control
Power control is capable of compensating the fading fluctuation.
Received power from all MS are controlled to be equal.
Near-Far problem is mitigated by the power control.
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Frequency Allocation (1/2)
In FDMA or TDMA, radio resource is allocated not to be interferedamong neighbor cells.
f1f2
f3f4
f5f6
f7
cell : a cell means covered area by one base station.
Neighbor cells cannot use thesame (identical) frequency band(or time slot).
The left figure shows the simplecell allocation with sevenfrequency sub-bands.
In actual situation, it is difficult toallocate the frequency (or time
slot) appropriately because ofcomplicated radio propagationand irregular cell allocation.
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Frequency Allocation (2/2)
In the CDMA system, identical radio resource can be allocated
among all cells as explained in Introduction.
Frequency allocation in
CDMA is not necessary.
In this sense, CDMA
cellular system is easy to
be designed.
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Soft Handover (1/2)
Handover :Cellular system tracks mobile stations in order to maintain their communication links.
When mobile station goes to neighbor cell, communication link switches from currentcell to the neighbor cell.
Hard Handover :
In FDMA or TDMA cellular system, a new communication link is established afterbreaking the current communication link by hard handover.
Communication between MS and BS instantaneously breaks by switching a frequencyor a time slot.
Hard handover: make connection (new cell B) after break (old cell A)
switching
Cell B Cell A
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Soft Handover (2/2)
Cell B Cell A
Soft handover : break (old cell A) after make connection (new cell B)
BS A and BS B transmit the same
signal to the MS simultaneously
In CDMA cellular system, communication link keeps a connection even inthe handover procedure. Because the system does not require the
frequency or time slot switching.
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Conclusion
CDMA is based on the spread spectrum technology
which has been used in military field.
CDMA cellular system has many advantages
compared with the FDMA and TDMA cellular
systems.
CDMA system was adopted as the international
standard for the 3rd generation mobile
communications.
The number of CDMA users will dramaticallyincrease in the next five years all over the world.
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Forward channel link structure
The forward channel includes :
1. Pilot channel- Walsh code 0 repeated every
26.66 msec
2. Sync channel Walsh code 323. Paging Channels Walsh codes 1-7
4. Rest of the codes are used as Traffic
channels each trafffic channels carries a
fundamental traffic channel informationalong with the concerned power control
information.
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Frequency Reuse and Large
Capacity
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Comparison between CDMA & GSM System (1)
Cell Coverage - CDMA: varies with traffic load No load: 3 GSM coverage
20 channels/sector: 2 GSM coverage
GSM: coverage not affected by traffic load
Number of BTS
CDMA=20% GSM
1000 km2 coverage: CDMA 45 BTS, GSM 200
BTS
Capacity:
CDMA=5 GSM=10 AMPS
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Voice quality: vocoder
CDMA 8K> GSM 13K, CDMA 13K approaches
64K PCM
Handoff
CDMA : soft handoff, GSM: hard handoff,
more dropped calls
Network Planning and Expansion
CDMA : simple ( N=1), GSM: more
complicated (N=4/7)
Comparison between CDMA & GSM System (2)
13
2
4
3
2
4
2
4
4
1
2
3
14
2
3
1
4
GSMN4 CDMAN1
11
1
11 1
1
11
1
1
1
1
1
1
1
11
1
11
1
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Spread Spectrum
Ensures high transmission and voice quality, security
Short PN, long PN and Wash codes are used for coding Multiple Access
Code Division:Improve frequency reuse and guarantee largecapacity
Soft Handoff
Seamless communication without call dropping High communication quality
Power Control
Ensure optimum power level with least interference to otherchannels, reducing Near and Far Effectand thus increasingcapacity
Low radiation and longer battery usage time
Diversity Receiver (Rake Receiver)
Achieve signal gain and avoid Multi-path Effect
Voice Activation- Lower transmitting power and low speed
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Spread Spectrum-Basis for CDMA Technology
Spread spectrum technique ,employ a transmissionbandwidth that is several orders of magnitude greater
than the minimum required signal bandwidth.
Theoretic Basis: Shannons Law C=Blog2(1+S/N)
C: Channel Capacity B: bandwidth S/N:
signal to noise ratio
Conclusion: When C is a fixed value, S/N is a
reciprocal ratio of B
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Traditional radio communication systems
transmit data using the minimum bandwidth
required to carry it as a narrowband signal,
e.g. FDMA and TDMA systems.
TRADITIONAL COMMUNICATIONS SYSTEM
SlowInformationSent
TX
SlowInformationRecovered
RX
NarrowbandSignal
Spread Spectrum Principles
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SHANON Formula
C = Blog2(1+S/N)
Spread Spectrum Principles (Continued)
Where,C is capacity of channel, b/s
B is signal bandwidth, Hz
S is average power for signal, W
N is average power for noise, W
It is the basic principle and theory for spreadspectrum communications.
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Direct-Sequence Spread spectrum systems mixtheir input data with a fast spreading sequence andtransmit a wideband signal
The spreading sequence is independentlyregenerated at the receiver and mixed withthe incoming wideband signal to recover theoriginal data
SPREAD-SPECTRUM SYSTEM
FastSpreadingSequence
SlowInformation
Sent
TX
SlowInformationRecovered
RX
FastSpreadingSequence
WidebandSignal
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The de-spreading gives substantial gain
proportional to the bandwidth of the spread-
spectrum signal The gain can be used to increase system
performance and range, or allow multiple codedusers, or both
Processing Gain For SPREAD-SPECTRUM SYSTEM
Gp=10log(B/Bm)
Where, Gp is processing gain, dB, B is spreading signalbandwidth, Hz , Bm is original signal bandwith, Hz
E.g., it is 21 dB for IS-95A CDMA system.
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Basic Spreading & DeSpreading
Example
User Data Spread, Sent, Recovered
XORExclusive-OR
Gate
1
1
Input A: Received Signal
Input B: Spreading Code
Output: User Original Data
Input A: User Data
Input B: Spreading Code
Spread Spectrum Signal
XORExclusive-OR
Gate
At Originating Site: Input A: Users Data @
19,200 bits/second
Input B: Walsh Code #23 @
1.2288 Mcps Output: Spread spectrum
signal
At Destination Site: Input A: Received spread
spectrum signal Input B: Walsh Code #23 @
1.2288 Mcps
Output: Users Data @19,200 bits/second just asoriginally sent
via airinterface
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Antenna Antenna
Channel Coding
SS
Carrier
Modulation
DS-PN
Radio
ChannelSource
Coding
Channel
DecodingCarrier
Demodulation
DS-PN
Source
Decoding
Transmit Receive
Channel
Decoding
Carrier
Demodulation
DS-PN
Radio
ChannelSource
Decoding
Channel
Coding
SS
Carrier
Modulation
DS-PN
Source
Coding
TransmitReceive
A B
Spread Spectrum1
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f
Sf
f0
Signal Frequency Before Decoding
f
Sf
f0Signal Frequency Before SS
Signal
Signal
Noise
f
Sf
f0Signal Frequency after SS
Signal
f
Sf
f0
Signal Frequency After Decoding
Signal
Noise
Signal Pulse Noise Other Noise
Spread Spectrum (2)
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Spread Spectrum (3)- Spreading Codes
Spreading Code Rate: 1.2288Mc/s
Multi-path separation,(delay:1--100s)
Delay1 MHZMultiples of base band rate 9.6 kbps
Spreading CodesForward : Walsh code
Reverse: Long PN Codes (242-1)
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Spread Spectrum (4)
Advantages: Avoid interference arising from jamming signal or
multi-path effects
SS and demodulation, noise is
suppressed and filtered Security: difficult to detect
Privacy: Difficult to demodulate
Multiple Access:
Improve Frequency Reuse
Enlarge Capacity
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CDMA Spreading Principle
Any data bitstream can be combined with a spreading
sequence
The resulting signal can be de-spreading and the datastream recovered if the original spreading sequence isavailable and properly timed
After de-spreading, the original data stream is recoveredintact
ORIGINATING SITE DESTINATION
SpreadingSequence
SpreadingSequence
InputData
RecoveredData
Spread Data Stream
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Multiple spreading sequences can be applied in successionand then reapplied in opposite order, to recover the original
data stream - the spreading sequences can havedifferent desired properties
All spreading sequences originally used must be availablein proper synchronization at the recovering destination
Multiplesuccessive sequencearereversible
SpreadingSequence
A
SpreadingSequence
B
SpreadingSequence
C
SpreadingSequence
C
SpreadingSequence
B
SpreadingSequence
A
InputData
X
RecoveredData
X
X+A X+A+B X+A+B+C X+A+B X+ASpread-Spectrum Chip Streams
ORIGINATING SITE DESTINATION
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Code Division Multiple Access (1)
Orthogonal Walsh function
Forward link: Spreading and building of coded
channels
Reverse link: orthogonal modulation of MS signal
Long PN Code ( cycle length: 2421)
Forward link: identification of MS
Reverse link: Spreading and user MS identification
Short PN Code (cycle length: 215-1)
Forward and Reverse link: both for orthogonal QPSKmodulation, with different phase for different BS and
identical phase for different MS (0 offset)
C d Di i i M lti l A (2)
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Forward Link Pilot: continuous transmission, for synchronization
and handoff, no message
Synchronization : for the mobile to capture initial
timing or synchronization when initializing
Paging Channel: for the transmission of system
message and paging message, registration and traffic
channel assignment
Forward Traffic Channel: transmission of voice, data
and related signalling
Reverse Link
Access : used for initiating communication with BS
Code Division Multiple Access (2)
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Code Division Multiple Access (3)
Traffic
UsertrafficMS powercontrol
Sub-channel
Forward CDMA
Channels
Pilot Sync. Paging Paging Traffic Traffic
W0 W32 W1 W7 W8 W62 W63
Reverse CDMA
Channels
Access Access Traffic Traffic Traffic
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CDMA Spreading Code
64Sequences,each 64 chipslong
Each Walsh Codeis preciselyOrthogonal withrespect to allotherWalshCodes
Walsh Code
EXAMPLE:Correlation of Walsh Code #23 with Walsh Code #59
#23 0110100101101001100101101001011001101001011010011001011010010110
#59 0110011010011001100110010110011010011001011001100110011010011001
Sum 0000111111110000000011111111000011110000000011111111000000001111
Correlation Results: 32 1, 32 0: Orthogonal!!
Unique Properties:
Mutual Orthogonality
WALSH CODES# ---------------------------------- 64-Chip Sequence ------------------------------------------
0 00000000000000000000000000000000000000000000000000000000000000001 0101010101010101010101010101010101010101010101010101010101010101
2 00110011001100110011001100110011001100110011001100110011001100113 01100110011001100110011001100110011001100110011001100110011001104 00001111000011110000111100001111000011110000111100001111000011115 0101101001011010010110100101101001011010010110100101101001011010
6 00111100001111000011110000111100001111000011110000111100001111007 01101001011010010110100101101001011010010110100101101001011010018 00000000111111110000000011111111000000001111111100000000111111119 0101010110101010010101011010101001010101101010100101010110101010
10 001100111100110000110011110011000011001111001100001100111100110011 011001101001100101100110100110010110011010011001011001101001100112 000011111111000000001111111100000000111111110000000011111111000013 0101101010100101010110101010010101011010101001010101101010100101
14 001111001100001100111100110000110011110011000011001111001100001115 011010011001011001101001100101100110100110010110011010011001011016 000000000000000011111111111111110000000000000000111111111111111117 0101010101010101101010101010101001010101010101011010101010101010
18 001100110011001111001100110011000011001100110011110011001100110019 011001100110011010011001100110010110011001100110100110011001100120 000011110000111111110000111100000000111100001111111100001111000021 0101101001011010101001011010010101011010010110101010010110100101
22 001111000011110011000011110000110011110000111100110000111100001123 011010010110100110010110100101100110100101101001100101101001011024 000000001111111111111111000000000000000011111111111111110000000025 0101010110101010101010100101010101010101101010101010101001010101
26 001100111100110011001100001100110011001111001100110011000011001127 011001101001100110011001011001100110011010011001100110010110011028 000011111111000011110000000011110000111111110000111100000000111129 0101101010100101101001010101101001011010101001011010010101011010
30 001111001100001111000011001111000011110011000011110000110011110031 011010011001011010010110011010010110100110010110100101100110100132 000000000000000000000000000000001111111111111111111111111111111133 0101010101010101010101010101010110101010101010101010101010101010
34 001100110011001100110011001100111100110011001100110011001100110035 011001100110011001100110011001101001100110011001100110011001100136 000011110000111100001111000011111111000011110000111100001111000037 0101101001011010010110100101101010100101101001011010010110100101
38 001111000011110000111100001111001100001111000011110000111100001139 011010010110100101101001011010011001011010010110100101101001011040 000000001111111100000000111111111111111100000000111111110000000041 0101010110101010010101011010101010101010010101011010101001010101
42 001100111100110000110011110011001100110000110011110011000011001143 0110011010011001011001101001100110011001011001101001100101100110
44 000011111111000000001111111100001111000000001111111100000000111145 0101101010100101010110101010010110100101010110101010010101011010
46 001111001100001100111100110000111100001100111100110000110011110047 011010011001011001101001100101101001011001101001100101100110100148 000000000000000011111111111111111111111111111111000000000000000049 0101010101010101101010101010101010101010101010100101010101010101
50 001100110011001111001100110011001100110011001100001100110011001151 011001100110011010011001100110011001100110011001011001100110011052 000011110000111111110000111100001111000011110000000011110000111153 0101101001011010101001011010010110100101101001010101101001011010
54 001111000011110011000011110000111100001111000011001111000011110055 011010010110100110010110100101101001011010010110011010010110100156 000000001111111111111111000000001111111100000000000000001111111157 0101010110101010101010100101010110101010010101010101010110101010
58 001100111100110011001100001100111100110000110011001100111100110059 011001101001100110011001011001101001100101100110011001101001100160 000011111111000011110000000011111111000000001111000011111111000061 0101101010100101101001010101101010100101010110100101101010100101
62 001111001100001111000011001111001100001100111100001111001100001163 0110100110010110100101100110100110010110011010010110100110010110
Hn Hn
H2n = ___Hn Hn
0110
1100
1010
0000
10
000
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CDMA Spreading Code(Continued)
Short Code The PN Sequence is
32,768(215) chips long
a two-dimensional binarysector with distinct I andQ component
sequences, each 32,768chips long
The PN Sequence (and anysequence) correlates withitself perfectly if compared ata timing offset of 0 chips
The Short PN Sequence isspecial: Orthogonalcompared with itself using anypossible timing offset otherthan 0
IQ
I
QI
Q
Total Correlation: All bits = 0
Short PN Sequence vs. Itself @ 0 Offset
I
QI
Q
Orthogonal: 16,384 1 + 16,384 0
Short PN Sequence vs. Itself @ Any Offset
U
niqu
e Properties:
32,768 chips long26.666 ms.
(75 repetitions in 2 sec.)
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CDMA Spreading Code(Continued)
Summary ofCharacteristics & Functions
Walsh Code
Short Code
Long Code
Type of Sequence
MutuallyOrthogonal
Orthogonal withitself at any timeshift value
near-orthogonalif shifted
Special Properties
64
1
1
HowMany
64 chips1/19,200 sec.
32,768 chips26-2/3 mS
75x in 2 sec.
242 chips~40 days
Length
Modulation
Quadrature Spreading(Zero offset)
Distinguish users, allowrecovery
Reverse LinkFunction
User identity
within logicchannel
Distinguish Cells& Sectors
Data Scramblingto distinguish
users
Forward LinkFunction
Each CDMA spreading sequence is used for a specificpurpose on the forward link and a different purpose onthe reverse link
The sequences are used to form code channels forusers in both directions
Cell
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Forward CDMA channel modulation process
User data from
BS in 9600bps
4800bps 2400bps
1200bps
Convolutional
Encoder and
Repetition
interleaver
r=1/2,K=9
19.2kbps
Data
scrambling
MUX
Power
contrl bit
Walsh code
Long code
generator
Long code
for userDecimator
1.2288Mcps
Decimator
4
800Hz
Base
band
Filter
Base
band
Filter
I Q
I-channel Pilot PN Sequence
Q- channel Pilot PN Sequence
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Reverse IS-95 channel modulation for a single user
Information
Bit
9600bps
4800bps
2400bps
1200bps
Conver
lutional
Encoder and
Repetition
r=1/3 K=9
Block
Inter-
leaver
Code
Symbol
28.8kbps
64-aryOrtho-
gonal
Modulator
Code
Symbol
DataBurst
Rand-
omizer
Walsh
chip
307.2
kcps
Long Code Generator
Long Code Mask
for user PN chip
1.2288Mcps
Base-band
Filter
I-channel
PN chip
DBaseband
Filter
I(t)
Q(t)Q-channel
1/2 PN chip Delay=406.9ns
IQ :Zero-offset Pilot Sequence
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41 33 32 28 27 25 24 9 8 0
110001111 ACN PCN BASE_ID PILOT_PN
ACN:number of access channel;PCN:number of paging chBASE_ID, PILOT_PN.
Access channel long code mask:
Public long code mask:
41 32 31 0
1100011000 Permuted ESN
What is mask ?
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Different approaches to bandwidth problem
CDMA
TDMAFDMA
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Coding Process on CDMA Forward Channels
Each user is assigned one of the 64 Walsh Codes and their traffic is
mixed with the Walsh code to establish a dedicated code channel Each Users Long code is applied incidentally for data
scramblingAll user code signals are then analog-summed to produce one
composite waveform
The composite waveform is the combined with the PN sequence usinga s ecific offset to uni uel identif this cell sector
BTSPilot Walsh 0
Walsh 19
Paging Walsh 1
Walsh 6
Walsh 11
Walsh 20
Sync Walsh 32
Walsh 42
Walsh 37
Walsh 41
Walsh 55
Walsh 60
Walsh 55
PN OFFSET 372
PN OFFSET 116BTS
PN OFFSET 226BTS
PN OFFSET 511BTS
7ANALOG
SUM
PN
372
WALSH
19
x
x
x
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Functions of the CDMA Forward
channelsPilot Walsh 0
Walsh 19
Paging Walsh 1
Walsh 6
Walsh 11
Walsh 20
Sync Walsh 32
Walsh 42
Walsh 37
Walsh 41
Walsh 55
Walsh 60
Walsh 55
PILOT: WALSH CODE 0 The Pilot is a structural
beacon which does notcontain a character stream.It is a timing source used in
system acquisition and as ameasurement device duringhandoffs
SYNC: WALSH CODE 32
This carries a data stream
of system identification andparameter information usedby mobiles during systemacquisition
PAGING: WALSH CODES 1 up to 7
There can be from one toseven a in channels as
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Analog Summing for Multiple Access
This simplified demonstration shows analog summing using only fourabbreviatedWalsh codes, each 4 bits long. Four users are talking.
Each user signal is XORed with their assigned Walsh code, and theresults are analog-summed and sent over a single medium, much like inCDMA.
At the other end, the Walsh codes are applied to recover each userdata.
X
X
X
X
User A
User B
User C
User D
User A
User B
User C
User D
Walsh 0
Walsh 1
Walsh 2
Walsh 3
Walsh 0
Walsh 1
Walsh 2
Walsh 3
A + 0
B + 1
C + 2
D + 3
Analog
Summing
Input Bits
#1 #2 Spreading De-Spreading
PowerIntegration
Output Bits
#1 #2
InCDMA,this isthe air
interface
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Coding Process on CDMA Reverse Channels
Each mobile is uniquely identified by an offset of the User Long Code,
which it generates internallyAll mobiles transmit simultaneously on the same 1.25-MHz wide
frequency band
Any nearby BTS can dedicate a channel element to the mobile andsuccessfully extract its signal
Mobiles also use the other CDMA spreading sequences, but not forchannel-identifying purposes
Short PN Sequence is used to achieve phase modulation
Walsh Codes are used as symbols to give ultra-reliablecommunications recovery at the BTS
User Long CodeBTS BSC MSC
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Functions of the CDMA Reverse
channelsACCESS: It is used by mobiles not yet
in a call to transmit registration
requests, call setup requests, page
responses, order responses, and other
signalling information
an access channel is definedby a special public long code
mask
Access channels are paired
with Paging Channels. Therecan be up to 32 access
channels per paging channel TRAFFIC:It is used by individual users
during their actual calls to transmittraffic to the BTS
911
REG
BTS
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Technical Advantages of CDMA Technology
For the Telecom Service Provider
High Efficiency of Frequency Utilization
Large Capacity Network
Simple Frequency Planning
Compatible with Analog Mobile Network
Smooth migration to 3G
For the Subscriber
Crystal-clear Voice Quality Good Anti-jamming
Inter system soft handoff reduces call dropping
Low radiation and Long Standby time (longbattery duration)
Reliable Security
Development of CDMA Technology
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Development of CDMA Technology
CDMA One : core technology IS95 :
IS 95A: only 1 spreading code for 1 traffic
channel, 14.4 Kbps
1980, First field test by Qualcomm
1990, first version of CDMA UM interface standard
by Qualcomm
1995, N-CDMA standard IS-95A by TIA
IS 95B : max. 8 codes for 1 traffic channel (one
user for high-speed packet data service
enhanced Air interface, hardware compatible with
IS-95A
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Contents
Overview of Mobile Communications
Technical Features of CDMA
Dynamics of 3 G ( the 3rd Generation
Communications System)
Dynamics of 3G
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Dynamics of 3G
Background Higher demand of QoS
Seamless internal roaming, wideband, flexible
Large capacity, frequency resource usage
IMT-2000
Naming commercial use expected in 2002
First phase frequency band around 2 G HZ.
Requirements QoS: voice/coverage, transmission/delay(BER
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Dynamics of 3G
UIM MT RAN CNOther CN of
IMT-2000
family
UIM: user identity module
MT: mobile terminal
RAN: radio access networkCN: core network
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RTT: Radio Transmission Technology
Proposed standards: 10 (FDD: 8 ,
TDD 5)
Dynamics of 3G
No. RTT Proposed Duplex Proposer
1 J: W CDMA FDD, TDD Japan: ARIB
2 ETSI UTRA - UMTS FDD, TDD Europe: ETS
I
3 WIMS W - CDMA FDD US: TIA
4 WCDMA/NA FDD US: TIPI
5 Global CDMA II FDD SK: TTA
6 TD - SCDMA TDD China: CATT
7CDMA 2000 FDD, TDD US: T
IA
8 Global CDMA I FDD SK: TTA
9 UWC - 136 FDD US: TIA
10 DP DECT TDD Europe: ETSI1. 1 5 : similar to WCDMA, harmonization forms 3GPP WCDMA
2. 7 8 similar to CDMA 2000, harmonization forms 3GPP2 CDMA 2000
3. 9 : UWC 136, based on IS 136 TDMA (D-AMPS)
Dynamics of 3G
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Dynamics of 3G
Wireless Access Network
Various standards:
W-CDMA FDD, W-CDMA TDD(TD-
SCDMA), CDMA-2000 Multi-carrier,
UWC-136 TDMA
Widely accepted standards:
CDMA 2000
W-CDMA
UWC-136
Core Network
ANSI TIA/EIA-41 MAP
GSM MAP
Comparison Between W-CDMA & CDMA 2000
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Comparison Between W CDMA & CDMA 2000
Item W-CDMA CDMA-2000
Min. Band
Width
SS technique Single Carrier DS Multi-carrier Or DS
Code chip rate 4.096Mcpsreduced to3.84Mc
Nv1.2288Mcps
Sync. Between
BS
Async, Sync. Can be
selected
Sync. (GPS)
Frame length 10ms 20ms
Voice Coding Fixed rate Variable rate
Power Control
Rate
1600Hz 800Hz
Dynamics of 3 G
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Dynamics of 3 G
Wireless Access Standards Development from 2 G to 3
G
GSM
GSM-----GRPS and EDGE (up to 384 kbps)---W-CDMA (5 MHZ)
CDMA
IS 95A/B(14.4-64 kbps) cdma2000-1X (144 kbps)
cdma2000-3X
cdma2000-1X-EV
TDMA (TIA-EIA-136)
2.5 G 3 G
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Consolidation of ITU IMT-2000 Very
complicated task
Technical difference:
SS, code chip rate, Sync. Mode, Pilot, corenetwork(GSM-MAP and IS-41)
Conflict of interest of various parties involved
current market status of mobile
communications,IPR, interest of serviceprovider and manufacturers
3GPP1998-12
Initiated by ETSI and joined by ARIBTCC
TITTA
Dynamics of 3 G
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Typical IS95A Network Structure of ZTE
MSC/
VLR
HLR/AUC
MS
Abis
Abis
Abis
PSTN/PLMN
BSC
BSC
Abis
BSC
A-ISO2 .x
Um IS41D/E
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Evolution from 2G System to 3G Syste
HDR
IS-95Acdma2000-3x
1X-EV
IS-95B
cdma2000-1x
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CDMA Network Evolution of ZTE
IS95A Cdma 2000 1X
Transition
methods
Data service rate
Adopts IOS4.0 for A Interface
144K 2M
Smooth evolution
to 3G
MSS evolves from current Circuit Switching
mode to full IP mode
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CDMA2000-1X Network Structure
MSC/
VLR
HLR/AUC
2G BTS
3G BTS (1X) or2G
BTS+upgrade
2G/3G
MS
Abis
Abis
Abis
PSTN/PLMN
2G BSC+upgradeor
3G BSC/ PCF (1X)
Internet
PDSN
HAAAA
server
router router
Ethernet
ATM
2G BTS
2G BSC
Abis
BSM
E1Um
IS95
Um
IS2000 E1STM-1
E1
STM-1
Ethernet
2G BSC+upgradeor
3G BSC/ PCF (1X)
3G BTS (1X) or2G
BTS+upgrade
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The end !
