010 CDMA-Theory Moudle

8/3/2019 010 CDMA-Theory Moudle

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CDMA Theory

Unit 1 CDMA Basic Principle

Unit 2 CDMA Channel Structure andModulation


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CDMA Theory Unit 1


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Main Content

Definitions of CDMA and How to realize

Spread spectrum modulation

Spreading codes used in CDMA

Vocoding in CDMA


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Multiple Access

Types of Media -- Examples: Twisted pair - copper Coaxial cable Fiber optic cable Air interface (radio signals)

Advantages of Multiple Access Increased capacity: serve more users Reduced capital requirements since

fewer media can carry the traffic Decreased per-user expense Easier to manage and administer

Each pair of usersenjoys a dedicated, private circuit through

the transmissionmedium, unaware that the other users exist.

Since the beginning of telephony and radio,system operators have tried to squeeze themaximum amount of traffic over each circuit.

Multiple Access: Simultaneous private use of a transmission

medium by multiple, independent users.

Transmission

Medium


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Channels

FDMA Frequency Division Multiple Access Each user on a different frequency

A channel is a frequencyTDMA Time Division Multiple Access Each user on a different window period in

time ( time slot ) A channel is a specific time slot on a

specific frequency

CDMA Code Division Multiple Access A channel is a unique code pattern Each user uses the same frequency all the

time, but mixed with differentdistinguishing code patterns

Power

Power

Power

FDMA

TDMA

CDMA

C hannel: An individually-assigned, dedicated

pathway through a transmissionmedium for one users information.

The transmission medium is a resource that can be subdividedinto individual channels according to the technology used.


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Defining Our TermsCDMA Channel or CDMA Carrier or CDMA Frequency

Duplex channel made of two 1.25 MHz-wide bands of electromagnetic spectrum, one for Base Station to Mobile Station communication (called the FORWARD LINK or theDOWNLINK) and another for Mobile Station to Base Station communication (called theREVERSE LINK or the UPLINK)

In 800 Cellular these two simplex 1.25 MHz bands are 45 MHz apart In 1900 MHz PCS they are 80 MHz apart

CDMA Forward Channel

1.25 MHz Forward Link

CDMA Reverse Channel 1.25 MHz Reverse Link

CDMA Code Channel Each individual stream of 0s and 1s contained in either the CDMA Forward Channel or in

the CDMA Reverse Channel Code Channels are characterized (made unique) by mathematical codes Code channels in the forward link: Pilot, Sync, Paging and Forward Traffic channels Code channels in the reverse link: Access and Reverse Traffic channels

45 or 80 MHz

CDMA

CHANNELCDMA

ReverseChannel1.2 5 MHz

CDMAForwardChannel1.2 5 MHz


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Main Content




Vocoding in CDMA


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W hat is Spread Spectrum

ORIGI NAT ING S ITE D EST INAT IO N

SpreadingSequence

SpreadingSequence

InputD ata

R ecoveredD ata

Spread D ata Stream

Definition:Spread spectrum technique ,employ a transmission bandwidth that isseveral orders of magnitude greater than the minimum required signal bandwidth.

Sender combines data with a fast spreading sequence, transmits spread datastream

Receiver intercepts the stream, uses same spreading sequence to extractoriginal data


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SHANON Formula

Spread Spectrum Principles

W here,C is capacity of channel, b/sB is signal bandwidth, HzS is average power for signal, WN is average power for noise, W

C=B*log 2(1+S/N)

It is the basic principle and theoryfor spread spectrum communications.It is the basic principle and theoryfor spread spectrum communications.


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CDMA Is a Spread-Spectrum System

y Traditional technologies try tosqueeze the signal into theminimum required bandwidth

y Direct-Sequence Spread spectrum

systems mix their input data witha fast spreading sequence andtransmit a wideband signal

y The spreading sequence isindependently regenerated at thereceiver and mixed with theincoming wideband signal torecover the original data

S pread S pectrum Payoff:Processing Gain

Spread SpectrumTR AD ITIO NAL C O MMUN IC ATIO NS SYSTEM

SlowInformation

Sent

TX

SlowInformationR ecovered

R X

NarrowbandSignal

SP R EAD -SPE C TR UM SYSTEM

FastSpreadingSequence

SlowInformation

Sent

TX

SlowInformationR ecovered

R X

FastSpreadingSequence

Wideband Signal


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1.2 5 MHz30 KHz

Power is Sp read Over a Larger Bandwidth


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Many code channels are individuallyspread and then added together tocreate a com posite signal


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Main Content




Vocoding in CDMA


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Spreading code chip speed 1.2288Mc/s

Spreading code Forward link W alsh code & Short PN

Reverse link Long PN

Spreading code chip speed 1.2288Mc/s

Spreading code Forward link W alsh code & Short PN

Reverse link Long PN

Spreading Codes in CDMA

Spreading codes selection is the key of spreadingSpectrum modulation!Spreading codes selection is the key of spreadingSpectrum modulation!


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W alsh Code Defination

The Walsh function is named after Walsh, the mathematician who proved it an orthogonal function in 1923. It is expressed as Walsh (n,t),n for the serial number. The CDMA system of IS-95 is differentiatedwith the Walsh function.

Walsh code is an orthogonal square matrix. It is just composed of +1(0)and 1(1).

The Walsh function is named after Walsh, the mathematician who proved it an orthogonal function in 1923. It is expressed as Walsh (n,t),n for the serial number. The CDMA system of IS-95 is differentiatedwith the Walsh function.

Walsh code is an orthogonal square matrix. It is just composed of +1(0)and 1(1).

0110

1100

1010

0000

10

000

H n H n

H 2n = ___ H n H n


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W alsh Codes 6 4 Sequences, each 6 4 chips long

A chip is a binary digit (0 or 1)Each Walsh Code is Orthogonal to allother Walsh Codes This means that it is possible to

recognize and therefore extract a

particular Walsh code from a mixtureof other Walsh codes which arefiltered out in the process

Two same-length binary strings areorthogonal if the result of XORing

them has the same number of 0s as 1s

WALSH CODES# ----------------------------- ----- 64-Chip Sequence --------------------------- ---------------0 00000000000000000000000000000000000000000000000000000000000000001 01010101010101010101010101010101010101010101010101010101010101012 00110011001100110011001100110011001100110011001100110011001100113 01100110011001100110011001100110011001100110011001100110011001104 00001111000011110000111100001111000011110000111100001111000011115 01011010010110100101101001011010010110100101101001011010010110106 00111100001111000011110000111100001111000011110000111100001111007 01101001011010010110100101101001011010010110100101101001011010018 00000000111111110000000011111111000000001111111100000000111111119 0101010110101010010101011010101001010101101010100101010110101010

10 001100111100110000110011110011000011001111001100001100111100110011 011001101001100101100110100110010110011010011001011001101001100112 000011111111000000001111111100000000111111110000000011111111000013 010110101010010101011010101001010101101010100101010110101010010114 001111001100001100111100110000110011110011000011001111001100001115 011010011001011001101001100101100110100110010110011010011001011016 000000000000000011111111111111110000000000000000111111111111111117 010101010101010110101010101010100101010101010101101010101010101018 001100110011001111001100110011000011001100110011110011001100110019 011001100110011010011001100110010110011001100110100110011001100120 000011110000111111110000111100000000111100001111111100001111000021 010110100101101010100101101001010101101001011010101001011010010122 001111000011110011000011110000110011110000111100110000111100001123 011010010110100110010110100101100110100101101001100101101001011024 000000001111111111111111000000000000000011111111111111110000000025 010101011010101010101010010101010101010110101010101010100101010126 001100111100110011001100001100110011001111001100110011000011001127 011001101001100110011001011001100110011010011001100110010110011028 000011111111000011110000000011110000111111110000111100000000111129 010110101010010110100101010110100101101010100101101001010101101030 001111001100001111000011001111000011110011000011110000110011110031 011010011001011010010110011010010110100110010110100101100110100132 000000000000000000000000000000001111111111111111111111111111111133 010101010101010101010101010101011010101010101010101010101010101034 001100110011001100110011001100111100110011001100110011001100110035 011001100110011001100110011001101001100110011001100110011001100136 000011110000111100001111000011111111000011110000111100001111000037 010110100101101001011010010110101010010110100101101001011010010138 001111000011110000111100001111001100001111000011110000111100001139 011010010110100101101001011010011001011010010110100101101001011040 000000001111111100000000111111111111111100000000111111110000000041 010101011010101001010101101010101010101001010101101010100101010142 001100111100110000110011110011001100110000110011110011000011001143 011001101001100101100110100110011001100101100110100110010110011044 000011111111000000001111111100001111000000001111111100000000111145 010110101010010101011010101001011010010101011010101001010101101046 001111001100001100111100110000111100001100111100110000110011110047 011010011001011001101001100101101001011001101001100101100110100148 000000000000000011111111111111111111111111111111000000000000000049 010101010101010110101010101010101010101010101010010101010101010150 001100110011001111001100110011001100110011001100001100110011001151 011001100110011010011001100110011001100110011001011001100110011052 000011110000111111110000111100001111000011110000000011110000111153 010110100101101010100101101001011010010110100101010110100101101054 001111000011110011000011110000111100001111000011001111000011110055 011010010110100110010110100101101001011010010110011010010110100156 000000001111111111111111000000001111111100000000000000001111111157 010101011010101010101010010101011010101001010101010101011010101058 001100111100110011001100001100111100110000110011001100111100110059 011001101001100110011001011001101001100101100110011001101001100160 000011111111000011110000000011111111000000001111000011111111000061 010110101010010110100101010110101010010101011010010110101010010162 001111001100001111000011001111001100001100111100001111001100001163 0110100110010110100101100110100110010110011010010110100110010110

EXAMPLE:

Correlation of Walsh Code #23 with Walsh Code #59#23 0110100101101001100101101001011001101001011010011001011010010110#59 0110011010011001100110010110011010011001011001100110011010011001XOR 0000111111110000000011111111000011110000000011111111000000001111

Correlation Results: 32 1s, 32 0s: Orthogonal!!


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Correlation and Orthogonality

Code #23 0110100101101001100101101001011001101001011010011001011010010110

( Code #23) 1001011010010110011010010110100110010110100101100110100101101001

Code #59 0110011010011001100110010110011010011001011001100110011010011001

PA R ALLEL

X OR: all 0s

Correlation: 100%(100% match)

OR TH OGO NAL

X OR: half 0s, half 1s

Correlation: 0%(5 0% match, 5 0% no-match)

ANT I-PA R ALLEL

X OR: all 1s

Correlation: 100%(100% no-match)

#23#23

(#23)

#23

#23

#59

C orrelation is a measure of the similarity between two binary strings


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W alsh Code Functionin Forward Link

A Mobile Station receives a Forward Channel from a sector in aBase Station.The Forward Channel carries a composite signal of up to 6 4

forward code channels.Some code channels are traffic channels and others are overheadchannels.A set of 6 4 mathematical codes is needed to differentiate the 6 4

possible forward code channels. The codes in this set are called Walsh Codes

S yncPilot

FW Traffic(for user #1)

Paging




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Short PN Sequences

Together, they can be considereda two-dimensional binary vector with distinct I and Q componentsequences, each 32,7 6 8 chips

longEach Short PN Sequence (and, asa matter of fact, any sequence)correlates with itself perfectly if compared at a timing offset of 0chips

Each Short PN Sequence isspecial: Orthogonal to a copy of itself that has been offset by anynumber of chips (other than 0)

IQ

32,768 chips long26 2 /3 ms.

(75 repetitions in 2 sec.)

IQI

Q100% C orrelation: All bits = 0

Short PN Sequence vs. Itself @ 0 O ffset

IQI

QO rthogonal: 16 ,384 1 s + 16 ,384 0 s

Short PN Sequence vs. Itself @ Any O ffset

U nique Properties:

The two Short PN Sequences,I

andQ , are 32,7 6 8 chips long


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Short PN Functionin Forward Link

A mobile Station is surrounded by Base Stations, all of them transmittingon the same CDMA Frequency.

Each Sector in each Base Station is transmitting a Forward TrafficChannel containing up to 6 4 forward code channels.

A Mobile Station must be able to discriminate between different Sectorsof different Base Stations.

Two binary digit sequences called the I and Q Short PN Sequences (or Short PN Codes) are defined for the purpose of identifying sectors of different base stations.

These Short PN Sequences can be used in 512 different ways in a CDMAsystem. Each one of them constitutes a mathematical code which can beused to identify a particular sector.

A B

Up to 6 4Code Channels

Up to 6 4Code Channels


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The Long PN Sequence

Each mobile station uses a unique User Long Code Sequence generated byapplying a mask, based on its 32-bit ESN, to the 42-bit Long Code Generator which was synchronized with the CDMA system during the mobile stationinitialization.

Generated at 1.2288 Mcps, this sequence requires 41 days, 10 hours, 12minutes and 19.4 seconds to complete.

Portions of the User Long Codes generated by different mobile stations for the duration of a call are not exactly orthogonal but are sufficiently differentto permit reliable decoding on the reverse link.

Long C ode R egister (@ 1 .2288 M C PS)

Public Long C ode Mask(STAT IC )

User Long C ode

Sequence(@ 1 .2288 M C PS)

1 1 0 0 0 1 1 0 0 0 P E R M U T E D E S N

AND

=S U M

Modulo-2 Addition


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Long PN Functionin Reverse Link

The CDMA system must be able toidentify each Mobile Station that mayattempt to communicate with a BaseStation.

A very large number of MobileStations will be in the market.

One binary digit sequence called theLong PN Sequence (or Long PN Code)is defined for the purpose of uniquelyidentifying each possible reverse codechannel.

This sequence is extremely long andcan be used in trillions of differentways. Each one of them constitutes amathematical code which can be usedto identify a particular user (and is thencalled a User Long Code) or a

particular user Reverse Trafficchannel .

RV Trafficfrom M.S.

#1 837732 00 8RV Trafficfrom M.S.

#199 706110 4

RV Trafficfrom M.S.

#199 401150 8System AccessAttempt by M.S.

#2 0000 71 301(on access channel # 1 )


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Summary of Characteristics& Functions

Each CDMA spreading sequence is used for a specific purpose on the forward link and a different purpose onthe reverse link.The sequences are used to form code channels for users in both directions.

WalshC odes

Short PNSequences

Long PNSequences

Type of Sequence

MutuallyO rthogonal

O rthogonal

with itself atany timeshift valueexcept 0

near-orthogonal

if shifted

SpecialProperties

6 4

2

1

H owMany

6 4 chips1/19 ,200

sec.

32,7 6 8chips26 -2 /3 ms

75 x in 2sec.

242 chips~4 1 days

Length

O rthogonalModulation

(informationcarrier)

Q uadratureSpreading(Zero offset)

D istinguishusers

R everseLinkFunction

User identity

within cellssignal

D istinguishC ells &Sectors

D ataScrambling

to avoidstrings of 1 s or 0 s

ForwardLinkFunction

IQ

32,7 6 8 chips long26 -2 /3 ms.

(75 repetitions in 2 sec.)

6 4codes

6 4 chips long

AND

=SUM

Modulo-2 Addition

C ell


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Main Content




Vocoding in CDMA


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Variable Rate Vocoder

Speech coding algorithms (digital compression) are necessary to increasecellular system capacity.

Coding must also ensure reasonable fidelity, that is, a maximum level of quality as perceived by the user.

Coding can be performed in a variety of ways (for example, waveform,time or frequency domain).

Vocoders transmit parameters which control reproduction of voice insteadof the explicit, point-by-point waveform description.

A-to- DC

O

NV

ER

TER

6 4 Kbps

VOC

OD

ER

C odebookInstruction8Kbps

6 4 Kbps

MS C


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Variable Rate Vocoding

CDMA uses a superior Variable Rate Vocoder Full rate during speech Low rates in speech pauses Increased capacity More natural soundVoice, signaling, and user secondary data may be mixed in CDMAframes

D SP Q C ELP VO C O D ER

C odebook

Pitch

Filter

FormantFilter

C oded R esult Feed-back

20 ms Sample


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Variable Rate Vocoding

R ate Set 2 Frame Sizesbits

Full R ate Frame

1/ 2 R ate Frame

1/ 4 R t.

1/ 836

72

1 44

288

R ate Set 1 Frame Sizesbits

Full R ate Frame

1/ 2 R ate Frame

1/ 4 R t.

1/ 824

48

96

19 2

5DWH VHW . 4&(/3 (95& 5DWH VHW . 4&(/3)XOO UDWH .ESV )XOO UDWH .ESV+DOI UDWH .ESV +DOI UDWH .ESV

UDWH .ESV UDWH .ESVUDWH .ESV UDWH .ESV

5DWH VHW . 4&(/3 (95& 5DWH VHW . 4&(/3)XOO UDWH .ESV )XOO UDWH .ESV+DOI UDWH .ESV +DOI UDWH .ESV

UDWH .ESV UDWH .ESVUDWH .ESV UDWH .ESV


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Variable Rate Voice Bit and PCM

W here is vocoder?

B TS B S CB S C MS CMS C

Analog voiceVariable Rate PCM


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CDMA Theory Unit 2


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Main Content

The Forward Channels in IS-95

The Reverse Channels in IS-95

New Channels in CDMA20001X


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IS-95 Channel Structure


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Pilot Channel

Used by the mobile station for initial system acquisitionTransmitted constantly by the base station

The same Short PN sequences are shared by all base stations

Each base station is differentiated by a phase offset

Provides tracking of:

Timing reference

Phase reference

Acquisition by mobile stations is enhanced by:

Short duration of Pilot PN sequence

Uncoded nature of pilot signalFacilitates mobile station-assisted handoffs

Used to identify handoff candidates

Key factor in performing soft handoffs

Used by the mobile station for initial system acquisitionTransmitted constantly by the base station

The same Short PN sequences are shared by all base stations

Each base station is differentiated by a phase offset

Provides tracking of:

Timing reference

Phase reference

Acquisition by mobile stations is enhanced by:

Short duration of Pilot PN sequence

Uncoded nature of pilot signalFacilitates mobile station-assisted handoffs

Used to identify handoff candidates

Key factor in performing soft handoffs


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Pilot Channel Generation

PilotC hannel(All 0 s)

1 .2288Mcps

I PN

Q PN

WalshFunction 0

The Walsh function zero spreading sequence is applied to the Pilot

The use of short PN sequence offsets allows for up to 512 distinct Pilots per CDMA channel

The PN offset index value (0-511 inclusive) for a given pilot PN

sequence is multiplied by 6 4 to determine the actual offset Example: 15 (offset index) x 6 4 = 9 6 0 PN chips

Result: The start of the pilot PN sequence will be delayed96 0 chips x 0.8138 microseconds per chip = 781.25 microsecond

The Walsh function zero spreading sequence is applied to the Pilot

The use of short PN sequence offsets allows for up to 512 distinct Pilots per CDMA channel

The PN offset index value (0-511 inclusive) for a given pilot PN

sequence is multiplied by 6 4 to determine the actual offset Example: 15 (offset index) x 6 4 = 9 6 0 PN chips

Result: The start of the pilot PN sequence will be delayed96 0 chips x 0.8138 microseconds per chip = 781.25 microsecond


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Sync Channel

(Acquired Pilot)

Sync C hannel

Used to provide essential system parameters

Used during system acquisition stage

Bit rate is 1200 bps

Sync channel has a frame duration of 26 2/3 ms

Frame duration matches the period of repetition of the PNShort Sequences

Simplifies the acquisition of theSync Channel once the PilotChannel has been acquired

Mobile Station re-synchronizes at theend of every call

Used to provide essential system parameters

Used during system acquisition stage

Bit rate is 1200 bps

Sync channel has a frame duration of 26 2/3 ms

Frame duration matches the period of repetition of the PNShort Sequences

Simplifies the acquisition of theSync Channel once the PilotChannel has been acquired

Mobile Station re-synchronizes at theend of every call


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Sync Channel Generation

1 200 bps

Walsh Function 32

1 .2288 Mcps

I PN

C onvolutionalEncoder and

R epetition

B lockInterleaver

R = 1/ 2 K= 9

ModulationSymbols

48 00 sps 48 00 sps

B its C hips

Q PN


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Paging Channels

Paging C hannel

Used by the base station totransmit system overhead informationand mobile station-specific messages.

There is one paging channel per sector per CDMA carrier

The Paging Channel uses Walsh function 1

Two rates are supported: 9 6 00 and 4800 bps

There is one paging channel per sector per CDMA carrier

The Paging Channel uses Walsh function 1

Two rates are supported: 9 6 00 and 4800 bps


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Paging Channel Generation

9600 bps

48 00 bps

Walshfunction

1 .2288Mcps

Q PN

1 .2288Mcps

19 .2

Ksps

19 .2Ksps

Paging C hannelAddress Mask

R = 1/ 2 K= 9

D ecimator

C onvolutionalEncoder &R epetition

I PN

B lockInterleaving

Scrambling

Long PN C odeG

enerator


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CDMA Forward Traffic Channels

Forward Traffic C hannel


Sync

Paging



Pilot

CD MA C ell Site

Used for the transmission of user and signaling information to a specificmobile station during a call.

Maximum number of traffic channels: 6 4 minus one Pilot channel, one Syncchannel, and 1 Paging channel.

This leaves each CDMA frequency with at least 55 traffic channels.

Unused paging channels can provide up to 6 additional channels .

Used for the transmission of user and signaling information to a specificmobile station during a call.

Maximum number of traffic channels: 6 4 minus one Pilot channel, one Syncchannel, and 1 Paging channel.

This leaves each CDMA frequency with at least 55 traffic channels.

Unused paging channels can provide up to 6 additional channels .


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Forward Traffic Channel Generation

Walsh

function

Power C ontrol

B it

I PN

9600 bps

48 00 bps24 00 bps1 200 bps(Vocoder) C onvolutional

Encoding andR epetition

1 .2288McpsLong PN C ode

G eneration 800 H z

R = 1/ 2, K= 9

Q PND ecimator D ecimator

User AddressMask

(ESN-based)

19 .2

ksps

1 .2288Mcps

Scrambling

bits symbols chips

19 .2ksps

CH ANNEL ELEMENT

MUX

B lockInterleaving

8 kb Vocoding


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Q uadrature Phase Shift Key(Q PSK) Modulation

The forward traffic channel is combined with two differentPN sequences: I and QBaseband filtering ensures the waveforms are containedwithin the 1.25 MHz frequency rangeThe final step is to convert the two baseband signals to radiofrequency (RF) in the 800 MHz or 1900 MHz range

C onvolutionalEncoding

C ode SymbolR epetition

Vocoder Processing

B aseband Trafficto R F Section

P C M Voice

B lockInterleaving

D ata Scrambling

Power C ontrolSubchannelO rthogonalSpreading

Q uadratureSpreadingB asebandFiltering

(SymbolPuncturing)

WalshFunction

1 .2288Mcps

19 .2 kspsfrom Power C ontrol Mux

I-C hannel Pilot PN Sequence1 .2288 Mcps

B asebandFilter

B asebandFilter

I

Q

7I

Q

Q -C hannel Pilot PN Sequence1 .2288 Mcps

cos(2 T f ct)

sin(2 T f ct)

GAIN


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Forward Traffic Channel Generation

Walshfunction

Power C ontrol

B it

I PN

1 44 00 bps72 00 bps3600 bps1 800 bps(Vocoder) C onvolutional

Encoding andR epetition

1 .2288McpsLong PN C ode

G eneration 800 H z

R = 1/ 2, K= 9

Q PND ecimator D ecimator

User AddressMask

(ESN-based)

19 .2

ksps

1 .2288Mcps

Scrambling

bits symbols chips

28.8ksps

CH ANNEL ELEMENT

MUX

B lockInterleaving

SymbolPuncturing(1 3 kb only) 19 .2

ksps

13 kb Vocoding


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Main Content

The Forward channels in IS-95

The Reverse channels in IS-95



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Reverse Access Channels

48 00 bps

Used by the mobile station to:

Initiate communication with the base station

Respond to Paging Channel messages

Has a fixed data rate of 4800 bps

Each Access Channel is associated with only one PagingChannel

Up to 32 access channels (0-31) are supported per PagingChannel

Used by the mobile station to:

Initiate communication with the base station

Respond to Paging Channel messages

Has a fixed data rate of 4800 bps

Each Access Channel is associated with only one PagingChannel

Up to 32 access channels (0-31) are supported per PagingChannel


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28.8kspsC onvolutional

Encoder &R epetition

R = 1/ 3

1 .2288McpsAccess C hannel

Long C ode MaskLong PN C ode

G enerator

28.8ksps O rthogonal

Modulation

30 7.2kcps

1 .2288Mcps

Q PN (No O ffset)

I PN (No O ffset)

D

1/ 2 PNC hip

D elay

B lockInterleaver

Access C hannelInformation

(88 bits /Frame)

4.8 kpbs

D irectSequenceSpreading

Access Channel Generation

Message attempts are randomized to reduce probability of collisionTwo message types: A response message (in response to a base station message) A request message (sent autonomously by the mobile

station)


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CDMA Reverse Traffic Channels

R everse Traffic C hannel

Used when a call is in progress to send: Voice traffic from the subscriber

Response to commands/queries from the base station

Requests to the base station

Supports variable data rate operation for:

8 Kbps vocoder

Rate Set 1 - 9 6 00, 4800, 2400 and 1200 bps

13 Kbps vocoder

Rate Set 2 - 14400, 7200, 3 6 00, 1800 bps

Used when a call is in progress to send: Voice traffic from the subscriber

Response to commands/queries from the base station

Requests to the base station

Supports variable data rate operation for:

8 Kbps vocoder

Rate Set 1 - 9 6 00, 4800, 2400 and 1200 bps

13 Kbps vocoder

Rate Set 2 - 14400, 7200, 3 6 00, 1800 bps


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9600 bps48 00 bps24 00 bps1 200 bps

28.8ksps

R =1/ 3,K= 9

1 .2288McpsUser Address

MaskLong

PN C odeG enerator


ModulationD ata B urst

R andomizer

30 7.2kcps

1 .2288Mcps

Q PN(no offset)

I PN(no offset)

D

1/ 2 PNC hip

D elay



B lockInterleaver

Reverse Traffic Channel Generation

8Kb Vocoding


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1 44 00 bps

72 00 bps3600 bps1 800 bps

28.8ksps

R =1/ 2,K= 9

1 .2288McpsUser Address

MaskLong

PN C ode

G enerator


Modulation

D ata B urstR andomizer

30 7.2kcps

1 .2288Mcps

Q PN(no offset)

I PN(no offset)

D

1/ 2 PNC hip

D elay



B lockInterleaver

Reverse Traffic Channel Generation

13 kb Vocoding


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Main Content

The forward channels in IS-95

The reverse channels in IS-95



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CDMA2000-1X New Features

High speed 153. 6 kbps packet data capabilities;Increased mobile standby battery life;Total backward compatibility to reuse switch and call

processing features;Voice capacity 1.5 2times larger than IS-95

High speed 153. 6 kbps packet data capabilities;Increased mobile standby battery life;Total backward compatibility to reuse switch and call

processing features;Voice capacity 1.5 2times larger than IS-95

CD MA2000 1 x R F C apacity


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CDMA20001X New Technology

Forward link Fast power control

IS-95 50Hz;IS-2000 800Hz Transmitting diversity

Release A OTD orthogonal transmit diversity ; Use variable length Walsh code, support multiple code channels for one user

adopt turbo code for error correction modulationReverse link Support pilot channel, help BTS demodulate MS; Walsh code is used to distinguish code channels,not

orthogonal modulation; support multiple code channels for one user adopt turbo code for error

correction modulation

Forward link Fast power control

IS-95 50Hz;IS-2000 800Hz Transmitting diversity

Release A OTD orthogonal transmit diversity ; Use variable length Walsh code, support multiple code channels for one user

adopt turbo code for error correction modulationReverse link Support pilot channel, help BTS demodulate MS; Walsh code is used to distinguish code channels,not

orthogonal modulation; support multiple code channels for one user adopt turbo code for error

correction modulation

CDMA2000 1x = 1. 25 MHz Radio Transmission Technology

1 Ch l


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1x New Channelsin Commercial Network

IS-95B built on the IS-95A channels, and introduced two new channels Fundamental channel was the same as IS-9A traffic channel Supplemental code channels assigned to support rates above 14.4Kbps

IS-2000 1xRTT continue to build on the IS-95 channels IS-95 channels continue to be supported in IS-2000 to support IS-95

mobiles

Pilot channelSync channelPaging channel Access channelForward Traffic C hannel R everse Traffic C hannel

Fundamental channel Fundamental channelSupplemental C ode channel (F-S CCH ) Supplemental C ode channel ( R -S CCH )

Supplemental channel (F-S CH ) Supplemental channel ( R -S CH )Q uick Paging channel (F- Q P CH ) R everse Pilot channel ( R -P ICH )

IS- 95 B

1 xR TT

IS- 95 A

Forward R everse


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R Pil Ch l


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Reverse Pilot Channel(R-PICH)

Mobile transmits well-known pattern (pilot)Allows base station to do timing corrections without having to guess wheremobile is (in search window)Mobile can transmit at lower power, reducing interference to others

Mobile transmits well-known pattern (pilot)Allows base station to do timing corrections without having to guess wheremobile is (in search window)Mobile can transmit at lower power, reducing interference to others


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Reverse SupplementalChannel (R-SCH)

Used for high-speed packet data (>9. 6 kbps)Difference between F-SCH and R-SCH is in Walsh code based spreading

F-SCH supports Walsh code lengths of 4 to 128 (1xRTT) or 1024 (3xRTT)depending on data rate and chip rate

Walsh code allocation sequence is pre-determined and common to all mobiles

Users are differentiated using long PN code with user mask

Used for high-speed packet data (>9. 6 kbps)Difference between F-SCH and R-SCH is in Walsh code based spreading

F-SCH supports Walsh code lengths of 4 to 128 (1xRTT) or 1024 (3xRTT)depending on data rate and chip rate

Walsh code allocation sequence is pre-determined and common to all mobiles

Users are differentiated using long PN code with user mask


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ZTE U i i iii

Documents

010 CDMA-Theory Moudle