CDMA presen

8/9/2019 CDMA presen.

1/18

Prepared byPrepared byMital Marvaniya &Mital Marvaniya &

Sonal MalavaniyaSonal Malavaniya


2/18

INTRODUCTION TO CDMAINTRODUCTION TO CDMA

CDMA stands for Code Division MultipleCDMA stands for Code Division Multiple

Access.Access.

A digital communication technologyA digital communication technology

provides crystal clear voice quality .provides crystal clear voice quality .

Using a digital encoding spread spectrumUsing a digital encoding spread spectrumradio frequency (RF) techniques.radio frequency (RF) techniques.


3/18

MULTIPLE ACCESSMULTIPLE ACCESS

Multiple access means that multiple, simultaneousMultiple access means that multiple, simultaneoususers can be supported.users can be supported.

There are three primary multiple access systems:There are three primary multiple access systems:

1) FDMA (analog)1) FDMA (analog)

2) TDMA (digital)2) TDMA (digital)

3) CDMA(digital)3) CDMA(digital)


4/18

CDMACDMA

CDMA assigns eachCDMA assigns eachsubscriber a uniquesubscriber a uniquecode to put multiplecode to put multipleuser on the same wideuser on the same wide

band channel at theband channel at thesame time.same time.

And these codes areAnd these codes areused by the mobileused by the mobilestation and basedstation and basedstation to distinguishstation to distinguishbetween conversations.between conversations.


5/18

WIRELESS LOCAL LOOP(WLL)WIRELESS LOCAL LOOP(WLL)

TheWLL is a telecommunication service that usesTheWLL is a telecommunication service that uses

wireless networks to carry communication from thewireless networks to carry communication from the

wired subscriber network.wired subscriber network.

Installation ofWLL costs no more than half that for aInstallation ofWLL costs no more than half that for a

wired system.wired system.


6/18

WHY CDMA BETTERWHY CDMA BETTER

1) Better reception1) Better reception

2) Security of CDMA2) Security of CDMA


7/18

GENERATION OF CDMAGENERATION OF CDMA

First generation :First generation :

AMPSAMPS

FDMAFDMA

22ndnd

Generation:Generation:TDMATDMA

GSMGSM

2.5 Generation:2.5 Generation:

GPRS & CdmaOneGPRS & CdmaOne33rdrd Gneration:Gneration:

CDMACDMA


8/18

HOW CDMAWORKSHOW CDMAWORKS

CDMA signal genarationCDMA signal genaration

The types of code used inThe types of code used inCDMACDMA

Forward and reverse linkForward and reverse link

code channelscode channels

CDMA call processingCDMA call processing


9/18

CDMA SIGNAL GENERATIONCDMA SIGNAL GENERATION

Analog to digitalAnalog to digitalconversion.conversion.

CDMA uses pulse codeCDMA uses pulse codemodulation techniquemodulation technique(PCM)(PCM)

to accomplish the A/Dto accomplish the A/Dconversion.conversion.


10/18

VOICE COMPRESSIONVOICE COMPRESSION

CDMA uses a diviceCDMA uses a divicecalled vocoder tocalled vocoder toaccomplish voceaccomplish voce

compression.compression.

The term vocoder isThe term vocoder isconstaction of voice andconstaction of voice andcode.code.

VRIABLE RATEVRIABLE RATEVOCODERVOCODER


11/18

HOW ENCODING WORKHOW ENCODING WORK

The type of encodingThe type of encodingdone at this stage isdone at this stage iscalled "convolutionalcalled "convolutionalencoding."encoding."

A burst error is a typeA burst error is a typeof error in receivedof error in receiveddigital telephonedigital telephonesignals. Burst errorssignals. Burst errors

occur in clumps ofoccur in clumps ofadjacent symbols.adjacent symbols.These errors areThese errors arecaused by fading andcaused by fading andinterference.interference.


12/18

HOW INTERLEAVING WORKSHOW INTERLEAVING WORKS

InterleavingInterleaving

DeDe--interleavinginterleaving


13/18

CHANNELIZING THE SIGNALCHANNELIZING THE SIGNAL

The encoded voice data isThe encoded voice data isfurther encoded to separatefurther encoded to separateit from other encoded voiceit from other encoded voicedata. The encoded symbolsdata. The encoded symbols

are then spread over theare then spread over theentire bandwidth of theentire bandwidth of theCDMA channel. This processCDMA channel. This processis called channelization.is called channelization.

Two kinds of codesTwo kinds of codes

1)Walsh code1)Walsh code

2) Pseudorandom Noise2) Pseudorandom Noise(PN) codes(PN) codes


14/18

CODES CHANNEL USED IN CDMACODES CHANNEL USED IN CDMA

A code channel is aA code channel is a

stream of datastream of data

designated for a specificdesignated for a specific

use or person. Thisuse or person. This

channel may be voicechannel may be voice

data or overhead controldata or overhead control

data.data.

1) The forward links

2) The reverse links


15/18

FORWORD LINK CHANNELSFORWORD LINK CHANNELS

The forward link usesThe forward link uses

four types of channelsfour types of channels

to transmit voice andto transmit voice and

control data to thecontrol data to the

mobile.mobile.

1) Pilot, 2) Sync, 3)1) Pilot, 2) Sync, 3)

Paging, 4) TrafficPaging, 4) Traffic


16/18

REVERSE LINK CHANNELSREVERSE LINK CHANNELS

The reverse linkThe reverse link

uses two types ofuses two types of

channels to transmitchannels to transmit

voice and controlvoice and controldata to the BTS.data to the BTS.

1) Access,1) Access,

2)Traffic2)Traffic


17/18

RECEIVER SIDE WORKSRECEIVER SIDE WORKS

Conversion of RFConversion of RF

signal to digital signalsignal to digital signal

Despreading theDespreading thesignalsignal

Deinterleaving andDeinterleaving and

decodingdecoding

Voice decompressionVoice decompression


18/18

BENEFITS OF CDMABENEFITS OF CDMA

Capacity increases .Capacity increases .

Improved call quality.Improved call quality.

Simplified system planning through the use of theSimplified system planning through the use of the

same frequency in every sector of every cell .same frequency in every sector of every cell .Enhanced privacyEnhanced privacy

Improved coverage characteristics.Improved coverage characteristics.

Increased talk time for portablesIncreased talk time for portables

Bandwidth on demandBandwidth on demand

Documents

CDMA presen