cdma call processing

CDMACALL PROCESSING

0 1 2 16 31

We have 32 Time slots for E1I,e TS 0 to TS 31Each slot having data rate of 64 Kbps.

PSTN

AM

CM

SM-2000E1

5ESS SWITCH

E1

D.L

ECPCOMPLEX

D.L

SS7

AM

CM

SM-2000 SM-2000 SM-2000

ATM

PSTN

CELL

ECPCOMPLEX

PSTN

IWF IFRPH

IBC

SVC CELL

555

SMPSTN

DLTU2

PSU 2PHV

0

16

PHV

16

0

FRPH

0

30

TSICELL SITE

DLTU 2

1

64

DFI

ECSU

TSI

PP

DATAFANOUT

VOCODER

PHV

PCM VOICE

CDMA PACKET

PACKET

BUS

PACKET HANDLER FOR VOICE

PHV 1: 8Kbps (9.6Kbps)PHV 2: 13Kbps(14.4Kbps)

PHV 3: Both 8Kbps & 13Kbps

100Mbps

A Data channel employs Radio Link Protocol(RLP), which enhances delivery of user dataacross air link by detecting missing user data and retransmitting it.

Mobile originated calls(Ckt-mode) : The mobile down loads its stored modem configuration in to the IWF.(Ex: Tel No. of PSTN-connected modem etc.)

SH

PHV

FRAMESELECTOR

FRPH PHA

ATM

PHA

TSI

SM X

CMAM

PSTN DFI DFI SITE

SM Y

CDN

CDNSS7

SS7

RPCN

CSN

CSN

IMS RING

DATA LINKS

RPCN :RING PERIPHERAL CONTROL NODE

Interconnects the ECP and IMS Ring.

CSN : Cell site Node Terminates up to 8 Cell site data links.

CDN : Call processing/data base node Performs many of the call processing functions.

PHV FRPH IFRPH

DFI

ISDNPRI

ISDNFRAMERELAY

IWF

CELL

PSTN

FRAMESELECTOR

DATACHANNEL

FOR DATA

PSTN TO IWF : ANALOG TONESIWF TO MOBILE : DIGITAL DATA

VSC

PHV PHV FRPH FRPH

DATA FAN OUT

PACKET BUS

PSU-2

DFI

DFI

DFI

DFI

DFI

DLTU

TSI

ECP CELL SITE

DCS

PSTN

PSTN TO MOBILE STATION

PCM VOICE(64kBPS)

SIGNALLING(DL-0 & DL 1)

VOICE PACKETS (In the form of DS0)

One P.P with PHV 1

One P.P with PHV 2

DS0 s (64Kbps)

2

3

4

5

6

7

8

6

30

26

22

18

14

10

22

19

16

13

10

7

4

PHV PHV FRPH FRPH

DATA FAN OUT

PACKET BUS

PSU-2

DFI

DFI

DFI

DFI

DFI

DLTU

TSI

ECP CELL SITE

DCS

DFILAT

CELL SITE

MOBILE STATION TO MOBILE STATIONCALL IN THE SAME SM

DFI

PHV3

FRPH

ChanlGroups

PSU 2

TSI DFIIn D L T U 2

12..89..1617..222425

23

8

10

PP

12

CSN

IMS

Acculink

1

8

1

32

DFIE1

1

24

DL -0

SWITCH SIDE CELL SIDE

DFI

CCC8

CCC10

CCC12

E1 MAPPING FOR 1st E1.

LN 00

DFI

PHV3

FRPH

ChanlGroups

PSU 2

TSI DFIIn D L T U 2

12..8

23

14

PP

CSN

IMS

Acculink

1

8

1

32

DFIE1

1

24

DL -1


DFI

CCC14

E1 MAPPING FOR 2nd E1.

LN 32

DFI

PHV3

FRPH

ChanlGroups

PSU 2

TSI DFIIn D L T U 2

12..89..1617..24

25

31

20

22

PP

24


DFI

CCC20

CCC22

CCC24

E1 MAPPING FOR 3rd E1.

16

CCC16

DFI

PHV3

FRPH

ChanlGroups

PSU 2

TSI DFIIn D L T U 2

12..89..1617..24

25

31

26

28

PP

30


DFI

CCC26

CCC28

CCC30

E1 MAPPING FOR 4th E1.

18

CCC18

AM

CM

SM

PSTN

CELL SITE

SM SM

ACCULINK DACS

IMSDLN RPCN

ACDN CDN

SS 7 CSN

ECP

OMP

AUTO PACE

CELL SITE P.Ps

CELL SITE DATA LINKS(BX.25)

DCS

Dual X.25

DS1 0 or DL-0 or Ist E1

DS0 0 1-8 9-16 17-22 23 24-25 26-31SYNCP.P 8 10 12 NOT USEDDL 0 12

No. DS0s 1 8 8 6 1 2 6

DS1 1 or DL-1 or 2nd E1

DS0 0 1-8 9-22 23 24-31SYNCP.P 14 DL 1

No. DS0s 1 8 14 1 8

NOT USED NOT USED

P.P POSITION IN E1

DS1 2 or 3rd E1

DS0 0 1-8 9-16 17-24 25-31SYNCP.P 20 22 24 16

No. DS0s 1 8 8 8 7

DS1 3 or 4th E1

DS0 0 1-8 9-16 17-24 25-31SYNCP.P 26 28 30 18

No. DS0s 1 8 8 8 7

8DS 0s : 30 Calls7DS 0s : 26 Calls

CCC CCU1

CCU2

CCU3

ACU BCR

BIUBBA

TxRx0

Rx1

RCC

DFI

SCT

E1

RFTG

GPS ANTENNA

CDMA CLUSTER

CBUS

TDM BUS

19.66MHZ,2PPSGPS TIME

15MHZ,1PPSGPS TIME

CELL SITE

CCU : Performs the digital base band signal functions

BIU : Controls ACU,BCR and provides TDM bus to RCC

ACU : Converts the signals from one or two CCCs to Analog Base band signals.

BCR : Converts Analog base band signals from up to 3 ACUs to RF Signals. To antenna faces.

CCC8

CCC10

CCC12

ACU

ACU

ACU

BCR

BCR

BCR

BIU

BIU

BIU

DFIE1

E1

SCT RFTG GPSRECEIVER

GPS ANTENNA

TDM BUS

1.2Kbps

2.4Kbps

4.8Kbps

9.9Kbps

1.8Kbps

3.6Kbps

7.2Kbps

14.4Kbps

8Kbps VocodedSpeech data(20msec block)


1/2Rate

3/4Rate

Interleaver

19.2Kbps

19.2Kbps

Encoder &Code repetition

Scrambling

Long CodeGenerator

Decimator

19.2Kbps

1.23Mbps

MUX

Pwr controlbit position

800bps

Power control Bits(800bps)

Walsh codeGenerator

64 Bits

I-Chl PilotPN offset

Q-Chl PilotPN offset

1.23Mbps

1.23Mbps

1.23Mbps

CALL PROCESSING IN CELL SITE

CDMA FRAME FORMATS

1 1719.6Kbps Frame

4.8Kbps Frame

2.4Kbps Frame

1.2Kbps Frame

12 8

1 79 88

1

1 15

39 8

8

: Mixed mode bit

: Information bits

: CRC(Cyclic redundancy check)

: Encoder tail bits.

Total Bits 1+171+12+8=192 Bits in 20ms Block

Total Bits 1+79+8+8=96 Bits in 20ms Block

Total Bits 1+39+8=48 Bits in 20ms Block

Total Bits 1+15+8=24 Bits in 20ms Block

20ms FRAMES

WALSH CODES REPRESENTATION IN CDMA BAND

23 54 49 28 8 60 59 56 41 24 20 2 25 16 40 30 16 46 9 15 13 32 14 48 21 64 7

1.25MHz

Walsh Code 0 : Pilot Channel

Walsh Code 1-7: Paging Channel

Walsh Code 32 : Sync Channel

Walsh Code 8-63: Forward Traffic channel except 32

CDMA Carrier

PILOT PN Sequence Offset 0


PILOT PN Sequence Offset X



FORWARD CDMA Chal

PILOT Chal PAGING Chal SYNC ChalTRAFFIC

ChalTRAFFIC

Chal

We have 4 channels

160 Chl No. 4201 Chl No. 3242 Chl No. 2283 Chl No. 1

Concerned Down link Frequencies for the above channels are

160 X 0.03 MHz + 870 MHz = 874.8 MHz

201 X 0.03 MHz + 870 MHz = 876.03 MHz

242 X 0.03 MHz + 870 MHz = 877.26 MHz

283 X 0.03 MHz + 870 MHz = 878.49 MHz

Each Band contains 41 ChannelEach Channel is 30 KHz or 0.03 MHzSo channel separation is 41 X 0.03 MHz = 1.23 MHz

Note: Down link is Base station to Mobile.

Concerned Up link Frequencies for the above channels are

160 X 0.03 MHz + 825 MHz = 829.8 MHz

201 X 0.03 MHz + 825 MHz = 831.03 MHz

242 X 0.03 MHz + 825 MHz = 832.26 MHz

283 X 0.03 MHz + 825 MHz = 833.49 MHz

Up link down link separation is 45 MHz.

Total down link bandwidth is 870 - 885 MHzand Up link bandwidth is 825 - 840 MHz

Note : Up link is Mobile to Base station.

140

160

180

181

201

221

222

242

262

263

283

303

Chl 4 Chl 3 Chl 2 Chl 1

139

131

304

312

GuardBand

GuardBand

41 FDMA Chls (1.23MHz)

U.L: 829.8MHzD.L: 874.8MHz


U.L: 831.03MHzD.L: 876.03MHz



9 Chls (0.27MHz)

U.L: 832.26MHzD.L: 877.26MHz

U.L: 833.49MHzD.L: 878.49MHz

9 Chls (0.27MHz)

NOTE : U.L :Up Link D.L : Down Link

Total B.W required for 4 Chals is 1.23 MHz x 4 = 4.92 MHzGuard Band 0.27 MHz x 2 = 0.54 MHz

= 5.46 MHz

FORWARD LINK CHANNEL FORMAT

PN SpreadingPN Spreading




D/A ConvertD/A Convert




PILOT Chal

SYNC Chal

PAGING Chals1 up to 7 Chals

TRAFFIC Chals1 up to 55 Chals

All 0’s

Walsh code 0

Walsh code 32

Walsh code 1 to 7

Walsh code 8-31,33-63

4.8Kbps

19.2Kbps

19.2Kbps

1.23Mbps

1.23Mbps

1.23Mbps

1.23Mbps

I

Q

I Data

Q Data

Q Data

Q Data

Q Data

I Data

I Data

I Data

CDMA REVERSE TRAFFIC CHANNEL

1.2Kbps

2.4Kbps

4.8Kbps

9.9Kbps

1.8Kbps

3.6Kbps

7.2Kbps

14.4Kbps



1/3Rate

1/2Rate

Interleaver

28.8Kbps

28.8Kbps

Encoder &Code repetition

Long CodeGenerator

1.23Mbps

IPN offset 0

307.2Kbps

Code 63

Code 62

Code 61

Code 1

Code 2

Code 0Q

PN offset 0

1.23Mbps

1.23Mbps

D/AConvert

D/AConvert

T/2

Q

I64-Ary Mod

64-ary Modulation

W 63=……………………..

W 0 =……………………..

W 1 =……………………..

64 Bits

W 2 =……………………..

101100110100111000010

Decimal value of Last 6 bits is 2. This will mapp in to Walsh code 2(Consistes 64 bits)

I/p Data rate is 28.8 Kbps

O/p Data rate is 28.8 Kbps x 64 bits

6 Bits = 307 Kbps

ADVANTAGES :

Different ratings of Coders.(When users assigned to CDMA carrier are not talking, all other on the same carrier benefit with less interference.)

Frequency reusage factor : 1

Low RF Power.

Multipath fading can avoid using rake receiver.

Soft hand off: A call to be carried by the two or six cells or sectorsat the same time.

Security : It is spread spectrum Technology.

Each OMNI Cell /Cell sector operating on CDMA carrier is identified by PN sequenceoffset. There are 512 Pilot PN sequences offsets (0 to 511) Forward chals on one CDMAcarriers.

Primary CDMA carrier is 283.

Each PN consists 64 Chips

PILOT PN sequence is Quadrature pair of identical PN binary codes operating at 1.23Mbpsfor F.W and Reverse CDMA Chals.

Each PN sequence is Maximum length binary sequence of :

512 Offsets X 64 Chips = 32768 in 26.7 msec.

Note: Forward CDMA Chal always contains one PILOT may be one SYNC may be seven PAGING up to 63 TRAFFIC Chanals

Number of Walsh codes : 64 (0 to 63)Each Walsh code contains 64 Bits. Long and operating 1.23Mbps

Walsh functions are orthonagal

0 : PILOT1 to 7 : Paging or Traffic32 : SYNCRemains Traffic.

All codes are Information Bearing Chals Except PILOT Chal consists 64 Zeros.

A Mobile initially acquires the CDMA system by searching and locking on to strongest PILOT Chal.

REVERSE CDMA CHANNEL

CDMA CARRIER

PN SequenceOffset 0

REVERSR CDMA Chal

ACCESSChal 1

ACCESSChal N

TRAFFICChal 1

TRAFFICChal N

REVERSE CDMA Chal is sum of all MS transmission on a CDMA Carrier.

N : Number of Mobiles currently accessing the CDMA system on the CDMA Carrier.

Common CDMA carrier(283) has its own PILOT,SYNC,PAGING and TRAFFIC channels.

FORWARD

Non common CDMA carriers(160,201,242) has own PILOT& TRAFFICChannels. It may or may not have sync and paging Chals.

For every paging Chal in Forward atleast on Access chal in reverse.

42 Bit Long code is for 1) Identify the traffic (Reverse) 2) Paging and Traffic chal scrambling.

Each code binary sequence of 4.4 Trillion (42 days)REVERSRECommon carrier has its own Paging & Traffic ChalsBit other carriers has its own Traffic chals but may or may not have ownAccess Chals.

Global Positioning System

The start of CDMA system time coincides with GPS time.(Jan 6,1980 00:00:00)

The present CDMA time is Number of seconds elapsed from the above time.

Cell Site

MS

MS

Cell Site

5micro Sec/mile 5micro Sec/mile

CDMA Call is processed by different stages Stage 1 : MSC : It is combination of DCS and ECP Complex

Stage II: Cell site

Here ECP complex consists ECP,IMS token ring and OMP

ECP is heart of heart of Call processing. It controls call processing in DCS via SS7 link and Cell site via Data links.

Each SM-2000 consists 1) Packet handler for Voice(PHV)

Each Packet Handler can have of 16 Vocoders(or Speech handlers(SH)) Each Vocoder process one call and it converts PCM 64Kbps to 9.6/14.4Kbps

packets or vice versa. Each SH will also have function of Frame selector, which selects best

frame(by CRC)in Softhandoff reverse call process.

2) PH4(FRPH) Each FRPH can handle 64 calls or 32 DS0s. Since our network Packet

Pipe(PP) consists 8DS0s(equal to 30 calls), each FRPH may handle two PPs

3) Packet Bus(100Mbps)

4) PHA(Packet handler for ATM) for SM to SM call processing.

In forward call processing E1 lands on SM/DLTU, which consists of DFI cards(up to 20)and ECSU.During data compression(By Vocoders) there will be some time delay. Because of this ECHO may

raise. To avoid ECHO, we have ECSU(Echo cancelled and signaling unit). The signaling information from E1 goes to ECP complex via DCS.

Now each Vocoder(SH) takes one 64Kbps PCM line and compress the data rate to PHV1(9.6Kbps) orPHV2(14.4Kbps) or PHV3(both 9.6 (EVRC)& 14.4Kbps) Packets, depends upon the rate set of

Vocoder

The vocoded data can be Full rate(9.6Kbps),Half rate(4.8Kbps),quarter rate(2.4Kbps) or 1/8th rate(1.2Kbps), depends upon the voice rate.

This CDMA packets from different Vocoders go to FRPH via Packet Bus(100Mbps). CDMA packetsfrom PHVs to FRPH (& from FRPH to PHVs) is Dynamic.

FRPH converts these packets in to Packet pipe.(We have 12 Packet pipes for each cell site. I.e. 8,10,12,14,16,18,20,22,24,26,28 and 30)

These Packet pipes are going to DLTU, where DFI mux the Packet pipes and Datalink(it is coming from Cell site node of IMS ring) and forms E1. For each cell site 4E1s are allotted.

Only Ist and 2nd E1 for each cell site requires Data links. D.L(Data link)-0 will go along with Ist E1 and D.L-1 go along with 2nd E1. 3rd and 4th E1s consists only PPs.

In the reverse link DFI extracts the D.Ls coming from Ist and 2nd E1s and sent to CSNs.and sends PPs to concerned FRPHs. Here PPs from FRPH to DFI is static. The particular

FRPH,DFI at SM in DCS is constant for particular cell site.

FRPH converts PPs to Packets and sends to PHV via packet bus, in case the call is to PSTN. The Frame selector selects good frame(20msec) in case the call is from more than one cell sites or sectors.

The Vocoder now decodes CDMA packets to 64Kbps PCM line.

In case the call is within DCS and with in same SM, then first CDMA packet from FRPH goes to PHVconverts to 64Kbps data, goes to DFI and loop back to again DFI(Called loop around trunk:LAT) and goes to PHV and converts to CDMA packet and goes to FRPH , and from there to concerned cell site.

In case the call is within DCS and different SM, then concerned CDMA packet to PHA and lands ondifferent PHA,which is located in different SM. The SM to SM connection is trough ATM.

ECP complex consists ECP,IMS Token ring and OMP. IMS ring nodes having protection byLink node 00(LN00) and and Link node 32(LN 32). Each Link Node consists 1) CSNs(Cell site Nodes)

2) CDNs(Call Processing & data base node) 3) SS7 node

4) RPCN(Ring peripheral and control node)

CSNs controls the cell site by Data links. Each cell CSN can have up to 8 D.Ls. LN00 CSN haveeight D.L-0s and LN32 CSN have eight D.L-1s. So one pair of CSNs will manage eight cell sites.

If sites are more than eight then we have to go for one more pair of CSNs.

SS7 Node in IMS ring control call process in DCS. The signaling information from PSTN will cometo IMS ring via this SS7 link. Both Link nodes in IMS ring has SS7 nodes for protection.

CDNs in IMS ring will do call processing.

RFCN will connect IMS ring to ECP. Even RFCN is duplicated for protection.

Now CSN will have eight D.Ls. These Data links are connected to ACCULINK, where it formsE1. Acculink even gets D.Ls from other CSN. This E1 is connected to DFI, which is available

in DLTU of SM.

DIFFRENCE BETWEEN DATA & VOICE CHANNELS

FRAME SELECTOR

FRAME SELECTOR

VOCODERDATA CHAL

PHV PHV

PACKET SWITCHING N.W(VOICE) CKT MODE DATA

(DATA)

For Voice PHV contains VOCODER with Frame selectorFor Data PHV contains DATA Channel with Frame selector.

One PHV can support three Data channels with reducing its any of its voice processing capacity.Service option 3 uses for EVRC(Bot rate sets)

Service option 4 : Asynchronous data service for Computer at CDMA NIU with rate set 1(9.6Kbps)This can connects with existing asynchronous modem in the PSTN. This requires IWF

A Data channel can support any circuit-mode data.

Service option 5: Asynchronous data access to fax for rate set-1. It can connect with Group-3 Fax in PSTN.

It requires IWF(Inter Working Function) & down loading radio link protocol(RLP) on to existing PHV boards.

Service option 6 : It is for sending “SHORT MESSAGE SWITCH(SMS)” to NIU.

Service option 12 : Asynchronous data service for Computer at CDMA NIU with rate set2(14.4Kbps)

Service option 13 : Asynchronous data access to fax for rate set-2. It can connect with Group-3 Fax in PSTN.

IWF provides protocol conversion between protocols carried over air interface and modemprotocols required for voice-band data in the PSTN path.

TIA STANDARDS

IS-95A : For Air-Interface Packet-switched service.(@ 800Mhz)IS-95B : For Air-Interface Packet-switched service.(@ 800Mhz & 1900Mhz)

IS-99 : CDMA Air interface for Ckt-mode data service with rate set-1IS-707 : CDMA Air interface for Ckt-mode data service with rate set-2

IS-658 : Defines interface between IWF & MSC

CSN to DFI uses BX.25

Mobile data path : Mobile to/from IWFAnalog Modem tones IWF to/from PSTN.

IWF supplied by 3-com communication corporation.

In case of Data channel the CDMA packet which is coming from P.P goes toPHV, it sends to IFRPH(ISDN FRPH), where it can handle 40 simultaneous Ckt-mode Data calls. Each Ckt-mode data call requires one SVC(Switched Virtual circuit) for on

an IFRPH for sending Data call to IWF. It converts to ISDN B Chal(IBC) and enters PSTN environment.

A Data channel employs Radio Link Protocol(RLP), which enhances delivery of user dataacross air link by detecting missing user data and retransmitting it.

Mobile originated calls(Ckt-mode) : The mobile down loads its stored modem configuration in to the IWF.(Ex: Tel No. of PSTN-connected modem etc.)

Each cell site caters 4 E1s. These E1s lands on DFI card in cell site and from there toBUS 0 and BUS 1(These two bus are connected to RCC(Radio control complex). Now

all the 12 CCC(In CDMA Cluster complex) are connected to BUS 0 and/or Bus 1. TDMBus supplies Clock,frequency and data to the each CCC. Now CCC extracts one Packetpipe from E1. So One packet pipe from FRPH in DCS will serve on one CCC in cell site.

We have three ECU's(Enhanced channel unit) for each CCC. CCC demux the Packetpipe and disassemble packets and sends to ECU. Now each ECU consists 10 Channel

elements. So one CCC can handle 30 Channel elements.(CE s)

CCC = 3 ECU's = 10 X 10 CE = 30 CE s

One CE in cell site is equal to one trunk(connects on vocoder/SH) in DCS.

In reverse Call processing packets coming from different CE s assemble and become Packet pipe(P.P) at CCC and mux in to E1 and goes to DCS via ADM.

CCU performs the Digital base band signal functions.

CE performs the Digital band signal processing for a single CDMA channel.In CE the packet which contains 9.6Kbps Data(Can be full rate,half rate,quarter

rate,1/8 rate depends upon vocoder data rating) will be doubled i ,e 19.2Kbpsand scramble with 42Bit register Long code. This PN code is users algorithm

A long code sequence is a PN sequence, operating at 1.23Mbps used to spread the access and reverse traffic channels and to scramble the paging and forward traffic channels. The long

code uniquely identifies access channels on the same CDMA carrier and uniquely identifies amobile station on both reverse and forward traffic channels.

Each Long code sequence is maximum length binary sequence repeats every 4.4 Trillion(Approx........ 42 days), this also called as long PN code. Where PN is pseudo Noise on CDMA carrier.

This 1.23Mbps long code decimated by 64 and gives 19.2Kbps and this will scramble the originaldata, so that the resultant data becomes coded data at the rate of 19.2Kbps. From the same Long

code for every 800 or for every 1.25msec bits one bit will be inserted( I ,e 1/800=1.25msec) into the data for increasing and decreasing the power depends upon the NIU requirement.

Tx power + Rx power = -75 dBm.

NIU will extract this bit from data for every 1.28msec and increases/decreases the power byone d B depends upon the bit one or zero.

The narrow band signals are associated with code channel are spread by specialized binary sequencecalled Walsh functions and then spread by the Pilot PN sequence operating at an signed time

offset. There are 64 different Walsh functions, 0 to 63, each 64 bits long and operating at1.2288Mbps. Code Channel 0 is spread by Walsh function zero, code channel 1 is spread by Walsh function 1,…

and code channel 63 is for Walsh function 63.

Code channel zero is assigned to the pilot channel. Code channels 1 through7 may be assigned to either the paging channels or the traffic channels. Code

Channel 32 may be assigned to either a sync channel or a traffic channel. The Remaining code channels may be assigned to traffic channels.All code

channels are information-bearing channels except the pilot channel. The pilot channel is un modulated by information and is assigned Walsh

function zero, which consists of 64 zeros. Thus, the pilot channel signal consists only of the pilot PN sequence operating at an assigned time offset.A mobile initially acquires the CDMA system by searching and locking onto

the strongest pilot channel, which typically corresponds to the nearest cell site. During a call, the mobile

distinguishes its particular signal by despreading the received data with a synchronized representation of the same Walsh function used to spread

the signal at the cell.

The primary carrier(Carrier 283 consists sync) and noncommon(160,201 242)carriers may or may not have sync and paging channels. The Walsh

functions, themselves, are aligned to the locally generated Pilot PN sequence.

Now this 1.23Mbps(19.2Kbps X 64 = 1.23Mbps wide spread) is divided in to I(Inphase) and Q(Quadrature phase) digital channels.

From GPS antenna We are getting GPS Clock one PPS(1 Hz)and GPS timingto GPS Antenna and it is generating 15 Mhz and 1PPS. This is going to RFTG

(Reference Frequency and Timing Generator). We have two Reference generatorsRG-0 and RG-1(Protection). This will give clock and frequency to SCT(Synchronised

clock and tone), where it gives 19.6608MHz and clock 2PPS(one pulse for twoseconds:0.5Hz) to TDM Bus. We have duplicated SCTs for protection for each Growth

Frame. Each Frame caters for six CCCs. This SCT output goes to CCC complex forcall processing. The start of CDMA system time coincides with of GPS time, Jan 6th,1980 00(Hr):00(Min):00(Sec)UTC(Universal time code). The present CDMA time is

number of seconds elapsed from the above time.Mobile receives time with SYNC Chal from the Base station.

Pilot PN sequence is getting time from GPS. We have time difference from place to place. By creating time offset one sector carrier to another sector carrier and from

one cell site to another cell site, even we use same carrier in all the three sectorscarrier interference will not happen. That is the reason why CDMA carrier reusage

factor is 1. We are maintaing sector to sector same carrie offset is 168.

Pilot PN sequence, which is Quadrature pair of identical PN binarycodes operating at 1.23Mbps for Forward and Reverse CDMA channels.Each sector(Alpha,Beta and gamma) transmits same PN sequence but

with different time offset.

We have 512 offset 0 to 511, each offset having 64 chips. So Maximum length of binary sequence is 32768 (512 offsets X 64 Chips) and repeats

every 26.7msec.

00

11

10

01

I

Q

PN SequenceOffset

I

Q

Example for one C.E Pilot PN offset coding

The Forward (Base station to Mobile) CDMA channel contains Pilot channel and may carry up to one Sync and up to seven paging and up to 63 traffic channels.

All code channel are information bearing channels except Pilot channel(Unmodulated by information) consists all 64 Zeros. A mobile initially acquires the

CDMA system by searching the strongest the PILOT channel.

Now In Radio Unit contains BBA trio(Base Band) which includes BIU(BusInterface Unit),ACU(Analog conversion unit) and BCR(Base band combiner &

Radio).

CCC

CCU

CCU

CCU

CE 0

CE 1

CE 9ACU

ACU converts all CE digital base band signals to single Analog Base band signal.BIU controls both ACU and BCR and also connected to TDM bus.

In BCR the Analog base band signal which is coming from particular ACUcup converts to required Radio Frequency(RF) and goes to concerned Sector.

Since each carrier serves 3 CCCs, BCR of a Alpha sector even connected to ACU of another BBA

Here for 283 carrier CCC 8,10,12 is connected. Like for carrier 160 CCC14,16,18and for carrier 242 CCC 20,22,24 and for carrier 201 CCC 26,28,30 are connected.

CCC 8 ACU BCR

CCC 10

CCC 12 ACU

ACU

BCR

BCR

Example on 283 Carrier

Alpha

Beta

Gamma

CDMA Overhead Channels and Overhead CEsCDMA overhead channels are the control channels used by a CDMA system to establish call setup prior to assigning the call to a traffic channel. There are four types of CDMA overhead

channels:1)Pilot channel The pilot channel is an unmodulated, direct-sequence spread-spectrum signal transmitted continuously by each sector of a CDMA cell. It allows the mobile to acquire the timing of the forward control channels and provides a coherent carrier phase reference for

demodulating the sync and paging channels.2)Sync channel The sync channel provides time-of-day and frame synchronization

to the mobile. The mobile uses this channel to acquire cell and sector-specific information.3)Paging channel The paging channel transmits control information to idle mobiles during mobile power-up and when a mobile is acquiring a new cell site. It conveys

pages to the mobiles.4)Access channel The access channel is a CDMA reverse channel used for short

signaling message exchange such as mobile registration, mobile call origination, and response to pages..In the Lucent Technologies CDMA system, a CE can be configured as an overhead channel or a traffic channel. There are three types

of overhead CEs: an overhead CE configured as the pilot/sync/access channel, known as the P/S/A CE, an overhead CE configured as a pilot only channel, known

as the pilot CE, and an overhead CE configured as the paging channel, known as the page CE.

In the reverse CDMA call, vocoded 20msec data(May be 9.6Kbps for Rate set-1) becomes 28.8Kbps by one third rate by code repetition & encoder. We have 64 Ary modulator, where

it 64 codes, and each code contains 64 bits. Ex W1,W2….W63. The decimal value of last 6bits in the Data, will decide which W code represents this data. For example the decimal

value of lst 6 bits for a frame is 000011, it is equivalent of decimal 3. So W 3 converts this bits its coded 64 bits. So for 28.8Kbps data 28.8Kbps X 64 Bits

6 BitsEqual to 307.8Kbps. With this data the users mask(Long code )which at the rate 1.23Mbps

will be mixing. The resultant data i.e. 1.23Mbps. This Data is again dividing in to I & Qchannels. Here with zero offset of Pilot PN sequence it will modulate the data. Unlike in

forward channel, here the Q channel will be delayed by T/2 for OQPSK modulation.

cdma call processing

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