CDMACALL PROCESSING

0

1

2

16

31

We have 32 Time slots for E1 I,e TS 0 to TS 31 Each slot having data rate of 64 Kbps.

5ESS SWITCHSS7

ECPCOMPLEX

AM CM

D.L

PSTN

E1 SM-2000

D.L E1

PSTN

AM CM

ECP COMPLEX

PSTN

SM-2000 SM-2000IBC

SM-2000 ATM

CELL

IWF

SVC

IFRPH

CELL

PSTN

SMPSU 2PHV0

D L T U 2

DFI16

0

1

ECSU0

PP5 5 5 30 16

CELL SITETSI

TSI

64

FRPH

DLTU 2

PHV

CDMA PACKET P A C K E T

DATA FANOUT VOCODERPCM VOICE

B U S

100Mbps PHV

PACKET HANDLER FOR VOICE PHV 1: 8Kbps (9.6Kbps) PHV 2: 13Kbps(14.4Kbps) PHV 3: Both 8Kbps & 13Kbps

A Data channel employs Radio Link Protocol(RLP), which enhances delivery of user data across 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.)

AM

CM SM X

ATM

SM Y FRAME SELECTOR PHA

SHPHV

FRPH

PHA

PSTN

DFI

TSI

DFI

SITE

DATA LINKS

SS7 RPCN SS7

CDN IMS RING CDN

CSN

CSN

RPCN :RING PERIPHERAL CONTROL NODEInterconnects the ECP and IMS Ring.

CSN : Cell site NodeTerminates up to 8 Cell site data links.

CDN :

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

FOR DATAFRAME SELECTOR DATA CHANNEL

CELL

PSTN TO IWF : ANALOG TONES IWF TO MOBILE : DIGITAL DATA

PHV

FRPH

IFRPH

PSTN

DFI

VSC

ISDN PRI IWF

ISDN FRAME RELAY

PSTN TO MOBILE STATIONPSTN

ECP

CELL SITE

DCSDLTU

TSI

DFI

DFI PSU-2 DATA FAN OUT DFI PHV PHV FRPH FRPH DFI DFI

PACKET BUS

PCM VOICE(64kBPS) SIGNALLING(DL-0 & DL 1) VOICE PACKETS (In the form of DS0)

DS0 s (64Kbps) 2 3 4 5 6 7 8

One P.P with PHV 1 6 10 14 18 22 26 30

One P.P with PHV 2 4 7 10 13 16 19 22

MOBILE STATION TO MOBILE STATION CALL IN THE SAME SM

ECP

CELL SITE

DCS TSIDLTU DFI DFI DFI PSU-2 DATA FAN OUT DFI PHV PHV FRPH FRPH DFI DFI LAT

CELL SITE

PACKET BUS

E1 MAPPING FOR 1st E1.

SWITCH SIDE TSI 1 DFI 2 In

CELL SIDE

. . PSU 28 D F I P H V 3 F R P H Chanl Groups 10 12 8 9 . . 16 17 . . 22 24 25 231 11

D L T U 2

CCC 8

DFI

CCC 10

PP

CSN8

E132

DFI24

DL -0

IMS LN 00 Acculink

CCC 12

E1 MAPPING FOR 2nd E1.

SWITCH SIDE TSI 1 DFI 2 In

CELL SIDE

. .8

PSU 214 D F I P H V 3 F R P H Chanl Groups

D L T U 2

CCC 14

DFIPP

231 11

CSN8

E132

DFI24

DL -1

IMS LN 32 Acculink

E1 MAPPING FOR 3rd E1.

SWITCH SIDE TSI 1 DFI 2 In

CELL SIDE

. . PSU 220 D F I P H V 3 F R P H Chanl Groups 22 24 16 25 8 9 . . 16 17 . . 24

CCC 20

D L T U 2 CCC 22 DFI

PP

CCC 24

31

CCC 16

E1 MAPPING FOR 4th E1.

SWITCH SIDE TSI 1 DFI 2 In

CELL SIDE

. . PSU 226 D F I P H V 3 F R P H Chanl Groups 28 30 18 25 8 9 . . 16 17 . . 24

CCC 26

D L T U 2 CCC 28 DFI

PP

CCC 30

31

CCC 18

PSTN

AM CM SM SM SM

DCS CELL SITE

AUTO PACE ACCULINK DACS

OMP Dual X.25

SS 7 IMS

CSN RPCN CDN ECP

DLN ACDN

CELL SITE P.Ps CELL SITE DATA LINKS(BX.25)

P.P POSITION IN E1

DS1 0 or DL-0 or Ist E1

DS0 P.PNo. DS0s

0SYNC 1

1-8 88

9-16 108

17-22 126

23DL 0 1

24-25 122

26-31NOT USED 6

DS1 1 or DL-1 or 2nd E1

DS0 P.PNo. DS0s

0SYNC 1

1-8 148

9-22NOT USED 14

23DL 1 1

24-31NOT USED

8

DS1 2 or 3rd E1

8DS 0s : 30 Calls 7DS 0s : 26 Calls

DS0 P.PNo. DS0s

0SYNC 1

1-8 208

9-16 228

17-24 248

25-31 167

DS1 3 or 4th E1

DS0 P.PNo. DS0s

0SYNC 1

1-8 268

9-16 288

17-24 308

25-31 187

GPS ANTENNA

RCC RFTG19.66MHZ,2PPS GPS TIME

15MHZ,1PPS GPS TIME

SCT

CCC

CCU1 CCU2

ACU

BCR

Tx Rx0 Rx1

DFI

CBUS

BIUBBA

CCU3CDMA CLUSTER

E1

TDM BUS

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.

TDM BUS CCC 8

BIU

ACUBIU

BCR

CCC 10

ACUBIU

BCR

CCC 12

ACU

BCR

SCTE1 E1

RFTG

GPSRECEIVER GPS ANTENNA

DFI

CALL PROCESSING IN CELL SITE

8Kbps Vocoded Speech data Power control (20msec block) Encoder & Bits(800bps) 1.2Kbps Code repetition 2.4Kbps 1/2 Rate 19.2Kbps 4.8Kbps Scrambling 1.23Mbps 9.9Kbps Interleaver MUX 1.8Kbps 800bps 3.6Kbps 3/4 19.2Kbps Pwr control Rate 7.2Kbps bit position 14.4Kbps 13Kbps Vocoded Speech data (20msec block) 64 Bits Walsh code Generator

1.23Mbps I-Chl Pilot PN offset

Q-Chl Pilot PN offset 1.23Mbps

19.2Kbps Long Code Generator Decimator

1.23Mbps

CDMA FRAME FORMATS20ms FRAMES

9.6Kbps Frame

1 1

171 79

12 8 8 8

Total Bits 1+171+12+8=192 Bits in 20ms Block Total Bits 1+79+8+8=96 Bits in 20ms Block

4.8Kbps Frame

2.4Kbps Frame

1

39

8

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

1.2Kbps Frame

1

15

8

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

: Mixed mode bit : Information bits

: CRC(Cyclic redundancy check) : Encoder tail bits.

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 6 4 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 1

PILOT PN Sequence Offset X

PILOT PN Sequence Offset 510

PILOT PN Sequence Offset 512

FORWARD CDMA Chal

PILOT Chal

PAGING Chal

SYNC Chal

TRAFFIC Chal

TRAFFIC Chal

We have 4 channels 160 201 242 283 Chl No. 4 Chl No. 3 Chl No. 2 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 Channel Each Channel is 30 KHz or 0.03 MHz So 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 MHz and Up link bandwidth is 825 - 840 MHz Note : Up link is Mobile to Base station.

Guard Band

Chl 4

Chl 3

Chl 2

Chl 1

Guard Band

1 3 1

1 3 9

1 4 0

1 6 0

1 8 0

1 8 1

2 0 141 FDMA Chls (1.23MHz)

2 2 1

2 2 2

2 4 2

2 6 2

2 6 3

2 8 3

3 0 3

3 0 4

3 1 2

9 Chls (0.27MHz)

41 FDMA Chls (1.23MHz)

41 FDMA Chls (1.23MHz) U.L: 832.26MHz D.L: 877.26MHz

41 FDMA Chls (1.23MHz) U.L: 833.49MHz D.L: 878.49MHz

9 Chls (0.27MHz)

U.L: 829.8MHz D.L: 874.8MHz

U.L: 831.03MHz D.L: 876.03MHz

NOTE : U.L :Up Link

D.L : Down Link

Total B.W required for 4 Chals is 1.23 MHz x 4 = 4.92 MHz Guard Band 0.27 MHz x 2 = 0.54 MHz = 5.46 MHz

FORWARD LINK CHANNEL FORMATWalsh code 0 PILOT Chal All 0s 1.23Mbps I Data PN Spreading Q Data Walsh code 32 SYNC Chal 4.8Kbps Walsh code 1 to 7 PAGING Chals 1 up to 7 Chals 19.2Kbps Walsh code 8-31,33-63 TRAFFIC Chals 1 up to 55 Chals 19.2Kbps 1.23Mbps PN Spreading Q Data I Data D/A Convert 1.23Mbps PN Spreading Q Data I Data D/A Convert 1.23Mbps I Data PN Spreading Q Data D/A Convert D/A Convert

I

Q

CDMA REVERSE TRAFFIC CHANNEL1.23Mbps I PN offset 0

8Kbps Vocoded Speech data (20msec block) Encoder & 1.2Kbps Code repetition 2.4Kbps 1/3 Rate 28.8Kbps 4.8Kbps 9.9Kbps Interleaver 1.8Kbps 3.6Kbps 1/2 28.8Kbps Rate 7.2Kbps 14.4Kbps 13Kbps Vocoded Speech data (20msec block)

64-Ary Mod Code 63 Code 62 Code 61307.2Kbps

I D/A Convert Q D/A Convert

Code 2 Code 1 Code 01.23Mbps Q PN offset 0

T/2

Long Code Generator 1.23Mbps

64-ary Modulation

W 63=.. 64 Bits

101100110100111000010

W 2 =.. W 1 =.. W 0 =..

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 = 307 Kbps

O/p Data rate is 28.8 Kbps x 64 bits 6 Bits

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 sectors at the same time. Security : It is spread spectrum Technology.

Each OMNI Cell /Cell sector operating on CDMA carrier is identified by PN sequence offset. There are 512 Pilot PN sequences offsets (0 to 511) Forward chals on one CDMA carriers. Primary CDMA carrier is 283. Each PN consists 64 Chips PILOT PN sequence is Quadrature pair of identical PN binary codes operating at 1.23Mbps for 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 : PILOT 1 to 7 : Paging or Traffic 32 : SYNC Remains 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 CHANNELREVERSE CDMA Chal is sum of all MS transmission on a CDMA Carrier.

CDMA CARRIER

PN Sequence Offset 0

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

REVERSR CDMA Chal

ACCESS Chal 1

ACCESS Chal N

TRAFFIC Chal 1

TRAFFIC Chal N

Common CDMA carrier(283) has its own PILOT,SYNC,PAGING and TRAFFIC channels. FORWARD Non common CDMA carriers(160,201,242) has own PILOT& TRAFFIC Channels. 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) REVERSRE Common carrier has its own Paging & Traffic Chals Bit other carriers has its own Traffic chals but may or may not have own Access Chals.

Global Positioning SystemThe 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.

5micro Sec/mile 5micro Sec/mile

Cell Site

MS

MS

Cell Site

CDMA Call is processed by different stages Stage 1 : MSC : It is combination of DCS and ECP Complex Cell site Stage II: 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) or PHV2(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 packets from 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 PHV converts 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 on different 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 by Link 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 have eight 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 come to 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 forms E1. 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 CHANNELSPHV PHVFRAME SELECTOR FRAME SELECTOR

DATA CHAL VOCODER

PACKET SWITCHING N.W (VOICE)

CKT MODE DATA (DATA)

For Voice PHV contains VOCODER with Frame selector For 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 modem protocols required for voice-band data in the PSTN path.

TIA STANDARDSIS-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-1 IS-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 IWF Analog 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 to PHV, 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 data across 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 to BUS 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. TDM Bus supplies Clock,frequency and data to the each CCC. Now CCC extracts one Packet pipe 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 Packet pipe 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 19.2Kbps and 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 a mobile 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 original data, 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) in to 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 by one d B depends upon the bit one or zero. The narrow band signals are associated with code channel are spread by specialized binary sequence called 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 through 7 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 timing to GPS Antenna and it is generating 15 Mhz and 1PPS. This is going to RFTG (Reference Frequency and Timing Generator). We have two Reference generators RG-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 two seconds: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 for call 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 sectors carrier 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 binary codes 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.

I 10 Q 11 01 00

I Q

PN Sequence Offset

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(Un modulated 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(Bus Interface Unit),ACU(Analog conversion unit) and BCR(Base band combiner & Radio).

CE 0 CE 1 CCU CE 9 CCC CCU CCU ACU

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 ACU cup 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 CCC14,16,18 and for carrier 242 CCC 20,22,24 and for carrier 201 CCC 26,28,30 are connected.

Example on 283 Carrier

CCC 8 CCC 10

ACU

BCR

Alpha

ACU ACU

BCR BCR

Beta Gamma

CCC 12

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 6 bits 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 Bits Equal 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 & Q channels. 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.