GSM Vs. CDMA An Overview Bhushan G. Jagyasi Lecturer, Elex & Tele Comm Dept. Thadomal Shahani Engineering College

Classification Of Existing Systems Technologies TDMA/FDMA CDMA GSM (European Standard) IS 136 (U.S Standard) PDC (Japnese Standard) IS 95 (U.S Standard)

Evolution Chart Broad Band 4G Service type Narrow Band Wide Band 1G 2G 3G Multimedia Wireless Internet Mobile system Digital IS 95 IS 136 GSM IMT 2000 Voice Analog AMPS ~ 24kbps ~64kbps ~2Mbps ~20Mbps 1980 1990 2000 2010 Years

Access technology PN Code Freq Freq Freq Time Time Time FDMA TDMA CDMA

Comparison BetweenTechnologies Digital Mobile technology User’s Dec-02 User’s Dec-03 Growth in2003 % Growth Share Of Growth CDMA 145.2 181.0 35.4 24.3% 15.6% GSM 790.5 970.8 180.3 22.8% 79.5% PDC 60.1 63.1 3.0 5.0% 1.3% TDMA 107.4 113.0 5.5 5.1% 2.4% 3 GSM (W CDMA) 0.2 2.8 2.6 1708.5% 1.2% GLOBAL USER BASE 1103.7 1330.6 226.9 20.69% 100%

GSM An Overview

GSM The European TDMA Digital Cellular Standard Services Provided By GSM 1. Telephony - Basic Teleservice 2. Other Services -Emergency calling -Voice Messaging

GSM The European TDMA Digital Cellular Standard Services Provided By GSM (Cont..) 3. Bearer Services - Low Speed data transfer (upto 9.6 Kbps) -Group 3 Fax and Sms 4. Suplementary Services - call offering , call forwarding, call restriction, call waiting, call hold. - Multiparty teleconferencing, special schemes

GSM The European TDMA Digital Cellular Standard General Architecture Of GSM HLR VLR BSC BTS PSTN, ISDN MSC SIM BTS BSC ME EIR AuC Abis Um A MS BSS NS Mobile station Base Station Subsystem Network Subsystem

GSM The European TDMA Digital Cellular Standard Mobile Station (MS): Two Blocks Mobile Equipment (ME) Subscribers Identity Module (SIM) Function of Mobile Station: 1. Personal Mobility

GSM The European TDMA Digital Cellular Standard Function of Mobile Station: 1. Personal Mobility SIM SIM SIM SIM SIM SIM SIM

GSM The European TDMA Digital Cellular Standard Mobile Station (MS): Two Blocks Mobile Equipment (ME) Subscribers Identity Module (SIM) Function of Mobile Station: 1. Personal Mobility 2. IMEI (International Mobile Equipment Identity) 3. IMSI (International Mobile Subscriber Identity)

GSM The European TDMA Digital Cellular Standard Base Station Subsystem (BSS) Base Transceiver Station (BTS) Base Station Controller (BSC) BSC

GSM The European TDMA Digital Cellular Standard BSC: Base station Controller 1. It manages radio resources for one or more BTS. 2. Allocation and Deallocation of channels. 3. Transmitter power control. 4. Handoff control BTS : Base Tranceiver station 1. It defines the cell . 2. It handles the radio link protocol with the mobile station BSC

GSM The European TDMA Digital Cellular Standard HLR VLR PSTN, ISDN BSC MSC EIR AuC Network Subsystem MSC: Mobile Switching Center HLR: Home Location Register VLR: Visitor Location register AuC: Authentication Center EIR: Equipment Identity Register

GSM The European TDMA Digital Cellular Standard Mobile Switching center:(MSC) call set up/supervision/release call routing billing information colllection mobility management paging, alerting, echo cancellation connection to BSC, other MSC and other local exchange networks Access to HLR and VLR

GSM The European TDMA Digital Cellular Standard Home Location Register (HLR) One HLR per GSM operator Contains permanent database of all the subscribers in the network contains MSRN(mobile station routing no.) It is reffered for every incomming call

GSM The European TDMA Digital Cellular Standard Visitor Location Register(VLR) Temporary visitors database One VLR per MSC Authentication Center(AuC) Provides security Authentication and encryption Equipment Identity Register: Contains IMEI

GSM The European TDMA Digital Cellular Standard Location Update VLR BSC MSC HLR GMSC BSC MSC PSTN. ISDN VLR

GSM The European TDMA Digital Cellular Standard Mobile call originating VLR BSC MSC HLR GMSC BSC MSC PSTN. ISDN VLR

GSM The European TDMA Digital Cellular Standard Mobile call terminating VLR BSC MSC HLR GMSC BSC MSC PSTN. ISDN VLR

GSM The European TDMA Digital Cellular Standard Handoff GMSC Handoff is of 3 types 1. Intra BSC 2 Inter BSC 3. Inter MSC MSC MSC BSC BSC BSC

GSM The European TDMA Digital Cellular Standard GSM Radio Aspects : Uplink(Mobile to base) 890-915 MHz (Total 25 MHz) Downlink ( Base to Mobile) 935-960 MHz (Total 25 MHz) Total 45 MHz spacing for duplex operation GSM uses TDMA and FDMA

GSM The European TDMA Digital Cellular Standard GSM Using FDMA 200KHz 1 2 3 4 5 124 890MHz 915Mhz Uplink Freq Total Frequency range(Uplink)=25Mhz Spacing between two carriers= 200kHz No. of Carriers=25MHz/200KHz = 124

GSM The European TDMA Digital Cellular Standard GSM Using TDMA TDMA Frame is divided into 8 time slots. Freq Time slots Down Link carrier 1 2 3 4 5 6 7 200 KHz 45MHz Up Link carrier 0 3 1 3 2 3 4 5 5 6 7 4.6 ms 0.57ms Time

GSM The European TDMA Digital Cellular Standard Classification of channels in GSM Two types Traffic channels (TCH) Control channels (CCH) Channels are used to carry speech , data and control information. Traffic Channels are defined using 26 TDMA frame multiframe.

GSM The European TDMA Digital Cellular Standard Length of 26 TDMA frames = 120 msec Length of 1 TDMA frame =120/26 = 4.615 msec 1 TDMA frame consists of 8 burst frames Length of 1 burst frame = 0.577msec Out of 26 frames  24 are TCH used for traffic 1 is SACCH used for control 1 is unused

GSM The European TDMA Digital Cellular Standard Frame Multiframe Duration=120ms 1 2 10 24 25 Tdma Frame Duration=4.615ms 1 2 3 4 5 6 7 Format of a single Burst Duration=0.577ms 3 57 1 26 57 25 Data Training Data

GSM The European TDMA Digital Cellular Standard Speech coding Speech is digitized by PCM, o/p of PCM is 64Kb/s It is further reduced by Regular pulse excited-Linear predictive coder, bit rate achieved 13kb/s for full rate (260 bits in 20 msec) Further encoded for error correction, 456 bits per 20 msec, bit rate = 22.8 Kb/s 456 bits are divided into 8 blocks and transmitted during 8 burst periods.

GSM The European TDMA Digital Cellular Standard Classification of Channels 1 Traffic (TCH) Speech Full rate 22.8 kb/s Half rate 11.4 kb/s Data 9.6kb/s 4.8kb/s 2.4kb/s

GSM The European TDMA Digital Cellular Standard 2 Control (CCH) Broadcast (BCCH) Freq correction (FCCH) Synchronization (SCH) Common (CCH) Paging (PCH) Access grant (AGCH) Random Access (RACH) Dedicated (DCCH) Fast Associative (FACCH) Slow Associative (SACCH) Stand alone (SDCCH)

GSM The European TDMA Digital Cellular Standard GSM Security MS NETWORK Random no Ki Ki Ki Ki A3 A8 A3 A8 SRES Kc Kc Equal SRES

Code Division Multiple Access (CDMA) An Overview

CDMA Classification of CDMA Systems CDMA SYSTEMS CDMA one CDMA 2000 Wide Band IS95 IS95B JSTD 008 Narrow Band

CDMA Multiple Access in CDMA: Each user is assigned a unique PN code. Each user transmits its information by spreading with unique code. Direct Sequence spread spectrum is used. Users are seperated by code not by time slot and freq slot.

CDMA Concept of CDMA Users share same bandwidth User axis shows cumulative signal strength of all users User Code 4 Code 3 Code2 Code 1 Freq

CDMA Spread Spectrum and Multiple Access: Spread Spectrum In Spread spectrum data is transmitted with BW in excess to minimum BW necessary to send it. Spread spectrum is achieved by spreading with PN code at transmitter . Same code is used to despread the received signal at reciever How do we get increased spectrum Wide band code seq Narrow band inputsignal Wide band Spreaded seq X

CDMA Advantages of spread spectrum: Multipath Rejection Immunity to interference and jamming Multiple access Code 1 Code2 Code 3 Code 4 Freq User

CDMA Comparison between CDMA and TDMA/FDMA: In TDMA Band width available for transmission is small which leads to compromise in quality of transmission. Whereas in CDMA systems entire spectrum is used which enhances voice quality. In TDMA/FDMA, cell design requires more frequency planning which is tough job. Whereas in CDMA frequency planning is minimal. TDMA is Band limited system. CDMA is Power limited system

CDMA Types of Codes used in CDMA: Walsh code Short PN code(16 bit) Orthogonal codes In IS 95A and IS 95B 64 Walsh codes are used In CDMA 2000 128 Walsh codes are used Short PN code(16 bit) Used to identify the BS and hence the cell Long PN code(42 bit code) Used to identify mobile station on reverse link

CDMA Formation of channels (IS 95) PN Code( Chip code) has rate of 1.23 MHz Chip rate = 1.23 MHz (spread BW)

CDMA Forward Link (BS to MS) Forward CDMA Channels PILOT SYNC PAGE TRAFFIC TRAFFIC W0 W32 W1 W7 W9 W0 TRAFFIC DATA POWER CNTRL SUB CH

CDMA Reverse Link Channel (BS to MS) Here CDMA ch does not follow strictly orthogonal rule. It consists of 242 logical channels. 42 bit long PN code is used to distinguish between channels. Reverse CDMA Channels Access Ch 1 Access Ch n Traffic Ch 1 Traffic Ch m m mobiles tryin to gain access to system m mobiles engaged in calls

CDMA Other key Factors Diversity Power Control Time diversity Frequency diversity Space(Path) diversity Power Control Handoff: It supports Soft Handoff

CDMA Soft Handoff Signal strength Distance

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