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GSM vs. CDMA

GSM vs. CDMA

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GSM vs. CDMA

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  1. GSM vs. CDMA Comparing the two most prevalent mobile communication technologies

  2. What is …? • GSM (Global System for Mobile Communication) • Based on TDMA technology • Mainly used in Europe, Middle-east and Africa • CDMA (Code Division Multiple Access) • Based on a spread-spectrum technology • Mainly used in North America

  3. Power Time CH 3 Frequency CH 4 Technology: FDMA • Transmission over Radio Frequency (800MHz – 1900MHz) • Frequency Division Multiple Access • An analog system. Each user is given one channel (i.e., one frequency). Bad utilisation. CH 2 CH 1

  4. GSM uses TDMA (Time Division Multiple Access) CDMA is a "spread spectrum" technology, allowing many users to occupy the same time and frequency allocations in a given band/space. Each mobile station has a unique digital code. The signals are spread over the entire spectrum of 1.25MHz unlike FDMA/TDMA. Technology: TDMA Power Time Frequency Channel 3 Channel 4 Channel 1 Channel 2

  5. Spectrum • Mobile communication uses Radio Frequency (RF) • GSM uses frequencies 824 – 849 MHz (25 MHz band) and 869 – 895 MHz (25 MHz band)

  6. Cellular Architecture HLR BSC A Abis VLR Um PSTN MSC BSC EIR AuC BTS Mobile Station Base Station Subsystem Network Subsystem

  7. Cell Site Cells • The coverage area is divided into hexagonal cells • A BTS is situated at three of the vertices of each cell • In USA, the spectrum in each cell is divided into two bands: A-band and B-band, each 25 MHz • Each 25 MHz band is divided into 832 30 kHz channels • Two channels separated by 45 MHz forms a full-duplex channel • The number of channels used in a cell varies from as low as 4 to as many as 80

  8. GSM Frames and Burst periods BP – Burst Period TCH – Traffic Channel SACCH – Assoc. Control Channel

  9. Handover/Handoff • Internal Handovers (only one BSC involved) • Channels in the same cell • Cells under the same BSC • External Handovers (involved the MSC) • Cells under different BSCs under the same MSC • Cells under different MSCs (anchor MSC and relay MSC) • Techniques used: • Minimum acceptable performance: increase power i.s.o. handover • Power budget: handover i.s.o. increasing power

  10. Services • SMS (Short Message Service) http://www.gsmworld.com/technology/sms/intro.shtml • Facsimile (for receiving fax on a mobile station) • WAP (Wireless Application Protocol) – a standard to let wireless equipment access the Internet. A Wireless Markup Language (WML) is used to encode the pages instead of HTML. • MMS (Multimedia Message Service) • EDGE (Enhanced Data rates for GSM evolution) • The ever elusive “Killer app”

  11. Group Spéciale Mobile Cellular services started in Europe in 1982 13 operators in Europe sign a MoU in 1987 Radiolinja Oy became the first GSM network operator in 1992 cdmaOne (2G) IS-95A (First CDMA cellular standard) First deployed in Sep 1996 by Hutchison IS-95B (2.5G) First deployed in Sep 1999 in Korea CDMA2000 (3G) CDMA2000 1X (Phase 1) Deployed in Korea in 2000 CDMA2000 1x EV-DO CDMA2000 1x EV-DV History and proponents

  12. GSM coordinated by 3GPP Release 99 Release 4 (was Release 2000) W-CDMA (Widebad CDMA) coordinated by 3GPP2 B-CDMA (Broadband CDMA) cdmaOne (2G) IS-95A 1.25MHz CDMA channels circuit switched data connections at 14.4kbps IS-95B (2.5G) CDMA2000 (3G) CDMA2000 1X (Phase 1) Standards and standardization

  13. Over 1 billion GSM subscribers Over 170 million CDMA subscribers Statistics (Geography-wise)

  14. Statistics (Subscriber growth)

  15. Glossary • GPRS – General Packet Radio Service; GPRS represents first implementation of packet switching within GSM, precursor to 3G • GGSN – Gateway GPRS Support Node; the gateway between the cellular network and the IP network

  16. References • GSM Association website, at http://www.gsmworld.com • CDMA Development group, at http://www.cdg.com • UMTS World, at http://www.umtsworld.com • How Stuff Works: Cell Phones, at http://electronics.howstuffworks.com/cell-phone.htm • Cellular Telephone Basics, at http://www.privateline.com/Cellbasics/Cellbasics.html • GSM overview, at http://ccnga.uwaterloo.ca/~jscouria/GSM/gsmreport.html