GSM vs. CDMA

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
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
Technology TDMA

• 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.

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
A
BSC
Abis
VLR
Um
PSTN
MSC
BSC
EIR
AuC
BTS
Mobile Station
Base Station Subsystem
Network Subsystem
7
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.co
  m/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
History and proponents

• 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

12
Standards and standardization

• 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)

13
Statistics (Geography-wise)

• Over 1 billion GSM subscribers

• Over 170 million CDMA subscribers

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.co
  m
• 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.ht
  m
• Cellular Telephone Basics, at http//www.privatel
  ine.com/Cellbasics/Cellbasics.html
• GSM overview, at http//ccnga.uwaterloo.ca/jscour
  ia/GSM/gsmreport.html