1. Comparing the two most prevalent mobile communication technologies
Apr-17
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 3
CH 4
Frequency
Time
Power
CH 1
CH 2

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 1
Channel 2
Channel 3
Channel 4

5. Spectrum Mobile communication uses Radio Frequency (RF)
Apr-17
Spectrum
Mobile communication uses Radio Frequency (RF)
GSM uses frequencies 824 – 849 MHz (25 MHz band) and 869 – 895 MHz (25 MHz band)
The EMSpec.gif is from

6. Cellular Architecture
Apr-17
Cellular Architecture
HLR
BSC A
Abis
VLR Um
PSTN
MSC
BSC
EIR
AuC
Mobile Station (MS)
Subscriber Identity Module (SIM)
International Mobile Equipment Identity (IMEI)
Base Station subsystem, consisting of:
Base Transceiver Station (BTS)
Base Station Controller (BSC)
Network subsystem, consisting of:
Mobile services Switching Centre (MSC)
Home Location Register (HLR)
Visitor Location Register (VLR)
Equipment Identity Register (EIR)
Authentication Centre (AuC)
BTS
Mobile Station
Base Station Subsystem
Network Subsystem

7. Cells The coverage area is divided into hexagonal cells
Apr-17
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 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
Cell Site

8. GSM Frames and Burst periods
Apr-17
GSM Frames and Burst periods
GSM has four types of burst. The above figure shows the normal burst that is used to carry data and most of the signalling. It has bits of information.
TCH – Traffic Channel
SACCH – Assoc. Control Channel
BP – Burst Period

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)
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)
Apr-17
Statistics (Subscriber growth)
Data from and
In Feb 2004, GSM announced having reached 1 billion subscribers.

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
UMTS World, at
How Stuff Works: Cell Phones, at
Cellular Telephone Basics, at
GSM overview, at