Transcript GSM vs. CDMA Comparing the two most prevalent mobile communication technologies CONFIDENTIAL What is …?  GSM (Global System for Mobile Communication)  Based on TDMA.

GSM vs. CDMA
Comparing the two most prevalent mobile
communication technologies
CONFIDENTIAL
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
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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.
Power

Frequency
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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.
Power
 Each mobile station has a unique
digital code. The signals are spread
over the entire spectrum of
1.25MHz unlike FDMA/TDMA.
Frequency
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Spectrum
 Mobile communication uses Radio Frequency (RF)
 GSM uses frequencies 824 – 849 MHz (25 MHz band) and 869 – 895
MHz (25 MHz band)
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Cellular Architecture
BSC
A
HLR
Abis
VLR
Um
MSC
BSC
PST
N
EIR
AuC
BTS
Mobile
Station
Base Station
Subsystem
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Network
Subsystem
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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
Cell Site
forms a full-duplex channel
 The number of channels used in a cell
varies from as low as 4 to as many as 80
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GSM Frames and Burst periods
TCH – Traffic Channel
SACCH – Assoc. Control Channel
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BP – Burst Period
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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
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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”
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History and proponents
 cdmaOne (2G)
 Group Spéciale Mobile

Cellular services started in
Europe in 1982

IS-95A (First CDMA cellular
standard)


13 operators in Europe sign
a MoU in 1987

Radiolinja Oy became
the first GSM network
operator in 1992

IS-95B (2.5G)

First deployed in Sep 1999
in Korea
 CDMA2000 (3G)

CDMA2000 1X (Phase 1)

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First deployed in Sep 1996
by Hutchison
Deployed in Korea in 2000

CDMA2000 1x EV-DO

CDMA2000 1x EV-DV
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Standards and standardization
 GSM coordinated by 3GPP
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Release 99

Release 4 (was Release
2000)
 cdmaOne (2G)

 W-CDMA (Widebad CDMA)
coordinated by 3GPP2
 B-CDMA (Broadband CDMA)

IS-95A

1.25MHz CDMA
channels

circuit switched data
connections at 14.4kbps
IS-95B (2.5G)
 CDMA2000 (3G)

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CDMA2000 1X (Phase 1)
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Statistics (Geography-wise)
 Over 1 billion GSM subscribers
 Over 170 million CDMA
subscribers
Millions
500
400
300
200
100
0
A
si
N aP
or
th aci
A fi c
S
ou m
th eri
A ca
m
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ic
a
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GSM
CDMA
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Statistics (Subscriber growth)
Millions
1,000
900
800
700
600
500
400
300
200
100
0
D
ec
.2
00
D
1
ec
.2
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D
2
ec
.2
00
3
GSM
CDMA
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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
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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
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