Outline
• Introduction and history.
• GSM architecture.
• Implementation.
• Technology and standards.
• Summary
Introduction
• Global System for Mobile Communication (GSM)
– Anybody – 500 million users (may 2001)
– Anywhere – 168 countries (may 2001)
– Any media – voice, messaging, data, multimedia
Source: Hillebrand, 1
GSM Specifications
Carrier Separation - 200 kHz
No. of RF Carriers - 124
Access Method - TDMA/FDMA
Modulation Method - GMSK
Transmission Rate - 270.833 Kbps
Speech Coding - Full rate 13 Kbps
Half rate 6.5 Kbps
Duplex Distance - 45 MHz
GSM FDMA(Frequency Division Multiple Access)
25 MHz 25 MHz
Mobile to Base
0 1 2
890.2 890.4 890.6(MHz)
Base to Mobile
0 1 2
935.2 935.4 935.6
200 kHz45MHz
Channel layout and frequency bands of operation
890 935 960915
200 kHz
GSM TDMA(Time Division Multiple Access)
87
65
43
21
87
65
43
21
45 MHz
Frequency
F2’F1’
(Cell transmit)
F2F1
(Cell Rx)
Amplitude
Typical TDMA/ FDMA frame structure
FDMA/TDMA Scheme
BP1
BP2
BP3
BP4
BP5
BP6
BP7
BP8
BP1
BP2
TIME
890.0890.2
890.4890.6
890.8891.0
891.2 915.8
FREQ
MHz
BURSTF
R
A
M
E
GSM Architecture
OMC
Home Location Register
AuC
Equipment ID
Network
Management
Center
B
T
S
B
T
S
B
T
S
ME
ME
ME
Subscriber
Identity
Module
Subscriber
Identity
Module
Subscriber
Identity
Module
Base station
controller
PSTN
Mobile
switching
center
Data
communication
network
BTS = Base Transceiver Station
AuC = Authentication Center
OMC = Operation and Maintenance Center
PSTN = Public Switched Telephone Network
ME = Mobile Equipment
Source: Stallings, 313
Source: Mehrotra, 27
Visitor Location
Register
GSM Architecture
F1 F2 F1' F2'
Frequency
1
2
3
4
5
6
7
8
Year Introduced 1990
Access method TDMA
Channel Bandwidth 200 kHz
Number of duplex
channels
125
Users per channel 8
Speech coding bit
rate
13 kbps
Data coding bit rate 12 kbps
Frame size 4.6 ms
45 MHz
BS Transmission
Band : 935 – 960
MHZ
MS Transmission
Band : 890 – 915
MHZ
SIM (Subscriber Identity Module)
Billions of Calls
Millions of Subscribers
Thousand of Different Types of Telephones
Hundreds of Countries
Dozens of Manufacturers….
And only one Card: The SIM
Source: Hillebrand, 369
http://ucables.com/products/simcards/
•Administrative data
•Security data
•Subscriber data
•Roaming data
•PLMN (Public Land Mobile Network
Implementation
SIM = Subscriber Identity Module
Central processor, clock and tone, internal bus system, keyboard (HMI)
Voice encoding Ciphering Modulation
Voice decoding
>Channel Decoding
>De-Interleaving
>Re-formatting
Deciphering
Amplifier
>Channel encoding
>Interleaving
>Burst generation
Receiver
Transmitter
Demodulation
Source: Heine, 14
Implementation
Abis-
Interface
O&M Module Operation and maintenance functionality/clock distribution
Digital signal
processing (NF
functionality)
HF Transmitter
(HF-TX)
Input filter
Output filter
HF Receiver
(HF-RX) Slo
w f
requ
en
cy
ho
pp
ing
Tra
nsm
issio
n
syste
m
TRX
Block Diagram of a BTS with one TRX
Source: Heine, 20
GSM Variants
Variant Uplink
(MHz)
Downlink
(MHz)
Total
Bandwidth
Duplex-
frequency
Channels
GSM-400 451-458 and
479-486
461-468 and
489-496
Twice 14 MHz 10 MHz Twice 72
GSM-900
(primary
band)
890-915 935-960 Twice 25 MHz 45 MHz Twice 124
Extended
GSM-900
880-915 925-960 Twice 35 MHz 45 MHz Twice 174
GSM-R 876-880 921-925 Twice 4 MHz 45 MHz Twice 19
DCS-1800 1,710-1,785 1,805-1,880 Twice 75 MHz 95 MHz Twice 373
PCS-1900 1,850-1,910 1,930-1,990 Twice 60 MHz 80 MHz Twice 300
Source: Bekkers, 299
References
Bekkers, Rudi. Mobile Communications Standards: GSM, UMTS, TETRA, and ERMES. Norwood, MA: Artech House, Inc., 2001.
Halonen, Romero, and Melero. GSM, GPRS, and EDGE Performance: Evolution Towards 3G/UMTS. England: John Wiley & Sons Ltd., 2003.
Hillebrand, Friedhelm. GSM and UMTS: The Creation of Global Mobile Communications. England: John Wiley & Sons Ltd., 2002.
Heine, Gunnar. GSM Networks: Protocols, Terminology, and Implementation. Norwood, MA: Artech House, Inc., 1999.
Mehrotra, Asha. GSM System Engineering. Norwood, MA: Artech House, Inc., 1997.
Harte, Levine, and Livingston. GSM Superphones. United States: APDG Publishing, Inc. A Division of McGraw-Hill, 1999.
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