ebook4u.vn-00_OMA000001 GSM Fundamentals ISSUE4.0_2 pot

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Inte rnal
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GSM Fundamentals
ISSUE 4.0
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Upon completion of this course, you will be able to:

Grasp basic idea of GSM system such as
frequency spectrum, frequency reuse etc.

Grasp the structure of the GSM system and the
protocol used.

Grasp certain numbers that refer to BSS

Grasp the 4 kinds of channel combination and
understand the idea of multi-frame.

Know some radio techniques

Get the idea of EDGE
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References


BSS Feature Description

BSS Signaling Analysis Manual

BSC Technical Manual
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Chapter 1 GSM System Overview
Chapter 1 GSM System Overview
Chapter 2 GSM Network Structure
Chapter 2 GSM Network Structure
Chapter 3
Chapter 3
Service Area and Number Planning
Service Area and Number Planning
Chapter 4
Chapter 4
Channels on the Wireless Interface
Channels on the Wireless Interface
Chapter 5 Radio Techniques
Chapter 5 Radio Techniques
Chapter 6 GPRS & EDGE Introduction
Chapter 6 GPRS & EDGE Introduction
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GSM system overview


The GSM system is a frequency- and time-division cellular system,
each physical channel is characterized by a carrier frequency and a
time slot number

Cellular systems are designed to operate with groups of low-power
radios spread out over the geographical service area. Each group of
radios serve MSs presently located near them. The area served by
each group of radios is called a CELL

Uplink and downlink signals for one user are assigned different
frequencies, this kind of technique is called Frequency Division Duplex
(FDD)

Data for different users is conveyed in time intervals called slots ,
several slots make up a frame. This kind of technique is called Time
Division Multiple Access (TDMA)
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GSM Development
Standard Protocol for GSM take effect
System was named as Global System for
Mobile Communication
GSM system began to provide service in Europe(2G)
Provide services for the whole world
Micro Cell Technique is used in GSM system
1989
1991
1992
1994

1996
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Cell Technique

A certain radio coverage area formed by a set of transceivers that
connected to a set of antennas is called a CELL.

Macro Cell

In the beginning , High-Power BTSs are adopted to provide services.
The BTS covers a wider area , but its frequency utilization is not
efficient. So , it can only provide a few channels for subscribers.

Micro Cell

Later the Low-Power BTS joins the system for getting a better service
area with high capacity . At the same time it adopts the frequency
reuse technique to improve the efficiency of the frequency utilization
and also the whole capacity of the network.
Macro Cell and Micro Cell
Macro Cell and Micro Cell
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Multiple Access Technique

Multiple Access Technique allows many subscribers to use the
same communication medium.


There are three kinds of basic Multiple Access Technique :
FDMA , TDMA and CDMA.

GSM system adopt FDD-TDMA (FDMA and TDMA together).
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FDMA

FDMA uses different frequency
channels to accomplish
communication.

The whole frequency spectrum
available is divided into many
individual channels (for
transmitting and
receiving) ， every channel can
support the traffic for one
subscriber or some control
information.
Frequency
Time
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TDMA

TDMA accomplishes the

communication in different
timeslot.

A carrier is divided into
channels based on time.
Different signals occupy
different timeslots in certain
sequence , that is , many
signals are transmitted on
the same frequency in
different time.
Time
Frequency
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CDMA

CDMA accomplishes the
communication in
different code sequences.

Special coding is adopted
before transmission, then
different information will
lose nothing after being
mixed and transmitted
together on the same
frequency and at the
same time.

Time
Frequency
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GSM 900
GSM 900
Duplex Separation: 45MHz
Channel Bandwidth: 200KHz
The Frequency Spectrum

Uplink

890 915 935 960MHz
Downlink
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Duplex Separation: 95MHz
Channel Bandwidth: 200KHz
Base Station Receive

1710 1785 1805 1880MHz
Base Station Transmit
DCS 1800
DCS 1800
The Frequency Spectrum
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The Frequency Spectrum
Frequency
Spectrum
Range
(MHz)
Uplink Frequency
Frequency
Point
Available
Downlink
Frequency
GSM 450
450.4~457.6
460.4~467.6
Fu(n)=450.6+0.2(n-
259)
259<=n<=293 Fd(n)=Fu(n)+10
GSM 480
478.8~486
488.8~496
Fu(n)=479+0.2(n-306) 306<=n<=340 Fd(n)=Fu(n)+10
GSM 850
824~849
869~894
Fu(n)=824.2+0.2(n-
128)
128<=n<=251 Fd(n)=Fu(n)+45
E-GSM
900
880~915

925~960
Fu(n)=890+0.2n
Fu(n)=890+0.2(n-1024)
0<=n<=124
975<=n<=102
3
Fd(n)=Fu(n)+45
R-GSM
900
876~915
921~960
Fu(n)=890+0.2n
Fu(n)=890+0.2(n-1024)
0<=n<=124
955<=n<=102
3
Fd(n)=Fu(n)+45
PCS 1900
1850~1910
1930~1990
Fu(n)=1850.2+0.2(n-
512)
512<=n<=810 Fd(n)=Fu(n)+80
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Frequency Reuse

The frequency resource of mobile system is very limited.


The different Subscribers can use the same frequency in
different places.

The quality of communication must be ensured.
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Frequency Reuse
7(Site)X 1(Cell) reuse
2
1
2
3
4
5
6
7
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4 site X 3 cells reuse
1
8
9
2
10
4
6
5
3

7
11
12
R
Frequency Reuse
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Cell Types
Omni
1
120
degree
1
2
3
Omni-directional Cell
120 Degree Cell
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Chapter 1 GSM System Overview
Chapter 1 GSM System Overview
Chapter 2 GSM Network Structure
Chapter 2 GSM Network Structure
Chapter 3
Chapter 3
Service Area and Number Planning
Service Area and Number Planning
Chapter 4

Chapter 4
Channels on the Wireless Interface
Channels on the Wireless Interface
Chapter 5 Radio Techniques
Chapter 5 Radio Techniques
Chapter 6 GPRS & EDGE Introduction
Chapter 6 GPRS & EDGE Introduction
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GSM-GPRS Network Component
GSM /GPRS BSS
BTS
BSC
BTS
BSC
PCU


SS7
SMS system
PSTN
ISDN
Internet,
Intranet
MSC/VLR GMSC
HLR/AUC
SGSN
CG
BG

GGSN
GPRS Backbone
Other PLMN
MS
MS
OMC
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Interface Between Different Entities
GSM /GPRS BSS
BTS
BSC
BTS
BSC
PCU


SS7
SMS system
PSTN
ISDN
Internet,
Intranet
MSC/VLR GMSC
HLR/AUC
SGSN
CG
BG
GGSN

GPRS backbone
Other PLMN
A
Gb
Gi
Gp
C/D/Gs
Gr/Gs/Gd/Ge
Gc
Ga
Abis
Um
MS
MS
OMC
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Mobile Station—MS
International Mobile Equipment Identity (IMEI)
– Mobile Equipment
MS=ME+SIM
International Mobile Subscriber Identity (IMSI)
– Subscriber Identity Module
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Subscriber Identity Module – SIM

International Mobile Subscriber Identity

(IMSI)

Temporary Mobile Subscriber Identity
(TMSI)

Location Area Identity (LAI)

Subscriber Authentication Key (Ki)
SIM
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BTS
BTS
BSC
BSC
TC/SM
TC/SM
BSS
MSC
Base Station Subsystem – BSS

The Base Station Controller –
BSC

The Base Transceiver Station
– BTS

The Trans-coder – TC and
Sub multiplexer (SM)

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BTS
BTS
BSC
BSC
TC/SM
TC/SM
BSS
MSC
Packet Control Unit PCU

Packet data
switching

Bridge between
SGSN and BSC

Provide Pb and
Gb interface
GPRS
Backbone
PCU
PCU
SGSN
SGSN