02 GSM Fundamentals
Transcript of 02 GSM Fundamentals
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GSM Fundamentals
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Chapter 1 GSM System OverviewChapter 1 GSM System Overview
Chapter 2 GSM Network StructureChapter 2 GSM Network Structure
Chapter 3Chapter 3 Service Area and Number PlanningService Area and Number PlanningChapter 4Chapter 4 Channels on the Wireless InterfaceChannels on the Wireless Interface
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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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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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GSM 900GSM 900
Duplex Separation: 45MHz
Channel Bandwidth: 200KHz
The Frequency Spectrum
Uplink
890 915 935 960MHz
Downlink
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Duplex Separation: 95MHzChannel Bandwidth: 200KHz
Base Station Receive
1710 1785 1805 1880MHz
Base Station Transmit
DCS 1800DCS 1800
The Frequency Spectrum
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Chapter 1 GSM System OverviewChapter 1 GSM System Overview
Chapter 2 GSM Network StructureChapter 2 GSM Network Structure
Chapter 3Chapter 3 Service Area and Number PlanningService Area and Number Planning
Chapter 4Chapter 4 Channels on the Wireless InterfaceChannels on the Wireless Interface
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Interface Between Different Entities
GSM /GPRS BSS
BTS
BSC
BTS
BSC
PCUSS7
SMS system
PSTN
ISDN
Internet,
Intranet
MSC/VLR GMSC
HLR/AUC
SGSN
CG BG
GGSN
GPRS backbone
Other PLMN
A
Gb
Gi
Gp
Ga
Abis
Um
MS
MS
OMC
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Chapter 1 GSM System OverviewChapter 1 GSM System Overview
Chapter 2 GSM Network StructureChapter 2 GSM Network Structure
Chapter 3Chapter 3 Service Area and Number PlanningService Area and Number Planning
Chapter 4Chapter 4 Channels on the Wireless InterfaceChannels on the Wireless Interface
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Service Area
PLMN service area
......
Service Area
MSC service area...
Location area...
cell
PLMN service area PLMN service area
MSC service area...
Location area...
cell
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LAI
Location Area Identification
The LAI is the international code for a location area.
MCC: Mobile Country CodeIt consists of 3 digits .For example: The MCC of China is "460"
MNC: Mobile Network CodeIt consists of 2 digits .
For example: The MNC of China Mobile is "00"LAC: Location Area CodeIt is a two bytes hex code.
The value 0000 and FFFF is invalid.For example: 460-00-0011
MCC MNC LAC
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CGI
The CGI is a unique international identification for a cell
The format is LAI+CILAI: Location Area Identification
CI: Cell Identity. This code uses two bytes hex code to
identify the cells within an LAI.
For example : 460-00-0011-0001
CGI: Cell Global Identification
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BSIC
NCC: PLMN network color code. It comprises from 0-7. Itallows various neighboring PLMNs to bedistinguished.
BCC: BTS color code. It comprises from0-7, used todistinguish different cells assigned the samefrequency!
NCC BCC
BSIC
BSICBase Station Identification Color Code)
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Chapter 1 GSM System OverviewChapter 1 GSM System Overview
Chapter 2 GSM Network StructureChapter 2 GSM Network Structure
Chapter 3Chapter 3 Service Area and Number PlanningService Area and Number Planning
Chapter 4Chapter 4 Channels on the Wireless InterfaceChannels on the Wireless Interface
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2 30 16 74 52 3
The physical channel is the medium over which theinformation is carried: 200KHz and 0.577ms
0 1
TDMA FRAME
Timeslot
The information carried in one timeslot is called a burst
The information carried in one timeslot is called a burst
Physical Channel and Logical Channel
The logical channel consists of the information carriedover the physical channels
TDMA FRAME
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Two types of Logical Channel
Traffic Channel (TCH) :
Transmits traffic information, include dataand speech.
Control Channel (CCH) :
Or Signaling Channel, transmits all kinds ofcontrol information.
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Traffic Channel (TCH)
TCH
Traffic Channels
Speech
TCH/FS
Data
TCH/HSTCH/9.6 TCH/2.4
TCH/4.8
TCH Traffic Channel
TCH/FS Full rate Speech ChannelTCH/HS Half rate Speech ChannelTCH/9.6 Data Channel 9.6kb/sTCH/4.8 Data Channel 4.8kb/sTCH/2.4 Data Channel 2.4Kb/s
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FCCHSCH
CCH (Control Channels)
DCCH
SDCCH
BCH
BCCH Synch. CH.ACCH
SACCHFACCH CCCH
RACH CBCH
PCH/AGCH
Broadcast Control Channel BCCHCommon Control Channel CCCH
Dedicated Control Channel DCCH
Associated Control Channel ACCH
Control Channel (CCH)
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CCH
BCH
BCCHSynch.
Channels
SCH FCCH
The information carried on the BCCH
is monitored by the MS
periodically when it is in idle mode
BCCH: Broadcast Control Channel
FCCH: Frequency Correction Channel
SCH: Synchronization Channel
Broadcast Control Channel BCCH
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CCH
CCCH
RACHuplink
CBCHdownlink
PCH/AGCHdownlink
The CCCH is responsible for
transferring control informationbetween all mobiles and thenetwork.
RACH: Random Access Channel
PCH: Paging Channel
AGCH: Access Granted Channel
CBCH: Cell Broadcast Channel
Common Control Channel CCCH
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CCH
DCCH
SDCCH
FACCH SACCH
DCCH is assigned to a single
wireless connection formeasurement and handoverpurpose.SDCCH: Stand-alone Dedicated
Control ChannelACCH: Associated Control ChannelSACCH: Slow Associated
Control ChannelFACCH: Fast Associated Control
Channel
ACCH
Dedicated Control Channel DCCH
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RACH CCCH CCH
SDCCH
SACCH
FACCH
TCH/F
TCH/H
DCCH
TCH
DCH
Uplink Logical channel
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FCCH
SCH
BCCH
PCH
AGCH
BCCH
CCCH
CCH
SDCCH
SACCH
FACCH
TCH/F
TCH/H
DCCH
TCH
DCH
Downlink Logical channel
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Allocate signaling channel
FCCH
SCHBCCH
PCH
RACH
AGCH
SDCCH
SDCCHTCH
FACCH
Power-off
Idle mode
Dedicated mode
Idle mode
How to use these channels?
Search for frequency correction burst
Search for synchronous burst
Extract system information
Monitor paging message
Send access burst
Set up the call
Allocate voice channel
Conversation
Release the call
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