Huawei GSM Principles

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Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
GSM Principles

Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved. Page2
Objectives
 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

References
 BSS Feature Description
 BSS Signaling Analysis Manual
 BSC Technical Manual

Contents
1. GSM System Overview
2. GSM Network Structure
3. Service Area and Number Planning
4. Channels on the Wireless Interface
5. Radio Techniques
6. GPRS & EDGE Introduction

Contents
5. Radio Techniques

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)

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

Cell Technique
 Macro Cell and Micro Cell
 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.

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).

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

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

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

GSM 900
Duplex Separation: 45MHz
Channel Bandwidth: 200KHz
The Frequency Spectrum
Uplink
890 915 935 960MHz
Downlink

Duplex Separation: 95MHz
Channel Bandwidth: 200KHz
Base Station Receive
1710 1785 1805 1880MHz
Base Station Transmit
DCS 1800

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)+1
0
GSM 480
478.8~486
488.8~496
Fu(n)=479+0.2(n-306) 306<=n<=340
Fd(n)=Fu(n)+1
0
GSM 850
824~849
869~894
Fu(n)=824.2+0.2(n-
128)
128<=n<=251
Fd(n)=Fu(n)+4
5
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)+4
5
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)+4
5
PCS 1900
1850~1910
1930~1990
Fu(n)=1850.2+0.2(n-
512)
512<=n<=810
Fd(n)=Fu(n)+8
0

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.

Frequency Reuse
7(Site)X 1(Cell) reuse
2
1
2
3
4
5
6
7

4 site X 3 cells reuse
1
8
9
2
10
4
6
5 3
7
11
12
R
Frequency Reuse

Cell Types
Omni
1
120
degree
1
2
3
Omni-directional Cell
120 Degree Cell

Contents
5. Radio Techniques

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

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

Mobile Station—MS
International Mobile Equipment Identity
(IMEI)
– Mobile Equipment
MS=ME+SIM
International Mobile Subscriber Identity (IMSI)
– Subscriber Identity Module

Subscriber Identity Module – SIM
 International Mobile Subscriber
Identity (IMSI)
 Temporary Mobile Subscriber
Identity (TMSI)
 Location Area Identity (LAI)
 Subscriber Authentication Key (Ki)
SIM

BTS
BSC
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)

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

Mobile-service Switching Center – MSC
Home Location Register – HLR
Visitor Location Register – VLR
Equipment Identity Register – EIR
Authentication Center – AUC
Echo Cancellor – EC
AUC
HLR
MSC/VLR
PSTN
NSS
EIROMC
BSS
EC
The Network Switching System

Mobile-service Switching Center –
MSC
 Call Processing
 Operations and Maintenance Support
 Interface management
 Inter-network & Inter-working
 Billing

Home Location Register – HLR
 Subscriber ID (IMSI and MSISDN)
 Current subscriber VLR (current location)
 Supplementary service information
 Subscriber status (registered/deregistered)
 Authentication key and AuC functionality

Visitor Location Register – VLR
 Mobile Status (IMSI attached / detached / busy / idle etc.)
 Location Area Identity(LAI)
 Temporary Mobile Subscriber Identity(TMSI)
 Allocating the Roaming Number

IMEI is Checked In White List
IMEI is Checked in Black/Grey List
If NOT found
EIR focus on the
equipment , not the
subscriber!
Equipment Identity Register – EIR
 White List
 Black List
 Grey List

OMC Functional Architecture
OS
MMI
DB
Event/Alarm
Management
Security
Management
Configuration
Management
Performance
Management
Fault
Management

Contents
5. Radio Techniques

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

LAI
Location Area Identification
The LAI is the international code for a location area.
MCC: Mobile Country Code，It consists of 3 digits .
For example: The MCC of China is "460"
MNC: Mobile Network Code，It consists of 2 digits .
For example: The MNC of China Mobile is "00"
LAC: Location Area Code，It is a two bytes hex code.
The value 0000 and FFFF is invalid.
For example: 460-00-0011
MCC MNC LAC

CGI
The CGI is a unique international identification for a cell
The format is LAI+CI
LAI: 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

BSIC
NCC: PLMN network color code. It comprises 3 bit. It
allows various neighboring PLMNs to be
distinguished.
BCC: BTS color code. It comprises 3 bit, used to
distinguish different cells assigned the same
frequency!
NCC BCC
BSIC
BSIC（Base Station Identification Color Code)

CC: Country Code. For example: The CC of China is "86".
NDC: National Destination Code. For example: The NDC of
China Telecom is 139, 138, 137, 136, 135.
SN: Subscriber Number. Format:H0 H1 H2 H3 ABCD
Example: 86-139-0666-1234
MSISDN
CC NDC SN
National (significant)
Mobile number
Mobile station international
ISDN number

MCC: Mobile Country Code，It consists of 3 digits .
For example: The MCC of China is "460"。
MNC: Mobile Network Code，It consists of 2 digits .
For example: The MNC of China Telecom is "00"。
MSIN: Mobile Subscriber Identification Number. H1H2H3 S ABCDEF
For example: 666-9777001
NMSI: National Mobile Subscriber Identification，MNC and MSIN
form it together.
For Example of IMSI : 460-00-666-9777001
Not more than 15 digits
3 digits 2 digits
IMSI
MCC MNC MSIN
NMSI
IMSI

TMSI
 The TMSI is assigned only after successful subscriber
authentication.
 The VLR controls the allocation of new TMSI numbers
and notifies them to the HLR.
 TMSI is used to ensure that the identity of the mobile
subscriber on the air interface is kept secret.
 The TMSI consists of 4 bytes( 8 HEX numbers) and
determined by the operator.
TMSI: Temporary Mobile Subscriber Identification)

IMEI
TAC FAC SNR SP
IMEI
IMEI: International Mobile Station Equipment Identification
TAC: Type approval code, 6 bit, determined by the type approval center
FAC: Final assembly code, 2 bit, It is determined by the manufacturer.
SNR: Serial number, 6 bits, It is issued by the manufacturer of the MS.
SP: 1 bit , Not used.
Check the IMEI in your MS : *#06#

Contents
5. Radio Techniques

2 30 16 74 52 3
The physical channel is the medium over which the
information is carried: 200KHz and 0.577ms
0 1
TDMA FRAME
Timeslot The information carried in one time
slot is called a “burst”
Physical Channel and Logical Channel
The logical channel consists of the information carried
over the physical channels
TDMA FRAME

Two types of Logical Channel
Traffic Channel (TCH) :
Transmits traffic information, include data
and speech.
Control Channel (CCH) :
Or Signaling Channel, transmits all kinds of
control information.

Traffic Channel (TCH)
TCH
Traffic Channels
Speech
TCH/FS
Data
TCH/HS
TCH/9.6 TCH/2.4
TCH/4.8
TCH Traffic Channel
TCH/FS Full rate Speech Channel
TCH/HS Half rate Speech Channel
TCH/9.6 Data Channel 9.6kb/s
TCH/4.8 Data Channel 4.8kb/s
TCH/2.4 Data Channel 2.4Kb/s

FCCHSCH
CCH (Control Channels)
DCCH
SDCCH
BCH
BCCH Synch. CH.
ACCH
SACCHFACCH CCCH
RACH CBCH
PCH/AGCH
Broadcast Control Channel – BCCH
Common Control Channel – CCCH
Dedicated Control Channel – DCCH
Associated Control Channel – ACCH
Control Channel (CCH)

CCH
BCH
BCCH
Synch.
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

CCH
CCCH
RACH
uplink
CBCH
downlink
PCH/AGCH
downlink
The CCCH is responsible for
transferring control information
between all mobiles and the
network.
RACH: Random Access Channel
PCH: Paging Channel
AGCH: Access Granted Channel
CBCH: Cell Broadcast Channel
Common Control Channel – CCCH

CCH
DCCH
SDCCH
FACCH SACCH
DCCH is assigned to a single
wireless connection for
measurement and handover
purpose.
SDCCH: Stand-alone Dedicated
Control Channel
ACCH: Associated Control Channel
SACCH: Slow Associated
Control Channel
FACCH: Fast Associated Control
Channel
ACCH
Dedicated Control Channel –
DCCH

RACH CCCH
CCH
SDCCH
SACCH
FACCH
TCH/F
TCH/H
DCCH
TCH
DCH
Uplink Logical channel

FCCH
SCH
BCCH
PCH
AGCH
BCCH
CCCH
CCH
SDCCH
SACCH
FACCH
TCH/F
TCH/H
DCCH
TCH
DCH
Downlink Logical channel

Allocate signaling channel
FCCH
SCH
BCCH
PCH
RACH
AGCH
SDCCH
SDCCH
TCH
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

Packet logic channel
 Packet data channel (PDCH)
 Comprising packet service channel and packet control
channel
 Packet service channel (PDTCH)
 Combined into the single-directional service channel
 Packet control channel
 Broadcast control channel: PBCCH
 Public control channel: PPCH, PRACH, PAGCH
 Private control channel: PACCH, PTCCH
TCH
BCCH
SACCH
CCCH
TCH

GSM Logical Channel Combination
 Main BCCH combination – FCCH + SCH + BCCH + CCCH
 SDCCH combination – SDCCH/8 + SACCH/8
 Combined BCCH – BCCH + CCCH +SDCCH/4 + SACCH/4
 TCH/FR combination – TCH/F + FACCH/F + SACCH/F
 TCH/HR combination – TCH/H + FACCH/H + SACCH/H

Combination of packet logic
channel
 Packet logic channels (PDCH) can be combined via the
following three modes
 Mode 1: PBCCH+PCCCH+PDTCH+PACCH+PTCCH;
 Mode 2: PCCCH+PDTCH+PACCH+PTCCH;
 Mode 3: PDTCH+PACCH+PTCCH
 In case of small GPRS traffic, GPRS and circuit services use the
same BCCH and CCCH in the cell. In this case, only combination
mode 3 is needed in the cell
 With the increase of traffic, the packet public channel should
be configured in the cell. Channel combination mode 1 and
mode 2 should be adopted

TDMA Frames
0 1
0 1 2 43 46 47 48 5049
51 – Frame Multi-frames
0 1 10
CONTROL
CHANNELS
2 3 4 5 6 7 2 3 5 764
GSM Multi-frames

GSM Multi-frames
TDMA Frames
0 1
0 1 2 43 21 22 23 2524
26 – Frame Multi-frames
0 1 10
TRAFFIC
CHANNELS
2 3 4 5 6 7 2 3 5 764

Contents
5. Radio Techniques

Power Control
Saves battery power
Reduces co-channel and
adjacent channel interference
8W
0.8W
5W
Both Uplink and Downlink
power settings can be
controlled independently and
individually.
BCCH -------
Does not attend Power
control

DTX and VAD
Voice Activity Detection – VAD
Discontinuous Transmission – DTX
Battery Saving
Interference reduction

Timing Advance (TA)
Transmission delay t
Transmission delay t
TA
The mobile phone should
send the signal in advance!

Multi-path Fading
 Diversity
 Frequency Hopping
Time Dispersion

Diversity – What’s Diversity?
 Receive diversity provides an effective technique for both
overcoming the impact of fading across the radio channel
and increasing the received signal to interference ratio.
 The former is achieved by ensuring “uncorrelated” (i.e.
low enough correlated) fading between antenna
branches i.e. not all antennas experience fades at the
same time.

Kinds of Diversity
 Time diversity
Coding, interleaving
 Frequency diversity
Frequency hopping
 Space diversity
Multiple antennas
 Polarization diversity
Dual-polarized antennas
 Multi-path diversity
Equalizer
t
f

Frequency Hopping
Frequency
f 0
Frame
f 1
f 2
f 3
f 4
Time

Contents
5. Radio Techniques

57.6 kbps
115 kbps
384kbps
2Mbps
GSM
HSCSD
GPRS
EDGE
IMT-2000
9.6 kbps
2G
2.5G
3G
GSM Development Evolution

Data rate of EDGE and GPRS
8PSKGMSK
9.0
13.4
15.6
21.4
8.8
11.2
14.8
17.6
22.4
29.6
44.8
54.4
59.2
0.0
10.0
20.0
30.0
40.0
50.0
60.0
CS-1 CS-2 CS-3 CS-4 MCS-1 MCS-2 MCS-3 MCS-4 MCS-5 MCS-6 MCS-7 MCS-8 MCS-9
Kbps
GPRS
EGPRS

Huawei EDGE Test Result
Downlink, 4 TS, MCS-9：

Summary
 The basic idea of GSM
 The frequency spectrum used in GSM
 The structure of GSM
 Certain service area and numbers
 Some radio techniques used in GSM
 Evolution of GSM

Huawei GSM Principles

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