gsm fundamentals

Report
Internal
OMA000001
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 2 GSM Network Structure
Chapter 3 Service Area and Number Planning
Chapter 4 Channels on the Wireless Interface
Chapter 5 Radio Techniques
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
1989
Standard Protocol for GSM take effect
1991
GSM system began to provide service in Europe(2G)
1992
System was named as Global System for
Mobile Communication
1994
Provide services for the whole world
1996
Micro Cell Technique is used in GSM system
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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.
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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.
Frequency
 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.
Time
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TDMA
 TDMA accomplishes the
communication in different
timeslot.
Frequency
 A carrier is divided into
Time
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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.
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CDMA
 CDMA accomplishes the
communication in different
code sequences.
Frequency
 Special coding is adopted
Time
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before transmission, then
different information will
lose nothing after being
mixed and transmitted
together on the same
frequency and at the
same time.
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The Frequency Spectrum
GSM 900
Uplink
890
Downlink
915
935
Duplex Separation:
Channel Bandwidth:
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960MHz
45MHz
200KHz
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The Frequency Spectrum
DCS 1800
Base Station Receive
1710
Base Station Transmit
1785 1805
Duplex Separation:
Channel Bandwidth:
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1880MHz
95MHz
200KHz
Page 13
The Frequency Spectrum
Frequency
Point
Available
Frequency
Spectrum
Range (MHz)
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<=1023
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<=1023
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
Uplink Frequency
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Downlink
Frequency
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
7
23
1
6
4
5
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Frequency Reuse
1
5
3
7
11
9
8
6
2
10
4
12
R
4 site X 3 cells reuse
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Cell Types
Omni
Omni-directional Cell
1
1
120
degree
120 Degree Cell
3
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2
Chapter 1 GSM System Overview
Chapter 2 GSM Network Structure
Chapter 3 Service Area and Number Planning
Chapter 4 Channels on the Wireless Interface
Chapter 5 Radio Techniques
Chapter 6 GPRS & EDGE Introduction
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GSM-GPRS Network Component
MSC/VLR
PSTN
ISDN
GMSC
GSM /GPRS BSS
BSC
MS
HLR/AUC
BTS
PCU
SS7
BSC
SMS system
MS
BTS
Internet,
Intranet
GPRS Backbone
SGSN
GGSN
OMC
CG
BG
Other PLMN
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Interface Between Different Entities
MSC/VLR
PSTN
ISDN
GMSC
GSM /GPRS BSS
Abis
MS
A
BSC
HLR/AUC
BTS
C/D/Gs
PCU
SS7
Gb
BSC
MS Um
SMS system
Gr/Gs/Gd/Ge
Gc
BTS
GPRS backbone
SGSN
Gi
GGSN
Ga
OMC
CG
BG
Gp
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Internet,
Intranet
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Other PLMN
Mobile Station—MS
MS=ME+SIM
International Mobile Equipment Identity (IMEI)
– Mobile Equipment
International Mobile Subscriber Identity (IMSI)
– Subscriber Identity Module
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Subscriber Identity Module – SIM
 International Mobile Subscriber Identity
(IMSI)
SIM
 Temporary Mobile Subscriber Identity (TMSI)
 Location Area Identity (LAI)
 Subscriber Authentication Key (Ki)
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Base Station Subsystem – BSS
MSC
 The Base Station Controller –
BSC
BSS
 The Base Transceiver Station
– BTS
 The Trans-coder – TC and
Sub multiplexer (SM)
TC/SM
BSC
BTS
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Packet Control Unit-----PCU
MSC
 Packet data
switching
 Bridge between
SGSN and BSC
 Provide Pb and
BSS
TC/SM
GPRS
Backbone
Gb interface
BSC
PCU
BTS
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SGSN
The Network Switching System
AUC
HLR
EIR
NSS
OMC
EC
MSC/VLR
Mobile-service Switching Center
Home Location Register
Visitor Location Register
Equipment Identity Register
Authentication Center
Echo Cancellor
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– MSC
– HLR
– VLR
– EIR
– AUC
– EC
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BSS
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PSTN
Mobile-service Switching Center – MSC

Call Processing

Operations and Maintenance Support

Interface management

Inter-network & Inter-working

Billing
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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
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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
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Equipment Identity Register – EIR
 White List
 Black List
IMEI is Checked In White List
 Grey List
If NOT found
EIR focus on the
equipment , not the
subscriber!!
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IMEI is Checked in Black/Grey List
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OMC Functional Architecture
Security
Management
Event/Alarm
Management
MMI
OS
DB
Fault
Management
Configuration
Management
Performance
Management
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Chapter 1 GSM System Overview
Chapter 2 GSM Network Structure
Chapter 3 Service Area and Number Planning
Chapter 4 Channels on the Wireless Interface
Chapter 5 Radio Techniques
Chapter 6 GPRS & EDGE Introduction
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Service Area
Service Area
PLMN
PLMN service
service area
area
MSC service area...
PLMN service area
MSC service area...
Location area...
Location area...
cell
cell
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......
LAI
MCC
MNC
LAC
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
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CGI
CGI: Cell Global Identification
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
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BSIC
BSIC(Base Station Identification Color Code)
NCC
BCC
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!
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MSISDN
CC
NDC
SN
National (significant)
Mobile number
Mobile station international
ISDN number
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
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IMSI
Not more than 15 digits
3 digits
2 digits
MCC
MNC
MSIN
NMSI
IMSI
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
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TMSI
TMSI: Temporary Mobile Subscriber Identification)
 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.
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IMEI
IMEI: International Mobile Station Equipment Identification
TAC
FAC
SNR
SP
IMEI
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#
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Chapter 1 GSM System Overview
Chapter 2 GSM Network Structure
Chapter 3 Service Area and Number Planning
Chapter 4 Channels on the Wireless Interface
Chapter 5 Radio Techniques
Chapter 6 GPRS & EDGE Introduction
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Physical Channel and Logical Channel
The physical channel is the medium over which the
information is carried: 200KHz and 0.577ms
The logical channel consists of the information carried
over the physical channels
0
1 2
Timeslot
3 4
5 6
7 0
1 2
3
The information carried in one time
slot is called a “burst”
TDMA FRAME
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TDMA FRAME
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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.
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Traffic Channel (TCH)
TCH
Traffic Channels
Speech
TCH/FS
TCH/HS
Data
TCH/9.6
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
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TCH/2.4
TCH/4.8
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Control Channel (CCH)
CCH (Control Channels)
DCCH
SDCCH
FACCH
BCH
ACCH
BCCH
SACCH
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CCCH
SCH
Broadcast Control Channel – BCCH
Common Control Channel – CCCH
Dedicated Control Channel – DCCH
Associated Control Channel – ACCH
Synch. CH.
RACH
CBCH
PCH/AGCH
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FCCH
Broadcast Control Channel – BCCH
CCH
The information carried on the BCCH
is monitored by the MS
BCH
periodically when it is in idle mode
BCCH: Broadcast Control Channel
FCCH: Frequency Correction Channel
BCCH
Synch.
Channels
SCH
FCCH
SCH: Synchronization Channel
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Common Control Channel – CCCH
CCH
The CCCH is responsible for
transferring control information
between all mobiles and the
network.
CCCH
RACH: Random Access Channel
PCH: Paging Channel
AGCH: Access Granted Channel
CBCH: Cell Broadcast Channel
RACH
uplink
CBCH
downlink
PCH/AGCH
downlink
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Dedicated Control Channel – DCCH
CCH
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
DCCH
SDCCH
FACCH
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ACCH
SACCH
Uplink Logical channel
CCH
RACH
CCCH
SDCCH
SACCH
DCCH
DCH
FACCH
TCH/F
TCH/H
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TCH
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Downlink Logical channel
FCCH
CCH
BCCH
SCH
BCCH
CCCH
PCH
AGCH
SDCCH
DCH
DCCH
SACCH
FACCH
TCH
TCH/F
TCH/H
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How to use these channels?
Power-off
Search for frequency correction burst
FCCH
SCH
BCCH
Search for synchronous burst
Extract system information
Idle mode
Monitor paging message
PCH
RACH
AGCH
SDCCH
SDCCH
TCH
FACCH
Send access burst
Allocate signaling channel
Dedicated mode
Set up the call
Allocate voice channel
Conversation
Idle mode
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Release the call
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Packet logic channel
TCH
 Packet data channel (PDCH)
 Comprising packet service channel and packet control channel
TCH
 Packet service channel (PDTCH)
 Combined into the single-directional service channel
BCCH
CCCH
 Packet control channel
SACCH
 Broadcast control channel: PBCCH
 Public control channel: PPCH, PRACH, PAGCH
 Private control channel: PACCH, PTCCH
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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
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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
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GSM Multi-frames
TDMA Frames
0
1
0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7
0
1
2
3
4
46 47 48 49 50
51 – Frame Multi-frames
CONTROL
CHANNELS
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GSM Multi-frames
TDMA Frames
0
1
0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7
0 1 2 3 4
21 22 23 24 25
26 – Frame Multi-frames
TRAFFIC
CHANNELS
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Chapter 1 GSM System Overview
Chapter 2 GSM Network Structure
Chapter 3 Service Area and Number Planning
Chapter 4 Channels on the Wireless Interface
Chapter 5 Radio Techniques
Chapter 6 GPRS & EDGE Introduction
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Power Control
Both Uplink and Downlink
power settings can be
controlled
independently
and individually.
5W
0.8W
Saves battery power
Reduces co-channel and
adjacent channel interference
8W
BCCH ------Does not attend Power control
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DTX and VAD
Discontinuous Transmission – DTX
Voice Activity Detection – VAD
Battery Saving
Interference reduction
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Timing Advance (TA)
The mobile phone should
send the signal in advance!
TA
Transmission delay t
Transmission delay t
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Multi-path Fading
 Diversity
 Frequency Hopping
Time Dispersion
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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.
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Kinds of Diversity
t
 Time diversity
Coding, interleaving
 Frequency diversity
f
Frequency hopping
 Space diversity
Multiple antennas
 Polarization diversity
Dual-polarized antennas
 Multi-path diversity
Equalizer
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Frequency Hopping
Frequency
f0
f1
f2
f3
f4
Frame
Time
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Chapter 1 GSM System Overview
Chapter 2 GSM Network Structure
Chapter 3 Service Area and Number Planning
Chapter 4 Channels on the Wireless Interface
Chapter 5 Radio Techniques
Chapter 6 GPRS & EDGE Introduction
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GSM Development Evolution
3G
2.5G
115 kbps
2G
57.6 kbps
9.6 kbps
2Mbps
384kbps
IMT-2000
EDGE
GPRS
HSCSD
GSM
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Data rate of EDGE and GPRS
Kbps
59.2
60.0
54.4
GPRS
EGPRS
50.0
40.0
44.8
29.6
30.0
22.4
21.4
20.0
13.4
10.0
17.6
15.6
14.8
9.0
8.8
11.2
0.0
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
8PSK
GMSK
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Huawei EDGE Test Result
Downlink, 4 TS, MCS-9:
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 The basic idea of GSM
Summary
 The frequency spectrum used in GSM
 The structure of GSM
 Certain service area and numbers
 Some radio techniques used in GSM
 Evolution of GSM
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Thank You
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