Cellular Mobile Communications-III
Introduction to GSM
Dr. Nasir D. Gohar
AN INTRODUCTION TO GSM
 Second Generation Cellular Mobile Radio SystemsDigital Cellular Telephony:
 Main Advantages of Digital Cellular Networks
 Higher Spectrum Efficiency
 Speech Encoding
 Better Access Technologies: TDMA and CDMA
 Higher System Capacity
 Aggressive Frequency Reuse
 Low Infra-Structure and Terminal Cost
 Application of VLSI/VVLSI Chips
 Many Traffic Channels per Carrier Channel [Transceivers are shared among
several users)
 Low S/I Ratio (SIR) Allowing Smarter Equipment
 Better Integration with Digital PSTN [ISDN]
 New Services such as Data Communications, Fax, and SMS
 Better Privacy due to Encryption
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AN INTRODUCTION TO GSM
 Digital Cellular Standards
Table-L13.1: Overview of Second Generation Standards
Region
Europe
USA
Japan
Standard
Developing Organization
Remarks
GSM
ETSI
Harmonized European Standard
DCS-1800
ETSI
GSM Varient for 1800 MHz Band
D-AMPS, D-AMPS 1900 TIA [IS-54B, IS-136]
Digital AMPS works in 800 MHZ and 1900 MHz Bands
IS-95 CDMA
TIA/QualComm[IS-95]
Downward Compatible with AMPS, later modified to work with 1900 MHz Band
PCS-1900
ETSI
GSM Vairent to work with 1900 MHz Band
PDC
NTT
Works both in 800 MHz and 1500 MHz
 Why So Many Standards?
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AN INTRODUCTION TO GSM
 Digital Cellular Standards
Table-L13.2: Overview of Important Technical Parameters of Digital Cellular Standards
Parametrs
Standard
Standard
Frequency
band(Mhz)
Air Interface
Forward Ch.
Reverse Ch.
Duplex
Separation
Access Tech. Channel BW
Mod. Rate
Speech
Encoding
Tx Power of
MS
H/O
GSM/DCS-1800/PCS1900
900/1800
/1900
935-960/1805- 890-915/17101880/19301785/18501970
1890
45/95/80
TDMA, 8 Time
Slots, Later
16 Time Slots
200 KHz
271 Kbps
LPC,13 kbps
2W/1W/1W
MAHO
D-AMPS
800/1900
869-894/1930- 824-849/18501970
1890
45/80
TDMA, 3 Slots
30 KHz
48.6 Kpbps
VSELP, 7.95
kpps
1.2 W
MAHO
0.2 W
Soft
Handover
0.8 W
MAHO
IS-95 CDMA
800/1900
869-894/1930- 824-849/18501970
1890
45/80
CDMA
1.25 MHz
PDC
800-1500
810-826/1477- 940-956/14291489 + 1501- 1441 + 14531513
1465
130/48
TDMA, 3
Slots, later 6
Slots
25 KHz
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1.2 to 14.4
Kbps
QSELP, 1.2 to
Transmitted
8 kbps
at 1.339
Mchips/s
42 kbps
VSELP, 11.2
kbps
4
AN INTRODUCTION TO GSM
 Overview of GSM Milestones
 1982
 1986
 1987




1989
1992
1994
1996
 2006
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GSM Group, set up by CEPT, started Investigation to reserve a
Spectrum in 900 MHz band for Pan-European Cellular Digital
Telephony
Two 25 MHz frequency Blocks [890-915 MHz, 935-960 MHz]
reserved by EC, July 01, 1991 set as Introduction date.
Choice of Digital and Narrow band [Approx. 200 KHz] TDMA made.
13 Operators from 12 European Countries signed MOU to
Support GSM
ETSI established which took over GSM from CEPT
Introduction of first Commercial GSM Network
51 Commercial Networks Established
More Than 20 Million Subscribers in 191 Networks, More than
Double of all Subscribers of other Digital Systems [D-AMPS,
PDC, IS-95 CDMA]
More than 2 billion subscribers (30% of world population and
82% of cellular market)
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AN INTRODUCTION TO GSM
 Implementation Phases of GSM
 Phase-1: Most Essential Services [Voice, Data, SMS] Implemented.
Mostly all Current GSM Systems belong to this Phase.
 Phase-2: Half-Rate Speech Encoding, Doubling the System Capacity,
Several Encryption Algorithms, Conference Call Facility[ up to 5
Participants] ,
Call Waiting Facility,
Information on Call Charges, Calling or Called Part etc.,
Cell-Broadcast [Point to Multi-Point SMS].
Many of the Phase-2 Facilities have already been Implemented by some
Manufacturers.
 Phase-2 + GPRS[General Packet radio Service] for Packet Switched
Data Transmission to Support LAN and Internet Traffic.
[Considerably Delayed due to Lack of Interest on part of Network
Operators due to Large Investment required for Infra-Structure and MS
Modifications]
 GSM 3G…..
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AN INTRODUCTION TO GSM
2G EVOLUTION TO 3G
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AN INTRODUCTION TO GSM
GSM EVOLUTION
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AN INTRODUCTION TO GSM
 GSM SYSTEM ARCHITECTURE
 MS
MANAGEMENT SUBSYSTEM
 SIM Card
 EIN/ESN
Fault Management
Cost Management
 Base Station Subsystem
(BSS)
BTS
BTS
 Several Dozens of BTS
BTS
BTS
BTS
BTS
 Network &Switching
Subsystem
 MTX [up to 1 M users]
 Call set up , all Other
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Security Management
Performance Management
B
S
C
HLR = Home
HLR Location Register
MTX
under one BSC
 Each BTS has 3-5 Carrier
Channels
Functions
Config. Management
B
S
C
BTS = Base Transceiver Station
BSC = base Station Controller
MS
BASE STATION SUBSYSTEM[BSS]
GMTX =
Gateway MTX
IWF = Inter
Working
Function
VLR = Visitor
VLR Location Register
GMTX/
IWF
To Other Networks
NETWORK & SWITCHING SUBSYSTEM
•GMTX: An Interface to Other Networks
•HLR: Keeps Record of System’s Own Users
•VLR: Keeps Temporary Record of Visitors / Roamers [SID, ST,SVCES]
•Au C/EIR: Manages the Sub. Authentication and Encryption Data
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AN INTRODUCTION TO GSM
 GSM SYSTEM ARCHITECTURE-2
MANAGEMENT SUBSYSTEM
 Management
Subsystem [Operation
Subsystem (OSS)]
Fault Management
Cost Management
 Directly or Indirectly
BTS
BTS
Connected to all Other
Subsystems
 Fault Management
 System Configuration
 Performance Management
 Cost Management
 Security Management
BTS
Security Management
Performance Management
B
S
C
HLR = Home
HLR Location Register
MTX
BTS
BTS
BTS
B
S
C
BTS = Base Transceiver Station
BSC = base Station Controller
MS
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Config. Management
BASE STATION SUBSYSTEM[BSS]
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GMTX =
Gateway MTX
IWF = Inter
Working
Function
VLR = Visitor
VLR Location Register
GMTX/
IWF
To Other Networks
NETWORK & SWITCHING SUBSYSTEM
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AN INTRODUCTION TO GSM
 GSM SYSTEM ARCHITECTURE-3
 GSM Interfaces
 Radio Interface:
Describes Data
Interchange between MS
and BSS
 Abis Interface: Describes
Data Communications
between BTS and BSC,
allows Various
Manufacturers Equipment
 A Interface: Describes
Data Interchange
between BSS and NSS
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AN INTRODUCTION TO GSM
 LOGICAL CHANNELS
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AN INTRODUCTION TO GSM
Control Channels
Control channels fall into three categories:
Broadcast:: BCCH, FCCH, SCH
 One way, from base to mobile
Common Control: RACH, AGCH, PCH
 One way, some from base to mobile and some from mobile to
the base
Dedicated: SDCCH, SACCG, FACCH
 Two-way, stand-alone or embedded in the traffic channels
All signaling channels share one carrier in a cell
the dedicated control channels may be transmitted on traffic
carriers
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AN INTRODUCTION TO GSM
Broadcast Channels
Frequency Correction Channel (FCCH)
Carries information for frequency correction
Synchronization Channel (SCH)
Carries information for frame synchronization and for
identification of the BTS
Broadcast Control Channel (BCCH)
Broadcasts general information on the BTS
Broadcasts cell-specific information, e.g. Control channel
organization, frequency hopping sequences, cell
identification, etc.
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AN INTRODUCTION TO GSM
Common Control Channels
 Paging Channel (PCH) - downlink only
for paging purposes
 Random Access Channel (RACH) - uplink only
used by any MS to request allocation of a signaling channel
(SDCCH)
a slotted Aloha protocol is used, so collisions among MSs may
happen
 Access Grant Channel (AGCH) - downlink only
used to allocate a SDCCH or a TCH
 Notification Channel (NCH) - downlink only
notify MS of voice group and voice broadcast call (ASCI feature)
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AN INTRODUCTION TO GSM
Dedicated Control Channels
Stand Alone Dedicated Control Channel (SDCCH)
used for call setup (authentication, signaling,, traffic channel
assignment), location updates and SMS
Slow Associated Control Channel (SACCH)
always coupled with a SDCCH or TCH
for communicating measurement data and control
parameters
Fast Associated Control Channel (FACCH)
to respond to increased signaling demand, e.g. during
handover
bandwidth (bit slots) are stolen from the associated TCH
(traffic data are preempted)
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AN INTRODUCTION TO GSM
Traffic Channels
GSM support two types of traffic channels
full rate (TCH/F): 22.8 kbps
half rate (TCH/H): 11.4 kbps
Mapping to physical channel
full rate traffic channel - 1 timeslot
half rate traffic channel - 1 timeslot in alternating frames
Full rate channel may carry
13 kbps speech or data at 2.4, 4.8 or 9.6 kbps
Half rate channel may carry
6.5 kbps speech or data at 2.4 or 9.6 kbps
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AN INTRODUCTION TO GSM
Channel Usage &
MS Terminating Calls
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AN INTRODUCTION TO GSM
 GSM Call Setup Procedure
 Locating the Subscriber
HLR keeps record of the MSC area which the Subscriber last
registered
VLR keeps record of the Location Area[LA] in which Subscriber last
registered
Location Area: A Group of Neighboring Cells having the same LAC
LAC: Each Cell in the Area Broadcasts this Code
Each Mobile itself periodically registers itself with MSC
 Paging and Random Access Procedure [RAP]
GMSC interrogates HLR for MSC the Subscriber last registered
Call is Switched to that MSC
VLR tells about the LA the user last registered
MSC arranges a Paging in all the Cells in the LA
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AN INTRODUCTION TO GSM
 GSM Call Setup Procedure-2
 Paging and Random Access Procedure[RAP]-Cont’d
The Mobiles listen to the Paging Channels for their Number
If received a Paging Message, the Mobile starts a RAP
 It sends a Random Number [RN] + Brief Guide to describe the Purpose
 The System [MSC] responds to it by repeating the RN and providing the
decided Channel
 The Mobile listens to this RN, if it is the same, it gets hold of the
allocated Channel
 Reconfirmation is done by the System by sending again the Mobile
Number [in case some other Mobile has also sent the same RN at the
same time]
 If the Mobile hears its own number, it responds to the System and thus
it gets connected to the incoming Call,
 If it was a wrong number [other than its own number] it must leave that
Channel.
 In case, a Mobile listens no same RN from the System, it may repeat
RAP at some time later randomly.
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AN INTRODUCTION TO GSM
CALL PROCESSING &
MOBILE TERMINATING CALLS
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AN INTRODUCTION TO GSM
CALL PROCESSING &
MOBILE ORIGINATING
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AN INTRODUCTION TO GSM
 GSM Handover and Routing
 Handover
 The Mobile keeps updating MSC about the RSS levels from the neighboring
Cells.
 MSC, while looking at the quality of the existing link, decides whether a
Handoff/ Handover is necessary or not.
 If yes, it asks the Candidate Cell to prepare the Channel [ GSM uses Fixed
Channel Assignment]
 When Channel is allocated, it tells the Mobile to move to that Channel
 When Mobile has moved, it deactivates the old Channel
 Routing
 GMSC interrogates HLR to locate the Subscriber by telling the MSC where
the Mobile last registered.
 PROBLEM: Call originated from PSTN in CANADA for a US Mobile roaming in
CANADA will result in two International Calls
“TROMBONE PROBLEM”
????
[Don’t Worry, Be Happy, Other People will Take Care of this Problem]
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AN INTRODUCTION TO GSM
HANDOVER TYPES
Intra-BSC
Old and new BTSs are
controlled by the same BSC
The MSC is not involved
Intra-MSC
Old and new BTSs are
attached to different BSCs
The BSCs are attached to the
same MSC
Inter-MSC
Handover to a new MSC
Serving MSC becomes anchor
MSC
IMT (Inter Machine Trunk) is
required
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AN INTRODUCTION TO GSM
 GSM Numbering Scheme and Spectrum Efficiency
 GSM Numbering Scheme
Each GSM Mobile has at least three Numbers:
 MSISDN [Mobile Station Integrated Services Digital Network] stored in
SIM Card

SIM Card holds Subscriber ID[MSISDN, IMSI], some Extra Memory to store
phone numbers and Encryption Algorithms
 IMSI[International Mobile Subscriber Identity] not known to the User,
HLR does translation between MSISDN to IMSI and vice versa.
 ESN or IMEI:Permanently stored/wired in the Mobile Station
 Spectrum Efficiency
 TDMA, 200 KHz Channel BW, 8-Time Slots per Carrier Channel
 Radio Spectrum = 2 x 25 MHz bands can support 125[124] Duplex Carrier
Channels and 1000 Traffic Channels [1000 Simultaneous Calls].
 A typical GSM System Cluster Size = 12, so each Cell have Approx. 10
Carrier Channels and a Capacity of 80 Simultaneous Call [Traffic Channels]
 In case of half-rate Coder, Spectrum Efficiency will be Doubled.
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AN INTRODUCTION TO GSM
 Technical Realization of GSM
 GSM Speech Communications
 User Speech is Digitized using Adaptive PCM
 Speech Encoding using Linear Predictive Coding [LPC]
 User data flow = 13 kbps [ 6.5 kbps in case of half-rate coding]
 Adding an overhead of 9.8 kbps[for error detection, error correction, and
synchronization], we get an over all user data flow of 22.8 kbps.
 This user data flow is subdivided into short data blocks each of 456 bits, which
is divided into 8 sub-blocks, each of 57 bits, 2 such sub-blocks are used to
make a burst [to fit into a time slot of 0.58 ms]. See frame structure.
 These bursts from a user are interleaved over 8 time slots spread over 8
frames.
 TDMA/FDMA Mechanism
 Each Carrier Channels carries data burst of eight (8) users, each in its
allocated time slot in the frame.
 Time slots are transmitted on several Channels [Carrier Channel or
Frequency]
 Each Carrier Channel transmits the data of 8 users at 271 kbps.
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AN INTRODUCTION TO GSM
 Technical Realization of GSM [ Cont’d]
 GSM Speech Communications-2
 GSM Carrier Frequencies are numbered 1-124 Channels[Duplex]
Forward Channel = 935.2 MHz + (n-1) * 200 KHz
Reverse Channel = 890.2 MHz + (n-1) * 200 KHz
 Due to slightly more than 200 KHz bandwidth of the modulated signal,
Frequency
Consecutive Frequencies are not used in the same System
 Also, 1 and 124 Channels are generally not used.
 The Spectrum of 124 Channels is generally not allotted to one Service
Provider.
 Separation between two Duplex paired Channels is 45 MHz.
 Each user’s bursts are transmitted every 4.6ms apart.
97
96
95
94
93
92
1
2
3
4
5
6
7
8
1
2
3
5
6
7
8
1
2
3
4
5
6
7
8
Time
Frame [4.6ms]
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4
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AN INTRODUCTION TO GSM
SPEECH PROCESSING
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AN INTRODUCTION TO GSM
SPEECH CODING
SPEECH ENCODER
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AN INTRODUCTION TO GSM
SPEECH DATA PROCESSING
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AN INTRODUCTION TO GSM
CHANNEL ENCODING
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AN INTRODUCTION TO GSM
 INTERLEAVING
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AN INTRODUCTION TO GSM
 VOICE TRANSMISSION PATH
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AN INTRODUCTION TO GSM
 Technical Realization of GSM [ Cont’d]
 GSM Framing Structure
Hyper Frame 3 Hrs 28 Min
2048
1
1
1
51
26
One Super Frame Occurs when
when the Speech and Control Channel
restart at the same time.
Super Frame 6.12 Sec
Multi-Frame 120 ms
Multi-Frame 235 ms
26
1
26 x Frames 4.61 ms
Speech
Traffic
Control
Traffic
Each Frame is sub-divided into 8 time-slots 0.58 ms
8
1
51
1
Preamble
3
57 bits User Speech Data
26 bits
57 bits User Speech Data
Time Slot 0.58 ms
3
GuardTime
Block = 456 Bits
1
2
.
.
8
8 sub-blocks 57 bits each
1
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81
81
81
81
8 1
81
8 x Frames 4.61 ms, Slot-2 of each Frame is Allocated to the User
NDG Notes
Blocked User Signal
Inter-Leaved into 8 Time Slots
over 8 Frames
8 1
8
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AN INTRODUCTION TO GSM
 TIME-SLOT STRUCTURE
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AN INTRODUCTION TO GSM
 FRAME HIERARCHY
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AN INTRODUCTION TO GSM
 BURST
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AN INTRODUCTION TO GSM
 TYPES OF BURST
Five different types of bursts
Normal burst
Traffic and control payload
Frequency correction burst
All zeroes sequence
Synchronization burst
A special fixed sequence
Random access burst
Extended guard period of 68.25 bitts (252 μs)
Dummy burst
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AN INTRODUCTION TO GSM
 BURST STRUCTURES
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AN INTRODUCTION TO GSM
 Technical Realization of GSM [ Cont’d]
 GSM Modulation Scheme
Gaussian Minimum Shift Keying [GMSK]
(For Detail see Ch-5 of the
Text Book)
 No Speech, No Transmission
 Saves Energy in MS, Reduces Ave. Interference
 Comfort Noise added for the Listener’s Pleasure.
 GSM MS Power Classes
 Class 1: 20 W
Not (yet) Available
 Class 2: 8 W
Car Phone
 Class 3: 5 W
 Class 4: 2 W
Normal Pocket Phone
 Class 5: 0.8 W Limited Coverage Phone [Urban Areas Only]
 Maximum Cell Size: Depends on Max. Permitted Delay, 35 km.
 Maximum Mobile Speed: 250 km/hr
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AN INTRODUCTION TO GSM
 Technical Realization of GSM [ Cont’d]
 GSM SMS
Individual Messages:
 up to 160 Characters long can be sent and received by MS
 SMS uses Signaling Channel, thus, it can be received during current
Communication Session
 Max. rate 600 bps
Cell Broadcast:
 up to 93 Character long message can be sent to all users in a given area
[Cells].
 Uses Communication Channel, so, can’t be received during current
Communication Session
 Neither Addressed Nor Encrypted
Applications of SMS: .Network Operator Messages, Third Party
Messages, Public Interest Information Messages
SMS Cost: Differs from Operator to Operator and depends on type
of Application
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AN INTRODUCTION TO GSM
 Technical Realization of GSM [
Cont’d]
 GSM Security Aspects
GSM provides security about
the identity of MS
Guards against Eavesdropping
 Implementation
User Authentication [A3
Algorithm]: 128 bit Secret
Number, Ki, assigned to each
User, stored in SIM Card as
well as AuC, is used to create
SRES using Ki and 128 bit
RAND number from the
network, if SRES of MS
matches with SRES of the
network, the MS is accepted.
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AN INTRODUCTION TO GSM
Data Encryption [A8+A5 Algorithm]:
Frame # + (RAND+Ki(Alg-A8))(Alg-A5) -> 144 bit Code Train  144 bit
user Data Train -> [Network]  Frame # + (RAND+Ki(Alg-A8))(Alg-A5) >Original Message
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AN INTRODUCTION TO GSM
 Technical Realization of GSM [Cont’d]
 GSM Inter-Connection with Other Networks:
PSTN/ISDN for Voice
 GSM Speech data is Digital and Compressed
 Converted into audio of 3.1 KHz BW
PSTN/ISDN for Data
 For Data Interconnection, Modem Pools are used in GSM Network. Many
Telephone Modems at GMSC/IWF supporting all the important telephone
modem standards V.21[0.3 kbps, AS], V.22[1.2 kbps, AS and S], V.32
[4.8 kbps, S] etc.
PSDN (Basic PAD or Dedicated PAD) for Data
 300 bps to 9600 bps on AS/S links
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NEW DEVELOPMENTS IN GSM
 Frequency Shortage and Extended GSM Band
 In some European countries, up to half GSM band is occupied by Interim
Systems; NMT, ETACS etc.
 Additional frequencies adjacent to GSM band is recommended by
ERO[1996], new terminals for this extended band are not available in bulk
 New Encoding Techniques
 Half-Rate Speech Encoding
 Instead of 13 kbps only 6.5 kbps will be required for the same speech quality
 Standardized in early 1995, but, only few manufacturers have implemented
 lack of interest on part of system suppliers
 fear of investment decrease in network expansion [uCell]
 Enhanced Full Rate [EFR]:Developed by GSM and DCS-1800 Suppliers
 Same 13 kbps speed, but, considerable improvement in speech quality
 More Immunity to transmission errors
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NEW DEVELOPMENTS IN GSM
 Any Cellular Phone may have many Speech Coders, including
FR/HR/EFR, it must be able to switch, and at least support FR for roaming
purpose.
 Data Communications over GSM
 General Packet Radio Service[GPRS] offers packet-switched data
communications suitable for LAN and Internet Applications[PVC]
 Requires GPRS enabled Handsets and Changes at BSS[addition of Packet
Control Unit, PCU]
 Option of Upgrading of BTS to support Enhanced Data rate for GSM Evolution,
EDGE [8-PSK system]
 Multi-band Terminals
 Cellular phones to support more than frequency bands [GSM and DSC-1800 or
GSM and PCS-1900 or GSM/DCS/PCS or many more combinations]
 GSM Moving into 3G Mode
 GSM extends itself into 3G as Universal Mobile Telecomm. Services [UMTS]
 Radio Interface will use WCDMA technology [UMTS Terrestrial Radio Access, UTRA]
in two different modes: FDD [two different frequencies for uplink and downlink] or
TDD[same frequency for both uplink and downlink but time-shared]
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The Market Share of GSM Suppliers
[1/97]
 Networking & Switching Subsystems [NSS]
 Ericsson [48 %], Siemens [21 %], Nokia [14 %], and Alcatel [10%] = 93 %
 Others (Lucent, Motorola, Nortel, etc] = 7%
 Basestation Sub-System [BSS]
 Nokia [22%], Motorola [13%], Alcatel [10%] and Ericsson [7%] = 52%
 Others [Italtel, Lucent, Matra, Philips etc] = 48%
 GSM / DCS-1800 / PCS-1900 Mobile Terminals
 Ericsson [25 %], Nokia [24%], MOTOROLA [20 %], SIEMENS [9%] =78 %
 Others [Alcatel, Panasonic, Nortel, etc.] = 22 %
 Due to Licensing Problems, Unfair and Restricted Competition in
GSM Markets
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GSM and Health Problems
 GSM Terminals Cause Interference with
 Hearing Aid Devices and
 Pacemakers [Instruments used to regulate the heart functionality of
Heart Patients], and
 Some Research show that GSM phones cause Brain Tumors *
 Inherent in GSM TDMA setup to generate strongly pulsating
transmission signals [Continuously Tx is switched on and off that
generates LF signals 217, 434, 651 Hz]
 * Extensive Research required to prove the validity of GSM Cellular
Phones being the cause of Brain Tumors or Cancer.
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GSM Derivative Systems: DCS-1800 & PCS-1900
 Digital Cellular System[DCS]-1800
 Originally started [in 1990] as a separate system, but, later on became just
a GSM variant
 Main modifications were made only in Air Interface
 Developed [by ETSI] particularly for densely populated urban areas
 1.7 - 2.3 GHZ band [ 2 x 75 MHz spectrum, 1710- 1785 + 1805-1888 MHz]
 Duplex separation is 95 MHz, Channel BW is 200 KHz, 374 duplex channels
 Much smaller cells [cells within a building], lower power BTS and MS as
compared to GSM
 handoff problems are much cleverly settled using hierarchical Cell structure
 Max Cell size 8 km with Class 1 MS [1W]
 Max Cell size with Class II[0.25W] even smaller [0.5 -4/5 km]
 International as well as National roaming is possible [Country to Country,
Network to Network, and Intra-Network]
 Half-rate speech coding is possible/EFR is more likely to prevail.
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GSM Derivative Systems: DCS-1800 & PCS-1900
 Personal Communication Services [PCS]-1900






A GSM variant to adapt to US Market
Frequency band 1900 MHz [1850-1890, 1930-1970 MHz]
2 x 40 MHz bands with Duplex Separation of 80 MHz
Channel BW is 200 KHz, 200 Duplex Channels
TDMA 8 time-slots
EFR speech encoding is getting more Interest from US Service
Providers
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GSM Facing Challenges
 Higher Costs incurred on Network Capacity Increase
 Business Market Saturation
 More Money on Advertisement and Subsidies/Customer Discounts
 Interconnection Costs [to PSTN/ISDN] are very high
 Leased Line Costs to Interconnect own Infra-structural elements
are very high
 High License Costs
 With Implementation of De-regulation policies this
CHANGE.
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REFERENCES
www.utdallas.edu/~nhutnn/cs6v81/LECTURE
_06.pdf
http://www.gsmworld.com
Dr. Veselin Rakocevic
http://www.staff.city.ac.uk/~veselin/Wireless
Comms
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