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Overview of GSM Cellular
Network and Operations
By:
UJJWAL JAIN
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Network and switching subsystem
NSS is the main component of the public mobile network GSM
switching, mobility management, interconnection to
othernetworks, system control
Components
Mobile Services Switching Center (MSC)controls all connections
via a separated network to/from a mobile
terminal within the domain of the MSC - several BSC can belongto
a MSC
Databases (important: scalability, high capacity, low delay)
Home Location Register (HLR)central master database containing
user data, permanent andsemi-permanent data of all subscribers
assigned to the HLR(one provider can have several HLRs)
Visitor Location Register (VLR)local database for a subset of
user data, including data about alluser currently in the domain of
the VLR
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Operation subsystem
The OSS (Operation Subsystem) enables centralized
operation,management, and maintenance of all GSM subsystems
Components
Authentication Center (AUC)
generates user specific authentication parameters on request ofa
VLR
authentication parameters used for authentication of
mobileterminals and encryption of user data on the air
interfacewithin the GSM system
Equipment Identity Register (EIR)
registers GSM mobile stations and user rights
stolen or malfunctioning mobile stations can be locked and
sometimes even localized
Operation and Maintenance Center (OMC)
different control capabilities for the radio subsystem and
thenetwork subsystem
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Mobile Handset
TEMPORARY DATA PERMANENT DATA
- Temporary Subscriber Identity Permanent Subscriber
Identity
- Current Location Key/Algorithm for Authentication.
- Ciphering Data
Provides access to the GSM n/w
Consists of
Mobile equipment (ME)
Subscriber Identity Module (SIM)
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The GSM Radio Interface
AIR INTERFACE
UPLINK
890
-915
MHz
DOWNLI
NK935
-960M
Hz
MOBILE
BASE TRANSCEIVER STATION
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The GSM Network Architecture
Time division multiple access-TDMA
124 radio carriers, inter carrier spacing
200khz.
890 to 915mhz mobile to base - UPLINK
935 to 960mhz base to mobile -
DOWNLINK
8 channels/carrier
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GSM uses paired radio channels
0 124 0 124
890MHz 915MHz 935MHz 960MHz
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Access Mechanism
FDMA, TDMA, CDMA
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Frequency multiplex
Separation of the whole spectrum into smaller frequency
bands
A channel gets a certain band of the
spectrum for the whole time
Advantages:
no dynamic coordinationnecessary
works also for analog signals
Disadvantages:
waste of bandwidth
if the traffic isdistributed unevenly
inflexible
guard spaces
k2 k3 k4 k5 k6k1
f
t
c
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f
t
c
k2 k3 k4 k5 k6k1
Time multiplex A channel gets the whole spectrum for a certain
amount of
time
Advantages:
only one carrier in the
medium at any time
throughput high even
for many users Disadvantages:
precise
synchronization
necessary
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f
Time and Frequency Multiplex
Combination of both methods
A channel gets a certain frequency band for a certain
amount of time
t
c
k2 k3 k4 k5 k6k1
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f
Time and Frequency Multiplex Example: GSM
Advantages: Better protection against
tapping
Protection against frequency
selective interference Higher data rates compared to
code multiplex
But: precise coordination
required
t
c
k2 k3 k4 k5 k6k1
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GSM combines FDM and TDM: bandwidth
is subdivided into channels of 200khz,
shared by up to eight stations, assigningslots for transmission
on demand.
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GSM uses paired radio channels
0 124 0 124
890MHz 915MHz 935MHz 960MHz
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Code Multiplex
Each channel has a unique code
All channels use the same spectrum at the sametime
Advantages:
Bandwidth efficient
No coordination and synchronizationnecessary
Good protection against interference andtapping
Disadvantages:
Lower user data rates
More complex signal regeneration
Implemented using spread spectrum technology
k2 k3 k4 k5 k6k1
f
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c
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Various Access Method
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Cells
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Capacity & Spectrum Utilization
SolutionThe need: Optimum spectrum
usage More capacity High quality of
service
Low cost
I wish I could increase capacitywithoutadding NEW BTS!
What can I do?
Network capacity at required QoSwith conventional frequency
plan
Subscribergrowth
Time
Out of
Capacity!!!
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Representation of Cells
Ideal cells Fictitious cells
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Cell size and capacity
Cell size determines number of cellsavailable to cover
geographic area and (with
frequency reuse) the total capacity availableto all users
Capacity within cell limited by availablebandwidth and
operational requirements
Each network operator has to size cells tohandle expected
traffic demand
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Cell structure
Implements space division multiplex: base station covers a
certaintransmission area (cell)
Mobile stations communicate only via the base station
Advantages of cell structures:
higher capacity, higher number of users
less transmission power needed
more robust, decentralized
base station deals with interference, transmission area etc.
locally
Problems: fixed network needed for the base stations
handover (changing from one cell to another) necessary
interference with other cells
Cell sizes from some 100 m in cities to, e.g., 35 km on the
country side
(GSM) - even less for higher frequencies
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Capacity of a Cellular System
Frequency Re-Use Distance
The K factor or the cluster size
Cellular coverage or Signal to interference
ratio
Sectoring
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i
j
1
2
3
4
5
6
7
Frequency re-use distance is based on the cluster size K
The cluster size is specified in terms of the offset of the
center of a cluster from the
center of the adjacent cluster
K = i2 + ij + j2
K= 22 + 2*1 + 12
K = 4 + 2 + 1
K = 7
D = 3K * RD = 4.58R
1
2
35
6
7
D
R
The K factor and Frequency Re-Use Distance
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K = i2 + ij + j2
K= 22 + 2*0 + 02
K = 4 + 0 + 0
K = 4
D = 3K * RD = 3.46R i
D
R
The Frequency Re-Use for K = 4
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1
2
3
4
5
6
7
1
2
3
4
5
6
7
2
1
1
2
3
4
5
6
7
1
2
3
4
5
67
1
2
3
4
5
6
7
The Cell Structure for K = 7
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1
2
3
4
1
1
1
1
1
12
2
2
2
2
3
3
3
3
3
4
4
4
4
4
4
3
2
Cell Structure for K = 4
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1
11
1
2 2
22
3
3
3
3
4
4 4
45
5 5
5
6
6 6
6
7
7
7
7
8
8
889
99
9
10
1010
10
1111
1111
1212
12 12
Cell Structure for K = 12
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Increasing cellular system
capacity Cell sectoring
Directional antennas subdivide cell into 3 or 6
sectorsMight also increase cell capacity by factor of 3
or 6
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Increasing cellular system
capacity Cell splitting
Decrease transmission power in base and
mobileResults in more and smaller cells
Reuse frequencies in non-contiguous cell
groupsExample: cell radius leads 4 fold capacity
increase
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Tri-Sector antenna for a cell
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Highway
TownSuburb
Rural
Cell Distribution in a Network
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Optimum use of frequency
spectrum Operator bandwidth of 7.2MHz (36 freq of 200
kHz)
TDMA 8 traffic channels per carrier
K factor = 12
What are the number of traffic channels availablewithin its area
for these three cases
Without cell splitting With 72 cells
With 246 cells
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One Cell = 288 traffic channels
72 Cell = 1728 traffic channels
246 Cell = 5904 traffic channels
Re-use of the frequency
8 X 36 = 288
8 X (72/12 X 36) = 1728
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Concept of TDMA Frames and
Channels
f
t
c
GSM combines FDM and TDM: bandwidth is subdividedinto channels
of 200khz, shared by up to eight stations,
assigning slots for transmission on demand.
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GSM uses paired radio channels
0 124 0 124
890MHz 915MHz 935MHz 960MHz
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GSM delays uplink TDMA frames
T1 T2 T3 T5 T6 T7T4 T8
R T
R T
R1 R2 R3 R5 R6 R7R4 R8
Uplink TDMA
FrameF1 + 45MHz
Downlink TDMA
F1MHz
The start of the uplink
TDMA is delayed ofthree time slots
TDMA frame (4.615 ms)
Fixed transmit
Delay of three time-slots
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1 2 3 4 5 6 7 8
higher GSM frame structures
935-960 MHz
124 channels (200 kHz)
downlink
890-915 MHz124 channels (200 kHz)
uplink
time
GSM TDMA frame
GSM time-slot (normal burst)
4.615 ms
546.5 s577 s
guard
space
guard
spacetail user data TrainingS S user data tail
3 bits 57 bits 26 bits 57 bits1 1 3
GSM - TDMA/FDMA
LOGICAL CHANNELS
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LOGICAL CHANNELS
TRAFFIC SIGNALLING
FULL RATE
Bm 22.8 Kb/S
HALF RATE
Lm 11.4 Kb/S
BROADCAST COMMON CONTROL DEDICATED CONTROL
FCCH SCH BCCH
PCHRACH
AGCH
SDCCH SACCH FACCH
FCCH -- FREQUENCY CORRECTION CHANNEL
SCH -- SYNCHRONISATION CHANNEL
BCCH -- BROADCAST CONTROL CHANNEL
PCH -- PAGING CHANNEL
RACH -- RANDOM ACCESS CHANNEL
AGCH -- ACCESS GRANTED CHANNEL
SDCCH -- STAND ALONE DEDICATED CONTROL CHANNEL
SACCH -- SLOW ASSOCIATED CONTROL CHANNEL
FACCH -- FAST ASSOCIATED CONTROL CHANNEL
DOWN LINK ONLY
UPLINK ONLY
BOTH UP &
DOWNLINKS
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Broadcast Channel - BCH
Broadcast control channel (BCCH) is a base tomobile channel
which provides general informationabout the network, the cell in
which the mobile iscurrently located and the adjacent cells
Frequency correction channel (FCCH) is a base tomobile channel
which provides information forcarrier synchronization
Synchronization channel (SCH) is a base to mobilechannel which
carries information for framesynchronization and identification of
the basestation transceiver
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Common Control Channel -
CCH Paging channel (PCH) is a base to mobile channel
used to alert a mobile to a call originating from the
network Random access channel (RACH) is a mobile to base
channel used to request for dedicated resources
Access grant channel (AGCH) is a base to mobile
which is used to assign dedicated resources(SDCCH or TCH)
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Dedicated Control Channel -
DCCH Stand-alone dedicated control channel
(SDCCH) is a bi-directional channel allocated
to a specific mobile for exchange of locationupdate information
and call set up
information
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Dedicated Control Channel -
DCCH Slow associated control channel (SACCH) is a
bi-directional
channel used for exchanging control information between
base and a mobile during the progress of a call set up
procedure. The SACCH is associated with a particular
trafficchannel or stand alone dedicated control channel
Fast associated control channel (FACCH) is a bi-directional
channel which is used for exchange of time critical
information between mobile and base station during theprogress
of a call. The FACCH transmits control
information by stealing capacity from the associated TCH
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HIERARCHY OF FRAMES
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0 1 2 3 4 5 6 2043 2044 2045 2046 2047
0 1 2 3 4 48 49 50
0 1 2 24 25
0 1 2 3 24 25
0 1 2 3 4 48 49 50
0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0
0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0
1 HYPER FRAME = 2048 SUPERFRAMES = 2 715 648 TDMA FRAMES ( 3 H
28 MIN 53 S 760 MS )
1 SUPER FRAME = 1326 TDMA FRAMES ( 6.12 S )LEFT (OR) RIGHT
1 MULTI FRAME = 51 TDMA FRAMES (235 .4 ms )
1 SUPER FRAME = 26 MULTI FRAMES
1 SUPER FRAME = 51 MULTI FRAMES
1 MULTIFRAME = 26 TDMA FRAMES ( 120 ms )
TDMA FRAME NO.
0 1
0 11 2 3 4 155 156
1 TIME SLOT = 156.25 BITS
( 0.577 ms)
(4.615ms)
(4.615 ms)
1 bit =36.9 micro sec
TRAFFIC CHANNELS
SIGNALLING CHANNELS
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GSM Frame
0 1 2 3 4 5 6 7
3 57 1 26 1 57 3 8.25
0 1 2 12 24 25
Full rate
channel is
idle in 25SACCH is
transmitted
in frame 120 to 11 and 13 to 24Are used for traffic data
Frame
duration =
120ms
Frame
duration =
60/13ms
Frame
duration =15/26ms
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114 bits are available for data transmission.
The training sequence of 26 bits in themiddle of the burst is
used by the receiver to
synchronize and compensate for time
dispersion produced by multipath
propagation.
1 stealing bit for each information block
(used for FACCH)
LOGICAL CHANNELS
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TRAFFIC SIGNALLING
FULL RATE
Bm 22.8 Kb/S
HALF RATE
Lm 11.4 Kb/S
BROADCAST COMMON CONTROL DEDICATED CONTROL
FCCH SCH BCCH
PCHRACH
AGCH
SDCCH SACCH FACCH
FCCH -- FREQUENCY CORRECTION CHANNEL
SCH -- SYNCHRONISATION CHANNEL
BCCH -- BROADCAST CONTROL CHANNEL
PCH -- PAGING CHANNEL
RACH -- RANDOM ACCESS CHANNEL
AGCH -- ACCESS GRANTED CHANNEL
SDCCH -- STAND ALONE DEDICATED CONTROL CHANNEL
SACCH -- SLOW ASSOCIATED CONTROL CHANNEL
FACCH -- FAST ASSOCIATED CONTROL CHANNEL
DOWN LINK ONLY
UPLINK ONLY
BOTH UP &
DOWNLINKS
Location update from the mobile
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Mobile looks for BCCH after switching on
RACH send channel request
AGCH receive SDCCH
SDCCH authenticate
SDCCH switch to cipher mode
SDCCH request for location updating
SDCCH authenticate response
SDCCH cipher mode acknowledge
SDCCH allocate TMSI
SDCCH acknowledge new TMSI
SDCCH switch idle update mode
p
Call establishment from a mobile
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Mobile looks for BCCH after switching on
RACH send channel request
AGCH receive SDCCH
SDCCH do the authentication and TMSI allocation
SDCCH require traffic channel assignment
SDCCH send call establishment request
SDCCH send the setup message and desired number
FACCH switch to traffic channel and send ack (steal bits)
FACCH receive alert signal ringing sound
FACCH acknowledge connect message and use TCH
TCH conversation continues
FACCH receive connect message
Call establishment to a mobile
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Mobile looks for BCCH after switching on
Receive signaling channel SDCCH on AGCH
Receive alert signal and generate ringing on FACCH
Receive authentication request on SDCCH
Generate Channel Request on RACH
Answer paging message on SDCCH
Authenticate on SDCCH
Receive setup message on SDCCH
FACCH acknowledge connect message and switch to TCH
Receive connect message on FACCH
Receive traffic channel assignment on SDCCH
Mobile receives paging message on PCH
FACCH switch to traffic channel and send ack (steal bits)
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GSM speech coding
AIR INTERFACE
UPLINK
890
-915
MHz
DOWNLI
NK935
-960M
Hz
MOBILE
BASE TRANSCEIVER STATION
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Transmit Path
BS Side8 bit A-Law
to
13 bit Uniform RPE/LTP speech Encoder To Channel Coder
13Kbps
8 K sps
MS Side
LPF A/DRPE/LTP speech Encoder
To Channel Coder 13Kbps
8 K sps,
Sampling Rate - 8K
Encoding - 13 bit Encoding (104 Kbps)
RPE/LTP - Regular Pulse Excitation/Long Term Prediction
RPE/LTP converts the 104 Kbps stream to 13 Kbps
GSM S h C di
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GSM Speech Coding
GSM is a digital system, so speech which is
inherently analog, has to be digitized.
The method employed by current telephonesystems for multiplexing
voice lines over
high speed trunks and is pulse coded
modulation (PCM). The output stream fromPCM is 64 kbps, too high
a rate to be
feasible over a radio link.
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GSM Frame
0 1 2 3 4 5 6 7
3 57 1 26 1 57 3 8.25
0 1 2 12 24 25
Full rate
channel is
idle in 25SACCH is
transmitted
in frame 120 to 11 and 13 to 24Are used for traffic data
Frame
duration =
120ms
Frame
duration =
60/13ms
Frame
duration =15/26ms
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GSM Speech Coding
Speech is divided into 20 millisecond
samples, each of which is encoded as 260
bits, giving a total bit rate of 13 kbps. Regular pulse excited
-- linear predictive
coder (RPE--LPC) with a long term
predictor loop is the speech codingalgorithm.
The 260 bits are divided into three classes:
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The 260 bits are divided into three classes:
Class Ia 50 bits - most sensitive to bit errors.
Class Ib 132 bits - moderately sensitive to bit errors.
Class II 78 bits - least sensitive to bit errors.
Class Ia bits have a 3 bit cyclic redundancy code added for
error
detection = 50+3 bits.
132 class Ib bits with 4 bit tail sequence = 132 + 4 = 136.
Class Ia + class Ib = 53+136=189, input into a 1/2 rate
convolution
encoder of constraint length 4. Each input bit is encoded as two
outputbits, based on a combination of the previous 4 input bits.
The
convolution encoder thus outputs 378 bits, to which are added
the 78
remaining class II bits.
Thus every 20 ms speech sample is encoded as 456 bits, giving a
bit
rate of 22.8 kbps.
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To further protect against the burst errors common to the
radio interface, each sample is interleaved. The 456 bits
output by the convolution encoder are divided into 8
blocks of 57 bits, and these blocks are transmitted in
eightconsecutive time-slot bursts. Since each time-slot burst
can
carry two 57 bit blocks, each burst carries traffic from two
different speech samples.
3 57 bits 261 1 57 bits 3
3 57 bits 261 1 57 bits 3
3 57 bits 261 1 57 bits 3
3 57 bits 261 1 57 bits 3
3 57 bits 261 1 57 bits 3
3 57 bits 261 1 57 bits 3
3 57 bits 261 1 57 bits 3
3 57 bits 261 1 57 bits 3
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GSM Protocol Suite
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BTS
Radio interface
HLR
MSC
VLR
BSC
RR
MM + CM
SS
Li k L
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Link Layer
LAPDm is used between MS and BTS
LAPD is used between BTS-BSC
MTP2 is used between BSC-
MSC/VLR/HLR
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Network Layer
To distinguish between CC, SS, MM and RRprotocol discriminator
(PD) is used as networkaddress.
CC call control management MS-MSC.
SS supplementary services management MS-MSC/HLR.
MM mobility management(location management,
security management) MS-MSC/VLR. RR radio resource management
MS-BSC.
Messages pertaining to different transaction aredistinguished by
a transaction identifier (TI).
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Application Layer protocols
BSSMAP between BSC and MSC
DTAP messages between MS and MSC.
All messages on the A interface bear adiscrimination flag,
indicating whether themessage is a BSSMAP or a DTAP.
DTAP messages carry DLCI(information on type
of link on the radio interface) to distinguish whatis related to
CC or SMS.
MAP protocol is the one between neighbor MSCs.MAP is also used
between MSC and HLR.
GSM Functional Architecture and Principal Interfaces
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Q.921
Radio Interface
Q.931
Q.921
MAP
TCAP
CCS7 MTP
CCS7 SCCP
Mobile Application Part
Q931 BSSAP
SCCP
CCS7 MTP
A Interface
A-Bis Interface
Um
Base Station System
GSM Functional Architecture and Principal Interfaces
GSM protocol layers for
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GSM protocol layers for
signaling
CM
MM
RR
MM
LAPDm
radio
LAPDm
radio
LAPD
PCM
RR BTSM
CM
LAPD
PCM
RRBTSM
16/64 kbit/s
Um Abis A
SS7
PCM
SS7
PCM
64 kbit/s /2.048 Mbit/s
MS BTS BSC MSC
BSSAPBSSAP
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Protocols involved in the radio
interface Level 1-Physical
TDMA frame
Logical channels multiplexing
Level 2-LAPDm(modified from LAPD) No flag
No error retransmission mechanism due to real time
constraints
Level 3-Radio Interface Layer (RIL3) involves three sub
layers
RR: paging, power control, ciphering execution, handover
MM: security, location IMSI attach/detach
CM: Call Control(CC), Supplementary Services(SS), Short
Message Services(SMS),
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LAPDm on radio interface
In LAPDm the use of flags is avoided.
LAPDm maximum length is 21 octets of
information. It makes use of more bit todistinguish last frame
of a message.
No frame check sequence for LAPDm, ituses the error detecting
performance of the
transmission coding scheme offered by thephysical layer
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ADDRESS CONTROL INFORMATION 0-21 OCTETS
SAPI
N(S) N(R)
LAPDm Message structure
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LAPDm on radio interface
The acknowledgement for the next expected frame in theindicator
N(R ).
On radio interface two independent flows(one for
signaling, and one for SMS) can exist simultaneously. These two
flows are distinguished by a link identifier
called the SAPI(service access point identifier).
LAPDm SAPI=0 for signaling and SAPI=3 for SMS.
SAP1=0 for radio signaling, SAPI=62 for OAM andSAPI=63 for layer
2 management on the Abis interface.
There is no need of a TEI, because there is no need
todistinguish the different mobile stations, which is done
bydistinguishing the different radio channels.
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Protocols involved in the A-bis
interface Level 1-PCM transmission (E1 or T1)
Speech encoded at 16kbit/s and sub multiplexed in64kbit/s time
slots.
Data which rate is adapted and synchronized.
Level 2-LAPD protocol, standard HDLC
Radio Signaling Link (RSL)
Operation and Maintenance Link (OML).
Level 3-Application Protocol
Radio Subsystem Management (RSM)
Operation and Maintenance procedure (OAM)
i f bi f
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Presentation of A-bis Interface
Messages exchanges between the BTS and BSC.
Traffic exchanges
Signaling exchanges
Physical access between BTS and BSC is PCMdigital links of
E1(32) or T1(24) TS at 64kbit/s.
Speech:
Conveyed in timeslots at 4X16 kbit/s
Data: Conveyed in timeslots of 4X16 kbit/s. The initial user
rate, which may be 300, 1200, is adjusted to 16kbit/s
A
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FLAG ADRESS CONTROL INFORMATION 0260 OCT FCS FLAG
SAPI TEI
N(S) N(R)
LAPD message structure
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LAPD
The length is limited to 260 octets of information.
LAPD has the address of the destination terminal,
to identify the TRX, since this is a point tomultipoint
interface.
Each TRX in a BTS corresponds to one or several
signaling links. These links are distinguished by
TEI (Terminal Equipment Identities). SAPI=0, SAPI=3, SAPI=62 for
OAM.
Presentation of the A-ter
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interface
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BSC
TRAU
MSC
OMC
OAM
Transcoding
LAPD TS1
Speech TS
CCS7 TS
X.25 TS2
Speech TS
CCS7 TS
X.25 TS2
PCM
LINK PCM
LINK
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Presentation on the A-ter
interface Signaling messages are carried on specific timeslots
(TS)
LAPD signaling TS between the BSC and the TCU
SS7 TS between the BSC and the MSC, dedicated for BSSAP
messages transportation.
X25 TS2 is reserved for OAM.
Speech and data channels (16kbit/s)
Ater interface links carry up to:
120 communications(E1), 4*30
92 communications(T1).
The 64 kbit/s speech rate adjustment and the 64 kbit/s data
rate
adaptation are performed at theTCU.
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Presentation of the A interface
Signaling Protocol Model
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Presentation on the A-Interface
BSSMAP - deals with procedures that take place logically between
theBSS and
MSC, examples:
Trunk Maintenance,Ciphering, Handover, Voice/Data Trunk
Assignment
DTAP - deals with procedures that take place logically between
theMS and
MSC. The BSS does not interpret the DTAP information, it simply
repackages it
and sends it to the MS over the Um Interface. examples:
Location Update,MS originated and terminated Calls, Short
Message
Service, User Supplementary Service registration, activation,
deactivation
and erasure
I t MSC t ti
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Inter MSC presentation
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O
AM
L
A
P
D
BTS
MTP2
SCCP
MTP3
L
A
P
D
O
AM
RR
DT
A
P
BS
S
M
A
P
BSSAP
BSC
MTP1
MTP3
MTP2
SCCP
MTP2
MTP3
SCCP
BSSAP
DTAP/BSSMAP
T
CA
P
MM
CM M
A
P
NSS
R
R
MM
CM
MS
Um
Interface
A bis
Interface
A
Interface
MS BSC MSC
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SCCP Ref=R2
TRX:TEI=T1
Channel ID = N1
SCCP Ref=R1
DTAP
DLCI: SAPI=3
DLCI: SAPI=0
Channel=C1
Link: SAPI=3
Link: SAPI=0PD=CC
TI=a
TI=b
PD=MM
PD=RR
TI=A
Channel=C2 Channel ID = N1
Radio Interface Abis Interface
A Interface
PD: protocol discriminator
TI: Transaction Identifier for
RIL3-CC protocol
DLCI: Data Link connectionIdentifier
SAPI: Service Access Point
Identifier on the radio
Interface
TEI: Terminal Equipment
Identifier on the Abis I/F
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Bearer Services
Telecommunication services to transfer databetween access
points
Specification of services up to the terminal
interface (OSI layers 1-3)
Different data rates for voice and data (originalstandard)
Data service
Synchronous: 2.4, 4.8 or 9.6 kbit/s
Asynchronous: 300 - 1200 bit/s
Tele Services
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Tele Services Telecommunication services that enable voice
communication via
mobile phones.
All these basic services have to obey cellular functions,
security
measurements etc.
Offered services.
Mobile telephony
primary goal of GSM was to enable mobile telephony offering
thetraditional bandwidth of 3.1 kHz.
Emergency number
common number throughout Europe (112); Mandatory for all
service providers; Free of charge; Connection with the
highest
priority (preemption of other connections possible).
Multinumbering
several ISDN phone numbers per user possible.
Performance characteristics of GSM
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Performance characteristics of GSM Communication
mobile, wireless communication; support for voice and
dataservices
Total mobility
international access, chip-card enables use of access points
of
different providers
Worldwide connectivity one number, the network handles
localization
High capacity
better frequency efficiency, smaller cells, more customers per
cell
High transmission quality
high audio quality and reliability for wireless, uninterrupted
phone
calls at higher speeds (e.g., from cars, trains)
Security functions
access control, authentication via chip-card and PIN
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Disadvantages of GSM
No full ISDN bandwidth of 64 kbit/s to the user
Reduced concentration while driving
Electromagnetic radiation Abuse of private data possible
High complexity of the system
Several incompatibilities within the GSMstandards
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Thank You
