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Summer TrainingSummer TrainingononSummer TrainingSummer Trainingonon
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History of BSNL Bharat sanchar Nigam Ltd. Formed in
Oct 2000 is World·s largest
Telecommunication Company providingcomprehensive range of telecomservices in India : Wire line ,GSM
mobile, Internet, Broadband etc.
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WHAT IS GSM
GLOBAL SYSTEM OF MOBILE(GSM) IS A SECOND GENERATION
CELLULAR ST ANDAREDDEVELOPEDTO CATER VOICESERVICES AND DAT A DELIVERY
USING DIGIT A
L MODULA
TION
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EVOLUTION OF GSM
ST ANDARDS 1980s - Advance mobile phone services (AMPS),
in America. Early 1980s -European nations were developing
cellular solutions, but no common standardavailable. 1982 ² CEPT(Conference of European Posts and
Telegraph) formed a study group called theGroupe Special Mobile (GSM).
1989 ² GSM responsibility transferred to ETSI(European Telecommunications StandardsInstitute).
Global System for Mobile Communication. 1990 ² Phase I of GSM Specifications published. Mid 1991 - Commercial services started . 1997 ² Commercial services available in 110
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GSM RadFrequSpectrum
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GSM 900GSM-900
Uplink band 890-915MHZ
Downlink band 935-960MHZ
Channelspacing 200KHZ
Total#channel 124
Duplex spacing 45MHZ
#time slot 8
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GSM radio frequency
spectrum In the frequency range specifed for (gsm -
900) 124 frequency channel with abandwidth of 200khz are available for
both uplink and downlink direction. The uplink (mobile station to BTS) use the
frequencies between 890-915mhz anddownlink (BTS to mobile station ) use thefrequencies between 935-960mhz .Theduplex spacing , the spacing between theuplink and downlink channel , is 45 mhz
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Techniques used in GSM In the GSM system , TDMA in combination with
FDMA is used; the usage of each radio channel ispartitioned into multiple (eight) timeslots , and
each user is assigned a specific frequency/timeslot combination . Thus , only a single mobileis using a given frequency/ timeslot combinationat any particular time .
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Cellular concept Cells are in hexagonal in shape . Radio channels are
allocated to these smaller areas to minimize theinterference and provide adequate performance,cater to traffic loads in these areas . Each of theseareas is called cell. Group of cells is called clusters.
The reason of clustering is that adjacent cellscannot use the same frequency spectrum because ofinterference.
The interference due using the same frequencies incells of different clusters is referred as cochannelinterference. The cells that use the same set offrequencies or channels are called cochannelcells.The interference from different frequencieschannels used within cluster is called adjacentchannel interference
The cellular concept can increase the number ofcustomers that can be supported in avaliablefrequency spectrum.
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Frequency reuse in Cellular Telephony
Same frequency reused in the network
7 cell
cluster
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Frequency Reuse Channel reuse is implemented by using the same channels within
cell located at different positions in the cellular network servicearea. Cell clusttering radio channel can be reused provided theseparation between cell containg the same set . Cell using the sameset are called co-channel cells. Within a service area (PLMN),
specific channel sets are reused at different location (anothercell). For eg. There are 7 channel set A to G . Neighboring cells are not
allowed to use same frequencies. PLMN can divided into clusterof7 cell each . The number of channel set is k is called reuse factor .In fig k=7 the equation is
k=i2+j2+ij
- cell are shaped ideally hexagonals- The distance between cells using the same channel set is always
the same .
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MS BSCBTS MSC
HLR
VLR
EIR
AUC
SMS
OMC
GSM SYSTEM ARCHITECTURE
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Network Element
MSC- Mobile ² services Switching CenterIt perform the switching function for all mobile stations
located in the geographic area covered by its assignedBSSs.
It also interface with the public switched telephone network(PSTN) as well as with other MSCs and also with HLR . Acting as a gateway MSC to interrogate the HLR.
MS(Mobile station)-Mobile station is made of two entities-
1- ME (Mobile equipment)is a piece of hardware thatcustomer purchase from dealer.2- SIM(Subscriber identity module that is a smart card.
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Mobile equipment(ME) Portable and hand held devices Uniquely identify by an
IMEI(International mobile equipmentidentity. Voice and data transmission
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SIM(Subscriber Identity
Module) Smart card contain the international
mobile subscriber identity
module(IMSI) Allow user to send and receive callsand received other subscribedservices.
Protected by password or PIN.
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BSS(Base StationSubsystem)
BSS is composed of two part thatcommunicate across the standardizedA
bis interface allowing operationbetween component made bydifferent suppliers
Base tranceiver station(BTS)
Base station controller(BSC)
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BTS(Base Tranceiver
Station) BTS has a set of transceivers to communicate with mobiles
in its area. One BTS covers one or more than one cell The capacity of a cell depends upon number of tranceivers
in a cell. The BTS is connected to BSC through Abis interface . BTS transmit and receive voice at 13 kbps over air
interface to the mobile . BTS control the transmit power and commanding handovers
to the mobile stations.
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BSC (Base Station
Controller ) Several BTS are connected to 1BSC. BSC connected to each BTS on an Abis
interface and to the MSC onA
interface . BSC control various functions of BTS andmobile ,like assigning a channel forcall,handover etc.
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EIR(Equipment Identity
Register) EIR is the record of valid IMEIs. MSC ask mobile to send its IMEIs. MSC then checks the vailidity of IMEI with the EIR. All IMEI are store in EIR.
In the EIR , the IMEI are classified into three categories. White list:this contians the IMEI of type approved mobiles. Blacklist: list of IMEI which should barred because either
they are stolen are not functioning proprely. Greylist: list of IMEI who are to evaluated before they are
put in blacklist.
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AUC(Authentication
centre ) Authentification is a process by which is
SIM is verified.
Secret data and the verification processalogorithm are stored atAUC.
AUC is associated with the HLR
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HLR( Home Location
Register) HLR has all permanent subscriber
database. MSC communicates with HLR to get data
for subscribers on call .
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VLR(Visting location
Register ) VLR has temporary data pertaining to
each subscriber .(TMSI) Temporary
mobile subscriber identity. Location area where the mobilestation is registered.
Copy of the subscriber data from theHLR
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OMC(Operation &
Maintenance Centre) OMC is the centralized maintenance
and diagnostic heart of the BSS .
It allows the network provider tooperate , administer , and monitorthe functioning of the BSS.
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SMSC(Short Messageservice Centre
Message is send to a particularmobile .
Message transfer takes placethrough SMSC.
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Call Management
2.
. 3.
MS BSSMSC/VLR
RACH channel Request
SDCCH Assigh ACCH
Request for service SDCCH
Request for service
1.
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quipment Va idation
IMEI request
4.
IMEI Answer
5.
6.
7.
MS MSC/VLRNEW
EIRBSS
IMEI Check
IMEI Check request
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Call Set Up
Call set up request
10.
11.
12.
13.
MS BSSMSC/VLR
New
Call processing SDCCH
Assign trunk & radio
TCH assign
RR assigmentcompleted
RT assigncompleted
8.
9.
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CALL SET UP
Network set up
MS BSSMSC/VLR New
PSTN
Network alertingAlerting(FACCH)
Connect billing start
connect
connect ack.
14.
15.
16.
17.
18.
19.
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CALL SET UP
Release
Release complete
Clear
clear complete
MS BSS MSC/VLR New
PSTN
Disconnect
Network releaseStop billing
Channelrelease
20.
21.
22.
23.
24.
25.
26.
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Location Updation
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HANDOVER Between1&2interB
TS/intra BSC
Between 1&3interBSC/intraMSC
Between 1&4 inter
MSC
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GSM services Tele-services
Bearer or data services
Supplementry services
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Tele-services Telecommunication services that
enable voice communication via mobile
phone. Offered services
- Emergency call
- Short message services(SMS).
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Bearer services
Include various data services for informationtransfer between GSM and other network likePSTN, ISDN etc at rate from 300to 9600 bps.
Short message services(SMS)- upto 160 charater alphanumeric data transmission
to/from the mobile terminal.- fax- Voice mail box- Electronic mail
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Supplementry services Call related services:
Call waiting: Notification of incoming call while MS isengaged in an active.
Call hold: put a caller on hold to take another call.
Call forwarding : calls can be send to various numberdefined by the user.
Multi party call conferencing: link multiple calls together.
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Characteristics of GSM
Standard Fully digital system using 900,1800 MHZ
frequency band.
Fully international roaming capability. Low service cost.
ISDN compatibility.
Support of short message services(SMS).
Good speech quality.
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GSM Applications Mobile Telephony
Telemetry system
Automatic meter reading Toll collection
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T HANKS!!!!!!!!!!!
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