BSNL
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BSNL
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BSNL
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BSNL OBJECTIVESOBJECTIVES
Describe the Cellular Concept
Explain the GSM Access Network
Explain the GSM Core Network
Explain the GPRS Core Network
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BSNL
->GSM (Global System for Mobile
Communications).
->It is a standard set developed by the European
Telecommunications Standards Institute (ETSI) to
describe technologies for second generation (or
"2G") digital cellular networks.
->Developed as a replacement for first generation
analog cellular networks, the GSM standard
originally described a digital, circuit switched
network optimized for full duplex voice telephony.
->The standard was expanded over time to include
first circuit switched data transport, then packet
data trans ort via GPRS.
GSM
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BSNL
->The GSM standard is succeeded by the
third generation (or "3G") UMTS standard
developed by the 3GPP.
->GSM networks will evolve further as they
begin to incorporate fourth generation (or
"4G
") LTE Advanced standards.
-> "GSM" is a trademark owned by the GSM
Association.
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BSNL Technical details
GSM cell site antennas in the Deutsches
Museum, Munich, Germany
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BSNL
=>>GSM is a cellular network, which means thatmobile phones connect to it by searching for cells in
the immediate vicinity.
=>> There are five different cell sizes in a GSM
network²macro, micro, pico, femto and umbrellaCells.
=>> The coverage area of each cell varies according
to the implementation environment.
=>> Macro cells can be regarded as cells where the
base station antenna is installed on a mast or a
building above average roof top level. they are
typically used in urban areas
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BSNL
=>> Picocells are small cells whose coverage
diameter is a few dozen metres; they are
mainly used indoors.
=>> Femtocells are cells designed for use in
residential or small business environments
and connect to the service providers network
via a broadband internet connection. =>>Umbrella cells are used to cover shadowed
regions of smaller cells and fill in gaps in
coverage between those cells.
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BSNL Communication - Mobile
TelephoneExchange
SubscriberLine(2W)
Inter-Exchange
Junction
Mobile SwitchingCentre (MSC)
BSC BTSMS
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BSNL
CELLULAR MOBILE CONCEPTS
WHAT IS A CELL ?
� A base station (transmitter) having a number of
RF channels is called a cell.
� Each cell covers a a limited number of mobile
subscribers within the cell boundaries
( Coverage area) .
� Typical Cell Radius Aprrox = 30 Km(Start up), 1 KM (Mature) .
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BSNL
Top of a cellular radio towerA cellular network is a radio network distributed over land areas called cells, each served by at least one fixed-location transceiver known as a cell
Top of acellular radio tower
=>>A cellular network is a radio network
distributed over land areas called cells,each served by at least one fixed-location
transceiver known as a cell site or base
station.
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BSNL
=>>When joined together these cells provide
radio coverage over a wide geographic area.
=>> This enables a large number of portable
transceivers (e.g., mobile phones, pagers, etc.) tocommunicate with each other and with fixed
transceivers and telephones anywhere in the
network, via base stations, even if some of thetransceivers are moving through more than one
cell during transmission.
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BSNL
VoiceChannels
Or control
channels
Lines to
BSC
MS
A RADIO CELL
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BSNL Fundamental problems
� Radio range, or coverage
� No. of channels, or voice circuits
� Full, seamless service coverage
� Large no. of subscribers in the range
of millions
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BSNL GSM Specifications
Carrier Separation - 200 kHz
No. of RF Carriers - 124
Access Method - TDMA/FDMA
Modulation Method - GMSK
Transmission Rate - 270.833 Kbps
Speech Coding - Full rate 13 Kbps
Half rate 6.5 Kbps
Duplex Distance - 45 MHz
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BSNL
GSM FDMA
(Frequency Division Multiple Access
25 MHz 25 MHz
Mobile to Base
0 1 2
890.2 890.4 890.6(MHz)
Base to Mobile
0 1 2
935.2 935.4 935.6
200 kHz45MHz
Channel layout and frequency bands of operation
890 935 960915
200 kHz
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BSNL FDMA
� Frequency Division Multiple Access or
FDMA is a channel access method used
in multiple-access protocols as a
channelization protocol.
� FDMA gives users an individual
allocation of one or several frequencybands, or channels. It is particularly
commonplace in satellite
communication.
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BSNL FDMA
=>> FDMA, like other Multiple
Access systems, coordinates
access between multiple users.
Alternatives include TDMA,
CDMA, or SDMA.
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BSNL
GSM TDMA
(Time Division Multiple Access)
87
65
43
21
87
65
43
21
45 MHz
Frequency
F2¶F1¶
(Cell transmit)
F2F1(Cell Rx)
Amplitude
Typical TDMA/ FDMA frame structure
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BSNL TDMA
� Time division multiple access (TDMA) is a
channel access method for shared medium
networks.
� It allows several users to share the same
frequency channel by dividing the signal into
different time slots.
� The users transmit in rapid succession, one
after the other, each using its own time slot.
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BSNL TDMA
� This allows multiple stations to share the same
transmission medium (e.g. radio frequency
channel) while using only a part of its channel
capacity.
� TDMA is used in the digital 2G Cellular
system much as Global System for Mobile
Communication (GSM).
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BSNL FDMA/TDMA Scheme
BP1
BP2
BP3
BP4
BP5
BP6
BP7
BP8
BP1
BP2
TIME
890.0890.2
890.4890.6
890.8891.0
891.2 915.8
FREQ
MHz
BURSTF
R
A
M
E
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BSNL
LOGICAL CHANNELS� USER INFORMATION( TRAFFIC)
� SIGNALLING INFORMATION (CONTROL)
GSM RF CHANNELS
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BSNL
24
Network Architecture
B
T
S
MSC VLR
HLR
PSTNISDN
Data
Networks
Air interface
OSS
B
T
S
B
T
S
MSC VLR
BSCBSC
1MSC=
16BSC
1 BSC=1024 TRU
A Interface
A-bis interface
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BSNL
NETWORK ARCHITECTURE
� Network architecture is the design of a
communications network.
� It is a framework for the specificationof a network's physical components
and their functional organization and
configuration, its operationalprinciples and procedures, as well as
data formats used in its operation.
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BSNL NETWORK ARCHITECTURE
� In telecommunication, the specification
of a network architecture may also
include a detailed description of
products and services delivered via a
communications network, as well as
detailed rate and billing structures
under which services are compensated
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BSNL
27
GSM Network Structure
� GSM Service Area: Total area served by thecombination of all member countries where a mobile canbe served.
� PLMN Service Area: It is one N/W area.
� MSC Service Area: There can many MSC/VLR in onePLMN area.It is one Mobile Exch. Area.
� GMSC: All I/C calls for PLMN N/W will be routedthrough GMSC. In a GSM/PLMN N/W all mobileterminated calls will be routed to a Gateway MSC. Callconnections between PLMNs , or to fixed N/Ws must berouted to a GMSC.The GMSC contains the Inter workingfunctions to make these connections.
� Location Area
� Cells
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BSNL
LOCATION AREA : There are several LA in a MSC/VLR
combination. A LA is a part of the MSC/VLR service area in
which a MS may move freely without updating location
information to the MSC/VLR exchange that control the LA.
Within a LA a paging message is broadcast in order to find
the called mobile subs. LA can be identified by system using
the LAI.
CELL : A cell is an identity served by one BTS. The MS
distinguishes between cells using the BASE STATIONIDENTIFICATION CODE(BSIC) that the cell site broadcast
over the air.
GSM Network Structure
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BSNL
MSC/VLR
LA 1 LA 2
LA 6
LA 3
LA 4
LA 5
GSM
MSC Service Area
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BSNL
MSC/VLR
LA 1 LA 2
LA 6
LA 3
LA 4
LA 5
C1
C5C4
C7
C2
C3
C6
GSM
Cells
C = Cell
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BSNL
31
GSM
Functions of Mobile Station
� Voice and data transmission
� Frequency and time synchronization
� Monitoring of power and signal quality of
the surrounding cells
� Provision of location updates even during
inactive state
� Equalization of multi path distortions
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BSNL
32
GSM
Mobile Station
� Portable, vehicle mounted, hand held
� MS identified by unique IMEI(International
Mobile Equipment Identity).
� Shall display at least last ten received,dialled and missed calls.
� Minimum talk time of 1hr 30 min. and
standby time of 80 hrs.
� 160 characters long SMS.
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BSNL
33
GSM
Mobile Identification Numbers
IMEI
MSISDN
IMSI
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BSNL
34
GSM
IMSI� International mobile subscriber¶s
Identity
� The IMSI is an unique identity which isused internationally and used within thenetwork to identify the mobile subscribers.
� The IMSI is stored on the subscriber identity module (SIM), the HLR, VLR andAC database.
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BSNL
35
GSM
FUNCTION OF BTS -I
� Encodes, encrypts, multiplexes, modulates and
feeds the RF signals to the antenna
� Transcoding and rate adaption Functionality
� Time and frequency synchronisation signals
transmission.
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BSNL
36
GSM
FUNCTIONS OF BSC-I
� It is connected to BTS and offloads MSC
� Radio resource management
� Inter-cell handover
� Reallocation of frequencies
� Power control
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BSNL
37
GSM
MSC-BSC Configurations
BTSBTS
BTS
A-bis
BSC
BSS
Configuration -6 Multi - cell site =multi--BTS site
Many single
cell sites
BSS
MSC
BTS
A
A
A
Single - cell site
Configuration -1
Multi - cell site (sector Cells
Configuration -5
MCC: Mobile Switching Centre
BSS: Base Station System
BSC: Base Station Controller
BTS: Base Transceiver Station
A-bis
BTS BTS
BTS
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BSNL
38
GSMMSC ( MOBILE SWITCHING CENTRE)
Manages communication between GSM & other
network
Call setup functions, basic switching are done
MSC takes into account the RR allocation in
addition to normal exchange functions
MSC does gateway function while its customersroams to other network by using HLR /VLR
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BSNL
39
GSM
MSC Functions - I
Paging, specifically call handling
Location updationHandover management
Billing for all subscribers based in its area
Reallocation of frequencies to BTSs in its area
to meet heavy demands
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BSNL
General Packet Radio System
GPRS
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BSNL
BackboneNetwork
BackboneNetwork
Corporate
Network
Corporate
Network
ISP
Network
ISP
Network
G
b
Gs
G
d
Gr
Gi
G
nG
n
EDGETRUMS
BTS BSC MSC/VLR
SMS-G /IW MSC
AUCHLRMS
SGSN GGSN
P
C
U
UT
R
A
N
BTS
BTS
BTS
R
NC
R
N
C
MS
UMTS
Iu
Network Evolution
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BSNL
GPRS Architecture
EIR
SGSN HLR
AUC
GGSN
ISDN / PSTN / PLMN
Network
IP-Backbone
Network
ExternalIP Network
External
X.25 Network
GMSC
MSC/VLR
A
Gb
Gs
Gn
Gf
Gr
Gi
Gi
Gn
BTS
BSC
Abis
BSS
Um
TE
MT
MS
A GSM Interface
Abis GSM Interface (Proprietary of M/s Ericsson)
AUC Authentication Center
BSC Base Station Center
BSS Base Station System
BTS Base Transceiver Station
EIR Equipment Identity Register GGSN Gateway GPRS Support Node
GMSC Gateway Mobile services Switching Center
Gx GPRS Interfaces
HLR Home Location Register
MS Mobile Station
MSC Mobile services Switch ing Center
MT Mobile Terminal
SGSN Serving GPRS Support Node
TE Terminal Equipment
Um Air Interface
VLR Visitor Location Register
GPRS Network ElementsGSM Network Elements Traffic & Signaling Signaling
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BSNL GPRS COMPONENTS
� To ensure the interworking of the PLMN, PDN
and the wireless networks, two new major
components are required.
� These components are called GPRS Support
Nodes.
� There are two types of GPRS Support Nodes
1. Serving GPRS Support Node (SGSN)2. Gateway GPRS Support Node (GGSN)
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BSNL Serving GPRS Support Node (SGSN)
An SGSN delivers packets to mobile stations
within its service area. SGSNs send queries to
Home Location Registers (HLRs) to obtain profiledata of GPRS subscribers.
SGSNs detect new GPRS mobile stations in a
given service area; and, finally, SGSNs process
registration of new mobile subscribers and keep arecord of their location inside a given service area.
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BSNL Gateway GPRS Support Node (GGSN)
GGSNs are used as interfaces to external PDNs.
GGSNs maintain routing information that is
necessary to tunnel the Protocol Data Units(PDUs) to the SGSNs that service particular
mobile stations.
Other functions include network and subscriber
screening and address mapping. One or moreGGSNs may support multiple SGSNs.
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BSNL GPRS Network Enhancements
In addition to the new GPRS components,existing GSM and TDMA network elements mustalso be enhanced in order to support GPRS.
The following two pieces of equipment must beenhanced:
Base Station System (BSS): must be enhanced torecognize and send user data to the SGSN that isserving the area.
Home Location Register (HLR): must be enhanced toregister GPRS user profiles and respond to queriesoriginating from SGSNs regarding these profiles.
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BSNL Advantages of GPRS
� Increased revenues by moving in to the mobile
data market
� Gain new subscribers requiring the data services
without investing in to PCs to gain internet access
� Retain current subscribers by offering new
services
� Reduce costs due to efficient use of network resources
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BSNL
Thanks