1 GSM ARCHITECTURE
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GSM ARCHITECTURE
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ObjectivesUpon completion of this module the student should be able to:• Name the three subsystems of the GSM• List different network elements (generic architecture) and name
at least one task per element• Name differences between the generic GSM network architecture
and the Nokia implementation.• Name advantages of the DX 200 platform's modularity and
distributed processing• List different types of Nokia BTSs
GSM Architecture
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• Where is the subscriber
• Who is the subscriber
• What does the subscriber want
Information about the
subscriber
Mobile subscriber
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A
NMSNMS
NSSNSSBSSBSS
O&M
Air
MS
Network Switching Subsystem
• Switching• Mobility Management• Connection Management• Charging
Base Station Subsystem• Radio Resource Management• Radio Link Management Network Management
System• Fault Management• Configuration Management• Performance Management
GSM PLMN Organisation
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GMSC
VLR
MSC
HLR
HLR
AC
EIR
MSC Mobile services Switching CentreGMSCGateway MSCVLR Visitor Location RegisterHLR Home Location RegisterEIR Equipment Identity RegisterAC Authentication Centre
Network Switching Subsystem
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MSC GMSC• Call control• Mobility management• Initiation of paging• Collection of changing information• Often associated with the VLR
• Call control• Interrogation of HLR• Collection of changing information• Often used for interworking with external networks
Mobile services Switching Centre (MSC)
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VLR
• Identification numbers of subscribers• Security information• Services that the subscriber can use
HLR• Subscriber Profile• Routing Information
ACData for• Authenticating (SIM) and• Ciphering
EIR
• Lists for Mobile Equipment (ME) checks
Registers in the NSS
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Elements: – Base Station Controller (BSC), Base Transceiver Station (BTS), and
Transcoder and Rate Adaptation Unit (TRAU, TC)Functions:
– Radio path control, BTS and TC control, synchronisation with MSC– Air and A interface signalling, connection establishment MS-NSS– Mobility management, speech transcoding– Collection of statistical data
BTS
TC
BSC
BSC
TCBTS
BTS
Base Station Subsystem
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BSC
– Connection establishment between the MS and the NSS
– Mobility management
– Statistical raw data collection
– Air- and A-interface signalling support
– BTS and TRAU Control
Base Station Controller (BSC)
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– Air interface signalling
– Ciphering
– Speech processing (channel coding, interleaving, and burst formatting)
– Generation of alarms and statistics
– Baseband/Radio frequency transformation
Base Transceiver Station (BTS)
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Speech, 64 kbps
compression Channel Coding
= redundancy
Interleavingand ciphering
TDMA burst formatting
GMSKmodulation
22.8kbit/s
13kbit/s
33.8kbit/s
22.8kbit/sAir
Interface
MSC TRAU TRAU BTS
Speech Flow in BSS
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Omnidirectional BTS
f1,f2, f3
3 sectorised BTS
2 sectorised BTS
f2
f1, f2
f5, f6
f1
f3, f4
BTSBTS
BTS
BTS
BTS BTS
f = carrier frequency band
Omnidirctional and Sectorised Cells
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A InterfaceA ter’ Interface
A ter Interface
MSC
SM2M
TC
TC
TC
TC
Transcoder andSubmultiplexer (TCSM)
BSC
Position of the Transcoder
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Data CommunicationsNetwork
BTS
BTS
BTS
BTS
DN2
BSC
MSCVLR
HLRACEIR
SMSC
NMS/2000
Network Management Subsystem (NMS/2000)
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Fault management– Collects alarm reports from network elements.
– Provides one point for managing all fault situations.
Functions of NMS (1)
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Configuration management– Manages radio network configuration.
– Maintains up to date information on the network element’s status.
Functions of NMS (2)
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Performance management– Collects measurement data from network elements.
– Produces performance result from raw data.
Functions of NMS (3)
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BSC
TCBTS
BTS
VLR
(G)MSC
EIRHLR AC
Um
AAter
Abis
B C
D
VLR
G
F
(G)MSC
E
BSS NSS
BSC
TCBTS
BTS (G)MSC
Um
AAter
Abis
B C
DVLR
EIRHLR AC
VLR
G
F
(G)MSC
E
BSS NSS
Interfaces
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Mobile StationsBase Station Subsystem Network Management Subsystem
BaseTransceiverStations
Base StationController
TranscoderSubmultiplexer
Digital CrossConnect
A-Interface Air Interface X.25 Interface Abis Interface
IN Service Control PointShort MessageService Centre
Voicemail
Mobile Switching Centre/Visitor Location Register
Home Location Register/Authentication Centre/Equipment Identity
Register
Network Switching Subsystem
PSTN/ISDN
CommunicationsServer
DataCommunication
Network
Database Server
Workstations
NetworkPlanningSystemNetwork
MeasurementSystem
TCP/IP
Data CommunicationsServer
GSM network architecture
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ACEIR
BTS
OMC
MSC
VLR
HLR
BSC
BTS
BTS
BTS
BTS
BSC
BSS - Base StationSubsystem
NSS - Network Subsystem
NMS - Network Management SystemMS
AbisAir A
IWF
SC
PSPDN
PSTNISDN
Transcoder
Generic GSM architecture
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BTS
BTS
BTS
BTS
BTS
BSS - Base StationSubsystem
NSS - Network Subsystem
NMS / 2000Network
ManagementSystem
AbisAir A
PSPDN
PSTNISDN
SMSC
DX 200MSC/VLR
DX 200HLR/AC/EIR
DX 200BSC
DX 200TCSM
NSS Site
Nokia Implementation of GSM architecture
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Signalling towards subscribers
Collecting dialled numbers
Collecting charging data
Hunting for a free circuit
Making speech path connections
Signalling towards other exchanges
Analysing and subscriber data
Supervising the running processes
Collecting statistical data
Centralised CPU concept
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Exchange
Computer units
Message bus
Signalling towards
subscribers
Collecting dialled
numbers
Collecting charging
data
Making speech path
connections
Signalling towards
other exchanges
Collecting statistical data
Supervising the processes
running
Hunting for a free circuit
Distributed structure of the Nokia DX platform
04/11/23 Company Confidential
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Review Questions toReview Questions to“GSM Architecture““GSM Architecture“
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1. The three subsystems of GSM/DCS are:
2. Which of the two following network elements belong to the NSS?
a) NMS, PSTN, MSb) NMS, BSS, MSc) NSS, BSS, MSd) NSS, BSS, NMS .
a) Home Location Registerb) Base Station Controllerc) Mobile services Switching Centred) Transcoder (Transcoder and Rate Adaptation
Unit)
Review
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3. Which of the following is not a task of the Network Switching Subsystem (NSS)?
4. Which combination of the following best describes the Base Station Subsystem?
a) Identifying the calling subscriberb) Starting the location update procedurec) Sending charging data to the Billing Centred) Paging a subscriber for mobile terminated
calls
a) Base Station Controller, Transcoder, Base Transceiver Station
b) Mobile Station, Base Station Controller, Base Transceiver Station
c) Transcoder, Submultiplexer, Base Transceiver Stationd) Base Station Controller, Base Transceiver Station,
Mobile Equipment
Review
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5. The Base Station Subsystem (BSS):
6. Base Transceiver Station takes care of:
a) Is responsible for radio network controlb) Is located between air- and A-interfacesc) Receives its synchronisation signal from the
MSCd) All of the above
a) Transcodingb) Sub-multiplexingc) Speech codingd) Authentication
Review
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7. Please name the three main Network Management Subsystem function categories
8. In the Nokia Implementation of the GSM network:
a) Performance managementb) Configuration managementc) Fault management
a) The transcoder is included as part of the MSCb) The EIR is included as part of the MSCc) The VLR is included as part of the MSCd) The HLR is included as part of the MSC
Review
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9. The following subsystem is entirely built on the Nokia DX 200 switching platform:
10. The Authentication Centre is implemented as part of the:
a) Network Switching Subsystem (NSS)b) Network Management Subsystem (NMS)c) Base Station Subsystem (BSS)d) None of the above
a) Billing Centreb) Visitor Location Registerc) Short Message Service Centred) Home Location Register
Review
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11. Which of the following is a feature of the DX 200 platform?
12. Distributed processing in the DX 200 platform means:
a) Distributed processingb) The ability to start with a minimum number
of units and “add on” more later if and when required
c) 2N and N+1 redundanciesd) All of the above
a) Sharing tasks between different network elements like the MSC, the HLR and the BSC
b) Sharing tasks between different functional units within one network element such as the BSC
c) Using parallel processing techniques within one computer unit
d) Using the DX 200 platform
Review
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