Transcript GSM ARCHITECTURE - :: SNEA Tamilnadu

GSM Architecture
Network Components
•
•
Switching System(SS)
Base Station System(BSS)
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OSS
HLR
B
T
S
PSTN
ISDN
B
T
S
BSC
BSC
MSC VLR
A Interface
B
T
S
Air interface
(
Data
Networks
A-bis interface
MSC VLR
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ERICSSON’S GSM SYSTEM ARCHITECTURE
Switching System
MIN
SDP
EIR
AUC
SCF
HLR
ILR
BGW
Other PLMNsz
Public Data
Networks
PSTN
GMSC
MSC/VLR
DTI
SSF
MC
(MXE)
SOG
OSS
ISDN
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Base Station System
TRC
BSC
RBS
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Basic or
Abbrev.
Additiona
l
System Full component name
Platfor
m
Basic
MSC/VLR
SS
AXE
Basic
Basic
Basic
Basic
Basic
Basic
Basic
Basic
Basic
Basic
Basic
Additional
Additional
Additional
Additional
Additional
GMSC
HLR
ILR
AUC
EIR
DTI
TRC
BSC
BTS
OMC
NMC
MC
SSP
SCP
SDP
SOG
SS
SS
SS
SS
SS
SS
BSS
BSS
BSS
OSS
OSS
SS
SS
SS
SS
Mobile service Switching
Center/Visitor Location Register
Gateway MSC
Home Location Register
Interworking Location Register
Authentication Center
Equipment Identity Register
Data Transmission Interface
TRanscoder Controller
Base Station Controller
Base Transceiver Station
Operation and Maintenance Center
Network Management Center
Message Center
Service Switching Point
Service Control Point
Service Data Point
Service Order Gateway
Billing Gateway
AXE
AXE
AXE
Unix/AXE
Unix
AXE
AXE
AXE
RBS
TMOS
TMOS
MXE
AXE
AXE
Unix
Unix
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Unix
Network Structure
• Cell
A cell is the basic unit of a cellular
system and is defined as the radio
coverage given by one BS antenna
system.
Each cell is assigned a unique CGI.
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Network Structure
LOCATION AREA
A LA is defined as a group of cells.Within the
network, a subsriber’s location is known by the LA
which they are in.
The identity of the LA in which an MS is currently
located is stored in the VLR. (LAI)
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Cells & LA
LA2
LA3
LA1
VLR
LA4
MSC
LA5
C1
C6
LA6
C3
C2
C5
C4
C=CELL
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Network Structure
• MSC Service Area
An MSC Service Area is made up of
LAs and represents the
geographical part of the network
controlled by one MSC.
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MSC Service Area
LA2
LA1
VLR
MSC
LA4
LA3
LA6
LA5
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Network Structure
• PLMN SERVICE AREA
A PLMN service area is the entire set of
cells served by one network operator
and is defined as the area in which an
operator offers radio coverage and
access to its network.
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PLMN Service Area
I
II
I
MSC
MSC
MSC
VLR
VLR
MSC
III
VLR
V
IV
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Network Structure
• GSM SERVICE AREA
The GSM service area is the entire
geographical area in which a subscriber
can gain access to a GSM network.
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Relation between areas in GSM
Location
CellArea
Location Area
MSC Service Area
PLMN Service Area
GSM Service Area
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Mobile Station
GSM MSs consist of:
• Mobile Equipment
• Subscriber Identity Module
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Functions of Mobile Station
• Voice and data transmission& receipt
• Frequency and time synchronization
• Monitoring of power and signal quality
of the surrounding cells
• Provision of location updates even
during inactive state
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Mobile Station
• Discontinuous Transmission(DTX)
• Discontinuous reception(DRX)
• MS identified by unique IMEI
• STAR#06#
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SIM
Fixed data stored for the subscription:
• IMSI,
• Authentication Key, Ki
• Security Algorithms:kc,A3,A8
• PIN&PUK
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SIM
•Temporary network data:
Location area of subscriber and
forbidden PLMNs
•Service data:
language preference, advice of charge
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KEY TERMS
An MS can have one of the following states :
• Idle: the MS is ON but a call is not in
progress.
• Active: the MS is ON and a call is in
progress.
• Detached: the MS is OFF.
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The following table defined the key terms used to describe GSM mobile
traffic cases (there are no traffic cases in detached mode):
Mode
Idle
Term
Description
Registration
This is the process in which an MS
informs a network that it is attached.
Roaming
International
Roaming
When an MS moves around a
network in idle mode, it is referred to
as roaming.
When an MS moves into a network
which is not its home network, it is
referred to as international roaming.
MSs can only roam into networks
with which the home network has a
roaming agreement.
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Mode
Active
Term
Description
Location
Updating
An MS roaming around the network
must inform the network when it enters
a new LA. This is called location
updating.
Paging
This is the process whereby a network
attempts to contact a particular MS.
This is achieved by broadcasting a
paging message containing the
identity of that MS.
Handover
This is the process in which control of
a call is passed from one cell to
another while the MS moves between
cells.
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Network Identities
• MSISDN
• IMSI
• TMSI
• MSRN
• IMEI
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MSISDN
• Mobile Station ISDN Number
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The MSISDN is registered in the telephone directory and
used by the calling party for dialing.
MSISDN shall not exceed 15 digits.
NDC--National Destination Code
SN--Subscriber Number
1 to 3 digits
CC
Variable
Variable
NDC
SN
MSISDN : not more than 15 digits
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IMSI
• International mobile subscriber
Identity
• The IMSI is an unique identity which is used
internationally and used within the network to
identify the mobile subscribers.
• The IMSI is stored in the subscriber identity
module (SIM), the HLR, VLR database.
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IMSI 3 digits
MCC
3 digits
Not more than 9 digits
MNC
MSIN
NMSI
IMSI : Max. 15 digits
MCC--Mobile Country Code, MNC--Mobile N/W Code, MSIN--Mobile
Station Identification Number
NMSI--National Mobile Station Identity,assigned by Individual
Administration.
Mobile station Identification Number. It identifies the subs. In a PLMN.
First 3 digit identifies the Logical HLR-id of Mobile subs.
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Temporary Mobile subscriber Identity
• TMSI is a temporary IMSI no. made known to
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an MS at registration.
The VLR assigns a TMSI to each mobile
subscribers entering the VLR area.
Assigned only after successful authentication.
TMSI has only local significance i.e. within VLR
area & controlled by the VLR.
TMSI changes on location updation.
TMSI is less than 8 digit.
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MSRN
Mobile Station Roaming Number
• The MSRN is used in the GMSC to set up a
connection to the visited MSC/VLR.
• MSRN--is a temporary identity which is
assigned during the establishment of a call to a
roaming subs.
CC
NDC
SN
CC--Country Code, NDC--National Destination Code, SN– Servicing
Node
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IMEI
• International Mobile Equipment
Identity
• The IMEI is an unique code allocated to each
mobile equipment. It is checked in the EIR.
• IMEI check List
 White List
 Grey List
 Black List
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BASE STATION SYSTEM (BSS)
MSC/VLR
BSC
BSC
BSC
BSS
n BTS
n BTS
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FUNCTIONS OF BTS
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Radio resources
Signal Processing
Signaling link management
Synchronization
Local maintenance handling
Functional supervision and Testing
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FUNCTIONS OF BSC
• Radio Network management
• RBS Management
• TRC Handling
• Tx. Network Management
• Internal BSC O&M
• Handling of MS connections
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MSC-BSS Configurations
MSC
A
BSS
A-bis
BSC
BTS
BTS BTS
BTS
BTS
A-bis
BTS
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Switching System (SS)
SS7 Signalling
Traffic Path
VLR
D
C
F
HLR
AUC
E
EIR
A
Other
MSC
MSC
(PSTN)
(BSS)
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MSC Functions
• Switcing and call routing
• Charging
• Service provisioning
• Communication with HLR
• Communication with VLR
• Communication with other MSCs
• Control of connected BSCs
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MSC Functions
• Echo canceller operation control
• Signaling interface to databases like HLR, VLR.
• Gateway to SMS between SMS centers and
subscribers
• Handle interworking function while working as
GMSC
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VISITOR LOCATION REGISTER (VLR)
• It controls those mobiles roaming in its area.
• VLR reduces the number of queries to HLR
• One VLR may be incharge of one or more LA.
• VLR is updated by HLR on entry of MS its area.
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VLR assigns TMSI which keeps on changing.
• IMSI detach and attach operation
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Data in VLR
• IMSI & TMSI
• MSISDN
• MSRN.
• Location Area
• Supplementary service parameters
• MS category
• Authentication Key
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Home Location Register(HLR)
• Reference store for subscriber’s parameters,
numbers, authentication & Encryption values.
• Current subscriber status and associated VLR.
• Both VLR and HLR can be implemented in the
same equipment in an MSC.
• one PLMN may contain one or several HLR.
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Home Location Register(HLR)
• Permanent data in HLR
• Data stored is changed only by commands.
• IMSI, MS-ISDN number.
• Category of MS ( whether pay phone or not )
• Roaming restriction ( allowed or not ).
• Supplementary services like call forwarding
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Home Location Register(HLR)
• Temporary data in HLR
• The data changes from call to call & is dynamic
• MSRN
• RAND /SRES and Kc
• VLR address , MSC address.
• Messages waiting data used for SMS
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EQUIPMENT IDENTITY REGISTER ( EIR )
• This data base stores IMEI for all registered
mobile equipments and is unique to every ME.
• Only one EIR per PLMN.
• White list : IMEI, assigned to valid ME.
• Black list : IMEI reported stolen
• Gray list : IMEI having problems like faulty
software, wrong make of equipment etc.
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AUthentication Center (AUC)
To authenticate the subs. attempting to use a
network.
AUC is connected to HLR which provides it
with authentication parameters and ciphering
keys used to ensure network security.
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AUC Functions
To perform subscriber
authentication and to establish
ciphering procedures on the radio
link between the network and MS.
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AUC Functions
Information provided is called a
TRIPLET consists of:
1. RAND(non predictable random number)
2. SRES(Signed response)
3. Kc(ciphering key)
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Operations and Maintenance Centre
OMC
The centralized operation of the various units in
the system and functions needed to maintain the
subsystems.
Dynamic monitoring and controlling of the
network
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Functions Of OMC
-O&M data function
-Configuration management
--Fault report and alarm handling
-Performance supervision/management
-Storage of system software and data
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