2G GSM Archiitrcture Components (BSS, NSS, OSS) Interfaces (Um, Air, A) Network Overview Mobile Station (MS) BSS Architecture NSS Architecture OSS Architecture Handovers

1. 2G Network Architecture

2. 2G
• 2G- Second Generation mobile phone
networks
• 2G is also known as GSM
• GSM stands for Global Systems for Mobile
Communications

3. Components
• BSS(Base Station Subsystem)
– BTS (Base Transceiver Station)
– BSC (Base Station Controller)
– User Equipment-Mobile Phone
• NSS(Network and Switching Subsystem)
– MSC (Mobile Switching Center)
– VLR (Visitor Location Register)
– HLR (Home Location Register)
– AUC (Authentication Center)
– EIR (Equipment Identity Register)
• OSS(Operation Support Subsystem)
– NMS (Network Management System)
– Performance Management Tools

4. Interfaces
• Um Interface:
– Air interface between MS and the BTS
• Abis Interface:
– The interface between BTS and BSC
• A Interface:
– Provide communication between BSC and MSC or BSS and NSS

5. Network Overview
BSC MSC
BTS
OMC-R OMC-S
MS
BSS NSS
OSS
PSTN

6. Mobile Station
• The Mobile Station (MS) is composed of three parts:
– the handset
– the SIM card (Subscriber Identity Module-card)
– the battery.

7. Mobile Station
+G S M
Global GSM Mobility
Card
The Smart Card to use
SIM Card
+
BatteryHandset
battery
f153454
Mobile Station
=

8. Base Station Sub System
• Base Station Subsystem is composed of two parts that
communicate across the standardized Abis interface allowing
operation between components made by different suppliers
1. Base Transceiver Station (BTS)
2. Base Station Controller (BSC)

9. BSS ARCHITECTURE
BSCOMC-R
MSC Radio
InterfaceA Interface
Ater Interface
Abis Interface
NSS
BSS
OMN Interface
Public Telephone Network
MS
MS
Sun
StorEdge A5000
Radio
Interface

10. BTS(Base Transceiver Station)
• Equipment that facilitates wireless communication
between user equipment and a network.
• Encodes,encrypts,multiplexes,modulates and feeds
the RF signals to the antenna.
• Communicates with Mobile station and BSC
• Consists of Transceivers (TRX) units

11. BSC(Base Station Controller)
• Controls single or multiple BTS
• Power and signal measurements from the
Mobile Station
• Handles call setup
• Handover for each MS

12. NSS Architecture
MSC
MSC
BSC
BSC
AuC EIR
VLR HLR
PSTN

13. MSC(Mobile Switching Center)
• include registration, authentication, call location,
inter-MSC handovers and call routing to a mobile
subscriber
• also provides an interface to the PSTN so that calls
can be routed from the mobile network to a phone
connected to a landline
• Interfaces to other MSCs are provided to enable calls
to be made to mobiles on different networks.

14. HLR(Home Location Register)
• Is an intelligent database and service control
function responsible for management of each
individual subscriber’s records.
• Some of the information stored in an HLR includes
the international mobile subscriber identity (IMSI)
and the mobile station international subscriber
directory number (MSISDN) of each subscription.

15. VLR(Visitor Location Register)
The VLR contains a copy of most of the data
stored at the HLR. It is, however, temporary
data which exists for only as long as the
subscriber is “active” in the particular area
covered by the VLR.

16. Authentication Center (AUC)
• Protects against intruders in air interface
• Maintains authentication keys and algorithms
and provides security
• Generally associated with HLR

17. Equipment identity Register(EIR)
• Database that is used to track handsets using the IMEI
(International Mobile Equipment Identity)
• Only one EIR per PLMN

18. OSS(Operation Support System)
• Network Management
• Configuration Management
• Fault Management
• Performance Management
• Security Management

19. OMC Functional Architecture

20. OMC-S Functions
NSS OMC-S
MSC/VLR
Configuration
Fault
Performance
HLR/AUC Security
Facilities

21. OMC-S
• The Operation and Maintenance Center of the NSS part (OMC-S) may be able to achieve different kinds of
function.
• NSS configuration management:
– BSCs, Location Areas, Cells.
– Software configuration (downloading, file transfer).
– MSRN and handover number management.
• Fault management:
– Detection.
– Presentation.
– Re-configuration.
• Performance management:
– Traffic control.
– Service quality monitoring.
• Security management:
– User profiles.
• OMC-S operation:
– System management.
– File transfer operations.

22. Call Routing
• Call originating from MS
• Call termination to MS

23. Outgoing Call
1.MS sends dialled number to BSS
2.BSS sends dialled number to MSC
3,4 MSC checks VLR if MS is allowed
the requested service. If so, MSC asks
BSS to allocate resources for call.
5.MSC routes the call to GMSC
7.GMSC routes the call to local exchange
of called user
7, 8,
9,10 Answer back(ring back) tone is
routed from called user to MS via
GMSC,MSC,BSS

24. Incoming Call
1.Calling a GSM subscribers
2.Forwarding call to GSMC
3.Signal Setup to HLR
4.5. Request MSRN from VLR
6.Forward responsible MSC to GMSC
7.Forward Call to current MSC
8.9. Get current status of MS
10.11. Paging of MS
12.13. MS answers
14.15. Security checks
16.17. Set up connection

25. Incoming Call
• A call is made from the PSTN to a mobile subscriber's number
• The call enters the GMSC
• The GMSC queries the HLR for information about which MSC serves the MS
• The call is forwarded to the MSC in charge
• The MSC queries the VLR about which BSC is currently in charge of the MS
• BSC sends a paging call to all cells to find the exact location of the mobile
• The mobile signals that it answer.
• The call is completed

26. Handovers
• The process of transferring an ongoing call or
data session from one channel connected to
the core network to another channel.
• Two types of handovers
– Soft Handover
– Hard Handover

27. Handovers
Between 1 and 2 – Inter BTS / Intra BSC
Between 1 and 3 – Inter BSC/ Intra MSC
Between 1 and 4 – Inter MSC

28. Handovers
MSC-A MSC-B
BTS
A1
BTS
A2
BTS
B1
BTS
C1
BSC-BBSC-A
BSC-C

29. Thank You

30. SGSN
The Serving GPRS Support Node (SGSN) is a
main component of the GPRS network, which
handles all packet switched data within the
network, e.g. the mobility management and
authentication of the users. The SGSN performs
the same functions as the MSC for voice traffic.

31. GGSN
The Gateway GPRS Support Node (GGSN) is a
main component of the GPRS network.
The GGSN is responsible for the interworking
between the GPRS network and external packet
switched networks, like the Internet and X.25
networks.

32. Thank You