gsm architecture and fixed assignment

1. Name :Fabiha Chowdhury Ain
Id No:666-46-04
Subject: Wireless and Mobile Communication
Presentation on GSM Architecture and Fixed Assignment Schemes

2. Index of Topic (1)
Topic(1) : GSM Architecture
◦ GSM Introduction
◦ GSM History
◦ GSM Services And Features
◦ GSM Architecture
◦ GSM Network Architecture elements
◦ Network Switching Subsystem(NSS)
◦ Base Station Subsystem (BSS)
◦ Mobile Station (MS)
◦ Operations & Support System (OSS)
◦ Future of GSM

3. GSM- Introduction
GSM (Global System for Mobile communication) is a digital mobile
network that is widely used by mobile phone users in Europe and other
parts of the world.
Global System for Mobile (GSM) is a second generation cellular standard
developed to cater voice services and data delivery using digital
modulation .

4. GSM: History
• Developed by Group Spéciale Mobile (founded 1982)
which was an initiative of CEPT.
( Conference of European Post and Telecommunication )
• Under ETSI, GSM is named as “ Global System for Mobile
communication “ in 1989
• Full set of specifications phase-I became available in 1990
• Phase 2 of the GSM specifications occurs in 1995.
Coverage is extended to rural areas

5.  Telephonic Services
 Bearer Services or Data Services
 Supplementary ISDN Services
GSM Services And Features

6. GSM Architecture

7. GSM Architecture
The GSM network architecture provided a simple and yet effective architecture to
provide the services needed for a 2G cellular or mobile communications system.
There were four main elements to the overall GSM network architecture and these
could often be further split. Elements like the base station controller, MSC, AuC,
HLR, VLR and the like are brought together to form the overall system.
The 2G GSM network architecture, although now superseded gives an excellent
introduction into some of the basic capabilities required to set up a mobile
communications phone network and how all the entities operate together.

9. GSM network Architecture Elements
The GSM system operates together as a complete system, the overall network
architecture brings together a series of data network identities, each with several
elements.
The GSM network architecture is defined in the GSM specifications and it can be
grouped into four main areas:
Network and Switching Subsystem (NSS)
Base-Station Subsystem (BSS)
Mobile station (MS)
Operation and Support Subsystem (OSS)
The different elements of the GSM network operate together and the user is not aware
of the different entities within the system.

10. Network Switching Subsystem(NSS)

11. Network Switching Subsystem(NSS)
•Mobile Services Switching Centre (MSC): The main element within the core network area of the overall GSM
network architecture is the Mobile switching Services Centre (MSC). The MSC acts like a normal switching node
within a PSTN or ISDN, but also provides additional functionality to enable the requirements of a mobile user to
be supported. These include registration, authentication, call location, inter-MSC handovers and call routing to a
mobile subscriber. It also provides an interface to the PSTN so that the mobile communications 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.
•Home Location Register (HLR): This database contains all the administrative information about each subscriber
along with their last known location. In this way, the GSM network is able to route calls to the relevant base station
for the MS. When a user switches on their phone, the phone registers with the network and from this it is possible
to determine which BTS it communicates with so that incoming calls can be routed appropriately. Even when the
phone is not active (but switched on) it re-registers periodically to ensure that the network (HLR) is aware of its
latest position. There is one HLR per network, although it may be distributed across various sub-centres to for
operational reasons.
•Visitor Location Register (VLR): This contains selected information from the HLR that enables the selected
services for the individual subscriber to be provided. The VLR can be implemented as a separate entity, but it is
commonly realised as an integral part of the MSC, rather than a separate entity. In this way access is made faster
and more convenient.

12. Network Switching Subsystem(NSS)
•Equipment Identity Register (EIR): The EIR is the entity that decides whether a given mobile equipment may be
allowed onto the network. Each mobile equipment has a number known as the International Mobile Equipment
Identity. This number, as mentioned above, is installed in the equipment and is checked by the network during
registration. Dependent upon the information held in the EIR, the mobile may be allocated one of three states -
allowed onto the network, barred access, or monitored in case its problems.
•Authentication Centre (AuC): The AuC is a protected database that contains the secret key also contained in the
user's SIM card. It is used for authentication and for ciphering on the radio channel.
•Gateway Mobile Switching Centre (GMSC): The GMSC is the point to which a ME terminating call is initially
routed, without any knowledge of the MS's location. The GMSC is thus in charge of obtaining the MSRN (Mobile
Station Roaming Number) from the HLR based on the MSISDN (Mobile Station ISDN number, the "directory
number" of a MS) and routing the call to the correct visited MSC. The "MSC" part of the term GMSC is misleading,
since the gateway operation does not require any linking to an MSC.
•SMS Gateway (SMS-G): The SMS-G or SMS gateway is the term that is used to collectively describe the two
Short Message Services Gateways defined in the GSM standards. The two gateways handle messages directed in
different directions. The SMS-GMSC (Short Message Service Gateway Mobile Switching Centre) is for short
messages being sent to an ME. The SMS-IWMSC (Short Message Service Inter-Working Mobile Switching Centre)
is used for short messages originated with a mobile on that network. The SMS-GMSC role is similar to that of the
GMSC, whereas the SMS-IWMSC provides a fixed access point to the Short Message Service Centre.

13. Base Station Subsystem (BSS)

14. Base Station Subsystem (BSS)
The Base Station Subsystem (BSS) section of the 2G GSM network architecture that is fundamentally
associated with communicating with the mobiles on the network.
It consists of two elements:
•Base Transceiver Station (BTS): The BTS used in a GSM network comprises the radio transmitter receivers,
and their associated antennas that transmit and receive to directly communicate with the mobiles. The BTS is
the defining element for each cell. The BTS communicates with the mobiles and the interface between the two
is known as the Um interface with its associated protocols.
•Base Station Controller (BSC): The BSC forms the next stage back into the GSM network. It controls a
group of BTSs, and is often co-located with one of the BTSs in its group. It manages the radio resources and
controls items such as handover within the group of BTSs, allocates channels and the like. It communicates
with the BTSs over what is termed the Abis interface.

15. Mobile Station (MS)

16. Mobile Station (MS)
MOBILE EQUIPMENT(ME)
Portable, vehicle mounted, hand held device Uniquely identified by an IMEI
(International Mobile Equipment Identity) Voice and data transmission
Monitoring power and signal quality of surrounding cells for optimum handover
Power level : 0.8W – 20 W 160 character long SMS.
SUBSCRIBER IDENTITY MODULE(SIM)
Smart card contains the International Mobile Subscriber Identity (IMSI) Allows
user to send and receive calls and receive other subscribed services Protected by a
password or PIN Can be moved from phone to phone – contains key information to
activate the phone SYSTEM ARCHITECTUR

17. Operations & Support System (OSS)

18. Operations & Support System (OSS)

19. Future Of GSM
GSM, together with other technologies, is part of an evolution of wireless mobile
telecommunication that includes
High-Speed Circuit-Switched Data (HSCSD),
General Packet Radio System (GPRS),
Enhanced Data GSM Environment (EDGE),
and Universal Mobile Telecommunications Service (UMTS).

20. Index of Topic(2)
Topic(2) : Fixed Assignment Schemes
➢ Introduction
➢ Frequency Division Multiple Access ( FDMA ).
➢ Time Division Multiple Access ( TDMA ).
➢ Code Division Multiple Access ( CDMA ).

21. Introduction
❖ It is also called as circuit switched scheme.
❖ The Resource or Channel is shared by nodes based on Time, Frequency or Code.
❖ There are three types of schemes available
➢ Frequency Division Multiple Access ( FDMA ).
➢ Time Division Multiple Access ( TDMA ).
➢ Code Division Multiple Access ( CDMA ).

22. The multiple access schemes: a) FDMA, b) TDMA, c) CDMA.

23. Frequency Division Multiple Access ( FDMA)
❖ In FDMA the available bandwidth is divided into many narrow frequency band
called channels.
❖ Each user need a two link
➢ Forward link ( Mobile to Base Station ).
➢ Reverse Link ( Base Station to Mobile ).
❖ Two channels are allocated to one user.
❖ These 2 channels are unable to allocate to other users while on use.

24. Frequency Division Multiple Access ( FDMA)
❖ User never always uses this channel.
❖ When user on idle the channel utilization is very low.
❖ Implementation of this protocol is very easy.
❖ Big disadvantage is poor channel utilization

25. Time Division Multiple Access ( TDMA )
❖ TDMA allows the user to use multiple channels based on different time slots.
❖ All sources are uses the same channel but it will wait for time slots.
❖ The time slots are allocated in the round robin manner.
❖ Unused time slot makes the channel idle so this to leads to poor utilization of
channel.

26. Code Division Multiple Access ( TDMA )
❖ In CDMA Technology multiple users can use the same channel same time.
❖ No scheduling is needed.
❖ Message or data is encoded in the one end and decripted in the other end.
❖ Lot of users data are encoded and multiplexed and send in to same channel at
time.
❖ Each user uses only one code.

27. Code Division Multiple Access ( TDMA )
❖ Maximum utilization of channel is obtained.
❖ But we need a special mechanism to generate code as well encode and decode.
❖ Quite expensive procedure when compared to FDMA and TDMA.