PROJECT REPORT ON

HANDOVERS IN GSM

GUIDED BY:-MR. SURESH DHRUWEY

SUBMITTED BY:-Ankita JainTulika PrasadVandana BindHemant KumariAishwarya Jain

GSM

Global System for Mobile Communications

considered a second generation (2G) mobile phone system.

The GSM network is divided into three major systems:

1. the switching system (SS)2. the base station system (BSS)3. the operation and support system

(OSS).

GSM NETWORK

The GSM network can be divided into following broad parts:

1.The Mobile Station(MS)2.The Base Station Subsystem (BSS)3.The Network Switching Subsystem

(NSS)4.The Operation Support Subsystem

(OSS)

GSM ARCHITECTURE COMPONENTS

The added components of the GSM architecture include the functions of the databases and messaging systems:

Home Location Register (HLR) Visitor Location Register (VLR) Equipment Identity Register (EIR) Authentication Center (AuC) SMS Serving Center (SMS SC) Gateway MSC (GMSC) Chargeback Center (CBC) Transcoder and Adaptation Unit (TRAU)

GSM NETWORK

DESCRIPTION OF GSM SUBSYSTEM

THE MOBIE STATION (MS):

- Mobile Equipment(ME) - Subscriber Identity Module(SIM) BASE STATION SUBSYSTEM (BSS) - Base Transceiver Station(BTS) - Base Station Controller(BSC) NETWORK SWITCHING SUBSYSTEM

(NSS): Mobile Switching Center (MSC) Visitor Location Register (VLR)

HAND OVERS

Handover is a process in telecommunications and mobile communications in which a connected cellular call or a data session is transferred from one cell site (base station) to another without disconnecting the session.

It allows users to create data sessions or connect phone calls on the move.

PURPOSE OF HANDOVERS

when the phone is moving away from the area covered by one cell and entering the area covered by another cell .

when the capacity for connecting new calls of a given cell is used up .

in non-CDMA networks when the channel used by the phone becomes interfered by another phone using the same channel in a different cell.

again in non-CDMA networks when the user behaviour changes.

in CDMA networks , a handover may be induced in order to reduce the interference to a smaller neighbouring cell .

TYPES OF HANDOVERS

Inter System Handoff: 1. A handover, in which the source

and the target are different cells (even if they are on the same cell site).

2. The purpose of inter-cell handover is to maintain the call as the subscriber is moving out of the area covered by the source cell and entering the area of the target cell.

INTRA-CELL HANDOVER 1. A handover, in which the cell is not

changed.

2. The purpose of intra-cell handover is to change one channel, which may be interfered or fading with a new clearer or less fading channel.

HARD HANDOVERS

1. The channel in the source cell is released and only then the channel in the target cell is engaged.

2. is perceived by network engineers as an event during the call.

3. intended to be instantaneous in order to minimize the disruption to the call.

4. break-before-make.

SOFT HANDOVER

1.  The channel in the source cell is retained and used for a while in parallel with the channel in the target cell.

2. is perceived by network engineers as a state of the call, rather than a brief event.

3. Connections to three, four or more cells can be maintained by one phone at the same time.

4. make-before-break

IMPLEMENTATION For the practical realisation of handoffs in

a cellular network each cell is assigned a list of potential target cells.

They implement different algorithms and may use for input data from field measurements or computer predictions of radio wave propagation in the areas covered by the cells.

The downlink (forward link) and/or uplink (reverse link) directions may be monitored

In analog systems the parameters used as criteria for requesting a hard handover are usually the received signal power and the received signal-to-noise ratio .

In non-CDMA 2G digital systems the criteria for requesting hard handover may be based on estimates of the received signal power, bit error rate (BER) and block error/erasure rate (BLER), received quality of speech (RxQual), distance between the phone and the BTS (estimated from the radio signal propagation delay) and others.

In CDMA systems, 2G and 3G, the most common criterion for requesting a handover is Ec/Io ratio ( ratio of Received power of the carrier to the all over Noise)measured in the pilot channel (CPICH) and/or RSCP(Received Signal Code Power).

THANK YOU!