19-03-2012, 04:27 PM
GSM Overview
GSM Basic.ppt (Size: 526.5 KB / Downloads: 30)
WHAT IS A CELL ?
A base station (transmitter) having a number of
RF channels is called a cell
Each cell covers a a limited number of mobile
subscribers within the cell boundaries
( Coverage area)
Typical Cell Radius Aprrox = 30 Km
(Start up), 1 KM (Mature)
Fundamental problems
Radio range, or coverage
No. of channels, or voice circuits
Full, seamless service coverage
Large no. of subscribers in the range of millions
GSM Network Structure
GSM Service Area: Total area served by the combination of all member countries where a mobile can be served.
PLMN Service Area: It is one N/W area.
MSC Service Area: There can many MSC/VLR in one PLMN area.It is one Mobile Exch. Area.
GMSC: All I/C calls for PLMN N/W will be routed through GMSC. In a GSM/PLMN N/W all mobile terminated calls will be routed to a Gateway MSC. Call connections between PLMNs , or to fixed N/Ws must be routed to a GMSC.The GMSC contains the Inter working functions to make these connections.
Location Area
Cells
GSM Network Structure
LOCATION AREA : There are several LA in a MSC/VLR combination. A LA is a part of the MSC/VLR service area in which a MS may move freely without updating location information to the MSC/VLR exchange that control the LA. Within a LA a paging message is broadcast in order to find the called mobile subs. LA can be identified by system using the LAI.
CELL : A cell is an identity served by one BTS. The MS distinguishes between cells using the BASE STATION IDENTIFICATION CODE(BSIC) that the cell site broadcast over the air.