It’s area of radio coverage by a mobile tower. Each cell is assigned a unique number called Cell Global Identity (CGI).
LOCATION AREA (LA)
Mobile network identify location of a mobile station using location area identity. It is defined as a group of cells. Location area of a mobile station is always stored in VLR. This is used in routing of mobile call.
MSC SERVICE AREA
It is made up of large number of LAs and represents the area covered by one MSC. Subscriber MSC are is always stored in HLR. This is used in routing of mobile call. Roaming term is used in case of MSC change of mobile station.
PLMN SERVICE AREA
It is entire area or all cells covered by one network operator. For example: Complete Airtel Network or Vodafone network in one country. International roaming term is used in case of PLMN change of mobile station.
GSM SERVICE AREA
This is complete GSM covering area where a mobile station can access to GSM network.