What are Location Area&& Location Update?also write their need?

Location Area: - Location Area is a group of cells. - The subscriber is paged in this area - One or more base station controllers are used to serve each Location Area but by a single MSC. - Each Location Area has a unique Location Area Identity number b) Location Update: - IMSI attach or IMSI detach location update process is to be performed whenever a mobile is switched on or off. - Each mobile is needed to report regularly its location at a given time of interval by using a periodic location update process. - A random location update is required, whenever a mobile moves from one location to another while not on a call. - Hence, the subscriber has reliability to access the network and freedom of mobility within the coverage area.