(BTS), and for UMTS it is called a Node B. A group of base stations is named a location area, or a routing area.

The location update procedure allows a mobile device to inform the cellular network whenever it moves from one location area to the next. Mobiles are responsible for detecting location area codes (LAC). When a mobile finds that the location area code is different from its last update, it performs another update by sending to the network, a location update