Location area and Location area update

As the network needs to be able to forward an incoming call, the subscriber’s location must be known. After the mobile phone is switched on, its first action is to register with the network. Therefore the network becomes aware of the current location of the user, which can change at any time due to the mobility of the user. If the user roams into the area of a new cell it may need to inform the network of this change. In order to reduce the signaling load in the radio network, several cells are grouped into a location area. The network informs the mobile station via the BCCH of a cell not only of the cell-ID but also of the location area that the new cell belongs to. The mobile station thus only has to report its new location if the new cell belongs to a new location area. Grouping several cells into location areas not only reduces the signaling load in the network but also reduces the power consumption of the mobile. A disadvantage of this method is that the network operator is only aware of the current location area of the subscriber but not of the exact cell. Therefore, the network has to search for the mobile station in all cells of a location area for an incoming call or SMS. This procedure is called paging. The size of a location area can be set by the operator depending on his particular needs. In operational networks, usually 20 to 30 cells are grouped into a location area.