Location registration

Date: 2015-10-07; view: 463.

Signalling

Generally, one radio channel is set aside in each cell to carry signalling information between the network and mobile stations. In the land to mobile (L-M) direction, overhead information about the operating parameters of the network, including an area identifier code, is broadcast to all mobiles located in the cell's coverage area. In addition specific commands are transmitted to individual mobiles in order to control call setup and mobiles' location updating.

In the mobile to land (M-L) direction, the signalling channel is used by the mobiles to carry location updating information, mobile originated call setup requests, and responses to land originated call setup requests.

When a mobile is not engaged in a call, it tunes to the signalling channel of the cell in which it is located and monitors the L-M signalling information. As the mobile moves around the network, from time to time it will need to retune to the signalling channel of another cell when the signal from the current cell falls below an acceptable threshold.

When the mobile retunes in this way, it reads the overhead infor­mation broadcast by the new cell and updates the operating par­ameters as necessary. It also checks the location information being broadcast by the new cell and, if this differs from the previous cell, the mobile automatically informs the network of its new location by means of an interchange on the signalling channel (Figure 47.2). By means of this location registration procedure, the network is able to keep updated a database of the location area of all mobiles. This information is used in the call setup procedure for land to mobile calls.

Figure 47.2Mobile location registration