CH) to another network, the HLR would provide a roaming number to on which the location area is broadcast. The mobile monitors the allow the network to route the call to the customer. BCCH channel which it can receive. When the mobile receives a Figure 48.6 PCN network representation to illustrate mobility 48/8 Personal communications networks new location area identification, it will send a location update Speech channels. Full rate speech channels are defined and the request. This information updates the information stored on the algorithm is specified. However, the half rate algorithm is at VLR. If the MS enters a new VLR area, then the VLR informs the present being specified. HLR. This is illustrated in Figure 48.8. Note: 2. Data channels. The following data rates are specified: 300, 1200, 1200/75, 2400, 4800, 9600 bits per second. 1. If the mobile passes from LA2 to LA3, VLR1 information is updated. 48.8.2 Control channels 2. If mobile passes from LA4 to LA5, VLR2 is advised, which then advises the HLR. The control channels carry signalling and synchronisation data between the handset and the network. Three types of control chan- Once the location of the mobile has been determined, the call nels are specified, as in the following sections. needs to be routed to the customer. Consider a call coming from the PSTN. The call is received at the gateway MSC which interrogates the HLR to find the MS. The HLR advises which VLR the mobile 48.8.2.1 Broadcast channel is registered on. The call is routed to the appropriate MSC. The VLR advises which LA the mobile is in and the MSC pages for the MS This channel is used to broadcast information to the mobile station; across the location area. The MS responds, and the call is answered the channel is downlink only. There are three broadcast channels and connected. defined: 48.7.2 Handover 1. Frequency Correction Channel (FCCH), for mobile station frequency correction. As already mentioned, people with mobile phones might want to 2. Synchronisation Channel (SCH), for frame s