ynchronisation of move around when engaged in a call. It is therefore necessary for the mobile and BTS identification. the network to maintain the call even if the customer moves between 3. Broadcast Control Channel (BCCH), for the broadcast of cells. general information on an individual basis. Within DCS1800 there are 4 types of handover specified: 1. Intra-BTS, a handover from one channel on a BTS to another 48.8.2.2 Common Control Channel on the same BTS. 2. Inter-BTS, Intra-BSC, a handover from a channel on one BTS The Common Control Channel (CCCH) is used during the estab- lishment of a connection before dedicated control channel is as- to a channel on another BTS with both BTS's parented on the same BSC. signed. There are three downlink-only channels which are used for 3. Inter-BSC, Intra-MSC, a handover between BTS's on different paging, access grant and cell broadcast. BSC's which are parented on the same MSC. The single uplink-only channel is used for random access at- 4. Inter-MSC, a handover between BTS's on different BSC's tempts. which are parented on different MSC's. 48.8.2.3 Dedicated Control Channel The network overhead in terms of signalling messages increases as the type of handover moves from (1) to (4). With this in mind, inter switch and inter BSC handovers should be kept to a minimum. The Dedicated Control Channel is split into three types: Thus the network must be planned to achieve this. 1. Standalone Dedicated Control Channel (SDCCH) carrying sig- Handover can be initiated by either the mobile or the network. The nalling information following mobile to network connection mobile will request handover as a result of radio channel measure- establishment and channel assignment. ments indicating low signal or excessive interference. The network will initiate handover for reasons such as: 2. Slow Associated Control Channel (SACCH) is always associ- ated with a traffic channel or a SDCCH and maps on to the same physical channel. The SACCH carries general information 1. Mobile causing interferenc