llocation Speech channel Outgoing call: The dialed digits are sent to the network and a voice channel is allocated. Decreasing quality on the Handover: When the MS moves towards the edge of the border of the cell base station area, communication quality is decreased. A new cell is selected with the help of measuring results of the Switch over to the neighbor cells. A new channel is then allocated and BS and best neighbor MS switch to it at the same time. Paging mobile ID Incoming call: Paging message is sent over the common control channel. When MS receives its own identification, Channel request it requests a traffic or voice channel, which is then allocated. Speech channel Transmission power is controlled to be as low as possible Power control to minimize interference with other cells. Figure 5.4 Basic operation of the cellular network. Introduction to Telecommunications Network Engineering The MSC analyzes the dialed number, passes the digits to the public telephone network for call establishment through the PSTN, and requests a BS to allocate a dedicated speech channel for the calling mobile. The MS and BS switch to this channel when the called party answers and the conversation is allowed to start (Figure 5.4). 5.3.3 Incoming Call When a call is to be connected to the MS, the HLR determines to which VLR address the call should be routed. This address is global, containing the country and network codes according to international telephone numbering scheme. The call is then routed to the MSC/VLR, which knows the more exact location (the location area) of this specific subscriber inside its area. A paging message with MS identification is sent on the common control chan- nel of all BSs in that area where the subscriber is currently located. The receiving MS continuously listens to this channel and when it receives the message containing its own identification it requests a speech channel and a channel is allocated for this call. The BS and MS switch to the allocated channel, the telephone rings, and when the su