Network configuration

Date: 2015-10-07; view: 440.

Principles of operation

In a cellular radio system, the area to be covered is divided up into a number of small areas called cells, with one radio base station (BS) positioned to give radio coverage of each cell. Each base station is connected by a fixed link to a mobile services switching centre (MSC), which is generally a digital telephone exchange with special software to handle the mobility aspects of its users. Most cellular networks consist of a number of MSCs each with their own BSs, and interconnected by means of fixed links. The MSCs interconnect to the public switched telephone network (PSTN) for both outgoing calls to, and incoming calls from fixed telephones. Figure 47.1 shows a typical network arrangement.

Figure 47.1Cellular network configuration

A cellular network will be allocated a number of radio frequen­cies, or channels, for use across its coverage area, this number being dependent upon the amount of spectrum made available by the licensing authority and the channel spacing ofthe technical standard used by the network. The radio channels are grouped together into a number ofchannel sets, and these sets are then allocated to the cells, one set per cell, on a regular basis across the whole coverage area. Each channel will therefore be re-used many times by the network. The method ofradio planning and allocation ofchannels to the cells is described later in this chapter.