3Transmission Network Planning and Optimisation
3.1 Basics of Transmission Network Planning
3.1.1 Scope of Transmission Network Planning
In the GSM system, the transmission network is generally considered to be the network between the base stations and the transcoder sub‐multiplexers (TSCM). The transmission network connects the radio network to the mobile switching centre (MSC), and hence, by virtue of its position and functionality, it acquires an important position in the mobile network infrastructure (see Figure 3.1).
Figure 3.1 Scope of transmission network planning.
3.1.2 Elements in a Transmission Network
3.1.2.1 Base Station Transceiver (BTS)
An overview of the BTS is provided in Chapter 2. Here we consider the BTS from the transmission planning perspective, i.e. the transmission system within a base station, as shown in Figure 3.2. The base station consists of a transmission unit or TRU. This unit interacts with the Abis and Ater interfaces. It also reallocates the traffic and the signalling channels to the correct transceiver or TRX. These units may be capable of making cross‐connections at the 2 Mbps level and drop‐and‐insert functionalities at the 8 kbps level. Transmission units are capable of holding branching tables. These tables guide the transmission units on what to do with the traffic coming in from the PCM lines, e.g. should it just let it pass for the ...