y, Quality, etc Pre-Planning Microwave Transmission Detail Planning Site Selection Link Planning Network Plan Figure 3.4 The transmission network planning process TRANSMISSION NETWORK PLANNING AND OPTIMISATION of base stations and their capacities are known, transmission planners will start with defining the quality targets for the network. According to the transmission products available - such as radios, base stations, base station controllers, information on the media - an imaginary network topology is defined, or the topology principles that will be used in the transmission network are formed. This gives a better idea on where the transmission network should be heading. The final network design after the whole process will be somewhat different from the one drawn up at this stage. All along the media of transmission is considered. If microwave transmission is to be used, then the link budget aspects have to considered as well, so that the link design meets the availability and quality targets. Selection of sites is basically a radio planning issue, but the transmission planning engineers should get involved right at this early phase, so that it will be easier to find sites that have the desired lines of sight (LOS) with other sites. The line-of-sight process should be done very professionally, because once a site is constructed and there is no LOS with another site, that represents a big loss for the network owner. When microwave is the chosen medium of transmission, link budget calculations are generally based on ITU recommendations. Tools used for the link budget and availability calculations should be based on the ITU/ETSI, etc., recommendations. The detailed planning phase consists of frequency allocation/frequency planning, defin- ing of the time slot allocation plans, routing of the PCM signals, synchronisation principles, and network management planning. This whole process is usually an iterative one at different points, as the transmission planners try to achieve a balance between network capacity, qu