acon frequency. In such cases, the BSIC helps in distinguishing the channels of the same frequency. 2.5 RADIO NETWORK OPTIMISATION 2.5.1 Basics of radio network optimisation Optimisation involves monitoring, verifying and improving the performance of the radio network. It starts somewhere near the last phase of radio network planning, i.e. during parameter planning. A cellular network covers a large area and provides capacity to many people, SO there are lots of parameters involved that are variable and have to be continuously monitored and corrected. Apart from this, the network is always growing through increasing subscriber numbers and increases in traffic. This means that the optimisation process should be on-going, to increase the efficiency of the network leading to revenue generation from the network. RADIO NETWORK PLANNING AND OPTIMISATION As we have seen, radio network planners first focus on three main areas: coverage, ca- pacity and frequency planning. Then follows site selection, parameter planning, etc. In the optimisation process the same issues are addressed, with the difference that sites are already selected and antenna locations are fixed, but subscribers are as mobile as ever, with continu- ous growth taking place. Optimisation tasks become more and more difficult as time passes. Once a radio network is designed and operational, its performance is monitored. The per- formance is compared against chosen key performance indicators (KPIs). After fine-tuning, the results (parameters) are then applied to the network to get the desired performance. Op- timisation can be considered to be a separate process or as a part of the network planning process (see Figure 2.15). The main focus of radio network optimisation is on areas such as power control, quality, handovers, subscriber traffic, and resource availability (and access) measurements. Definition Network Performance Monitoring Parameter Tuning Network Planning Process Optimised Network Figure 2.15 Radio network optimisation 2.5.2 Key Performance In