r optimisation actions. Network Coverage and Capacity Enhancement Methods The performance of a mobile network is seen from several perspectives: Capacity. Each operator owns a limited frequency band which is shared by an increasing number of network users. Quality. Quality is measured by metrics such as the carrier-to-interferer ratio (C/I), bit error rate (BER), frame error rate (FER), dropped call rate (DCR) or call setup failure (CSF). Coverage. Service continuity is tremendously important in a cellular network. Cost. Technical requirement to achieve the best quality perception from the subscriber side should be balanced with costs. New services. Operators cannot differentiate and gain new customers if they do not offer enhanced data services on top of high data rate technologies (like GPRS, EDGE and WCDMA). Complexity and flexibility. Two very important criteria from an OPEX point of view (operation of the network) make it easy for maintenance teams to maintain the network. All these aspects are correlated between them and are interdependent. Commonly, a network transits mainly through the path shown in Figure 2.64. At the first roll-out stage, the most important thing is to provide coverage. Then, when the subscribers' base starts to increase and generate more traffic, capacity becomes the main issue for the operator. When a certain maturity of the network is reached in terms of subscriber behaviour and coverage/capacity levels, the operator should improve quality and end user perception. To achieve the best tradeoffs, especially between quality and costs, the operator tries to make use of several coverage and capacity enhancement methods. Coverage Enhancement Coverage improvement may result from different approaches. The first approach consists of improving the path balance. The second way can be through increasing radio performance. Boosting coverage also means expanding the indoor signal level. Path Loss Improvement Uplink and downlink transmissions should be balanced. This is why it is important to perfo