 mation serves not only to increase coverage and capacity, but also the quality of service experienced by end-users, which will be closely observed in EDGE networks. The optimum value of QoS will depend ultimately on traffic requirements. As will be seen in Chapter 7, interactive traffic has more stringent quality requirements than background traffic. Spec- trum efficiency will play a big role in achieving this. The tradeoff between the number of transceivers and interference levels (i.e. between higher throughput and more users) is a delicate issue. Final optimisation plans will be similar to those for GSM/GPRS networks, but with stringent QoS requirements guiding the results. Improvement of Throughput in EDGE Networks QoS depends on the service required, but higher throughput will be the main QoS-fulfilling requirement in an EDGE network. Throughput on the air interface and coverage (both at hot UCS-5 WCS-5P WCS-BR MCS-7 VICE-719 MCS-8 MCS-BR MCS-B MCS-BR Figure 6.11 C/I versus throughput (simulations) NETWORK OPTIMISATION spots and cell edges) will be the main focus in the planning as well as optimisation of the radio network. Throughput is dependent upon a number of factors such as C/I, handovers, MCS changes, etc. An increase in the C/I ratio will result in increased throughput (shown in the simulation in Figure 6.11). Measurement at the cell edges will be critical, and here performance im- provement can be achieved by using concepts such as antenna tilts, power increase/decrease, Increasing the number of handovers will also decrease throughput, so optimisation of the neighbours to reduce unnecessary handovers can be one possible solution to increase throughput. Throughput also decreases with the number of MCS changes from higher- throughput MCS to lower-throughput MCS. Optimisation can be achieved by parameter auditing after observing the C/I and receiver level statistics against MCS changes. Conclusions Traffic loads (both CS and PS), and the applications used, affect the performance of an EDGE network. C/