y on indoor coverage. The principal aspects of the pre-planning phase are: the area for which the network is planned subscriber database information 4G NETWORK PLANNING coverage and capacity requirements the number of channels that can be used (e.g. 13 in Europe and 11 in the USA) the number of channels that can be used simultaneously without interference propagation conditions (e.g. multipath in an indoor environment) equipment data (e.g. antenna gains and transmitted power) the air-interface radio link budget. Based on these factors, coverage, capacity and quality can be calculated. A WLAN network should provide coverage for 100% of the area for which it is being planned. Most of the issues that we have seen in earlier chapters on radio network planning - such as coverage threshold, signal quality, C/I etc. - will be involved in planning coverage, but with more stringent requirements. Methods to improve coverage include increasing the power levels, incorporating diversity schemes etc. Frequency planning is another area of challenge in WLAN networks. As the number of channels available is less than the capacity likely to be demanded, frequency planning becomes a crucial task. As frequency re-use becomes lower, the quality (and hence through- put) becomes lower. One rule of thumb could be to plan these networks with a frequency re-use of more than unity. 10.3 CHALLENGES IN 4G WIRELESS NETWORKS Two main challenges need to be addressed before fourth-generation networks become a reality. The first concerns accessibility to different types of cellular network. The second concerns how to maintain the desired end-to-end QoS for traffic that has varying require- ments of bandwidth, bit rates, channel characteristics etc., and especially the handover delays, which are a cause of worry. During the handover process, mobile subscribers are expected to face a drop in the QoS level. Fourth-generation networks are still 'unclear' from the perspective of defining the net- work planning processes. This is partly because the evol