Basic limits for fixed worldwide interoperability for microwave access optimisation based in economic aspects

In fixed worldwide interoperability for microwave access (WiMAX), radio and network planning can be optimised by tuning a cost/revenue function which incorporates the cost of building and maintaining the infrastructure and the effect of the available resources on revenues. Supported throughput typically decreases with larger cells because of the implied greater average distance of users from the base station, although the use of sub-channelisation can keep throughput steady up to a larger radius. Sectorisation can improve the throughput of the cell by facilitating the use of higher order modulation and coding schemes; besides, sectorisation equipment is more expensive, and there is the need for three times more spectrum bandwidth, increasing costs while increasing system capacity by a factor of 3. On a multi-cell level, system capacity is determined by the chosen frequency reuse pattern, K. In this study, under the assumption of a revenue per Mbyte of information transfer somewhere between 0.0025∉ and 0.010∉ , the choice of K = 3 or 4 with sectorial cells is preferable to the use of omnidirectional cells with K = 7. This study also concludes that a cell radius in the range 1000-1500 m is preferable, corresponding to profit in percentage terms of near the achievable maximum, while keeping costs acceptable.