Basic Limits for Fixed WiMAX Optimization Based on Economic Aspects

In Fixed WiMAX, radio and network planning can be optimized 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 due to the implied greater average distance of users from the base station, although the use of subchannelisation can keep throughput steady up to a larger radius. Sectorization can improve the throughput of the cell by factiliting the use of higher order modulation and coding schemes; besides, sectorization equipment is more expensive, and there is the need for three times more spectrum bandwidth, increasing costs whilst 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 paper, 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 paper also concludes that a cell radius in the range 1000-1500m is preferable, corresponding to profit in percentage terms of near the achievable maximum, while keeping costs acceptable.