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Basic Limits for System Capacity and Cost/Revenue Optimisation: a formulation for Fixed WiMAX

Velez, F. J. ; del Camino Noguera, M. ; Aghvami, H. ; Holland, O.

Basic Limits for System Capacity and Cost/Revenue Optimisation: a formulation for Fixed WiMAX, Proc Wireless Personal Multimedia Communications Symp. - WPMC, Recife, PE, Portugal, Vol. -, pp. 1 - 6, October, 2010.

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Abstract
In Fixed WiMAX, the cost/revenue radio and network planning optimisation function 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 it steady up to a larger cell radius. Sectorization facilitates the use higher order modulation and coding schemes in the cell and may improve the throughput; however, sectorization equipment is more expensive, and there is the need for three times more spectrum bandwidth, increasing costs. In turn, the use of Relay Stations (RSs) may significantly reduce the deployment cost of the system. With relays, only the consideration of tri-sectored Base Station (BS) antennas with K=3 (at the cost of extra channels, where 9 channels corresponds to a bandwidth of 31.5 MHz) enables to obtain values of throughput comparable to the ones without using relays. This is due to the more favourable frame format. With no RSs and sectorization with K=3 the economic performance is weak, as only one carrier may be used. However, with omnidirectional BSs with K=3, under the same total bandwidth, three carriers may be used and the profit in percentage varies between ~900 and 800% for coverage distances lower than 1000 m. With RSs, the use of tri-sectored BSs corresponds to a clear advantage relatively to the “no RS” case up to R~1300 m. When the price per MB, R144, increases from 0.0025 to 0.005 €/MB the profit in percentage increases more than 100%.