Cost/Revenue Tradeoff in the Optimization of Fixed WiMAX Deployment With Relays

In fixed Worldwide Interoperability for Microwave Access (WiMAX), the contribution from each transmission mode can be incorporated into an implicit formulation to obtain the supported throughput as a function of the carrier-to-interference ratio. This is done by weighting the physical throughput in each concentric coverage ring by the size of the ring. In this paper, multihop cells are formed by a central coverage zone and three outer coverage zones, which are served by cheaper low-complexity relays. Although the reuse distance in this case is augmented by a factor of √(3), we show that, with the use of relays in frequency-division duplexing (FDD) mode with an adapted time-division duplexing (TDD) uplink (UL) subframe structure to accommodate communication from/to the relay station (RS) to/from subscriber station (SS), only the consideration of trisectored base stations (BSs) with a reuse pattern of K = 3 enables attainment of values for the cell per sector throughput that is comparable with cases without the use of relays. Cost/revenue optimization results show that trisectored BSs in topologies with relays enable us to achieve more profitable reuse configurations than with omnidirectional BSs and no relays. Under the same total bandwidth and with the coverage distance set at R ~ 500 m, we show that it is preferable to consider K = 1 with three carriers per sector instead of K = 3 with one carrier per sector, whereby the profit in this case is increased from ~ 1000% to ~ 1450%. Furthermore, if the price [in (€ /MB)] is increased from 0.0025 to 0.005, the achievable profit more than doubles.