The infrastructure efficiency of cellular wireless networks
Providing downlink wireless coverage is expensive and represents a dominant variable cost for mobile communication operators. It is vital that operators select base station locations so that efficiency is achieved, with high coverage relative to total cost of the selected operational base stations. However, efficiency in this context has not previously received explicit analysis. In this paper, we explicitly study cell plan infrastructure efficiency. We determine the density of macro cells which gives maximal coverage at minimal cost, modelling an irregular dispersion of candidate base station locations with varying procurement costs. An empirical investigation is undertaken consisting of 585 experiments using 45 synthesised test problems. The results provide evidence indicating the optimal relative size for inter-cell overlap. This is a new and important observation. We introduce and assess the marginal cost of service coverage. This represents the lowest rate at which infrastructure cost must increase to facilitate higher levels of service coverage. Two important conclusions are drawn. Firstly, the results quantify a significant advantage from increasing candidate site density. Secondly, marginal cost emerges as a powerful concept for analysing the impact of investment. We observe common trends in the behaviour of this function, which quantify a rapid diminishing return (in terms of service coverage) for additional infrastructure expenditure. Finally we consider the spectral implications of increased cell density. As cell overlap increases, we determine the additional span of channels needed to satisfy signal-to-interference requirements for service area coverage. We explain how these results are of practical use in cellular network planning. these results are of practical use in cellular network planning.