Evaluating the Opportunity for Optimization of Various RF Parameters in IEEE 802.16e Multi-Cell Networks

The likely sensitivity of an IEEE 802.16e system to optimization of sub-channel preamble power, antenna down-tilt, azimuth and beam-width is evaluated. A simple optimization scheme for these parameters is developed and an initial evaluation is performed. The various criteria by which an 802.16e system may be evaluated are identified and defined. These include signal-to-interference plus noise ratio, blocking and down link data rate and outage. A static model of the air interface is developed to predict these quantities. This model is simplified for reduced computation times, thus enabling a searcher-based optimization. The optimizer is a single-objective greedy local search scheme, driven by the air interface model and including intelligent hot-spot identification. This optimizer is employed to adjust various subsets of the sub-channel preamble power and antenna orientation parameters of the base stations in a simulated system based on a real cellular network. The performance improvements in the chosen criteria predicted by the simplified model are compared for the different scenarios. The predicted average down link rate is seen to increase by more than 50% when all degrees of freedom are exploited. Optimization of antenna parameters is predicted to be significantly more effective than preamble power optimization for enhancing predicted system performance.