Optimizing downlink coexistence performance of WiMAX services in HAP and terrestrial deployments in shared frequency bands

In this paper, we investigate techniques for optimizing the coexistence performance of providing WiMAX (IEEE802.16a) from High Altitude Platforms (HAPs) and terrestrial deployments in shared 3.5 GHz frequency bands are presented. The paper will show that it is effective to provide WiMAX services from HAPs with optimized performance by appropriate choice of parameters, including varying the HAP deployment spacing radius and directive antenna beamwidth based on the adopted antenna models for HAPs and receivers. Illustrations and comparisons of changing the antenna pointing offset, narrowing the transmitting and receiving antenna beamwidth as well as keeping the accepted CINR performance across the HAP coverage area, will demonstrate that that efficiently utilizing these techniques are able to enhance the HAP system performance while effectively coexisting with the terrestrial WiMAX systems.