Enhanced Fast Base Station Switching

Abstract

IEEE 802.16-2009 specifies two fast handover mechanisms, fast base station switching and macro diversity handover, to streamline communication for a mobile station (MS). Both operate with a diversity set that lists base stations among which an MS can move its connection readily. In view that an unduly chosen diversity set may cause prohibitive cost, we provide means to prevent the diversity set from including base stations that are less likely to serve the MS in the near future. Inspired from the working-set model, our approach develops predictive handover using numerical extrapolation to accommodate temporal locality of the MS. While a joint entry-replacement strategy is exercised to evict least-preferred entries in the diversity set, its capacity is reviewed and tuned periodically allowing for reasonable space demand. Simulation results show that our approach, compared with the counterpart scheme, reduces handover executions by over 48 percent, handover delay by over 51 percent, and diversity-set space requirement by up to 17.9 percent on average. As another salient strength, our approach conforms fully to the standard, keeping current protocols on the MS side operable without modification. Qualitative and quantitative performance discussions indicate the usefulness of our approach in pragmatic settings.