While localization is essential to many applications, there are quantities of wireless nodes whose accurate locations remain unknown or hard to tell. As a remedy, this paper is leveraging a GPS-capable Android handset that features portability and computing capability to collect data and display localization results thereof. Our objective is to locate the unknown nodes in consideration of radio-signal irregularity. To this end, we devise a hybrid means to incorporate received signal strengths used in range-based schemes with the notion of estimative regions adopted in range-free methods to refine the area of interest for localization. Our scheme operates without involved computations such as to accommodate many usable reference coordinates. Our treatment mitigates the errors of estimation resulting from different radio signal propagation scenarios, by taking an additional parameter to narrow region size for ameliorating localization accuracy. Experiments are conducted to demonstrate our performance results overlying Google Maps on the handset and through quantitative comparisons with trilateration under different settings. Performance results show the effectiveness of our development.

Radio interfaces and channels are two sorts of resources in a multi-channel, multi-radio wireless mesh network. An efficient allocation of radio resources to mesh devices should reduce co-channel interference for higher throughput while maintaining network connectivity. Unlike much research effort on such optimization dealing with link- or higher-level interference, this study is concerned with physical-layer interference. We propose a two-stage radio allocation scheme. The first stage assigns channels to radios using a game-theoretic approach while the second stage assigns the resulting radio-channel pairs to links using a greedy method. In the proposed game, wireless interfaces are modeled as players participating in a radio resource game with a utility function defined to minimize co-channel interference from other players. We prove that the game eventually reaches a pure-strategy Nash equilibrium regardless of the game's initial configuration. Simulation results indicate that the proposed scheme leads to more operative links than previous methods.

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.

This paper is concerned with caching support of access points (APs) for fast handoff within IEEE 802.11 networks. A common flavor of current schemes is to let a mobile station preauthenticate or distribute the security context of the station proactively to neighboring APs. Each target AP caches the received context beforehand and can save itself backend-network authentication if the station reassociates. We present an approach to ameliorating cache effectiveness under the least recently used (LRU) replacement policy, additionally allowing for distinct cache miss penalty indicative of authentication delay. We leverage the widely used LRU caching techniques to effect a new model where high-penalty cache entries are prevented from being prematurely evicted under the conven-tional replacement policy so as to save frequent, expensive authentications with remote sites. This is accomplished by introducing software-generated reference requests that trigger cache hardware machinery in APs to refresh certain entries in an automated manner. Performance evaluations are conducted using simulation and analytical modeling. Performance results show that our approach, when compared with the base LRU scheme, reduces authentication delay by more than 51 percent and cache miss ratio by over 28 percent on average. Quantitative and qualitative discussions indicate that our approach is applicable in pragmatic settings.