A new cooperative diversity algorithm with quality of service (QoS) awareness for wireless local areanetwork (WEAN) is proposed.According to this protocol,cooperation is invoked only if a direct trans-mission cannot meet user-specific QoS requirements.If cooperation is implemented,partner choice de-pends on who can achieve the minimum data rate required to have a successful transmission.The closed-form expressions for the system throughput and the power consumption are provided.Theoretical analysisand simulation results indicate that the QoS-aware cooperative scheme can significantly improve the systemperformance in terms of throughput and energy efficiency by avoiding negative effect of unconditional co-operation.
In order to improve the performance of peer-to-peer files sharing system under mobile distributed en-vironments,a novel always-optimally-coordinated(AOC)criterion and corresponding candidate selectionalgorithm are proposed in this paper.Compared with the traditional min-hops criterion,the new approachintroduces a fuzzy knowledge combination theory to investigate several important factors that influence filestransfer success rate and efficiency .Whereas the min-hops based protocols only ask the nearest candidatepeer for desired files,the selection algorithm based on AOC comprehensively considers users' preferencesand network requirements with flexible balancing rules.Furthermore,its advantage also expresses in theindependence of specified resource discovering protocols,allowing for scalability.The simulation resultsshow that when using the AOC based peer selection algorithm,system performance is much better thanthe min-hops scheme,with files successful transfer rate improved more than 50% and transfer time re-duced at least 20%.
