导　　师： 褚丽莉

学科专业： 081001

授予学位： 硕士

作　　者： ;

机构地区： 辽宁工业大学

摘　　要： 近年来，无线局域网（WLAN）以其布置便捷、灵活性等优势，得到了广泛的应用与部署。WLAN承载的业务也覆盖了从标准互联网业务到新型实时业务（VoIP）的范围。VoIP技术可以承载语音、视频、数据及其它业务，符合当今互联网多业务的发展趋势，且具有较低的通信服务开销。因此，无线IP语音（VoWLAN）技术应运而生。随着VoWLAN的未来发展，与其它业务势必融合应用，这也对网络性能提出了更高要求。对于整个融合网络中侧重的业务不同，而网络状态的衡量指标也有着不同要求。 本文基于VoWLAN存在的QoS问题，分析了QoS保证的前提下，研究了典型的QoS改进方案：增强分布式信道访问（EDCA，Enhanced Distributed Channel Access）机制与自适应增强型分布式协调功能（Adaptive EDCF）机制，对现有的一些改进机制特点进行了分类研究。在此基础上，提出了一种基于AC（Access Category）队列流的面向业务QoS需求保障机制，利用时隙利用率因子估计信道负载程度，自适应调整竞争窗口CW大小，并结合退避中止率概念，针对非时延敏感业务随机选取的退避值，设置一个与网络负载状况有关的非零值下限，从而进一步扩展EDCA机制功能。通过NS-2仿真验证了改进算法SA-EDCA的可行性和高效性，结果表明该算法确实能够提高WLAN的网络性能，改善实时业务的服务质量。 最后，对当前基于IEEE802.1le EDCA机制的主要接纳控制方案作了分析研究，提出了一种利用CW参数进行接纳控制的方案，并给出了基于接纳控制策略的QoS保证机制架构模型。 Recently, Wireless Local Area Networks is applied and disposed in large scale becauseof its easy disposition, flexibility and so on. The applications on WLAN range from standardInternet services to new fashioned real-time services /(VoIP/). VoIP could carry voice, video,data and other services, which is in line with the development trend of Internet multi-serviceand with lower expense in communication service. Therefore VoWLAN emerged. With thefurther development, VoWLAN /(VoIP over Wireless LAN/) will achieve convergence withother services inevitably, which would bring forward a higher requirement for networkperformance. The difference of service emphases on the whole converged network wouldaffect the measurement of network status. According to the QoS problems exist in VoWLAN, and under the premise of analyzingthe QoS guarantee, classical improvement schemes: EDCA /(Enhanced Distributed ChannelAccess/) and AEDCF /(Adaptive EDCF/) mechanism for VoWLAN QoS are studied in thispaper, and the existing improvement mechanism features are classified. On this basis, a novelservice-oriented QoS guarantee mechanism based on access category traffic is proposed inthis paper, which draw on the slot utilization factor to evaluate channel loading level andadjust contention window size adaptively. Combined with the concept of backoffdiscontinuation rate and in view of the backoff value of non-real-time traffic chosen randomly,in order to achieve further expansion of EDCA function, a situation of the lower limit ofnon-zero value associated with network load is set. In addition, the feasibility and efficiencyof SA-EDCA algorithm are proved by NS-2. The simulation results show that this algorithmcan improve the performance and QoS of the WLAN. At last, the up-to-date admission control algorithms in IEEE802.1le EDCA are studiedand analyzed in this paper. Then an admission control scheme based on CW is proposed, andan admission control model with QoS based on the admission control scheme is gave in thispaper.

关 键 词： 语音 无线局域网 服务质量 仿真 接纳控制

分 类 号： [TN925.93]

领　　域： [电子电信] [电子电信]