【作者】 晋晓辉；

【导师】 李建东；

【作者基本信息】 西安电子科技大学 ， 通信与信息系统， 2002， 博士

【摘要】 基于TCP/IP的Internet的巨大成功和移动通信技术的日益成熟，促成了无线局域网技术的飞速发展。无线局域网，通过基于IP的小范围的无线覆盖和与有线网络的互联，改变了人们的工作方式，满足了人们对高传输速率和个人行为移动性的要求。作为一门新兴技术，无线局域网仍处在飞速发展的阶段，物理层的调制/解调技术、编码技术，媒体访问控制层的QoS支持、AP之间的互联，以及安全性等正成为该领域研究的热点问题。随着Internet的日益商业化，对一个能为不同用户/应用提供不同服务质量的网络的需求显得越来越迫切。除了提供更高的带宽外，主要的解决技术集中在设计合理的体系结构、资源预约、接入控制技术、排队算法等方向。 本文研究工作基于国家863重大课题“宽带无线IP技术”及自然科学基金项目“高速信息网中的高速无线技术研究”，得到教育部高校骨干教师资助计划的资助，对无线局域网和IP QoS的若干关键技术进行了深入研究，主要工作和贡献包括以下几个方面： 第二章介绍和分析了移动通信系统的位置管理策略，介绍了计算机网络中的网桥、Mobile IP协议、动态路由解析协议的工作原理，分析了Mobile IP的位置管理和WLAN中的位置管理的关系；结合WLAN的特点，通过数据库的不同分布方式和分布式系统(DS)上帧格式的不同，提出了四种位置管理策略，并提出了两种切换方法：简单越区切换和基于服务器的越区切换，给出了详细的通信流程。通过性能分析，得出了采用全分布式数据库和IEEE802.11无线DS的帧格式的策略和基于服务器的越区切换在数据库查询、位置更新代价、差错恢复等方面性能最好的结论。 第三章首先介绍了IEEE802.11f工作组的相关工作，对基于IEEE802.3有线网的DS实现的拓扑结构进行了分类，介绍并分析了现有的三种IAPP协议。提出了增强型IAPP协议，该协议改进了DS信标帧，增加了“激活的DSCC”域，提高了网络管理员对网络的控制能力，增强了DSC在切换过程、查询过程的作用，通过DS信标帧的检测和利用切换检测DSC的组合方式提高了对失效DSC的检测速度，并给出了具体的通信流程、详细的差错恢复机制和性能分析。分析结果表明，增强型IAPP协议在失效DSC检测、新DSC重建的平均时延、DS的一致性、数据库的连续性等等方面都具有很好的性能。 第四章首先介绍了IEEE802.11e工作组的进展，分析了DCF协议和PCF协议饱和吞吐率的性能。提出了为不同等级帧提供不同竞争窗口的改进型DCF：M-DCF协议，并给出了M-DCF的调度模型，通过采用不同的竞争窗口，为不同n西安电子科技大学博士学位论文:无线局域网和IP服务质量关键技术的研究的应用提供了不同的接入概率，保证了Qos;仿真结果证明了M一DCF在系统吞吐率、丢包率、高等级业务丢包率、不同等级业务的平均接入时延等方面都优于DCF协议。为防止一个终端过多地占用无线资源，提出了基于接入允许的改进型DCF:AA-入IDCF，通过子网带宽管理SBM和MAC层确认机制的结合，降低ACK的发送速率，限制一个终端对无线资源的过度消耗，并给出了建议的实现模型。M一DCF和AA一NIDCF都保证了和IEEE802.ll系列标准的完全兼容性。 第五章首先介绍了几种公平排队算法，重点分析了wFQ的性能，得出了WFQ具有一定的抗高等级突发的能力，该能力和业务的突发程度、系统负荷和各等级的权值分配有关。结合为每等级队列分配一个时标的OTPQ方法，提出了WFQ的两种简单实现算法:基于时间的T-WFQ和基于系统己发送虚拟比特的B一wFQ，给出了二者的分组选择规则和虚拟时间更新算法。仿真结果证明了T-wFQ具有和wFQ完全相同的性能，但是其实现更加简单;由于B一wFQ在统计上的不准确性，限制了其只适用于中等负荷网络。介绍了比例区分服务模型PDs，提出了基于测量的M一wFQ算法，利用它实现了PDS并进行子性能分析，仿真结果表明M一wFQ算法在各种系统负荷下都能满足PDS的要求，并且抗高等级业务突发的性能好，高等级业务的平均排队时延和时延抖动性能L匕低等级业务好。更多还原

【Abstract】 The explosive growth of Internet and rapid development of mobile communication led to the rapid development of the Wireless Local Area Network (WLAN). WLAN provides local wireless access to IP-based Internet. It satisfies the need of high transfer data rate in mobile environment and is changing people’s working manner, The recent researches on WLAN focus on high data rate modulation/demodulation and code/decode techniques in PHY layer, QoS support and MAC layer inter-connection among APs, security and so on. The commercialization of Internet makes the intense need for a QoS-aware network and providing different QoS for different users/applications. Except getting more bandwidth, the most solutions focus on design a reasonable architecture, resource reservation, access control, queueing algorithms and so on.The research work in this dissertation, supported by 863 key project "Wideband Wireless IP technique" and "Mobile Wireless Self-organizing Internetworking Network and Prototype System", the National Natural Science Foundation project "Research on high-speed wireless techniques in high-speed information network", and College Outstanding Teachers Program Funded by the Ministry of Education, carries a deep research on key techniques in WLAN and IP QoS. The major achievements are outlined as follows.Chapter 2 introduces and analyzes the location management techniques of mobile communication, describes the mechanism of Bridge/Switch, Mobile IP protocol, and Centralized Dynamic Route Resolution Protocol in computer network, and explains the relations of the location management between Mobile IP and WLAN techniques. Combined with WLAN characteristics, four new location management strategies and two handover methods are proposed in this chapter. The performance evaluations show that the proposed schemes, adopting distribution location database and IEEE802.il wireless DS frame format, and server-based handover are better in database query, cost of location update and error recovery.In chapter 3, the related researches in DEEE802.1 If workgroup are reviewed. We classify the topologies of DS into 3 kinds based on IEEE802.3 wired LAN, introduce and analyze 3 IAPP protocols. A new IAPP protocol, called IAPP enhancement protocol, is proposed. By introducing an "active DSCC" field in DS beacon, IAPP enhancement protocol improves the management capability of network administrator, and enhances the role of DSC in handover process and query process. Thecombination of the fault DS beacon detection and DSC detection while handover and query occurring speeds up the invalid DSC detecting procedure. The detail flow, error recovery mechanism, and performance analysis are represented. The analysis result proves that the IAPP enhancement protocol has better performance in invalid DSC detection, the average delay of a new DSC re-building, the DS consistency, database continuity and so on.In chapter 4, the research status of IEEE802.11e workgroup is introduced. The performance of DCF and PCF are analyzed first. A QoS-support protocol, M-DCF, and its schedule model are proposed. By providing different contention window for different classes, the higher class frames the higher access probability. The simulation proves that M-DCF has better performance than DCF protocol on system throughput, discard ratio, frame discard ratio of higher classes, average access delay of different classes. To avoid a terminal occupy channel excessively, Access Admission-base M-DCF (AA-MDCF) and its suggestion model are proposed. By combining subnet bandwidth management and ACK mechanism in MAC layer together, AA-MDCF can reduce the send rate of ACK frame and prevent a terminal consuming wireless resource excessively. M-DCF and AA-MDCF are both compatible with IEEE802. 1 1 protocols. ,:After review fair queuing algorithms, the Chapter 5 places emphasis on WFQ (Weighted Fair Queuing) performance analysis and concludes that WFQ has certain capability of resisting h更多还原