共享WiFi系统中快速切换方案的的研究与实现

发布时间：2018-05-07 01:16

本文选题：WiFi + IEEE　；参考：《西安理工大学》2017年硕士论文

【摘要】：自20世纪9如年代以来,无线局域网(Wireless Local Area Networks,WLAN) 因具有无线通信技术和计算机网络的覆盖范围广、布线灵活、传输速率快等诸多优点得到了快速的发展和应用。在无线局域网标准中,IEEE 802.11系列标准因简单规范、兼容性好和众多厂商支持等优势已然成为事实上近距离无线通信技术的通用标准,尽管WLAN能够为移动应用提供足够的带宽,然而由于无线接入点(Access Point, AP)发射功率受限,其服务覆盖的范围也就受限,用户越来越不满族于在固定AP的服务区域内上网,这使得移动终端(Mobile Node,MN)在移动过程中需要在不同AP之间频繁切换换。而IEEE 802.11“先断后连”的思想极大地限制了MN的切换性能,由此带来的切换延时严重影响了通信的服务质量和实时性应用程序的用户体验。因此,如何减少介质访问控制(Media Access Control ,MAC )层的切换延时,改善网络中MN的漫游切换性能,已经成为IEEE 802.11移动切换管理研究中一项亟待解决的关键技术。针对上述问题,本文作了如下3点研究:(1)从理论上分析了传统IEEE 802.11无线网络MAC层的切换机制和各阶段延时,分析出扫描阶段是造成切换延时的重要因素,井对该阶段算法采取了改进措施。(2)基信道优先级和掩码机制,本文设计了减少信道描数算法;在此基础上,改进的选择性邻居图缓存算法运用邻居图原理,将移动终端MN扫描和接入的AP相关信息上传给服务器,版务器根据接收信号强度,用户负载和历史接入数据对邻居AP进行优化排序。然后把AP列表信息缓存到本地,等待客户端移动切换。(3)最后在搭建的共享WiFi系统环境中,使用网络协议分析软件WireShark对移动终端MN在多AP间的MAC层水平切换性能进行分析。经实验测试,与传统的全信道扫描算法对比可知,改进的切换算法在该环境下可有效减少整体切换的延迟,从而满足实时性业务的服务质量要求。
[Abstract]:Since the 9th century, WLAN Wireless Local Area Networks (WLAN) has been rapidly developed and applied because of its wide coverage of wireless communication technology and computer network, flexible wiring, fast transmission rate, and so on. In the WLAN standards, the IEEE 802.11 series standards have become the common standard of the close-range wireless communication technology because of the advantages of simple specification, good compatibility and support from many manufacturers, even though WLAN can provide sufficient bandwidth for mobile applications. However, due to the limited transmission power of wireless access point (APs), its service coverage is also limited, and users are less and less able to access the Internet in the fixed AP service area. This makes the mobile terminal mobile NodeMN) need to switch frequently between different APs during the mobile process. However, the idea of "first breaking and then connecting" in IEEE 802.11 greatly limits the handoff performance of MN, and the resulting handoff delay seriously affects the quality of service of communication and the user experience of real-time applications. Therefore, how to reduce the handoff delay and improve the roaming handoff performance of MN has become a key technology in the research of IEEE 802.11 mobile handoff management. Aiming at the above problems, this paper makes the following three research points: 1) theoretically analyzes the handoff mechanism and delay of the MAC layer of traditional IEEE 802.11 wireless network, and analyzes that the scanning phase is an important factor to cause the handoff delay. In this paper, the algorithm of reducing channel number is designed, on the basis of which, the improved algorithm of selective neighbor graph cache is based on the principle of neighbor graph. The AP related information of mobile terminal MN scanning and accessing is uploaded to the server. The server optimizes the neighbor AP according to the received signal strength, user load and historical access data. Then the AP list information is cached to the local, waiting for the client mobile handover. Finally, the network protocol analysis software WireShark is used to analyze the performance of the mobile terminal MN in the MAC layer level switching between multiple APs in the shared WiFi system environment. The experimental results show that the improved handoff algorithm can effectively reduce the overall handoff delay and meet the quality of service requirements of real-time services compared with the traditional full-channel scanning algorithm.
【学位授予单位】：西安理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TN92

【参考文献】