Research On Key Techniques Of WLAN And IP QoS

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...