基于站的IEEE 802．11b／g无线局域网快速切换方案

由于实时应用对传输时延和抖动相对敏感，为减小WLAN切换过程对实时应用的影响，研究了WLAN切换过程的3个方面：触发切换，AP选择和快速切换算法．充分考虑到方案的可部署性和可扩展性，提出了一个以终端站为中心的快速切换方案．设计实现了基于动态阈值的切换触发机制、基于探寻时延的AP选择机制和信道区分选择结合动态缓存的快速切换算法．该方案完全在站上实现，不需要AP的配合或者对协议进行修改，因而具有良好的鲁棒性和可部署性．通过在实际的hotspot WLAN环境下测试和分析，该快速切换方案有效地减小了切换时延，同时使用户获得的实时应用网络性能有所增强．

Station based fast handoff solution for IEEE 802. 11 b/g wireless LANs

Real-time applications are sensitive to conditions such as transmission delay and jittering.To cut down on the influence generated by the WLAN handoff process,three parts of WLAN(wireless local area networks)handoff:handoff triggering,access point selection and the fast handoff algorithm are investigated.A fast handoff solution totally based on the station is proposed and it is composed of three parts:a handoff triggering mechanism based on dynamic threshold adjustment;an AP selection criterion based on probe delay;a fast handoff algorithm with differentiated channel selection and a dynamic cache.The station based solution is independent with AP's collaboration and avoids any changes in the IEEE 802.11 protocol.It is robust and has very good extensibility.Through tests and evaluation in a hotspot WLAN,the solution effectively reduces handoff latency and user experience of real-time applications is enhanced.