中文摘要：

目前的城市轨道交通CBTC车地通信系统大多采用无线局域网技术。针对同时存在无线自由波和漏泄波导车地通信技术的CBTC无线局域网车地通信系统,提出一种基于位置的无线局域网切换机制。在无线自由波覆盖区段,移动台在确定的位置直接发起重关联请求,而不需要进行探询扫描新AP的过程。而在漏泄波导覆盖区段,通过改变移动台扫描的信道数和最大信道扫描驻留时间,同样明显减小了切换时延。该方法不仅适用于无线自由波的覆盖区域,也可以应用于漏泄波导覆盖的区域,能够减少CBTC车地通信系统中的切换时延。

英文摘要：

Wireless LAN technologies are adopted in most train-wayside communication systems in CBTC.A location based handover scheme is proposed in this paper for the CBTC system where both wireless free space transmission and waveguide transmission exist.In the section where wireless free space transmission is used,the mobile train can initiate the re-association request directly without the process of scanning and the stage of probing.In the waveguide transmission section the number of scanning channels,the size of initial contention window and the maximum probe holding time in a channel can be adjusted to decrease the handover latency.The simulation results show that the proposed scheme can reduce the handover latency greatly for wireless LAN networks in the CBTC system.