Simulation Research On Preamble-based Interference Detection And Cancellation

With the rapid development of wireless local area network (WLAN), thecompetition of terminals to access the wireless channel is becoming increasingly fierce.The existing channel access method: request to send/clear to send (RTS/CTS) cannoteffectively solve the access problems in the high concurrent network. In order topromote the network concurrency, and solve the problem of bi-directional linkinterference caused by the exchange of control frames in high concurrent networks, wepropose a technique of preamble-based interference detection and cancellation(PID&C). PID&C is a technique of using the strong self-correlation property ofpreamble and the semantic dependency of control frames in WLAN to detect andestimate the interference frame, then reconstructing the interference, linearlycancelling it.The research work in this thesis is affiliated with the national Natural ScienceFoundation project “Research on Predicted Signal Detection/Cancellation and theConcurrent Access Control in Wireless Network”. First, the bi-directional linkinterference problem is introduced, which caused by control frames in the concurrentreceiving of hidden terminals and the concurrent transmitting of exposed terminals,and the technique of PID&C is presented. Then the principle of PID&C is introducedin detail, which mainly include the basic principle of direct sequence spread spectrumtechnology (DSSS), the principle of synchronization in spreading code s, carrier andtiming error, and the principle of interference detection and cancellation. Based onthese principles, the simulation model of PID&C is established, which is built byadding PID&C blocks to a DSSS model. In the final, the performance of PID&Cmodel is researched in different Signal-Interference Ratio (SIR), frequency offset andtiming error. The result shows PID&C can detect and cancel the interferenceeffectively.