Research Of MAC Protocol Based Environment-cognizing Wireless Mesh Networks

Recently,broadband wireless communication becomes the hot research of communication area.This thesis studies the broadband wireless network based on the environment cognition,known as cognitive wireless mesh network,which applies the cognitive technology into wireless mesh network. It is a new broadband wireless network having environment cognition,high spectral efficiency,high flexibility and wide coverage.In this thesis, we conduct the research of wireless mesh network mutli-channel protocol,and then mainly study the MAC protocol based on the frequency sensing,channel quality sensing and route sensing.Firstly,we introduce the Multi-channel MAC protocol and Dynamic Channel Assignment in detail and then analyze their performances through simulation,based on introduction of the MAC protocol of wireless local area network and wireless mesh network.Then,we present the mathematical model of Multi-channel MAC protocol of wireless mesh network,including the Bernoulli model and M/M/K queuing model.We take a DCA protocol for example to validate our model.The experiments show that simulation results match the analytical results very well,which indicates that our model is accurate.Based on the research of wieless cognitive radio technology,we introduce it into the MMAC and DCA protocol in wireless mesh network and propose the CWMN-MMAC and CWMN-DCA Multi-channel MAC protocol based on the frequency cognition,in which we add a dedicated control window to broadcast the frequency information.We build the channel use ratio model of prime user,the dynamical channel detection model based on random cognitive method,and then obtain the mathematical expression of network saturation throughput.With regard to the activity of prime user,we analyze the channel use ratio and the interference introduced by the secondary user. For the co-frequency interference,we add the channel coginition before the channel negotiation and propose the Channel Cognitive Multi-channel MAC protocol.The simulation results show our method is effective lighten co-frequency interfence. Due to the effect of fading and dispersion,channel quality varies as the time change,which has the significant impact on the network performance. Thus,we build the MAC protocol model based on the Gaussian channel and fading channel.Based on the study of rate-adaptation mechanism,we study the performance of rate-adaptation MAC protocol and propose the Oportunistic DCA protocol,which effectively improve the network throughput.Based on the research of Multi-path Route AODV protocol,we build the multiple next-hop MNH-MMAC protocol based on the introduction of the idea of next-hop in route into MAC layer and NDL-AODL route protocol based on the improvement of AODV protocol.Then we compare the NDL-AODV+MNH-MMAC protocol and AODV+MMAC protocol through simulation.The simulation results show that NDL-AODV+MNH-MMAC can improve the network performance under the relatively scare frequency environment...