Research On MAC Access Technology Based On Link Demand In Cognitive Wireless Mesh Networks

Wireless mesh networks attract extensive concern of the industry with its high bandwidth, high rate, networking flexibility, high network coverage, etc. But with the increasing of users and business, the limited spectrum resource becomes a bottleneck of wireless mesh networks’development. Cognitive radio technology allows users to get access to networks flexibly by opportunistic way, which alleviates the situation of spectrum shortage. Cognitive radio technology is applied to wireless mesh networks in order to provide users the better wireless service.In this paper, according to the feature of cognitive wireless mesh networks, we study the problem of MAC access control based on link demand in cognitive wireless mesh networks.Considering some constrains synthetically, including variability of users’ available channels, the restrictions on the number of radios equipped with, and so on, networks interference link and potential interference link are defined, and by quantifying communication power control levels, the joint power control and channel allocation model is established. Aiming at maximizing network capacity, channel allocation algorithm based on differential evolution is presented, and the corresponding encoding rules and constraint control mechanism is designed to ensure the effectiveness of individuals and the rapid convergence of the algorithm. The simulation results show that the network performance of differential evolution algorithm reaches or is near to the global optimal. Further, combined with the characteristic of distributed cognitive wireless mesh network, with the links which need to transmit data acting as game players, the potential function and utility function of game players are defined, and the channel allocation algorithm based on potential game is put forward. Each link selects channel and transmission power level dynamically, in order to maximizing network capacity, improving the utilization of spectrum and reducing the network interference. The simulation results indicate that the network performance of the channel allocation algorithm based on potential game is near to the global optimal, and the network interference is lesser.As for prioritized business, on the foundation of CSMA/CA mechanism, a MAC access control mechanism based on priority backoff is proposed. The corresponding backoff rule is designed and higher priorities business waits for shorter time and can get transmission more quickly. The simulation results indicate that, the MAC access control mechanism based on priority backoff designed in this paper enhances system throughput, and reduces access delay and end to end delay with low collision rate and package loss rate.