Study On MAC Protocol In Cognitive Wireless Mesh Networks

As a flexible, reconfigurable and reprogrammable intelligent communication technology, cognitive radio scenes the real-time wireless transmission environment, searches the high-quality free channel, and adaptively adjusts its operating parameters, such as transmission channel , transmit power, modulation mode, transmission rate etc, which provides reliable communication and efficient spectrum use. Wireless Mesh network has the advantage of the Ad Hoc network and fixed infrastructure network, which provides flexible deployment, broad bandwidth, easier configuration, good fault-tolerant capability etc. On the other hand, disadvantage is high node distribution density may result in network capacity reduction. In addition, the 2.4GHz ISM band used by wireless Mesh network infrastructure has been shared by a large number of WLAN and Bluetooth users, which may cause the channel blockage problem. Cognitive radio combined with the wireless Mesh network uses the spectrum sensing function of cognitive radio, and sets the free band which is temporarily unused by the primary users as the operating band of the wireless Mesh network. The node density per transmitting channel is reduced. Network throughput and the quality of transmitting channel are both improved. The paper focuses on MAC protocol which based on spectrum sensing and corresponding sense techniques, the main contents are:1) Analyzing and summarizing the basic characteristics of cognitive radio and wireless Mesh network; discussing the conferencing technology, key technology and infrastructure of the cognitive radio and wireless Mesh network.2) Based on the Mesh network and MMAC protocol, according to the two-stage strategy of the quiet period management specified in IEEE802.22 protocol, a distributed multi-channel Cognitive Wireless Mesh Network MAC (CR-MMAC) protocol is proposed Two-stage sensing mechanism and distributed consultation mechanism are integrated into MMAC protocol. Free spectrum bands are used for data transmission and reservation mechanism is used during the data channel consultation stage of ATIM window in MMAC protocol. This avoids the competition collision caused by the cognitive nodes which choose the same channel when reusing the CSMA/CA protocol in the subsequent data transmission stage. Performance analysis and simulations are tested in specific network condition.3) Whether the spectrum sensing is efficient and accuracy directly relates to the performance of Cognitive Wireless Mesh Network MAC protocol. Studying the two-stage sensing mechanism of CR-MMAC protocol, a cycle stationary detection algorithm based on peak-to-average power ratio judgment is proposed, and the sensing performance is simulated and evaluated.