Study On Access Protocol And Dynamic Spectrum Allocation Algorithm In Cognitive Wireless Mesh Networks

With the popularity of wireless communications applications, the confliction of the limited radio spectrum resources and the demand of the broadband services become increasingly prominent. In order to ease the resource and this contradiction between the needs of wireless communication, generally we got two ways: The first one to seek a more efficient modulation mechanism, enhance the spectral efficiency; the second one to improve the existing spectrum allocation method, through the opportunistic spectrum access, and efficient use of resources.Cognitive radio is a technology to change the traditional way of resources allocation from improve the spectrum efficiency. as the key technology which is focused recently, makes the spectrum more rational allocation of resources and efficiently., cognitive radio is based on such kind of fact: Spectrum lack is not due to lack of spectrum limited itself, but because of the result of the fixed spectrum allocation methods. Cognitive radio as an intelligent spectrum sharing technology, relying on the support of artificial intelligence, perception wireless communications environment, according to a certain degree of learning and decision-making algorithms, real-time adaptive changes in system operating parameters, dynamic detection and effective use of idle spectrum, in theory, allow the time domain, frequency domain and the airspace on a multidimensional reuse of spectrum and shared.Cognitive radio is a technology to change the traditional way of resources allocation from improve the spectrum efficiency. as the key technology which is focused recently, makes the spectrum more rational allocation of resources and efficiently., cognitive radio is based on such kind of fact: Spectrum lack is not due to lack of spectrum limited itself, but because of the result of the fixed spectrum allocation methods. Cognitive radio as an intelligent spectrum sharing technology, relying on the support of artificial intelligence, perception wireless communications environment, according to a certain degree of learning and decision-making algorithms, real-time adaptive changes in system operating parameters, dynamic detection and effective use of idle spectrum, in theory, allow the time domain, frequency domain and the airspace on a multidimensional reuse of spectrum and shared.1) Based on cognitive wireless MESH network structure and characteristics proposed a set of communications links solution. In the distributed network environment, use of cluster header in each sub-clusters center to connect each cluster as one.2) Base on the innovation 1 and combine the traditional CSMA/CA access mechanism, proposed an access mechanism which can be used under the cognitive radio environment. When the data is exchanging, each node exchange the CO-RTS/CO-CTS to understanding of accessible channel information, and work out the data channel which can be used by both side, and use the competition to avoid interference, and through performance simulation can find in a specific network conditions, this protocol algorithm can achieve a good results.3) Through a comprehensive analysis of the access mechanism, we can get to a conclusion that it got a problem of the Cog-Mesh network channel allocation in the cluster, and the low efficiency of the utilize of spectrum, so we proposed a fair and efficient dynamic spectrum allocation strategy, and comparing the performance of simulation test and evaluation.