Research On Cooperative Spectrum Sensing And Dynamic Spectrum Access Algorithms For The Cognitive Radio Networks

With the rapid growth of the wireless communication service, the valuable and limited spectrum resources become more scarce. The studies show that static spectrum management mode gives rise to the low average utilization ratio of most licensed spectrum. Cognitive radio is considered as the efficient method to improve the utilization of the spectrum. Spectrum sensing and spectrum sharing of the CR networks are very important research issues. The main function of the spectrum sensing is to detect the spectrum holes provided to CR users who coexist with the PUs. The essence of the spectrum sharing is the dynamic spectrum access, which have an effect on the performance of the CR networks such as network throughput, spectrum utilization, interference, etc. This paper focuses on the deeply research of the cooperative spectrum sensing and dynamic spectrum access technology.First of all, we discuss the research background, significance and research actuality of the CR. Then, we emphasize on the development status of the spectrum sensing technologies and the spectrum sharing.Followed by the analysis of multiple cognitive node cooperative detection schemes, we propose a cooperative sensing scheme based on energy-constraint, according to the influences resulted from the signal to noise ratio and cooperative nodes. The scheme takes into account the energy consumption of each node. The residual energy and signal to noise ratio are used as the parameters to select the node. The nodes that hold the high residual energy will have more opportunities for cooperation. In order to prolong the detection lifetime of the CR network, we combine the high SNR and relative low SNR nodes to perform dynamic cooperative sensing. The simulation results show that the proposed cooperative sensing scheme can efficiently extend the detection lifetime while improving the opportunities of low SNR nodes to participate in cooperation.In order to guarantee the quality of service for spectrum handoff, a multi-hop spectrum handoff algorithm is presented for the centralized cognitive radio networks, in which spectrum heterogeneity has been taken into account in the fifth chapter. At first, a user mobile model is developed to predict the usage time of allocated channel. Secondly, different processing approaches are designed for different types of nodes in the routing path. Finally, the cognitive radio base station selects the optimal path according to the predicted shortest path time and time stamp. Simulation results reveal that the proposed multi-hop routing algorithm can considerably decrease the handoff blocking probability, and the channel utilization is also enhanced. Moreover, further simulation results show that cognitive radio node’s mobility plays an important role in the channel available usage time.Finally, we summarize the full text and point out the further research work.