Research On Cooperative Spectrum Sensing Technology Based On Energy Detection

With the explosive growth of new wireless technology and user equipment, demand for the spectrum becomes more and more urgent.The existing distribution plan of fixed spectrum has caused a great waste of spectrum resource. In order to solve the contradictions between spectrum resource scarcity and spectrum under-utilization, cognitive radio has been proposed as a new technology. The key component of cognitive radio technology is spectrum sensing, a great challenge of carrying out spectrum sensing is the hidden terminal problem. Due to the existing hidden terminal problem, secondary user may fail to think that the primary user is not using the spectrum at this moment, and then will access the spectrum hole and cause interference to the primary user. In order to solve the hidden terminal problem in cognitive radio, the technology of cooperative spectrum sensing has been put forward.In this thesis we first analyze and summarize the concept of cognitive radio and several typical methods of spectrum sensing, then focus on analyzing energy detector. Taking account of relevant problems about the fixed threshold of energy detector and asynchronous cooperative sensing, we propose some relevant optimization algorithm and simulate these algorithms. The main contribution is as follows:Firstly, given that the fixed threshold of energy detector dose not only affects detection probability, but it also influences false-alarm probability in cognitive radio network. Therefore, the fixed threshold has not been able to satisfy the need of cognitive network, the thesis hereof has proposed an optimal cooperative sensing optimization algorithm based on threshold dynamic adjustment. According to different geographic location of secondary user, this algorithm gives different threshold, and then the number of optimal sensing nodes is obtained. In this thesis, we simulate the optimization algorithm, the simulation results show that the system’s detection error probability has been reduced and thus reduces the interference to primary user.Secondly, this thesis has analyzed the process of asynchronous cooperative sensing, and then proposes an asynchronous cooperative sensing algorithm based on trust value. The core point of the algorithm is that fusion center not abandons the later reports but weighed them with a smaller contribution value. After the completion of every round, some malicious secondary user will be discarded. In this thesis, we simulate the optimization algorithm, the simulation results show that this method can effectively improve the whole cognitive network’s performance.At last, in this thesis, we use the MATLAB simulator to evaluate the performance of the above-mentioned optimization algorithm, and then compare and analyze the simulation results.