Research On Joint Optimization Assisted Spectrum Allocation For Cognitive Radio System

With the flourish of the mobile Internet, the requirement of wireless access rate is growing larger and larger. However, the available frequency resource is becoming more and more scared. As an intelligent spectrum sharing technology, cognitive radio can reuse spectrum resource, which develops a new method of one's own to resolve the wireless communication problem that how to increase the utilization of the spectrum resource. Accordingly, as the key technology of cognitive radio, dynamic spectrum allocation has turn to be a hot topic in wireless communication field.Based on the research on the structures and key technologies of cognitive radio systems, the dissertation selects maximizing the utilization of the spectrum resource as the optimization objection, and a series of researches on joint optimization assisted apectrum allocation for cognitive radio system are carried out:1. A joint design of spectrum access and power control algorithm is proposed in underlay spectrum sharing model. According to the violation of primary user's interference constraint and secondary users'QoS constraint, the algorithm adjusts the number of secondary user that are permitted to share spectrum. Simulation results show that the algorithm achieve tradeoff between utilization of the spectrum resource and the time that admission control costs.2. Under overlay spectrum sharing model, aiming at OFDM based cognitive radio systems, a multiuser spectrum allocation algorithm with fairness consideration is proposed. The algorithm considers the multiuser spectrum allocation problem as convex optimization problem, and then finds the optimal sub-carrier and power allocation via Lagrange dual theory. Simulation results show that the algorithm improve the fairness of the system effectively. For the sake of practical application and reducing time cost, a low complexity multi-user spectrum allocation algorithm is proposed. The algorithm accomplishs resource allocation in two steps: the algorithm first carries out sub-carrier allocation according to secondary users channel state, and then carries out iterative waterfilling power allocation. Theoretical analysis and simulation result show that the proposed algorithm can remarkably reduce the computational complexity at the cost of little sum capacity loss.3. A joint spectrum allocation and optimal cooperative sensing algorithm based on confidience function is proposed. The algorithm introduces confidence function to reflect the confidence level that spectrum module believes the sensing result, and then obtains the approximate optimal sub-channel and power allocation and sensing thresholds via iteration. Simulation results show that the proposed joint design outperforms traditional separate design in the case of imperfect sensing.4. Aiming at multi-hop cognitive radio network, a joint design of spectrum allocation and routing is proposed. In the proposed design, each link first chooses optimal working channel and transmission power to maximize link capacity, and then otains the benefit of each path with consideration of congestion control and hops, and the optimal path can be slected based on this. Simulation results show that the proposed design remarkably improves the network throughput, and is more conformable to cognitive radio environment.5. The cognitive radio spectrum allocation simulation platform is devised in the thesis, and the development of correlative FPGA and DSP program and display control soft are accomplished, farther the process of the implement of spectrum allocation algorithm is discussed in in detail.