Research On The Key Technologe For Resource Management In Cognitive Radio Networks

As the fast development of wireless communication technologies, many new kinds of access technologies and diverse requirements of new wireless applications have appeared. This results in more and more spectrum resource is required and the spectrum resource becomes shortage. At the same time, surveys have shown that the spectrum utilization efficiency is vey low under current fixed spectrum allocation strategy, which results in the waste of spectrum resource. As a result, the contradiction between spectrum shortage and low spectrum efficiency has becoming serious. Cognitive radio technology, which can improve the spectrum effiency by allowing secondary users to use the authorized bands without influencing primary users, has been thought as a promising way to solve above contradiction and attracting significant reaserch interests.In cognitve radio networks, resource management is an effective way to protecting primary users and improving the throughput of secondary network. In this dissertation, we study the problems of spectrum sensing, admission control with QoS provisioning in cognitive radio networks, and the power control in cognitive radio networks with femtocells. Correspondingly, we propose several innovative schemes. And then we verify the performance of the proposed schemes by theoretical analysis and computer simulation methods. The main contributions of this dissertation are listed as follows:1) Dynamic control approaches for spectrum sensing based on Lempel-Ziv prediction algorithm are proposed for three different network scenarios respectively. For single user mult-band scenario, the free probability of each band is predicted and spectrum sensing sequence is optimized with the aim of decreasing sensing time and energy consumption, thus to increase data transmission time and the throughput of secondary network. For multi-user multi-band scenario with narrowband sensing technology, the total bands are divided into several groups firstly. Then the number of free bands in each group is predictied, and the number of secondary users for spectrum sensing is optimized with the aim of banlancing energy consumption and the throughput of secondary network. For multi-user multi-band scenario with compressed sensing-based wideband spectrum sensing technology, sparsity level of each band is predicted, and the number of secondary users for spectrum sensing is optimized with the aim of banlancing the energy consumption and sensing accuracy. Finally, simulation results are illustrated to demonstrate that the proposed scheme can significantly improve the spectrum sensing performance.2) We propose dynamic admission control schemes with QoS provisioning in cognitive radio networks based on discrete time Markov chain. Considering the spectrum usage of both primary users and secondary users, we model it with discrete time Markov chain, which is more suitable for practical networks worked in slotted fation. We also analyze status transition probabilities and the forced termination probability. Then to improve the QoS performace of secondary users who have been accessed in system, we propose three admission control schemes by considering the termination probability in different time scale (a time slot, average service time, lifetime of new service). Finally, the simulation results are presented to show that the proposed admission control schemes can greatly improve the forced termination probability of secondary users.3) Energy-efficient resource management scheme is proposed in cognitive radio networks with femtocells. Firstly, we study the interplay of cognitive radio and femtocell, and focus on the power control problem for energy-efficient transmission in cognitive radio networks with femtocells. Secondly, we formulate the power control in standalone femtocells as optimization problem, and propose a gradient-based iteration to find the optimal solution. Thirdly, formulate the power control in collocated femtocells as non-cooperative game, and propose a gradient-based iteration algorithm to obtain the Nash equilibrium solution. Fourthly, we analyze the asymptote of the revenue function of macrocell, based on which we calculate the approximate spectrum utilization price to reduce the computational complexity of the proposed scheme. Finally, simulation results are presented to show the effectiveness of the proposed scheme.