Research On Radio Resource Management Based On Relaying Cooperation In Cognitive Wireless Networks

Following with the flying development of the new generation wideband wireless communication technology, the conflict emerges more clearly between the request on excessive wireless service and the limit radio resource, which includes how to improve spectrum efficiency, and how to enhance the network performance such as capacity and enlarge the coverage. These problems will be the bottleneck of development of the new generation wideband wireless communication technology. However, the cognitive relay networks, which is the cognitive wireless network based on relaying cooperation, improves the system performance by diversity gain of relaying cooperation from the point of view of the radio resource management. This dissertation studies the basic theory and key technologies on this subject, which includes the schemes and strategies for the radio resource management and optimization in cognitive relay networks, from the system architecture, spectrum sharing, improving system capacity and coverage. The main items are listed as follows:First, the researches on cognitive relay networks are coordinated to analyze the requests on cooperative scenarios and key technologies. For the instruction from the technology framework, with consideration of the underlay spectrum sharing and decode-and-forward cooperation, the probability density function and cumulative distribution function of the signal-to-noise ratio of the cognitive destination node are derived based on the Nakagami-m channel model, which is more living than Rayleigh channel model. The impact on the outage probability from the channel fading exponent is analyzed. Then, the close formula of upper bound of the outage probability is derived, which can be the optimization goal and rule of performance estimation. Moreover, to support the cooperation between primary users and secondary users, the in-band control channel scheme is investigated based on the time slot division and network coding.Second, the problem is investigated on how to improve the spectrum efficiency in cognitive relay networks. Under the constraints of the underlay spectrum sharing, the cooperative spectrum sharing scheme is proposed based on cognitive sub-carrier division in the scenario in which the secondary users relay for the primary users. By relaying for the primary users, the secondary users can access the authorized spectrum as the reward. In this way, one side, the outage probability of primary users is reduced; the other side, the transmission request of secondary users is satisfied. In Chaper.4, under the constraints of the scenario, the outage probabilities of primary users and secondary users are derived respectively, and then the method of computing the ratio of cognitive sub-carrier division is designed. Based on these work, the cooperative spectrum sharing scheme based on cognitive sub-carrier is proposed.The last, for request on improving the capacity of cognitive relay networks, under the constraints of outage probability of secondary users and interference temperature of primary users, the cognitive relay selection is investigated to minimize the total transmission power and maximize the network capacity in two-hop scenario. The close formula is derived for power optimization. Then, the strategy for cognitive relay selection is proposed based on the power optimization. The proposed scheme is more suitable for cognitive networks than traditional relay selection strategies, because the reduction of interference to primary users is considered. Furthermore, the strategy is extended to cognitive multi-hop scenario to enlarge the coverage of cognitive relay networks. The route problem in the multi-hop scenario of cognitive relay networks is modeled as the multi-hop relay selection problem. Then, the relay selection strategy with multi-hop is proposed based on power optimization. Compared with the traditional route selection strategy, the proposed one reduces the complexity from O(TK) to O(K·T2) based the shortest path algorithm in the graph theory.