Research On The Cooperative Spectrum Sharing In Cognitive Radio Networks

With the rapid advance of the process of information society and the explosive development of wireless communication industry in recent years, the contradiction between the ever-increasing wireless service and the ever-decreasing radio spectrum resources becomes more and more obvious. Cognitive radio (CR) technology, which aims at easing this contradiction and breaking the traditional mechanism in the management and usage of spectrum resources, has gained a significant development in the past decade. This technology becomes the foundation of dynamic spectrum management (DSM). Under this technical framework, unlicensed radio systems are able to reutilize the licensed spectrum bands of other wireless systems, which will reduce the vacant licensed spectrum bands in time and space domain, and enhance the frequency utilization efficiency. The spectrum resource unbalance among SUs in CRNs is much more severe than in traditional wireless communication networks. Moreover, the traffic demands of SUs also can be quite different. Obviously, an important question is naturally led to, i.e., how to handle the optimal allocation of unbalanced resources, especially spectrum resources, within the CRNs to fulfill the network target and heterogeneous traffic demand from different users. This problem is also one of the greatest challenges of the specturm sharing in CRNs, which has drawn a lot of attention.Cooperative technique has been widely used in various types of wireless communication networks, including CRNs. By extending the concept of cooperative networks, and making use of the ability of CR terminals to self-adaptively connect to multiple coexistence radio systems, we can construct a CRN, i.e., cognitive radio relay networks (CRRNs), which are important extensions of CRNs. CRRNs combine the advantages of cooperative communication technologies and CR technologies, which can solve the problem of the optimal allocation of unbalanced resources to a great extent.However, up to now, the theoretical research on spectrum sharing in CRRNs is still not enough to work through challenges which arise in the process of realizing wireless personal communication5A (Anyone, Anytime, Anywhere, Anydevice, Anything) future. Based on this consideration, this paper researches the cooperative spectrum sharing in CRRNs to provided theory basis and instruction for the radio resource management in the next generation wireless communication networks. According to different types of participants, this paper studies the cooperative spectrum sharings among SUs, the cooperative spectrum sharings between PUs and SUs, and the cooperative spectrum sharings between a PS and a SS in CRRNs.The second chapter of this paper studies the cooperative spectrum sharing among SUs. To be specific, we take relay selection and power allocation in SSs for example. Different from other researches in this field, we consider the performance guarantee of the user which acts as the relay. The system model takes a three-node cooperative relay network as the fundament and considers two typical scenarios, where the relay node involves relay diversity and dual-hop transmission respectively. On the premise of meeting the quality of service (QoS) requirements of the source and the relay, our goal is to maximize the system throughput subject to PU received interference power constraints, and total transmit power constraints on the source and the relay. Correspondingly, an optimal relay selection and power allocation problem is formulated. The proposed optimal approaches can be solved in two steps:first implement optimal power allocation between the source and each relay candidate, and then search the most profitable relay which makes the system throughput maximized. For a given relay candidate, the power allocation optimization is convex in the first scenario and can be optimally solved through the dual method. However, the power allocation optimization in the second scenario appears to be non-convex and hence hard to be tractable. To tackle this, an algorithm using dual method in combination with search method is proposed to achieve the optimum. Moreover, in order to reduce complexity of repeating the optimal power allocation procedures at all the relay candidates while maintaining reasonable performance, we also develop a suboptimal relay selection approach based on the maximum PU received interference power threshold. Furthermore, simulation results are presented to illustrate the performance of proposed schemes, and the proposed schemes can protect the fairness between the source and the relay effectively.Than, the third chapter of this paper studies the cooperative spectrum sharing between PUs and SUs, and to be specific, takes power allocation and spectrum allocation in time domain between a PU and a SU for example. This paper mainly considers energy-limited wireless networks such as mobile ad-hoc networks (MANETs) or wireless sensor networks (WSNs). These networks aim at maximizing the network lifetime rather than maximizing the system transmission performance or minimizing system energy consumption, in order to realize uninterrupted data transmission without replenishing batteries frequently. In the scenario under consideration, the SU is allowed to relay PU signals in exchange for transmission opportunities, i.e., after the PU finishes its data transmission, the SU can access the licensed spectrum in the remaining transmission cycle. Different from other researches in this field, we focus on the energy supply-demand relationship in the system, and assume there are two virtual energy agencies corresponding to the PU and the SU, and these energy agencies have the right of disposal of their corresponding users’energy. By modeling the users as energy buyers, and the energy agancies as energy sellers, we can reduce and balanced the system energy consumption during each transmission cycle according to the minimum cost (MIC) criteria under appropriate energy prices. Thus, the joint power and bandwidth allocation problem between the PU and the SU can be solved based on the dual method and Newton’s method. And this paper proposes a cooperative spectrum sharing scheme based on energy price. The simulation results are presented to illustrate that the proposed scheme can significantly prolong the working time of the energy-limited nodes in CRRNs and increase the system spectrum efficiency. However, how to generalize this scheme to the scenarios which contains multiple PUs and SUs is still a unsolved problem.At last, the fourth chapter of this paper appropriately extends the participants of cooperative spectrum sharings, and considers the cooperative spectrum sharing between a PS and a SS. In spectrum leasing markets, there exists a lot of white spaces and grey spaces in the spectrum bands kept by the PS, which reduces the spectrum efficiency. This paper designs a hybrid spectrum sharing mechanism which is different from traditional spectrum leasing mechanisms, and allows SUs to share the spectrum bands kept by the PS through the OSA to further increase the spectrum efficiency. Moreover, this paper considers the interference to PUs caused by the SU spectrum sensing errors in the the spectrum bands kept by the PS, and then in order to compensate the system performance loss caused by the interference, proposes a hybrid bandwidth allocation scheme based on the equilibrium price theory. Furthermore, an iterative algorithm for distributed implementation of our scheme is also proposed. Simulation results illustrate that the hybrid bandwidth allocation scheme have an advantage over the OSA and the spectrum leasing in spectrum efficiency, and prove that the PS and the SS can both get higher profit under this mechanism.