Research On Spectrum Sharing In Cognitive Radio Networks

In the wake of rapid development of wireless communication, the conflict between increasing spectrum demand and spectrum scarcity is becoming more and more serious in recent years. The main reason of spectrum scarcity's status quo is low spectrum utility under the conventional spectrum policy. While promoting spectrum policy reform, people are also pursuing technologies which can realize diverse spectrum sharing and enhance spectrum utility. Due to its distinct advantages, the emerging cognitive radio soon became well recognized as a potential enabling technique for dynamic spectrum access and one of the research hotspot in the area of wireless communication. Cognitive radio network based on cognitive radio is the research highlight currently. In summary, cognitive techniques are still at the early stage of development with many problems and challenges in front both in theory and in practice. This dissertation investigate the spectrum sharing issues in cognitive radio networks with the emphases on spectrum leasing, cooperation pattern of cognitive users and energy-efficient power control. Specifically, our research work consists of the following parts:Investigation is made upon cooperative. communication mechanism based spectrum leasing. Fundamentals behind cooperative communication mechanism based spectrum leasing are that primary user lease spectrum to secondary users. In return, secondary users help primary user improving the QoS (quality of service) of the primary link via cooperative transmission. On the basis of spectrum leasing problem formalization and analysis, we propose a new pricing model based on a novel price definition. We employ Stackelberg game model to analyze the interactions between primary user and secondary users, discuss the game results in different cases and give out simple but effective pricing strategies. Simulation results verify the feasibility and effectiveness of proposed pricing model. Our pricing model provides a new viewpoint and a new standard approach for spectrum leasing. It can serve as a reference model to enrich the forms of spectrum leasing and to promote the development of secondary spectrum markets.Investigation is made upon bargaining problem based cooperation pattern design for cognitive users. Assuming that cognitive users have acquired some resources through competition, we propose a cooperation pattern that is suited for distributed cognitive radio networks based on the idea of mutual relaying. We model the cooperation between cognitive users into a two-user bargaining problem and derive the cooperation strategies based on Nash bargaining solution. By looking into the simulation results, we find that:1) the cooperation willingness of one user depends on the relay qualification provided by the other user; 2) the performance improvement of one user via cooperation depends on both the relay qualification provided by the other user and the channel condition of itself. By means of cooperation, both users can be benefited to reach a win-win situation.Investigation is made upon energy-efficient power control characterized by Stackelberg Equilibrium. All based on the assumption of Nash Equilibrium (NE), previous work on this topic apply network control based methods to adjust equilibrium point so to improve game results. By novelly introducing a more intelligent user, we employ Stackelberg Equilibrium (SE) to represent the game result. We prove that SE can improve the result obtained by NE without network control. Simulation results show that SE is more efficient that NE in that the utilities of all user get great increase in SE than that in NE and the transmit power of each user is remarkably decreased. From the cognitive perspective, the proposed viewpoint and scheme can be seen as a pratical case in which cognitive user utilizes cognitive information to improve the system overall performance.