Joint Scheduling and Cooperative Sensing in Cognitive Radios: A Game Theoretic Approach

In cognitive radio systems, cooperative spectrum sensing in the physical layer is highly desired to detect the primary user accurately and to guarantee the quality of service (QoS) of the primary user. Due to the energy consumption in sensing the channels, the selfish users may not be willing to contribute to the cooperative sensing while they want to occupy more idle channels observed. To deal with this problem, we propose in this paper a game theoretic approach which will advocate users to spend power to sense the channel by using the access opportunity in the MAC layer as a payoff. In this protocol, the users who sense the channel are given higher priority to access the idle channel and meanwhile, the multiuser diversity in the MAC layer is exploited to increase the throughput for cognitive systems. The expressions for the average throughput and consumed power for a single user will be derived and then Nash equilibrium will be studied for the game model. It will be shown that the game will be characterized by the prisoner´s dilemma. To guarantee the fairness and achieve higher throughput, we will design an evolutionary game protocol in which the Nash equilibrium can be dynamically changed based on the behaviors of cognitive users. Simulation results will show that the proposed protocol can achieve fairness and efficiency for cognitive users.