Research On Power Control Based On Game Theory In Cognitive Radio

Recent years, wireless communications are developing rapidly and going to play an important role in people's lives and social development. Radio frequency is a kind of nature resource. However, the static allocation of spectrum leads to lack of wireless resources, while the utilization of licensed spectrum is pretty low. Without occupying the unallocated spectrum, the new Cognitive Radio technology improves the spectrum efficiency by communicating in wireless spectrum holes after sensing the environment, so it is considered the best technology to solve the above contradictions.Power control is one of the key technologies in Cognitive Radio. If the transmission power is properly controlled, Cognitive Radio system can not only ensure the normal communication of authorized users, but also meet the needs of cognitive users. In this thesis, distributed power control based on game theory in Cognitive Radio is studied. In order to achieve a better optimization of transmission power, efficient communication should be ensured and fairness among cognitive users should be considered. Works and innovations are as follows:First, based on the non-cooperative power control game (NPG) proposed by David Goodman, an improved pricing function was adopted and a power control game algorithm suitable for cognitive radio system was proposed. Then the existence and uniqueness of the Nash equilibrium were proved for the proposed algorithm. The simulation results show that the proposed algorithm, which compared with several classical distributed algorithms, not only reduces the transmit power and improves the user's utility but also speeds up the convergence. So, it fits cognitive radio system for high demand of time-delay character.Second, based on the cognitive model in coalitional game, a distributed power control game for efficient cooperation in cognitive radio network was proposed. Then the existence and stability of coalition formation were proved for the proposed algorithm. The algorithm was divided into three steps; decreasing computational complexity of coalition formation, formatting coalitions with Merge & Split rules and controlling power in efficient manner. Simulation results show that the proposed algorithm not only reduces the computational complexity, decreases the transmission power, but also extends the battery life and obtains a higher throughput.Then, a summary is given at the end of this dissertation, where the future research directions are also pointed out.