Power Control Algorithm For Cognitive Radio Based On Game Theory

Cognitive radio technology can dynamically re-use the frequency bands assigned to the authorized user and other idle freqency bands to enhance the utilization of existing spectrum resources. Cognitive radio technology based on the spectrum sharing has become a new study direction of wireless communications. Its research involves many aspects, and power control of cognitive radio is currently a research focus.Game theory is the theory using a rigorous mathematical model to solve the terrible conflict of reality. Because conflict, cooperation, competition and other behaviors are common phenomenons in reality, game theory is applied to wide fields, such as economic, communications and military and so on. In multi-user cognitive radio system, he user would like to increase the transmitting power to get more SIR (signal to interference ratio), but it will increase the interference to others. Therefore, power control of cognitive radio system can be seen as an issue of non-cooperative game.In this paper, we consider the situation that the user of the cognitive radio system can only user the spectrum resources when them are not occupied by the authorized user. Therefore, the power control algorithm should not only consider how to further reduce the transmission powert to save power and minimize interference to other cognitive users, but also consider how to improve the convergence speed. Based on the above considerations, a new power control game algorithm was proposed based on CDMA CR system by designing an effective cost function. The uniqueness and existence of the Nash Equilibrium was proved for the scheme. Simulation results show that the lower powers are obtained with faster convergence compared with other four algorithms while the SIR (signal to interference ratio) is satisfied.