A Markovian approach to design criterion of cooperation in Cognitive Radio network

Cognitive Radio(CR) is a promising technology to fully utilize the constrained spectrum, and cooperative spectrum sharing in cognitive network is regarded as an important and challenging issue. This paper considers that primary user(PU) is willing to coexist with secondary users(SUs) once it is paid and its Signal to Interference-plus-Noise Ratio(SINR) is assured. Since the spectrum state is not deterministic, an 8-state continuous time Markov chain(CTMC-8) based on the scenario of 1PU and 2SUs is built to predict the reward and cost of PU in a future period. The formula of expected profit difference(EPD) between cooperative state and uncooperative state is deduced to help PU decide whether to permit the cooperation in a future period. The SINR of relay user is also assured in a way in order to prevent the cooperation from being badly affected. Simulation shows the predictions of the profit before the cooperation and after the cooperation respectively, and shows that the model can effectively help decide whether to permit the cooperation in different location distributions.