Study Cognitive Radio Spectrum Sharing Game Theory Methods

With the continued expansion of wireless communication services, fixed spectrum allocation mechanism of the spectrum have been unable to meet their needs. CR technology is a communication technology. Because of CR technology, wireless spectrum environment can be perceived and unused spectrum in the time domain, frequency domain and the airspace can be searched, limited spectrum resources can be fully utilized. The use of CR technology that improved the utilization of unlicensed bands of spectrum eased congestion predicament of non-authorized band and optimized the allocation of overall spectrum resources.Spectrum sharing involves many participants-cognitive user's interests. There are interactions between participants. Game theory provides a general mathematical method on analysis the situation involving multiple participants and their decisions affect each other's interests. Therefore, using game theory to study the problem of spectrum sharing between users is an effective way.This article established a spectrum sharing model based on market equilibrium. The spectrum sharing relationship between secondary users and primary users was modeled as the supply and demand relationship of goods in economic markets. Secondary users competing leased spectrum of the primary user. Under the constraints of the existence of Nash equilibrium, secondary user's benefit function was established. Spectrum demand of a secondary user is affected by other user's demand and spectrum price. By take into accounting both their own needs and free spectrum efficiency, primary user's function based on effective mechanisms of self-restraint was established, to ensure primary user's price is the price that the spectrum demand of secondary users is equal to the sum of free spectrum size of primary user system. Numerical analysis shows that the model can effectively solve the problem of spectrum sharing between secondary users with primary users, achieving spectrum market's supply and demand balance.The actual situation of cognitive networks was considered. Because of non-transparency of secondary user's information, price-based distributed dynamic spectrum sharing model was established. Secondary user can change the size of spectrum for demand. Based on feedback information of spectrum efficiency, Secondary users can adjust their strategies to close to the optimal strategy maximizing their benefits. Simulation results show that distributed dynamic algorithm can achieve fast convergence of the state in certain adjustment areas. Numerical results also show that Nash equilibrium is a balanced solution that static game and dynamic game both want to achieve and a stable state of spectrum sharing.Because of secondary users' selfishness, the overall benefits can not be maximized. Therefore, primary users and secondary users of spectrum sharing scheme based on the alliance was proposed. Analysis showed that, compared with non-cooperation scheme, the strategy based on cooperation sharing of spectrum makes the system whole benefits improved. And cooperation risk analysis show that the pricing of the model can constrain secondary users to maintain cooperation.