Robust Dynamic Spectrum Access in Uncertain Channels: A Fuzzy Payoffs Game Approach

Despite the great promises in next-generation wireless communications, dynamic spectrum access (DSA) remains still as a major challenge in uncertain environments, e.g., varying unknown channels. Existing popular schemes, i.e. potential game approaches, rely on the definite reward and a greedy strategy, which become unfortunately invalid in such varying and uncertain scenarios. In this paper, we propose a robust fuzzy-game approach to combat inherent channel uncertainties. Rather than the definite reward, we first project the decision space to another fuzzy-logical space and thereby characterize the varying uncertain information with the fuzzy numbers. Thus, the sensitiveness to random fluctuation in definite rewards would be alleviated. On this basis, we formulate DSA in uncertain channels as a centralized fuzzy payoffs game (FPG). We then develop a novel fuzzy-learning algorithm to achieve the optimal network throughput even in face of uncertain information, with which the network controller executes the decision making of sharing users by exploiting the fuzzy-logic method. Numerical results are finally provided to validate our new FPG scheme. Although uncertain environments render existing crisp-game approaches invalid, our new algorithm can converge after tens of iterations (even in fast-varying conditions), thereby permitting reliable shared accessing and improved throughput, which is of great significance to next- generation communications operated in dynamical and uncertain environments.