Research on optimal stopping problem based opportunistic channel access

In this paper, we exploit channel diversity for opportunistic spectrum access (OSA). Our approach uses channel quality as a key criterion in selecting channels to use for opportunistic transmission. The difficulty of the problem comes from the fact that when the channel condition is poor, further channel probing, although may lead to better channel conditions and hence yield higher throughput will result in the increasing of additional delay. The desired tradeoff boils down to judiciously choosing the optimal stopping rule for channel probing and distributed scheduling. In this paper, we using optimal stopping theory, we show that the optimal scheme turns out to be a pure threshold policy. The scheme models the random access control problem based on the optimal stopping theory and obtains the optimal access strategy by dynamic programming. Further, the paper finds out the optimal access strategies given any distribution and resolution for the optimal access threshold under Rayleigh fading channel in theory and proves the feasibility in decreasing the complexity of the strategy. The simulation demonstrated that the proposed scheme can efficiently improve the performance of throughputs compared with the random access strategy and the statistical access strategy.