An Asynchronous Interference-Aware Dynamic Spectrum Access Algorithm for Secondary Users

Dynamic spectrum access has become a focal issue recently. Lots of works have been done concerning secondary users (SU) synchronously accessing primary users´ (PU) network. However, on one hand, SU have to periodically synchronize with PU´s time tables, which will bring lots of unnecessary overhead. On the other hand, it is possible that SU have no idea about PU´s communication scheme at all or even communications among PU are not based on synchronous scheme. In order to address such problems, this paper advances an asynchronous algorithm, called A-DSA, for SU to asynchronously access CR-based Ad-Hoc network. We focus on three questions in this paper: 1) how to choose channels to sense; 2) how to sense the chosen channels; 3) how to determine the final access channel after sense. Three strategies are proposed towards each question. Our simulations show that choosing sense channels by A-DSA can attain 20% more success rate than randomly choosing. Moreover, sensing by A-DSA can not only achieve nearly 50% less interference probability than equal allocation of the overall sense time, but also well adapt to time-varying channels.