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.