Dynamic spectrum sensing and opportunistic access in cognitive communications enable secondary users to recognize and utilize the white spaces of the licensed bandwidth. Our prior work proposed a non-uniform scheme of bandwidth partition and traffic allocation with the aim of regularizing the primary user's (PU's) bandwidth occupancy pattern, which was able to improve the performance of the secondary user (SU). In the current paper, we study the non-uniform scheme under fading situations. The optimal bandwidth allocation under fading situations is defined as maximizing the spare capacity for the SU subject to satisfying the PU's demand. The problem is proved to be NP-hard. To lower the computational overhead, we further study the problem of maximizing the spare subcarriers for the SU, and propose an optimal algorithm for the PU traffic allocation with polynomial time complexity. By numerical simulations, we demonstrate that the algorithm is able to achieve almost identical performance to that of the optimal solution of the original problem. In addition, the non-uniform scheme, which is based on that algorithm, exhibits better performance than the uniform one even under fading situations.
['Song Huang', 'Anthony Ephremides', 'Di Yuan']
Optimal allocation of non-uniformly partitioned bandwidth for cognitive communications under fading conditions