Improved Cognitive Radio Receivers Using Timing Mismatch of Primary and Secondary Users

We consider an asynchronous cognitive radio framework, where the primary user (spectrum license holder) and the secondary user are, naturally, not aligned in their timing. We show that applying our optimal receiver design results in improving the performance compared to the case of synchronous cognitive radio. We optimize the rates subject to the constraint to keep interference imposed on the primary user below a certain level. We also derive the constraint for the receiver of the secondary user to perform interference cancellation. Simulation results show that our proposed oversampling secondary user receiver boosts the received signal. As a result, the secondary user's transmission power can be decreased without negatively affecting the quality of the received signal. Not only does our method reduce the interference to the primary user but also it saves power at the secondary user.