Sensing and transmission strategies in wireless cognitive radio systems

Sensing and Transmission Strategies in Wireless Cognitive Radio Systems by Babak Abbasi Bastami The main challenge in any cognitive radio system is to maximize secondary users throughput while limiting interference imposed on licensed users. In this regard, finding the optimal sensing and transmission timing strategies and accurate sensing techniques are of great importance in a cognitive radio network. In this thesis, we study a sensing-transmission scheme for secondary user in a cognitive radio system where the secondary user senses every primary channel independently and transmits a signal for a fixed duration if it finds the channel empty and stays idle for another fixed duration if it senses the channel busy. We obtain optimal idle and transmission durations which maximize access opportunity of the secondary user while keeping the interference ratios on the primary channels below some thresholds. Our results show that unless we have an error free perfect channel sensing, adding the idle duration improves the performance of the system. We also study a cooperative spectrum sensing scheme for cognitive radio systems where each sensor transmits multi-bit quantized information to a fusion center where the decision about the availability or occupancy of the channel is made. We compare