Spectrum Sensing and Power Efficiency Trade-off in Cognitive Radio Networks over Fading Channels

Multiple secondary users can cooperate to increase the reliability of spectrum sensing in cognitive radio networks. However, the total transmission power grows approximately linearly with the number of cooperative secondary users. This paper proposes a new approach to optimize the trade-off between sensing reliability and power efficiency in cooperative cognitive radio networks over fading channels. We assume K cooperative secondary users each collect N samples during the sensing time. The proposed approach is based on dividing the spectrum sensing into two phases. In the first phase, we use only n of N samples, (n ≤ N) to check the channels state, then k of K cooperative secondary users, (k ≤ K) which are in deeply faded channels are discarded. We call this n a check point of the sensing time. The spectrum sensing with relatively less-faded channels are continued during the second phase. Therefore, there is a check point at which the sensing time can be optimized in order to maximize the probability of detection and the power efficiency. Several experiments are carried out to test the performance of the proposed approach in terms of detection probability and power efficiency. The obtained results show that the proposed approach enhances the detection probability as well as it shortened the optimal sensing time. Moreover, it improves the overall power efficiency. Key-Words: cognitive radio, cooperative spectrum sensing, power efficiency.