Cooperative spectrum sensing with different sensing durations in cognitive radio systems

Cooperative spectrum sensing provides more accurate detection of the primary user's activity in cognitive radio (CR) systems. Since the report channels between the cognitive users and base station (BS) are imperfect, a transmit diversity scheme is also employed to improve the decision performance. Different clusters with space time block codes (STBC) are assigned to report the decision by TDMA method to BS. However, if a cluster reports sensing decisions to BS in the reporting slot, the other clusters do nothing but wait for their orders and the time efficiency will decrease. Here, we set the clusters in waiting status do not stop the spectrum sensing to improve the time efficiency. In this case, different clusters will get different sensing durations and energy consumption will not lead to the performance improvement certainly. To solve this problem, we assign the clusters with high sensing sensitivity different sensing durations to decrease energy consumption. Simulation results show that the proposed scheme improves the sensing performance significantly.