Study on efficient decision fusion in OR-rule based cooperative spectrum sensing

Efficient decision fusion technique for cooperative spectrum sensing based on the logical OR-rule is considered for dynamic spectrum sharing between primary users (PUs) and secondary users (SUs). Due to the use of the OR-rule, the fusion center (FC) only needs to know if any of the local decisions was ”1”. Therefore, it can be a waste of resources to communicate each local decision in an orthogonal channel. To reduce the resource consumption, we consider that the SUs that had local decision ”1” transmit simultaneously in the same channel using continuous wave (CW) signaling without a phase synchronization and that the FC will declare the PU is present if it detects the summed CWs. In this signaling, even with very large channel gain to noise power ratio (CNR) between the SUs and the FC the system may not reach error-free signaling due to destructive interference in the summed CWs. To address this problem, we propose power allocation to reduce the effects of the destructive interference, as with this technique it is possible to guarantee that the CWs are not going to fully cancel each other. The proposed method is very simple and although it is suboptimal, it could provide good detection performance. Numerical results show that it is possible to practically reach the upper bound with error-free signaling by the proposal, even with moderate CNR values.