Normalized Energy Detection Based Cooperative Spectrum Sensing with Reporting Errors in Heterogeneous Cognitive Radio Networks

In this paper, we investigated the cooperative sensing in a heterogeneous cognitive radio (CR) network scenario, where each secondary user (SU) may be equipped with different number of receive antennas and have different signal processing capacity, e.g., sampling rate. By considering the discrepancy in sensing reliability of different SUs, we extended the existing researches to propose an optimal cooperative sensing (OCS) scheme based on normalized energy detection (NED) by considering reporting errors, i.e., the fusion center (FC) may receive erroneous results from some SUs due to channel fading. It is derived that the proposed OCS scheme is the linear combination of modified local detection statistics. The optimal combining coefficient is just a function of the numbers of the antennas and the received signal samples, the signal to noise ratio (SNR) and the variance of the reporting errors at each SU. Meanwhile, the performance of the proposed OCS scheme, the well-known equal gain combination (EGC) method and the maximum normalized energy (MNE) detector with reporting errors is analytically derived, respectively. Furthermore, to avoid the prior information of each SU's SNR and the variance of the reporting errors, and simplify the decision-making as well as threshold setting, a sub-optimal cooperative spectrum sensing (SOCS) is proposed. Numerical results show that the proposed OCS and SOCS schemes all perform much better than the existing EGC and MNE methods.