An efficient cooperative spectrum sensing algorithm in time domain

Spectrum sensing is a fundamental issue to detect the presence of primary users´ signals in cognitive radio (CR) networks. In order to protect primary users from harmful interference, the spectrum sensing scheme is required to perform well even in extremely low signal-to-noise ratio (SNR) environments. Meanwhile, the sensing period is usually required to be short enough so that secondary (unlicensed) users (SUs) can fully utilize the available spectrum. In this paper, we propose an efficient cooperative spectrum sensing algorithm in time domain (TDCSS) based on energy detection (ED). In the proposed algorithm, the SU softly combines multiple sensing results obtained in different sensing periods to make an optimal decision on the existence of spectrum access opportunity. By considering the discrepancy of sensing reliability in different sensing periods, we demonstrate that the proposed TDCSS scheme is a linear combination of the conventional ED test statistic in each sensing period and its complexity is equal to that of the conventional ED. Moreover, the theoretical performance of the TDCSS under additive white Gaussian noise channel (AWGN) is derived. Numerical results show that the proposed TDCSS scheme performs better than the conventional ED.