An energy-detection based cooperative spectrum sensing algorithm for faded and low-power primary user signal over cognitive radio networks

Cognitive radio is a novel technology that is provision to overcome the spectrum scarcity problem in wireless networks. Cognitive radio network is founded to provide the capability of sharing the wireless channel between unlicensed users (secondary users) and licensed users (primary users) in an opportunistic manner. Primary user detection in low signal to noise ratio (SNR) regime is one of the main challenges of cognitive radios that measure the energy level of the primary user for sensing the spectrum. SNR fluctuations due to wireless channel effects complicate this process further. This paper utilizes the potential benefits of cooperative spectrum sensing method in a way that it can become applicable when the primary user´s SNR at secondary user receivers are low. The detection scheme is based on a set of evidences (primary-user´s energy level) which are obtained from distributed cooperating nodes. After estimating the channel and the primary user signal statistics accurately, they are utilized to set up a MAP hypothesis test scheme for decision about channel occupancy. When the SNR of the received primary user signal at the secondary user´s energy-detector is low, our results illustrate that utilizing just mentioned statistics can improve the performance of the energy detector significantly.