Performance analysis and threshold selection in co-operative spectrum sensing using soft-decision techniques

Spectrum sensing is a key function of cognitive radio to prevent the harmful interference with licensed users and identify the available spectrum for improving the spectrum utilization. In Spectrum Sensing, function of secondary users (SUs) is to detect the spectrum holes. However, in practice detection performance is often compromised with multipath fading, shadowing and receiver uncertainty issues. To mitigate the impact of these issues, cooperative spectrum sensing (CSS) is considered as an effective method to improve the detection performance by exploiting spatial diversity. In the current work centralized CSS is considered where all the SUs transmit their locally sensed information to fusion center (FC) and final decision is made by using soft-decision methods (SLC, SC, MRC) using energy detector (ED) at each CR as detection scheme. In this multi-path fading scenario with flat fading for narrowband spectrum sensing received SNR, total error probability, probability of false alarm, threshold value are considered as variable parameters in CSS. The current work focuses on performance of CSS, selecting a suitable threshold value for detection of primary user with minimum total error probability using diversity techniques and receiver operatting characteristics curves are also provided for various diversity techniques under different fading channels.