Relay-Based Cooperative Spectrum Sensing with Improved Energy Detection in Cognitive Radio

Cognitive radio has become an effective technology to solve the underutilisation problem of the spectrum. In recent times, spectrum sensing has been intensively studied as a key technology in realising the cognitive radio. In this paper, we consider an amplify-and-forward relay-based cooperative spectrum sensing using a double threshold energy detector. Each secondary cognitive user takes a local decision on spectrum occupancy based on two energy detection thresholds. If it detects the value out of both thresholds, it makes a decision first, amplifies and forwards the local result to the fusion center. If the detected value falls between the both thresholds, it amplifies and forwards this detected value to the fusion center. Finally, energy fusion and decision fusion are conducted at the fusion center to determine the primary user status. Cooperative probability of detection, probability of missed detection and probability of false alarm are derived theoretically with and without direct communication between the primary user and fusion centre. Simulation results show that the proposed method achieves an improvement in probability of detection.