Spectrum Sensing Time Optimization Algorithm for Spectrum Efficiency Maximization in the Low-power Cognitive Radio Ultra Wideband System

For energy detection in a cognitive radio (CR) system, the spectrum sensing time required to successfully detect a primary user (PU) is inversely proportional to the PU's signal strength. When the PU operates in low-SNR regime, the effective transmission time of the CR system with a fixed transmission window can be extremely short for the CR system to fully utilize the spectrum. This paper presents a sensing time optimization algorithm aiming at maximizing the spectral efficiency of the Ultra Wideband (UWB) based CR system by finding the optimal tradeoff between the length of the sensing window and the detection probability in low-SNR regime. Compared with the time fixed sensing methods, the optimization algorithm can produce a significantly longer transmission time for the UWB based CR system to effectively utilize the detected spectrum band while guaranteeing protection to the PUs.