Abstract
In the last years, most researches proved that spectrum holes are not efficiently utilized in wireless communications. Cognitive radio (CR) is an efficient solution to face inefficient utilization of spectrum resources. The key technique, which enables CR to provide efficient utilization of spectrum resources is called spectrum sensing. Spectrum sensing enables a secondary user (SU) to track the activity of the primary user (PU) and the availability of spectrum holes that can be used without any disturbance to the PU. Fixed sensing time schemes give inefficient throughput performance with varying received signal-to-noise ratios (SNRs). So, in this paper, an adaptive sensing time optimization scheme in cooperative CR based on energy detection is investigated with different fusion rules. The proposed scheme adapts the sensing time based on the value of received SNR to maximize the achieved throughput with an acceptable probability of false alarm. The performance of the proposed scheme is investigated with AND, OR, and Marjory fusion rules and compared to those of fixed sensing time schemes. Simulation results show that the proposed scheme significantly enhances the achieved throughput, and reduces the probability of false alarm compared to those of the fixed sensing time schemes. In addition, the proposed scheme provides better performance as the number of SUs increases with the marjory fusion rule.