Spectrum sensing algorithms for primary detection based on reliability in cognitive radio systems

One of the main requirements of cognitive radio systems is the ability to detect the presence of the primary user with fast speed and high accuracy. To achieve that, in this paper, we propose a spectrum sensing scheme by considering the reliability of spectrum sensing. Only the user with no reliable information will perform spectrum sensing again using one-order feature detection. Otherwise, the user directly transmits its binary decision (0 or 1) to the MAC layer. The performance of the one-order feature detection is studied and numerical results are presented to show that the one-order feature detector can perform better than the energy detector due to its robustness to the noise uncertainty. Since the feature detection is performed in time domain, the real-time operation and low-power consumption can be achieved. Furthermore, the performance of proposed spectrum sensing scheme based on reliability is also deduced and the analysis of the performance results indicate that the sensing performance is greatly improved as opposed to energy detector. However, due to the effects of channel fading/shadowing, individual cognitive radios may be not able to reliably detect the existence of a primary user. To solve this problem, cooperative sensing among secondary users are studied using the methodology proposed in this paper. The performance of cooperative spectrum sensing is investigated when various decision fusion rules are applied. We find that, regardless of the decision fusion rule used, the sensing performance can be significantly improved compared to conventional cooperative methods. (C) 2009 Elsevier Ltd. All rights reserved.