Efficient method for reducing the average control bits in a distributed cooperative sensing in cognitive radio system

Abstract

In cognitive radio (CR) networks, the incorrect detection of primary users causes inefficient spectrum utilisation and harmful interference to the primary users, so spectrum sensing is an important problem that must be well done. However, multipath fading and path loss effects always reduce the performance of spectrum sensing. Cooperative spectrum sensing improves the sensing performance of cognitive users. However, when the number of cognitive users cooperating with each other is very large, the reporting bits increase and therefore more bandwidth will be needed. In this study, the authors try to reduce the average number of control bits that is exchanged between CR users. The authors consider two different systems: single band detection system and wideband system. The analysis are done for perfect and imperfect control channels. By using a ring-based distributed spectrum sensing model, they propose a method with little required bandwidth to inform the CRs from the final decision about the activity of the primary user. Analytical and numerical results show that this method reduces the average number of control bits and therefore the required control bandwidth. Moreover, the analytical results represent that the imperfect control channels do not affect the performance of the proposed single band system and has a little effect on the performance of our wideband scheme.