On opportunistic use of location of licensed users in improving the throughput of cognitive radio

Abstract

The opportunistic spectrum access (OSA) and spectrum sharing (SS) are most commonly used schemes in accessing the underutilized licensed spectrum by a cognitive radio (CR) system. Unlike to SS scheme in which the CR users are permitted to co-exist on the same band being used by licensed users (LUs), in OSA scheme the unlicensed users (UUs) are allowed to access an idle band only. During a CR communication in OSA scheme, in order to remain aware of the re-appearance of LUs on the band of interest, the process of spectrum sensing is of high importance. During sensing, in order to decide the idle/busy status of the licensed band, the proper selection of decision threshold \({\uplambda }\) is of high importance. \({\uplambda }\) is mainly selected by using two principles called as constant detection rate (CDR) in which \({\uplambda }\) is calculated by taking fixed value of probability of detection \(\left( {{{\varvec{P}}}_{{\varvec{d}}} } \right) \) and constant false alarm rate (CFAR) in which \({\uplambda }\) is calculated by taking fixed value of probability of false alarm \(\left( {{\varvec{P}}}_{{\varvec{fa}}} \right) \). The CDR principle is favorable in protecting the communication of LUs while CFAR principle suits in improving the throughput of CR system. So, blind use of any of the principle lead to a compromise either in the security of LUs or throughput of CR. This paper proposes an approach which based on the mobile/stationary nature of UU node, and the distance of UU node from LU, makes selection of an appropriate scheme among the CDR-OSA, CFAR-OSA, and SS, to opportunistically improve the CR-throughput.