Pilot-based full-duplex spectrum-sensing and multichannel-MAC over non-time-slotted cognitive radio networks

In the non-time-slotted cognitive radio networks (CRNs), the synchronization between PUs and secondary users (SUs) cannot be guaranteed, resulting in two challenging problems: the reactivation-failure of PUs and the frequently unexpected hand-offs among SUs. The reactivation-failure of PUs is the incident that the SUs cannot detect the PUs' reactivation when the SUs are occupying the channels to transmit their data in non-time-slotted CRNs. The frequently unexpected handoffs among SUs are the events that the SU cannot distinguish between the PUs' reactivation and the other SUs' contention, thus causing many unexpected hand-offs among SUs, which severely degrade the achieved throughput of SUs in non-time-slotted CRNs. Employing the energy-detection based wireless full-duplex spectrum sensing schemes, the PUs' reactivation-failure problem can be efficiently solved, thus guaranteeing the required throughput of PUs. However, the key of CRNs is not only the throughput-guarantees for PUs, but also the throughput-boosts for SUs. To optimize the throughput of SUs in multichannel non-time-slotted CRNs, in this paper we develop the pilot-based full-duplex spectrum sensing (PF-SS) scheme and the pilot-based medium access control (P-MAC) protocol to not only guarantee the required throughput of PUs, but also significantly increase the throughput of SUs in multichannel non-time-slotted CRNs. Using the PF-SS scheme, the SUs can identify whether the PUs' signal or the SUs' signal, thus significantly reducing the frequently unexpected hand-offs among SUs. Then, based on the PF-SS scheme, the P-MAC protocol can significantly increase the throughput of SUs. We conduct extensive numerical analyses to show that our developed PF-SS scheme and P-MAC protocol can significantly increase the throughput of SUs while guaranteeing the required throughput for PUs in multichannel non-time-slotted CRNs.

I. Introduction

COGNITIVE radio networks (CRNs), where the secondary users (SUs) can sense the idle spectrum released by the primary users (PUs), can significantly increase the spectrum efficiency of the existing 4G and the expecting future 5G wireless networks [1]. Based on the relationships of timing control sequences between PUs and SUs, the CRNs can be classified into two categories: the time-slotted CRNs and the non-time-slotted CRNs. The time-slotted CRNs are defined as the wireless cognitive radio networks where the PUs and SUs are synchronous. The PUs access the licensed channels at the beginning of the time-slotted frames and leave the licensed channels at the end of the time-slotted frames in the time-slotted CRNs [2]. The non-time-slotted CRNs are defined as the wireless cognitive radio networks where the PUs and the SUs are asynchronous. The PUs randomly access and leave the licensed channels in the non-time-slotted CRNs.