Ad-Hoc Relay Selection Protocols for Multi-Hop Underlay Cognitive Radio Networks

In underlay cognitive radio networks (CRNs), transmit power of secondary user (SU) is a function of fading channel gain between the SU and primary destination. By exploiting this unique characteristic of CRNs, in this paper, we propose and study two novel ad-hoc routing protocols for path selection in cluster-based underlay multi- hop CRNs (MHCRNs). These protocols are termed as highest transmit power relay selection (HTPRS) protocol and improved HTPRS (IHTPRS) protocol. The exact end-to-end outage probability of cluster-based MHCRN is derived by taking both peak-power and peak-interference constraints into account for both proposed routing protocols. Moreover, we derive the average number of channel-state-information (CSI) estimates of forward channels required by the IHTPRS protocol. It is shown that the HTPRS is suitable for the systems with less implementation complexity, whereas the IHTPRS finds its application where high quality of service is required with slight increment in the CSI overhead.