A routing protocol for cognitive networks in presence of co-operative Primary User

In Cognitive Radio Network (CRN) Cognitive Users (CUs also called Secondary Users (SUs)) make use of frequency band used by Primary Users (PUs) in an opportunistic way. Routing in CRN is a challenging job because the packets within SUs need to be routed only when channels of PUs are idle. The CRN routing protocols proposed so far, does not assume that the PUs will take part in the route formation of SUs in the environment. In this paper we present a routing mechanism for CRN where some of the PUs will forward packets for Cognitive Users (CU) during their idle time. But before including the PUs in the path between any two SUs, PUs must express their willingness to forward packets. These PUs that agree to forward packets for SUs are named as cooperative PU (CPU). The proposed protocol is an extension of Cognitive Ad-hoc On-demand Distance Vector (CAODV) protocol to work in presence of co-operative PUs. The protocol is simulated in ns-2 and compared with CAODV. Result shows a significant improvement in packet loss rate and end-to-end delay over CAODV.