Joint packet retransmission and spectrum sensing for cognitive radio networks

We model and simulate a joint design of packet retransmission through a hybrid automatic repeat request (HARQ) protocol at the data link layer and spectrum sensing (SpSe) at the physical layer for cognitive radio networks (CRNs). We assume an adaptive modulation scheme at the physical layer that is incorporated with the SpSe and we focus on the maximization of the average spectral efficiency that is affected by both the number of retransmissions of the HARQ protocol and the probability of detection of the SpSe mechanism. The optimal results demonstrate the tradeoff between these two key parameters. We depict the optimal operational points, where the performance is maximized, using convex hull methodology.