What is Primary-Free Probability (of a channel)

In multi-channel Cognitive Radio Networks (CRNs), when the cognitive radio receivers cannot simultaneously sense more than one out of the many possible (groups of) channels, an important challenge is to determine a sensing order for each Cognitive User (CU) so as to optimize a given performance metric. The sensing-order problem is compounded in multi-user CRNs where the multiple users in the network could collide with each other. With the focus on multi-user CRNs, this chapter uses cognitive-throughput maximization as the performance metric and describes how the optimal sensing orders can be computed for different contention management strategies used by the network. In general, the optimal procedures involve a computationally expensive brute-force search, so the chapter also discusses several heuristic-based near-optimal procedures that can be used in practice.