Outage Performance and Diversity Analysis of Cognitive Triple-Hop Cluster-Based Networks Under Interference Constraint

In this paper, a full diversity for a triple-hop underlay cognitive network is investigated. In secondary network, multiple decode-and-forward (DF) relays located in two clusters help a source forwarding data to a destination under interference constraint with a primary user. We analyze and compare the outage performance and diversity order of two proposed protocols of the three hops model: the hop between a source node and multiple relays in the first cluster, the hop between the first and second clusters, and the hop between the second cluster and a destination node. One optimal relay (or a best relay) in each cluster is chosen by the selection strategies of two proposed protocols, which take the role of decoding and forwarding the message from the previous node to the next node. To be more specific, the optimal relay in the first cluster decodes the source signal and forward the re-encoded one toward the best relay in second cluster; next, the best relay in this cluster DFs the received signal to the destination node. Finally, we determine the approximate expressions of the end-to-end outage probability and obtain the diversity order for each protocol when the value of the Gaussian noise is small.