Secrecy Capacity of Hybrid, Outage-based Power Adaptive, Cooperative Relaying Networks with Imperfect CSI

We consider a two-hop adaptive decode-amplify-forward (DAF) relay network. The collaborative network consists of a source, multiple hybrid relays, a destination, and an eavesdropper. The relays would help forward source information reliably to the destination node in the eavesdropper’s presence. Specifically, the relays decode its received noisy signal from the source, amplify it adaptively, and then forward it to the destination. We derive and propose a lower bound on this adaptation factor at the relay to meet an outage probability constraint. Note that only one selected relay participates in the processing and forwarding the signal to the destination that uses the maximal ratio combining (MRC) diversity combining techniques with imperfect channel state information (CSI). For the proposed cooperative network model, we derive the expression for the received signal power to interference plus noise power ratio (SINR) and secrecy capacity in the presence of estimation errors. We compare the secrecy performance of the proposed outage-based power adaptive cooperative network for the MRC and the selection combining (SC) diversity techniques at the destination. The analysis and numerical results on secrecy capacity serve as a useful benchmark in cooperative networks with multiple hybrid relays.