Power Allocation and Relay Placement for Secrecy Outage Minimization over DF Relayed System

This paper presents a novel joint transmit power sharing and relay placement scheme for decode-and-forward relay assisted secure communication to a legitimate user in presence of external eavesdropper. Observing that secrecy outage minimization problem for the trusted user is non-convex, key insights on optimal power sharing between source and relay are first presented to derive an equivalent single variable problem. Next, tight analytical bounds for optimal relay placement are discoursed to ultimately come up with a computationally-efficient jointly global optimization algorithm. Finally, selected numerical results validate analysis, present key insights, and demonstrate performance gains of around 30dB over benchmark schemes.