Mobi-cliques for improving ergodic secrecy in fading wiretap channels under power constraints

We consider a cooperative secret communication scenario, in which a group of mobile and power constrained nodes, acting as relays, cooperatively transmit to a destination in the presence of an eavesdropper; both destination and eavesdropper are assumed stationary. The cooperative scheme entails motion control and optimal communication, in order to achieve a prescribed level of ergodic secrecy rate. The group of motion-controlled cooperating relays is here termed as mobi-clique. Under this setting, a novel, decentralized motion control scheme is derived, which effectively drives the relays to a formation configuration, so that a prescribed expected secrecy requirement is met, while at the same time the utilization of network resources is maximized. The effectiveness of the proposed approach is verified both theoretically and through numerical simulations.