Adaptive distributed beamforming and jamming in DF relay networks for physical layer secrecy

In this paper, we propose a joint distributed beamforming and jamming scheme in decode-and-forward (DF) relay networks to physical layer secrecy. Considering the special property of DF relay networks, where only the relays decoding the message from source correctly have to join in the forwarding phase, we let the relays decoding successfully perform distributed beamforming to transmit information signals and the left relays decoding in error transmit jamming signals to improve the system secrecy capacity. For this purpose, we design a CVX toolbox based bi-level optimization algorithm to search the optimal beamforming vector and jamming vector for the relays via the semi-definite relaxation (SDR). Finally, the simulation results show that the proposed scheme outperforms existing secrecy schemes in DF relay networks.