A New Cooperative Transmission Strategy for Physical-Layer Security with Multiple Eavesdroppers

In this paper, we propose a two-phase cooperative transmission strategy using decode-and-forward (DF) relaying and cooperative null-steering beamforming (CN-SB) to overcome the multi-eavesdropper problem that reduces the secrecy capacity of wireless networks. First, two groups are built from all available relays-the jamming group and the cooperating group. Second, based on the proposed cooperative transmission strategy, we develop a new relay assignment and power allocation scheme to achieve a higher secrecy rate. Simulation results show that the secrecy rate of the proposed scheme linearly proportional to the signal-to-noise ratio (SNR), which is significantly larger than that of the scheme in which all relays perform CN-SB simultaneously in high SNR regions.