LAUSR

This paper studies secrecy communications in a multi-antenna two-way relaying wiretap system. Each source node transmits user and jamming signals with distinct precoding vectors. Based on the assumption that the channel state information relating to the eavesdropper is unknown by the legitimate nodes, new precoding design algorithms are proposed. The jamming signals are designed to ensure that minimum interference is perceived by the other source node. The precoding vectors of the user signals are designed to form two parallel vectors in the equivalent wiretap channel at the eavesdropper. Two algorithms are proposed based upon the zero-forcing and matched-filter schemes, which are dubbed the selective zero-forcing-based precoding (SZFP) and matched-filter-based precoding schemes. Analytical and simulation results are presented to demonstrate that the SZFP algorithm is more applicable when the eavesdropper is equipped with a large number of antennas or the eavesdropper’s channels are in good condition.