In this paper, a bidirectional training based technique is proposed for multiantenna space hopping transmission, which ensures information security of two-way transmission in the physical layer. The proposed scheme can guarantee the identity of channel characteristics obtained by two legitimate transceivers via bidirectional training. A space hopping pattern generation algorithm is presented, which calculates the pattern according to channel characteristics. The antenna switching mode is controlled by the pattern that selects several antennas for fast switching transmission. Conventional schemes resort to a backward training method, hiding the channel between transceiver and eavesdropper so that an eavesdropper cannot receive correctly with wrong weighting, thus achieving security of transceivers. The default mode is that a receiver only receives. Contrarily, the proposed scheme uses a switching mode to ensure transmission secrecy. To improve training efficiency, a spatial frequency multiplexing training method is used, with almost identical accuracy and significantly enhanced efficiency. Simulation results show that the proposed scheme has good performance in anti-eavesdropping as it causes a high bit error rate for the eavesdropper.
