Switched Phased-Array Transmission Architecture for Secure Millimeter-Wave Wireless Communication

In this paper, we propose a new wireless communication transmission architecture called switched phased-array (SPA), to enhance physical layer security. SPA works as a platform for three different transmission techniques: 1) conventional phased-array transmission; 2) antenna subset transmission (AST) technique; and 3) silent antenna hopping (SAH) transmission technique. SPA consists of a conventional phased-array blacktransmitter followed by antennas with an on-off switching circuit. The proposed solution maintains the objective of scrambling the constellation points in both amplitude and phase in undesired directions, while preserving a clear constellation in the target direction. The proposed solution-SPA-is different from previously used methods in the following ways: 1) SPA is not restricted to the use of phase modulation, and can accept any modulation type including QAM; 2) it does not need to modulate the signal in the radio frequency (RF) domain, where the conventional phased-array transmitter circuits remain unchanged; 3) in the far field, SPA scrambles the signal constellation by randomly switching-off some of the transmitting antennas (AST), or only one of them (SAH); 4) SPA can be easily integrated with the current infrastructure of phased-array transmitters; 5) SPA breaks up the correlation between the data rates and the switching speed; and 6) SPA performs a variety of DM transmission techniques. We present the potential transmission techniques including PA, AST, and SAH. We analyze the performance for all cases and derive an exact expression of the bit error probability, and also we analyze the secrecy capacity. The results show that SPA, and its variants AST and SAH, are simple and very efficient solutions to improve the physical layer security of mm-wave communication.