Physical Layer Secure Communication based on MIMO Channel Constellation Flipping

We proposed a physical layer secure communication system for massive MIMO systems, utilizing channel entropy as the foundation. Our approach involves extracting a mask key and a flip key from the singular value decomposition (SVD) of the channel matrix. The mask key ensures the protection of the flip key during transmission. By applying a random flip to the constellation diagram of the transmitted message based on the flip key, we introduce a scrambling effect that cannot be deciphered by eavesdroppers. The flip key is securely delivered to the receiver, allowing for the proper demodulation of the message by eliminating the constellation flip. To address the computational burden associated with estimating massive MIMO channels, we employ precoding of the downlink channel guide signal in the system design. This reduces the channel estimation overhead at the terminal. However, it also creates an equivalent channel for the eavesdropper, enabling them to correctly decode the precoded signal and compromise communication security. Our scheme counters this by introducing the constellation diagram flipping, which cannot be extracted by eavesdroppers, thereby preventing correct decoding. Simulation experiments confirm even with a large number of antennas, the eavesdropper is unable to completely counteract the effects of constellation flipping, thus ensuring communication security. In summary, by exploiting the singular value decomposition and employing constellation diagram flipping, our physical layer secure MIMO communication system based on channel entropy achieves secure communication even in the presence of powerful eavesdroppers.