Physical layer security performance analysis of the time reversal transmission system

Thanks to its characteristics of temporal compression and spatial focusing, the time reversal (TR) transmission system has the intrinsic capability of anti‐eavesdropping. This study analyses the physical layer security performance of the TR transmission system. The probability density functions and cumulative distribution functions of the signal‐to‐noise ratio of the legitimate user and eavesdropper are given. On this basis, the theoretical expressions of the ergodic capacities of the legitimate channel and the wiretap channel, and the achievable ergodic secrecy rate are derived. The bit error rates of the legitimate user and eavesdropper for binary phase‐shift keying modulation are given too. The correctness of the theoretical derivation is verified by simulation. For the legitimate user, the signal power increases as the number of paths increases, which indicates a higher diversity gain can be obtained, and the inter‐symbol interference power decreases as the up‐sampling factor increases. So, the signal‐to‐interference‐plus‐noise ratio (SINR) of the received signal can be significantly improved by appropriately reducing the spectral efficiency. However, the received signal's SINR of the eavesdropper cannot be promoted obviously. That is to say, compared with the eavesdropper, the legitimate user can achieve a higher rate and a lower BER, so secure transmission can be realised.