Increasing the Secrecy Gap in Quasi-Static Rayleigh Channels with Secret Splitting

To secure transmissions in the presence of a passive eavesdropper whose Channel State Information (CSI) is unknown, classical Physical Layer Security (PLS) uses Artificial Noise (AN) in order to degrade the eavesdropper’s channel. This paper suggests an alternative way of achieving confidentiality which is based on Base Station (BS) cooperation on the downlink as supported in 3GPP LTE-advanced and future 5G networks. Each BS sends a sequence to the legitimate receiver who is able to reconstruct the information message by XoR-ing the received sequences. As long as the eavesdropper(s) is not at the same location as the legitimate receiver, there is a likelihood that one of the links will not be of high quality and, as such, she will not be able to acquire all sequences required for decoding the message. The proposed scheme has low complexity at the receiver and can be used in systems with finite-alphabet input, whereby most Artificial-Noise (AN) based schemes are ineffective.