On the physical layer security of analog joint source channel coding schemes

We propose the use of discrete-time all-analog joint source-channel coding over wireless channels in order to provide protection against eavesdropping. We consider a bandwidth expansion scheme using non-linear spiral-like curves and maximum likelihood detection with linear minimum mean square error estimation. Moreover, the transmitter uses truncated channel inversion, which significantly increases the signal-to-distortion ratio (SDR) at the intended receiver while keeping a low SDR at the eavesdropper. By considering the security gap as the performance metric, which is defined as the ratio between the channel signal-to-noise ratio (CSNR) of the legitimate receiver and of the eavesdropper for a given pair of target SDRs, we show that partial secrecy is possible in this setup.