Effect of source kurtosis on MIMO information rate

We consider how information rate in a Multiple-Input Multiple-Output (MIMO) wireless communication system is affected by the use of non-Gaussian source distributions. Of particular interest is the comparison of information rate for a legitimate receiver with that available to an eavesdropping receiver, as the source distribution becomes less Gaussian or, equivalently, as the magnitude of the source kurtosis increases. A legitimate receiver will usually be able to perform maximum likelihood channel estimation using knowledge of a symbol training sequence embedded in the transmitted data. An eavesdropper however may not have this prior knowledge and will therefore be unable to directly estimate the channel. We compare, via simulations, the performance of a well-known Blind Source Separation (BSS) algorithm with theoretically derived results and where the source distributions are taken from the discrete digital constellations: Quadrature Amplitude Modulation (QAM), Phase Shift Keying (PSK). By incorporating a sample timing offset in the simulations we show how the kurtosis of these digital sources is altered. We also show how the legitimate user and eavesdropper information rates are affected as the source kurtosis is varied.