Analysis of Differential Unitary Space-Time Modulation over Non-Identical MIMO Channels

We present an analytical study on the error performance of differential unitary space-time modulation (DUSTM) over multiple-input multiple-output (MIMO) channels with non- identical fading statistics. The channel for each transmit-receive antenna pair is assumed to be independent, non-identically distributed (i.n.i.d), and time-varying Rayleigh fading. We first show that the maximum-likelihood (ML) differential detector of DUSTM over such channels is involved except for differential cyclic group codes. Applying the distribution of quadratic forms of Gaussian vectors, we derive closed-form expressions for the exact error probabilities of two specific unitary classes, namely, cyclic group codes and orthogonal codes. Simple and useful asymptotic bounds are also obtained. Our analysis leads to several general findings.