Differential space-frequency modulation and 2D-detection for MIMO-OFDM

In this paper differential space-frequency modulation (DSFM) for transmission over multiple-input multiple-output channels using orthogonal frequency division multiplexing (MIMO-OFDM) and multiple-symbol differential detection (MSDD) without channel state information (CSI) at the receiver is considered. Inspired by previous work presented in the literature, a novel DSFM scheme is devised, which makes use of spatial and/or spectral (multipath) diversity and is particularly suited for MIMO-OFDM and power-efficient, low-delay MSDD. Furthermore, the application of a two-dimensional (213) observation window to MSDD (2D-MSDD) in order to exploit channel correlations in both time and frequency direction, is investigated and tree-search decoding is applied to solve the detection problem efficiently. An analytical approximation of the symbol-error rate of 2D-MSDD for MIMO-OFDM under spatially correlated fading is derived, which enables quick and accurate performance evaluations. Numerical and simulation results corroborate the efficacy of our approach and show that power efficiency close to that of coherent detection with perfect CSI is feasible in all standard fading scenarios at reasonable decoder complexity.