A space-frequency coding scheme providing high level of diversity and spectrum efficiency for non-coherent frequency-selective MIMO-OFDM systems

This paper proposes a space-frequency (SF) coding scheme for non-coherent (NC) Multiple Input Multiple Output (MIMO)-Orthogonal Frequency Division Multiplexing (OFDM) fading links, where neither the transmitter nor the receiver knows the channel. Our strategy consists in applying a convolutional encoder and an interleaver before applying a SF encoder. This SF encoder distributes the encoded and interleaved bits over the different OFDM symbols. In order to reduce the decoding complexity, each OFDM symbol is divided into several groups.Within each group, the obtained bits are broken into two substreams. The first substream is used to construct a systematic NC codeword which leads to a simple decoding rule over the multipath channel. The second subtream is mapped to a Grassmannian NC codeword obtained via an exponential map and that was proposed for NC space-time (ST) coding based system and has the advantage of using all the degrees of freedom of this system. We show through asymptotic Pairwise Error Probability (PEP) analysis and simulation results that our encoding strategy can provide full diversity gain and achieves better performance in terms of spectrum efficiency and bit error rate than both the systematic NC-SF coding and our proposed SF coding without convolutional encoding and interleaving.