A rate-3/2 full-diversity 4×4 space-time code with fast Maximum-Likelihood Decoding

Recently, Space-Time Block Codes (STBCs) with fast Maximum-Likelihood Decoding (MLD) have gained a lot of interest from a practical perspective. In [1] and [2], B. Rajan et.al proposed a systematic approach to build such codes from the representations of the real Clifford algebras. In the Sari-Sezginer code [8], another approach was proposed to build fast MLD STBC's. Indeed, the authors used the conditional detection principle and numerical optimization in order to have a large coding gain (thus full diversity) while maintaining a reduced complexity level at the receiver. In this paper we are interested in extending the principle of conditional detection to the case of four transmit antennas. We propose here a full-diversity 4×4 STBC achieving a rate of 3/2 complex symbols per channel use. To the best knowledge of the authors, the highest rate for full transmit diversity 4×4 codes with the same complexity level was reported to be 5/4 complex symbols per channel use (such codes were found independently in [10] and in [11]).