High-rate, 2-group ML-decodable STBCs for 2m transmit antennas

A space-time block code (STBC) in K-variables is said to be g-group ML-decodable (GMLD) if its maximum-likelihood (ML) decoding metric can be written as a sum of g independent terms, with each term being a function of a subset of the K variables. In this paper, a construction method to obtain high-rate, 2-GMLD STBCs for 2^m transmit antennas, m > 1, is presented. The rate of the STBC obtained for 2^m transmit antennas is 2^m-2 + 1/2^m complex symbols per channel use. The design method is illustrated for the case of 4 and 8 transmit antennas. The code obtained for 4 transmit antennas is equivalent to the rate-5/4 quasi-orthogonal design (QOD) proposed by Yuen, Guan and Tjung.