A class of four-group Quasi-Orthogonal STBC achieving full rate and full diversity for any number of antennas

We propose and construct a new class of full-rate fulldiversity Quasi-Orthogonal Space-Time Block Code (QO-STBC), namely Four-Group QO-STBC (4Gp-QOSTBC), which can support any number of transmit antennas. 4Gp-QOSTBC can linearly separate the symbols into four independent groups, such that symbols within a group is orthogonal to all other symbols in another groups, and the maximum-likelihood (ML) decoder of the code only needs to jointly decode the symbols within the same group. The number of symbols required for joint detection of the newly proposed 4Gp-QOSTBC is half of that required by the existing QO-STBCs with the same code rate, and their fulldiversity decoding performances are comparable. We also extend the proposed code construction to obtain 6Gp-QOSTBC and 8Gp-QOSTBC, which have even lower decoding complexity, albeit at a slight loss in code rate