Low-complexity, information-lossless STBCs for two-user MISO-MAC with partial CSIT

In this paper, Space-Time Block Codes (STBCs) with low Maximum-Likelihood (ML) decoding complexity and information-losslessness property are proposed for a two-user Multiple-Input Single-Output, frequency-flat fading multiple access channel. In particular, two distinct classes of STBC pairs which are derived from the well known class of real orthogonal designs are proposed. The first class of code pairs which are derived from a class of complex designs called separable orthogonal designs are shown to be (i) information-lossless for arbitrary values of N_t (where N_t denotes the number of transmit antennas of each user) and (ii) have reduced ML decoding complexity whereas the second class of code pairs are shown to be (i) information-lossless only for large values of N_t and (ii) are single-symbol ML decodable.