Full-Diversity Minimum Decoding Complexity Differential Quasi-Orthogonal STBC

In this paper, we introduce a low decoding complexity space-time modulation scheme that achieves full transmit diversity without the need of channel knowledge at the transmitter (Tx) nor at the receiver (Rx). The scheme is based on differential encoding of a low-complex quasi-orthogonal space-time block code (STBC). The idea of the differential encoding is based on mapping the original system to an equivalent system which is composed of two orthogonal subsystems. The differential encoding and decoding approach is described and the receiver metric is derived. The described technique is valid for any number of transmit antennas M for which a square orthogonal code of size M/2 exists, and is valid for any number of receive antennas. The proposed scheme is favourable in that it has single complex symbol decoding complexity while achieving a performance close to other differential quasi orthogonal codes of higher complexity and a remarkable performance advantage compared to differential orthogonal schemes especially at high data rates.