Space-time block codes for eight transmit antennas

In this paper we present full-rate complex nonorthogonal codes for eight transmit antennas and compare their performance to orthogonal designs that provide the same spectral efficiency. The proposed codes have a structure that allows simplified maximum likelihood decoding at the receiver. The decoding scheme is further simplified for rectangular constellations where the real and imaginary parts can be decoded separately. Finally it is shown that the performance of the nonorthogonal codes can be improved significantly by employing a constellation rotation scheme (Sharma et al. (2002)) and this improvement can be attributed to the change in the rank distribution of the code.