Orthogonal space-time block codes: performance analysis and comparisons

We derive a simple method to directly compute the exact bit error probabilities (BEPs) of orthogonal space-time block codes (OSTBCs) over Rayleigh fading channels for arbitrary I-PSK and square I-QAM signal constellations with coherent detection. Based on the derived BEPs, we study the performance of various OSTBCs for numerous numbers of receive antennas and bit rates. Our analysis shows that even at low bit rates and with only a single receive antenna, OSTBC for four transmit antennas would be the best choice for most practical cases. Furthermore, if the receiver has multiple antennas, OSTBCs for more than four transmit antennas only degrade performance while adding more complexity. We conclude that in most cases, OSTBCs for four transmit antennas or less should be the choice.