Systematic design of unitary space-time constellations

We propose a systematic method for creating constellations of unitary space -time signals for multiple-antenna communication links. Unitary space-time signals, which are orthonormal in time across the antennas, have been shown to be well-tailored to a Rayleigh fading channel where neither the transmi tter nor the receiver knows the fading coefficients, The signals can achiev e low probability of error by exploiting multiple-antenna diversity. Becaus e the fading coefficients are not known, the criterion for creating and eva luating the constellation is nonstandard and differs markedly from the fami liar maximum-Euclidean-distance norm. Our construction begins with the first signal in the constellation-an oblon g complex-valued matrix whose columns are orthonormal-and systematically pr oduces the remaining signals by successively rotating this signal in a high -dimensional complex space. This construction easily produces large constel lations of high-dimensional signals. We demonstrate its efficacy through ex amples involving one, two, and three transmitter antennas.