Signal design for trellis-coded unitary space-time modulation

In this paper, we present a new formulation of the problem of signal design for trellis-coded unitary space-time communication systems. Our approach differs from other methods in that we not only combine the constellation design and set partitioning process together, we also use directly the Chernoff bound of the pairwise probability of error as design metric, which is a better figure of merit than the previously used chordal distance, for unitary constellation design. By novelly employing a theorem regarding the Clarke subdifferential of the sum of the k largest singular values of the unitary matrix, we present a numerical optimization procedure for finding good constellations and report the best signal constellations found. Simulation results show that these constellations achieve 1 dB gain against the previously used constellations of unitary space-time signals.