Communicating under channel phase uncertainty

For a multiple antenna equipped wireless system, a new signal constellation design and decoding strategy is proposed to combat errors in the phase estimate of the channel coefficients when the channel coefficient magnitudes can be estimated accurately. For the single antenna case, the proposed constellation is a superposition of phase-shift-keying (PSK) and pulse-amplitude-modulation (PAM) constellations, where at the receiver, the PSK symbols are decoded first followed by the PAM symbols. PSK is used to provide protection against phase errors, while PAM is used to increase the transmission rate using the knowledge of the magnitude of the channel coefficient. The performance of the proposed constellation is shown to be significantly better than the widely used QAM constellation in terms of the probability of error. Using similar ideas, for multiple antenna case, the signal design is a superposition of the codebook developed for non-coherent communication and multi-dimensional PAM.