In this letter, we propose a novel bandwidth-efficient noncoherent trellis-coded MPSK scheme, in which a particularly-designed differential encoder is added in front of the trellis encoder. With this differential encoder, trellis-coded MPSK proposed by Ungerboeck is no longer noncoherently catastrophic and thus achieves better error performance. Moreover, new trellis codes which, for the proposed scheme, have better bit error rates than Ungerboeck's codes are found by computer searches.
