TRELLIS-CODED MODULATION USING PARTIALLY OVERLAPPED SIGNAL SETS OF NONEQUIPROBABLE SIGNALING

In conventional trellis coded modulation convolutional code is employe d not to expand the transmitted bandwidth. This forces the system to b e attended with signal constellation expansion and increasing the aver age signal power. As the solutions to avoid signal constellation expan sion, TCM systems using totally overlapped signal sets (TO-TCM and RU- TCM) were proposed. These schemes can realize a coded modulation syste m without signal constellation expansion and achieve more coding gain compared with the conventional TCM. However, a problem that the system s with totally overlapped signal sets might be catastrophic has been r emained. In this paper, we propose a novel TCM system using partially overlapped signal sets of non-equiprobable signaling (PO-TCM-NE). This scheme employs the partially overlapped signal constellation to contr ol increasing signal points, and to avoid catastrophic error propagati on. The non-equiprobable signaling is employed to reduce average signa l power. Coding gain of the proposed PO-TCM-NE is considerably improve d in consequence the average signal power is reduced much lower than t hat of other TCM systems with equiprobable signaling.