Trellis coded modulation using totally overlapped signal sets

In conventional trellis coded modulation (TCM), a bit rate of m/m+1 convolutional encoder is employed for n information bits (m⩽n), where 2ⁿ⁺¹ signal points are required. The authors propose a novel TCM system using totally overlapped signal sets (TO-TCM), i.e., each signal point is used twice Thus, TO-TCM can realize only half the signal points (2ⁿ) compared with those of a conventional TCM system (2ⁿ⁺¹), and it is possible to implement a coded modulation system without doubling the signal points by the insertion of redundant bits. The proposed schemes, which have a process to extend the minimum free distances between the signal points can achieve a considerable coding gain in comparison to the traditional uncoded systems with 2ⁿ, signal points. Moreover, as the proposed scheme needs only half the signal points (2ⁿ) of conventional TCM, the average power is lower and it is less sensitive to the carrier phase offset