COMBINATION OF BLOCK-CODED MODULATION AND TRELLIS-CODED MODULATION

It is known that trellis-coded modulation (TCM) can give a significant coding gain without compromising bandwidth efficiency, by the concepts of signal set partition and trellis coding scheme. It is also known that block-coded modulation (BCM) can be used to approach closely the maximum energy saving that can be obtained by using the densest lattice over the rectangular lattice (QAM). In this paper a systematic scheme is proposed to combine TCM and BCM, such that the constructed coded modulation is similar to part of Wei's multidimensional TCM. The main idea is that the signal points that are used in multidimensional TCM should be partitioned according to the-dense lattices formed by proper BCM. Hence a higher coding gain is obtained which is a combination of both the distance gain of TCM and the density gain of BCM. In the 2n-dimensional case, for n greater-than-or-equal-to 4, the net asymptotic coding gain of this scheme can theoretically reach (6-3/n) dB.