Multidimensional Trellis-coded Modulation Research Articles

Trellis Coded Modulation for Non-Orthogonal Multiple Access Systems: Design, Challenges, and Opportunities

Capable of achieving massive connectivity and high reliability, the NOMA technique has been well recognized as a potential candidate for 5G mobile communications. Being a key technique of code-domain NOMA, codebook design has drawn great attention due to its potential to improve the coding gain of the system. Trellis coded modulation (TCM) techniques have been considered as an effective approach to optimize the coding gain through signal set expansion without causing bandwidth expansion. In this article, we propose a framework to apply the multi-dimensional TCM (MD-TCM) techniques in code-domain NOMA to jointly design the superposed codewords. Starting with a basic TCM-based NOMA system, we present the design criteria based on which joint multi-layer codeword design for code-domain NOMA is elaborated. Three TCM-based NOMA applications are extended: TCM-based NOMA for MIMO systems, TCM-based NOMA for cooperative relay systems, and TCM-based NOMA for vehicular systems. Open research issues in these scenarios are also discussed.

Performance evaluation of super-orthogonal space-time trellis codes using a moment generating function-based approach

A new class of space-time codes called super-orthogonal trellis codes was introduced that combine set-partitioning with a super set of orthogonal space-time block codes in such a way as to provide full diversity with increased rate and improved coding gain over previous space-time trellis code (STTC) constructions. Here, we extend the moment generating function-based method, which was previously applied to analyzing the performance of space-time block orthogonal and trellis codes, to the above-mentioned super-orthogonal codes. It is shown that the maximum-likelihood metric and expressions for the pairwise error probability previously developed for the Alamouti (1998) space-time block code combined with multidimensional trellis-coded modulation can be readily extended to the super-orthogonal case. As such, the evaluation of the pairwise error probability for the latter can be performed in a similar manner to that previously described with the specific results depending on the particular trellis code design.

Enhancement of ADSL design through concatenated coding

Reed-Solomon (RS) code and multidimensional trellis-coded modulation (MTCM) can be concatenated to improve the performance of Discrete Multitone (DMT) modulated digital subscriber line (DSL) systems. The criteria to design an effective coding scheme with MTCM and RS code including an efficient interleaver are described in this paper. The results of simulation to evaluate the performance of the proposed coding scheme are presented. The performance is compared with the earlier designs and some useful findings are observed. In addition, a novel iterative decoding scheme is also proposed for ADSL channel.

Optimal interleaver design for concatenated coding in DSL systems

The Reed-Solomon code and multidimensional TCM (MTCM) can be concatenated to improve the performance of discrete multitone (DMT) modulated digital subscriber line (DSL) systems. The criteria for designing an effective multidimensional TCM (MTCM) scheme with efficient interleaver are described. The results of simulations for evaluating the performance of the proposed coding scheme are presented.

Multidimensional TCM schemes for ADSL

Multidimensional TCM schemes can be used to improve the performance of the asymmetrical digital subscriber line (ADSL). The operating principle of how M-D (multidimensional) TCM works in an ADSL channel is analysed and criteria for evaluating and choosing effective multidimensional TCM schemes are described. The results of a simulation for evaluating the performance is presented.

Synchronising voiceband modems

Modern voiceband modems often use a symbol rate that is not a factor of their data rate. Combined with the possible use of multidimensional trellis-coded modulation, this means that modems must transmit a fractional number of bits per symbol. To allow for this, bits must be mapped in blocks of symbols. This raises the issue of how to synchronise these blocks. The Letter gives a fast and reliable means to do this.

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 ≥ 4, the net asymptotic coding gain of this scheme can theoretically reach (6–3/n) dB.

Trellis-coded modulation with multidimensional constellations

Trellis-coded modulation schemes using four-, eight-, or 16 -dimensional constellations have a number of potential advantages over the usual two-dimensional schemes: a smaller constituent two-dimensional constellation, easier tolerance to phase ambiguities, and a better trade-off between complexity and coding gain. A number of such schemes are presented and evaluated. Starting with a variety of multidimensional lattices, we show how to select multidimensional constellations, how to partition them into subsets, how to construct trellis codes using those subsets, and how to map hits to constellation points. Simplifications of the Viterbi decoding algorithm are presented. We conclude that there are multidimensional trellis-coded modulation schemes that perform better for the same complexity than do two-dimensional schemes.