Rate-adaptive constellation shaping for near-capacity achieving turbo coded BICM

Abstract

Abstract-In this paper the problem of constellation shaping is considered. Mapping functions are designed for a manyto-one signal shaping strategy, combined with a turbo coded Bit-interleaved Coded Modulation (BICM), based on symmetric Huffman codes with binary reflected Gray-like properties. An algorithm is derived for finding the Huffman code with such properties for a variety of alphabet sizes, and near-capacity performance is achieved for a wide SNR region by dynamically choosing the optimal code rate, constellation size and mapping function based on the operating SNR point and assuming perfect channel quality estimation. Gains of more than 1dB are observed for high SNR compared to conventional turbo coded BICM, and it is shown that the mapping functions designed here significantly outperform current state of the art TurboTrellis Coded Modulation and other existing constellation shaping methods.

Constellation Shaping for Fiber-Optic Channels With QAM and High Spectral Efficiency

“…Dyadic PMF is achieved by a many-to-one mapping function. We found that the original design from [11] performs poorly if the required SE increases beyond a certain point [7]. This is partly due to the 256QAM size constraint in [11], and also due to the PMF and mapping not being optimized for high SNR.…”

“…2, the original mapping function from [11], and also a 256QAM mapping we designed as part of our previous work [7]. At η = 6 bits/s/Hz/polarization (Fig.…”

“…This requirement is due to the fact, that these ambiguities can be seen as non-stationary puncturing of the bits, and the turbo codes respond better if the puncturing is performed on the parity bits, instead of the data bits. Due to space limitations, the algorithm for obtaining the mapping function is omitted here, but can be found in [7], together with a more detailed explanation and performance analysis. Here we only state that binary reflected Gray-like mapping structure is one of the requirements.…”

“…In [6], digital back-propagation is performed, something which will often be difficult, especially in WDM systems, where the coupling between the channels must be considered. As part of our previous work [7], near-capacity achieving coded modulation scheme was designed for AWGN channel, based on turbo-coded Bit-Interleaved Coded Modulation (BICM), employing QAM constellations and constellation shaping. In this letter, a feasibility study is performed for that method on the fiber-optic communication channel, and a bit-to-symbol mapping function is proposed that achieves high SE.…”

Approximating the constellation constrained capacity of the MIMO channel with discrete input

“…Furthermore, in that region the largest shaping gain can be expected for constellations of practical size [12]. The main contributions of this paper are as follows:…”