30 research outputs found
Improved Decoding of Staircase Codes: The Soft-aided Bit-marking (SABM) Algorithm
Staircase codes (SCCs) are typically decoded using iterative bounded-distance
decoding (BDD) and hard decisions. In this paper, a novel decoding algorithm is
proposed, which partially uses soft information from the channel. The proposed
algorithm is based on marking certain number of highly reliable and highly
unreliable bits. These marked bits are used to improve the
miscorrection-detection capability of the SCC decoder and the error-correcting
capability of BDD. For SCCs with -error-correcting
Bose-Chaudhuri-Hocquenghem component codes, our algorithm improves upon
standard SCC decoding by up to ~dB at a bit-error rate (BER) of
. The proposed algorithm is shown to achieve almost half of the gain
achievable by an idealized decoder with this structure. A complexity analysis
based on the number of additional calls to the component BDD decoder shows that
the relative complexity increase is only around at a BER of .
This additional complexity is shown to decrease as the channel quality
improves. Our algorithm is also extended (with minor modifications) to product
codes. The simulation results show that in this case, the algorithm offers
gains of up to ~dB at a BER of .Comment: 10 pages, 12 figure
Miscorrection-free Decoding of Staircase Codes
We propose a novel decoding algorithm for staircase codes which reduces the effect of undetected component code miscorrections. The algorithm significantly improves performance, while retaining a low-complexity implementation suitable for high-speed optical transport networks
Generalized Spatially-Coupled Product-Like Codes Using Zipper Codes With Irregular Degree
Zipper codes with irregular variable degree are studied. Two new interleaver
maps -- chevron and half-chevron -- are described. Simulation results with
shortened double-error-correcting Bose--Chaudhuri--Hocquenghem constituent
codes show that zipper codes with chevron and half-chevron interleaver maps
outperform staircase codes when the rate is below 0.86 and 0.91, respectively,
at output bit error rate operating point. In the miscorrection-free
decoding scheme, both zipper codes with chevron and half-chevron interleaver
maps outperform staircase codes. However, constituent decoder miscorrections
induce additional performance gaps.Comment: 6 pages, 11 figures, paper accepted for the GLOBECOM 2023 Workshop on
Channel Coding Beyond 5
Binary Message Passing Decoding of Product-like Codes
We propose a novel binary message passing decoding algorithm for product-like
codes based on bounded distance decoding (BDD) of the component codes. The
algorithm, dubbed iterative BDD with scaled reliability (iBDD-SR), exploits the
channel reliabilities and is therefore soft in nature. However, the messages
exchanged by the component decoders are binary (hard) messages, which
significantly reduces the decoder data flow. The exchanged binary messages are
obtained by combining the channel reliability with the BDD decoder output
reliabilities, properly conveyed by a scaling factor applied to the BDD
decisions. We perform a density evolution analysis for generalized low-density
parity-check (GLDPC) code ensembles and spatially coupled GLDPC code ensembles,
from which the scaling factors of the iBDD-SR for product and staircase codes,
respectively, can be obtained. For the white additive Gaussian noise channel,
we show performance gains up to dB and dB for product and
staircase codes compared to conventional iterative BDD (iBDD) with the same
decoder data flow. Furthermore, we show that iBDD-SR approaches the performance
of ideal iBDD that prevents miscorrections.Comment: Accepted for publication in the IEEE Transactions on Communication
A Soft-Aided Staircase Decoder Using Three-Level Channel Reliabilities
The soft-aided bit-marking (SABM) algorithm is based on the idea of marking
bits as highly reliable bits (HRBs), highly unreliable bits (HUBs), and
uncertain bits to improve the performance of hard-decision (HD) decoders. The
HRBs and HUBs are used to assist the HD decoders to prevent miscorrections and
to decode those originally uncorrectable cases via bit flipping (BF),
respectively. In this paper, an improved SABM algorithm (called iSABM) is
proposed for staircase codes (SCCs). Similar to the SABM, iSABM marks bits with
the help of channel reliabilities, i.e., using the absolute values of the
log-likelihood ratios. The improvements offered by iSABM include: (i) HUBs
being classified using a reliability threshold, (ii) BF randomly selecting
HUBs, and (iii) soft-aided decoding over multiple SCC blocks. The decoding
complexity of iSABM is comparable of that of SABM. This is due to the fact that
on the one hand no sorting is required (lower complexity) because of the use of
a threshold for HUBs, while on the other hand multiple SCC blocks use soft
information (higher complexity). Additional gains of up to 0.53 dB with respect
to SABM and 0.91 dB with respect to standard SCC decoding at a bit error rate
of are reported. Furthermore, it is shown that using 1-bit
reliability marking, i.e., only having HRBs and HUBs, only causes a gain
penalty of up to 0.25 dB with a significantly reduced memory requirement
Improving HD-FEC decoding via bit marking
We review the recently introduced soft-aided bit-marking (SABM) algorithm and
its suitability for product codes. Some aspects of the implementation of the
SABM algorithm are discussed. The influence of suboptimal channel soft
information is also analyzed.Comment: OECC 201
30% Reach Increase via Low-complexity Hybrid HD/SD FEC and Nonlinearity-tolerant 4D Modulation
Current optical coherent transponders technology is driving data rates
towards 1 Tb/s/{\lambda}and beyond. This trend requires both high-performance
coded modulation schemes and efficient implementation of the
forward-error-correction (FEC) decoder. A possible solution to this problem is
combining advanced multidimensional modulation formats with low-complexity
hybrid HD/SD FEC decoders. Following this rationale, in this paper we combine
two recently introduced coded modulation techniques:the geometrically-shaped
4D-64 polarization ring-switched and the soft-aided bit-marking-scaled
reliability decoder. This joint scheme enabled us to experimentally demonstrate
the transmission of 11x218 Gbit/s channels over transatlantic distances at
5.2bit/4D-sym. Furthermore, a 30% reach increase is demonstrated over PM-8QAM
and conventional HD-FEC decoding for product codes.Comment: This work has been submitted to IEEE Photonics Technology Letter
Improved Soft-Aided Decoding of Product Codes With Dynamic Reliability Scores
Products codes (PCs) are conventionally decoded with efficient iterative bounded-distance decoding (iBDD) based on hard-decision channel outputs which entails a performance loss compared to a soft-decision decoder. Recently, several hybrid algorithms have been proposed aimed to improve the performance of iBDD decoders via the aid of a certain amount of soft information while keeping the decoding complexity similarly low as in iBDD. We propose a novel hybrid low-complexity decoder for PCs based on error-and-erasure (EaE) decoding and dynamic reliability scores (DRSs). This decoder is based on a novel EaE component code decoder, which is able to decode beyond the designed distance of the component code but suffers from an increased miscorrection probability. The DRSs, reflecting the reliability of a codeword bit, are used to detect and avoid miscorrections. Simulation results show that this policy can reduce the miscorrection rate significantly and improves the decoding performance. The decoder requires only ternary message passing and a slight increase of computational complexity compared to iBDD, which makes it suitable for high-speed communication systems. Coding gains of up to 1.2 dB compared to the conventional iBDD decoder are observed