27.6 An 821MHz 7.9Gb/s 7.3pJ/b/iteration charge-recovery LDPC decoder

Ou, Tai-Chuan; Zhang, Zhengya; Papaefthymiou, Marios C.

doi:10.1109/isscc.2014.6757514

Cited by 4 publications

(1 citation statement)

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“…The excellent performance of soft-decision codes comes, however, at the expense of a significantly increased decoding complexity. A comparison of the implementations of soft-and hard-decision decoders shows that softdecision decoders typically consume an order of magnitude more power than hard-decision decoders [2][3][4][5] operating at the same OH and throughput. 2 The Inner-Code Structure…”

Section: Introductionmentioning

confidence: 99%

Low-Complexity Concatenated LDPC-Staircase Codes

Barakatain

Kschischang

2018

J. Lightwave Technol.

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A low-complexity soft-decision concatenated FEC scheme, consisting of an inner LDPC code and an outer staircase code is proposed. The inner code is tasked with reducing the bit error probability below the outer-code threshold. The concatenated code is obtained by optimizing the degree distribution of the inner-code ensemble to minimize estimated data-flow, for various choices of outer staircase codes. A key feature that emerges from this optimization is that it pays to leave some inner codeword bits completely uncoded, thereby greatly reducing a significant portion of the decoding complexity. The trade-off between required SNR and decoding complexity of the designed codes is characterized by a Pareto frontier. Computer simulations of the resulting codes reveals that the net coding-gains of existing designs can be achieved with up to 71% reduction in complexity. A hardware-friendly quasi-cyclic construction is given for the inner codes, which can realize an energy-efficient decoder implementation, and even further complexity reductions via a layered message-passing decoder schedule. * The authors are with the Edward S. Rogers Sr.This paper continues the work of Zhang and Kschischang [6] on designing low-complexity concatenated FEC schemes for applications with high throughput. Their design consists of an inner soft-decision low-density generator-matrix (LDGM) code concatenated with an outer hard-decision staircase code. The degree distribution of the inner LDGM code ensemble is obtained by solving an optimization problem, minimizing the estimated data-flow of the inner-code decoder, while searching a table of staircase codes to find the optimal inner and outer code pair. At 20% OH, the codes proposed in [6] can achieve up to 46% reduction in complexity, when compared with other low-complexity designs.In this paper, we adopt the concatenated FEC structure of [6], but we consider a different ensemble of inner codes. The task of the inner code, similar to that of [6], is to reduce the bit error rate (BER) of the bits transferred to the outer staircase code to below the threshold, which enables the outer code to take the BER further down, below 10 −15 , as required by OTNs. We re-design the inner code to further reduce its data-flow, thereby achieving an FEC solution with even lower complexity than the codes reported in [6].A key characteristic that emerges from the re-designed inner-code optimization is that some inner codeword bits remain uncoded! These bits bypass the inner code, and are protected only by the outer-code. We propose a method to analyze and optimize the inner-code ensemble, and show that the resulting codes can reduce the inner-code data-flow by up to 71%, when compared to [6]. We show that, when block length is sufficiently large, codes generated according to the obtained inner-code ensembles perform as expected, verifying the design approach.To realize a pragmatic decoder implementation, we construct quasi-cyclic (QC) codes of practical length, generated according to the obtained inner-code ensembl...

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Section: Introductionmentioning

confidence: 99%