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Efficient Hardware Implementations of LDPC Decoders, through Exploiting Impreciseness in Message-Passing Decoding Algorithms

Abstract : The increasing demand of massive data rates in wireless communication systems will require significantly higher processing speed of the baseband signal, as compared to conventional solutions. This is especially challenging for Forward Error Correction (FEC) mechanisms, since FEC decoding is one of the most computationally intensive baseband processing tasks, consuming a large amount of hardware resources and energy. The conventional approach to increase throughput is to use massively parallel architectures. In this context, Low-Density Parity-Check (LDPC) codes are recognized as the foremost solution, due to the intrinsic capacity of their decoders to accommodate various degrees of parallelism. They have found extensive applications in modern communication systems, due to their excellent decoding performance, high throughput capabilities, and power efficiency, and have been adopted in several recent communication standards.This thesis focuses on cost-effective, high-throughput hardware implementations of LDPC decoders, through exploiting the robustness of message-passing decoding algorithms to computing inaccuracies. It aims at providing new approaches to cost/throughput optimizations, through the use of imprecise computing and storage mechanisms, without jeopardizing the error correction performance of the LDPC code. To do so, imprecise processing within the iterative message-passing decoder is considered in conjunction with the quantization process that provides the finite-precision information to the decoder. Thus, we first investigate a low complexity code and decoder aware quantizer, which is shown to closely approach the performance of the quantizer with decision levels optimized through exhaustive search, and then propose several imprecise designs of Min-Sum (MS)-based decoders. Proposed imprecise designs are aimed at reducing the size of the memory and interconnect blocks, which are known to dominate the overall area/delay performance of the hardware design. Several approaches are proposed, which allow storing the exchanged messages using a lower precision than that used by the processing units, thus facilitating significant reductions of the memory and interconnect blocks, with even better or only slight degradation of the error correction performance.We propose two new decoding algorithms and hardware implementations, obtained by introducing two levels of impreciseness in the Offset MS (OMS) decoding: the Partially OMS (POMS), which performs only partially the offset correction, and the Imprecise Partially OMS (I-POMS), which introduces a further level of impreciseness in the check-node processing unit. FPGA implementation results show that they can achieve significant throughput increase with respect to the OMS, while providing very close decoding performance, despite the impreciseness introduced in the processing units.We further introduce a new approach for hardware efficient LDPC decoder design, referred to as Non-Surjective Finite-Alphabet Iterative Decoders (FAIDs). NS-FAIDs are optimized by Density Evolution for regular and irregular LDPC codes. Optimization results reveal different possible trade-offs between decoding performance and hardware implementation efficiency. To validate the promises of optimized NS-FAIDs in terms of hardware implementation benefits, we propose three high-throughput hardware architectures, integrating NS-FAIDs decoding kernels. Implementation results on both FPGA and ASIC technology show that NS-FAIDs allow significant improvements in terms of both throughput and hardware resources consumption, as compared to the Min-Sum decoder, with even better or only slightly degraded decoding performance.
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https://tel.archives-ouvertes.fr/tel-01783859
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Submitted on : Wednesday, May 2, 2018 - 5:27:07 PM
Last modification on : Thursday, March 5, 2020 - 4:25:49 PM
Long-term archiving on: : Tuesday, September 25, 2018 - 8:05:22 PM

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  • HAL Id : tel-01783859, version 1

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Thien Truong Nguyen Ly. Efficient Hardware Implementations of LDPC Decoders, through Exploiting Impreciseness in Message-Passing Decoding Algorithms. Networking and Internet Architecture [cs.NI]. Université de Cergy Pontoise, 2017. English. ⟨NNT : 2017CERG0904⟩. ⟨tel-01783859⟩

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