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Optical Front-End for Soft-Decision LDPC Codes in Optical Communication Systems

JOURNAL OF OPTICAL COMMUNICATIONS AND NETWORKING 2011年第6期3卷 533-541页

作者： Sakib, M. N. Mahalingam, V. Gross, W. J. Liboiron-Ladouceur, O. McGill Univ Dept Elect & Comp Engn Photon Syst Grp Montreal PQ H3A 2A7 Canada McGill Univ Dept Elect & Comp Engn Integrated Microsyst Grp Montreal PQ H3A 2A7 Canada

A low-complexity soft-decision 12.5 Gb/s optical receiver for decoding low-density parity-check codes reusing conventional hard-decision receivers is investigated. The simulated and experimental results show that the proposed optical receiver exhibits coding gains of 2.75 and 6.73 dB for post-forward-error-correction bit error rates of 10(-4) and 10(-9), respectively, over a hard-decision uncoded system for a 60 km single-mode optical fiber transmission. The soft-decision circuitry consumes approximately 5 W and is optimized to provide two confidence levels, one above and one below the hard-decision levels.

关键词： Digital signal processing error correction coding Low-density parity-check codes Optical fiber communications

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Effective Communications: A Joint Learning and Communication Framework for Multi-Agent Reinforcement Learning Over Noisy Channels

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IEEE JOURNAL ON SELECTED AREAS IN COMMUNICATIONS 2021年第8期39卷 2590-2603页

作者： Tung, Tze-Yang Kobus, Szymon Roig, Joan Pujol Gunduz, Deniz Imperial Coll London Dept Elect & Elect Engn Informat Proc & Commun Lab IPC Lab London SW7 2AZ England Samsung Elect Res & Dev Inst UK Staines Upon Thames TW18 4QE England

We propose a novel formulation of the "effectiveness problem" in communications, put forth by Shannon and Weaver in their seminal work "The Mathematical Theory of Communication", by considering multiple agents communicating over a noisy channel in order to achieve better coordination and cooperation in a multi-agent reinforcement learning (MARL) framework. Specifically, we consider a multi-agent partially observable Markov decision process (MA-POMDP), in which the agents, in addition to interacting with the environment, can also communicate with each other over a noisy communication channel. The noisy communication channel is considered explicitly as part of the dynamics of the environment, and the message each agent sends is part of the action that the agent can take. As a result, the agents learn not only to collaborate with each other but also to communicate "effectively" over a noisy channel. This framework generalizes both the traditional communication problem, where the main goal is to convey a message reliably over a noisy channel, and the "learning to communicate" framework that has received recent attention in the MARL literature, where the underlying communication channels are assumed to be error-free. We show via examples that the joint policy learned using the proposed framework is superior to that where the communication is considered separately from the underlying MA-POMDP. This is a very powerful framework, which has many real world applications, from autonomous vehicle planning to drone swarm control, and opens up the rich toolbox of deep reinforcement learning for the design of multi-user communication systems.

关键词： Noise measurement Protocols Channel coding Semantics Reinforcement learning Modulation Wireless communication Learning to communicate reinforcement learning (RL) multi-agent systems joint source-channel coding error correction coding

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Improving the Accuracy of FDTD Approximations to Tangential Components of the Coupled Electric and Magnetic Fields at a Material Interface

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IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION 2011年第8期59卷 2924-2932页

作者： Millington, Tim M. Cassidy, Nigel J. Univ Keele Keele ST5 5BG Staffs England

The finite-difference time-domain (FDTD) method is one of the most popular tools used for modeling important electromagnetic wave propagation and scattering problems. Of the many variations on the basic formulation, conventional orthogonal schemes remain prevalent because of their high level of accuracy and relative ease of implementation. Inaccuracies do persist, however, and in this paper a simple, computationally efficient remedy to an error that occurs when simulating waves that impinge on a material interface is identified. The detail of when and how the error occurs is illustrated using a simplistic interface scenario, with an analytic electric field being used to drive a single FDTD magnetic field update step. The resulting FDTD approximations are compared to the analytic solution to reveal the extent of the error. The proposed modification is then introduced and its remedial effect shown by repeating the above comparison using the modified FDTD equations. The broader effects of the proposed modification are demonstrated using a practical, 3D, full-wave FDTD forward modeling tool, taking scenario examples from the application area of ground penetrating radar (GPR). It is concluded that the overall accuracy of conventional, orthogonal FDTD schemes is improved, without unduly increasing their computational burden or algorithmic complexity.

关键词： error correction coding finite-difference time-domain (FDTD) methods ground penetrating radar interface phenomena

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Non-binary SOVA algorithms for decoding of block codes on a sectionalized trellis

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WIRELESS COMMUNICATIONS & MOBILE COMPUTING 2007年第5期7卷 643-653页

作者： Labeau, Fabrice McGill Univ Dept Elect & Comp Engn Montreal PQ H3A 2A7 Canada

In this paper, we explore computationally efficient implementations of the soft output viterbi algorithm (SOVA) applied to Soft-Input Soft-Output (SISO) decoding of linear block codes. In order to simplify the trellis-based decoding of binary block codes with SOVA, we use the technique of sectionalization of the trellis, which has been successfully applied to the simplification of the MAP and Max-Log-MAP algorithms. Due to the branch complexity of the sectionalized trellis, we define a generalization of a non-binary version of SOVA. However, the computational complexity of directly applying this approach remains too high for efficient implementation;we thus introduce the concept of non-binary SOVA (NSOVA) with propagation of bit-level reliabilities (BLR). This new algorithm is analyzed from a computational complexity viewpoint. Both serial and parallel implementations are explored. Finally, optimal sectionalizations are derived for selected codes;since the normal SOVA decoding is a particular case of NSOVA with BLR, we show that our approach is more efficient than a bit-level trellis by showing that, for all the codes tested, the optimal trellis is a sectionalized one. Copyright (c) 2007 John Wiley & Sons, Ltd.

关键词： block codes error correction coding

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Unequal error Protection for Robust Streaming of Scalable Video Over Packet Lossy Networks

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IEEE TRANSACTIONS ON CIRCUITS AND SYSTEMS FOR VIDEO TECHNOLOGY 2010年第3期20卷 407-416页

作者： Maani, Ehsan Katsaggelos, Aggelos K. Northwestern Univ Sch Elect Engn & Comp Sci Evanston IL 60608 USA Northwestern Univ Dept Elect & Comp Engn Evanston IL 60208 USA

Efficient bit stream adaptation and resilience to packet losses are two critical requirements in scalable video coding for transmission over packet-lossy networks. Various scalable layers have highly distinct importance, measured by their contribution to the overall video quality. This distinction is especially more significant in the scalable H.264/advanced video coding (AVC) video, due to the employed prediction hierarchy and the drift propagation when quality refinements are missing. Therefore, efficient bit stream adaptation and unequal protection of these layers are of special interest in the scalable H.264/AVC video. This paper proposes an algorithm to accurately estimate the overall distortion of decoder reconstructed frames due to enhancement layer truncation, drift/error propagation, and error concealment in the scalable H.264/AVC video. The method recursively computes the total decoder expected distortion at the picture-level for each layer in the prediction hierarchy. This ensures low computational cost since it bypasses highly complex pixel-level motion compensation operations. Simulation results show an accurate distortion estimation at various channel loss rates. The estimate is further integrated into a cross-layer optimization framework for optimized bit extraction and content-aware channel rate allocation. Experimental results demonstrate that precise distortion estimation enables our proposed transmission system to achieve a significantly higher average video peak signal-to-noise ratio compared to a conventional content independent system.

关键词： Channel coding error correction coding multimedia communication video coding video signal processing

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Redundancy and Aging of Efficient Multidimensional MDS Parity-Protected Distributed Storage Systems

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IEEE TRANSACTIONS ON DEVICE AND MATERIALS RELIABILITY 2014年第1期14卷 275-285页

作者： Arslan, Suayb S. Quantum Corp Adv Dev Lab Irvine CA 92617 USA

The effect of redundancy on the aging of an efficient maximum distance separable (MDS) parity-protected distributed storage system that consists of MDS-parity protected array of storage units is explored. In light of the experimental evidences and survey data, this paper develops generalized expressions for the reliability of array storage systems based on more realistic time to failure distributions such as Weibull. For instance, a distributed disk array system is considered in which the array components are disseminated across the network and are subject to independent failure rates. Based on such, generalized closed-form hazard rate expressions are derived. These expressions are extended to estimate the asymptotical reliability behavior of large-scale storage networks equipped with MDS parity-based protection. Unlike previous studies, a generic hazard rate function is assumed, a generic MDS code for parity generation is used, and an evaluation of the implications of adjustable redundancy level for an efficient distributed storage system is presented. Results of this paper are applicable to any erasure correction code as long as it is accompanied with a suitable structure and an appropriate encoding/decoding algorithm such that the MDS property is maintained.

关键词： Aging big data management error correction coding hazard rate redundant array of inexpensive/independent disks (RAID) reliability

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Optical OOK-CDMA and PPM-CDMA systems with turbo product codes

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JOURNAL OF LIGHTWAVE TECHNOLOGY 2002年第9期20卷 1653-1663页

作者： Argon, C McLaughlin, SW Georgia Inst Technol Sch Elect & Comp Engn Atlanta GA 30332 USA

The application of turbo product codes (TPC) in intensity-modulated direct-detection optical code-division multiple-access (CDMA) systems with ON-OFF keying or binary pulse-position modulation is proposed in this study. Optical multiple-access interference caused by other users is the main source of noise that degrades system performance and limits the total number of active users in an optical CDMA system. In this work, the original turbo product decoding algorithm is modified according to the binary memoryless channel model. It is shown that the implementation of TPCs in an optical CDMA system provides significant improvement of the bit-error rate, hence, permitting a higher number of active users with optical orthogonal codes (OOC) of less weight. The proposed TPC has about 20% overhead, but the reduction in the weight of the OOC reduces the system bandwidth to less than half to that of the comparable uncoded system.

关键词： error correction coding optical code-division multiple-access (CDMA) optical fiber communication spread spectrum communication turbo product code (TPC)

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Traceback-Based Optimizations for Maximum a Posteriori Decoding Algorithms

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JOURNAL OF SIGNAL PROCESSING SYSTEMS FOR SIGNAL IMAGE AND VIDEO TECHNOLOGY 2008年第3期53卷 231-241页

作者： Schurgers, Curt Chandrakasan, Anantha MIT Microsyst Technol Labs Cambridge MA 02139 USA

Maximum A Posteriori (MAP) decoding is a crucial enabler of turbo coding and other powerful feedback-based algorithms. To allow pervasive use of these techniques in resources constrained systems, it is important to limit their implementation complexity, without sacrificing the superior performance they are known for. We show that introducing traceback information into the MAP algorithm, thereby leveraging components that are also part of Soft-Output Viterbi Algorithms (SOVA), offers two unique possibilities to simplify the computational requirements. Our proposed enhancements are effective at each individual decoding iteration and therefore provide gains on top of existing techniques such as early termination and memory optimizations. Based on these enhancements, we will present three new architectural variants for the decoder. Each one of these may be preferable depending on the decoder memory hardware requirements and number of trellis states. Computational complexity is reduced significantly, without incurring significant performance penalty.

关键词： error correction coding MAP estimation very-large-scale integration

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Iterative Decoding using Eigenmessages

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IEEE TRANSACTIONS ON COMMUNICATIONS 2009年第12期57卷 3618-3628页

作者： Moon, Todd K. Crockett, John S. Gunther, Jacob H. Chauhan, Ojas S. Utah State Univ Dept Elect & Comp Engn Logan UT 84322 USA

The eigenmessage approach to iterative decoding introduces a degree of nonlocality into a belief propagation decoder by representing an entire set of messages around a cycle of the Tanner graph as a linear operator. The eigenvector for the operator represents a fixed point of the belief propagation algorithm around a cycle, with incident messages fixed. A multiple eigenmessage approach is also presented, in which messages around several cycles are simultaneously expressed. The eigenmessage approach may be applied to any graph with cycles, but we demonstrate its use on LDPC decoding. In this setting, computational results compare eigenmessage methods with conventional belief propagation decoding showing, using simulation and EXIT charts, that the eigenmessage approaches slightly reduce the number of decoder iterations compared to belief propagation decoding while preserving the probability of error of conventional decoding.

关键词： error correction coding iterative methods decoding eigenvalues and eigenfunctions

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Using the Structure of Subfields in the Construction of Goppa Codes and Extended Goppa Codes

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IEEE TRANSACTIONS ON INFORMATION THEORY 2015年第6期61卷 3214-3224页

作者： Tomlinson, Martin Bezzateev, Sergey V. Jibril, Mubarak Ambroze, Marcel A. Ahmed, Mohammed Zaki Univ Plymouth Sch Comp & Math Plymouth PL4 8AA Devon England St Petersburg State Univ Aerosp Instrumentat Dept Technol Informat Secur St Petersburg 190000 Russia Nigerian Commun Satellite Ltd Abuja 932001 Nigeria

It is shown that for some location sets and some integral multiple power Galois fields that some new general subclasses of Goppa codes may be defined which have improved lower bounds to code dimension and minimum distance compared with ordinary Goppa codes. Some previously published results are shown to be particular cases of these general subclasses of codes. A new subclass of reversible Goppa codes is also presented. Examples of code construction for these subclasses, demonstrating the improved code parameters, are presented for both non binary and binary codes.

关键词： Codes Goppa BCH Reed Solomon error correction coding

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