| 1. |
- Agrell, Erik, 1965, et al.
(författare)
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Roadmap on optical communications
- 2024
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Ingår i: Journal of Optics. - 2040-8978 .- 2040-8986. ; 26:9
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Forskningsöversikt (refereegranskat)abstract
- The Covid-19 pandemic showed forcefully the fundamental importance broadband data communication and the internet has in our society. Optical communications forms the undisputable backbone of this critical infrastructure, and it is supported by an interdisciplinary research community striving to improve and develop it further. Since the first ‘Roadmap of optical communications’ was published in 2016, the field has seen significant progress in all areas, and time is ripe for an update of the research status. The optical communications area has become increasingly diverse, covering research in fundamental physics and materials science, high-speed electronics and photonics, signal processing and coding, and communication systems and networks. This roadmap describes state-of-the-art and future outlooks in the optical communications field. The article is divided into 20 sections on selected areas, each written by a leading expert in that area. The sections are thematically grouped into four parts with 4-6 sections each, covering, respectively, hardware, algorithms, networks and systems. Each section describes the current status, the future challenges, and development needed to meet said challenges in their area. As a whole, this roadmap provides a comprehensive and unprecedented overview of the contemporary optical communications research, and should be essential reading for researchers at any level active in this field.
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| 2. |
- Buchberger, Andreas, 1990, et al.
(författare)
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Learned Decimation for Neural Belief Propagation Decoders
- 2021
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Ingår i: ICASSP, IEEE International Conference on Acoustics, Speech and Signal Processing - Proceedings. - 1520-6149. ; 2021-June, s. 8273-8277
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Konferensbidrag (refereegranskat)abstract
- We introduce a two-stage decimation process to improve the performance of neural belief propagation (NBP), recently introduced by Nachmani et al., for short low-density parity-check (LDPC) codes. In the first stage, we build a list by iterating between a conventional NBP decoder and guessing the least reliable bit. The second stage iterates between a conventional NBP decoder and learned decimation, where we use a neural network to decide the decimation value for each bit. For a (128,64) LDPC code, the proposed NBP with decimation outperforms NBP decoding by 0.75dB and performs within 1dB from maximum-likelihood decoding at a block error rate of 10-4.
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| 3. |
- Buchberger, Andreas, 1990, et al.
(författare)
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Probabilistic Eigenvalue Shaping for Nonlinear Fourier Transform Transmission
- 2018
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Ingår i: Journal of Lightwave Technology. - 0733-8724 .- 1558-2213. ; 36:20, s. 4799-4807
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Tidskriftsartikel (refereegranskat)abstract
- We consider a nonlinear Fourier transform (NFT)-based transmission scheme, where data is embedded into the imaginary part of the nonlinear discrete spectrum. Inspired by probabilistic amplitude shaping, we propose a probabilistic eigenvalue shaping (PES) scheme as a means to increase the data rate of the system. We exploit the fact that for an NFT-based transmission scheme the pulses in the time domain are of unequal duration by transmitting them with a dynamic symbol interval and find a capacity-achieving distribution. The PES scheme shapes the information symbols according to the capacity-achieving distribution and transmits them together with the parity symbols at the output of a low-density parity-check encoder, suitably modulated, via time-sharing. We furthermore derive an achievable rate for the proposed PES scheme. We verify our results with simulations of the discrete-time model as well as with split-step Fourier simulations.
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| 4. |
- Buchberger, Andreas, 1990, et al.
(författare)
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Pruning and Quantizing Neural Belief Propagation Decoders
- 2021
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Ingår i: IEEE Journal on Selected Areas in Communications. - 0733-8716 .- 1558-0008. ; 39:7, s. 1957-1966
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Tidskriftsartikel (refereegranskat)abstract
- We consider near maximum-likelihood (ML) decoding of short linear block codes. In particular, we propose a novel decoding approach based on neural belief propagation (NBP) decoding recently introduced by Nachmani et al. in which we allow a different parity-check matrix in each iteration of the algorithm. The key idea is to consider NBP decoding over an overcomplete parity-check matrix and use the weights of NBP as a measure of the importance of the check nodes (CNs) to decoding. The unimportant CNs are then pruned. In contrast to NBP, which performs decoding on a given fixed parity-check matrix, the proposed pruning-based neural belief propagation (PB-NBP) typically results in a different parity-check matrix in each iteration. For a given complexity in terms of CN evaluations, we show that PB-NBP yields significant performance improvements with respect to NBP. We apply the proposed decoder to the decoding of a Reed-Muller code, a short low-density parity-check (LDPC) code, and a polar code. PB-NBP outperforms NBP decoding over an overcomplete parity-check matrix by 0.27–0.31 dB while reducing the number of required CN evaluations by up to 97%. For the LDPC code, PB-NBP outperforms conventional belief propagation with the same number of CN evaluations by 0.52 dB. We further extend the pruning concept to offset min-sum decoding and introduce a pruning-based neural offset min-sum (PB-NOMS) decoder, for which we jointly optimize the offsets and the quantization of the messages and offsets. We demonstrate performance 0.5 dB from ML decoding with 5-bit quantization for the Reed-Muller code.
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| 5. |
- Buchberger, Andreas, 1990, et al.
(författare)
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Pruning Neural Belief Propagation Decoders
- 2020
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Ingår i: IEEE International Symposium on Information Theory - Proceedings. - 2157-8095. ; 2020-June, s. 338-342
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Konferensbidrag (refereegranskat)abstract
- We consider near maximum-likelihood (ML) decoding of short linear block codes based on neural belief propagation (BP) decoding recently introduced by Nachmani et al.. While this method significantly outperforms conventional BP decoding, the underlying parity-check matrix may still limit the overall performance. In this paper, we introduce a method to tailor an overcomplete parity-check matrix to (neural) BP decoding using machine learning. We consider the weights in the Tanner graph as an indication of the importance of the connected check nodes (CNs) to decoding and use them to prune unimportant CNs. As the pruning is not tied over iterations, the final decoder uses a different parity-check matrix in each iteration. For ReedMuller and short low-density parity-check codes, we achieve performance within 0.27dB and 1.5dB of the ML performance while reducing the complexity of the decoder.
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| 6. |
- Graell I Amat, Alexandre, 1976, et al.
(författare)
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Forward Error Correction for Optical Transponders
- 2020
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Ingår i: Springer Handbooks. - Cham : Springer International Publishing. - 2522-8692 .- 2522-8706. ; , s. 177-257
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Forward error correction is an essential technique required in almost all communication systems to guarantee reliable data transmission close to the theoretical limits. In this chapter, we discuss the state-of-the-art forward error correction (FEC) schemes for fiber-optic communications. Following a historical overview of the evolution of FEC schemes, we first introduce the fundamental theoretical limits of common communication channel models and show how to compute them. These limits provide the reader with guidelines for comparing different FEC codes under various assumptions. We then provide a brief introduction to the general basic concepts of FEC, followed by an in-depth introduction to the main classes of codes for soft decision decoding and hard decision decoding. We include a wide range of performance curves, compare the different schemes, and give the reader guidelines on which FEC scheme to use. We also introduce the main techniques to combine coding and higher-order modulation (coded modulation), including constellation shaping. Finally, we include a guide on how to evaluate the performance of FEC in transmission experiments. We conclude the chapter with an overview of the properties of some state-of-the-art FEC schemes used in optical communications and an outlook.
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| 7. |
- Song, Jinxiang, 1995, et al.
(författare)
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Blind Frequency-Domain Equalization Using Vector-Quantized Variational Autoencoders
- 2023
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Ingår i: 2023 European Conference on Optical Communications, ECOC 2023. ; In press
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Konferensbidrag (refereegranskat)abstract
- We propose a novel frequency-domain blind equalization scheme for coherent optical communications. The method is shown to achieve similar performance to its recently proposed time-domain counterpart with lower computational complexity, while outperforming the commonly used CMA-based equalizers.
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| 8. |
- Thobaben, Ragnar, et al.
(författare)
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Joint Source-Channel Coding with Inner Irregular Codes
- 2008
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Ingår i: 2008 IEEE INTERNATIONAL SYMPOSIUM ON INFORMATION THEORY PROCEEDINGS. - NEW YORK : IEEE. - 9781424422562 ; , s. 1153-1157
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Konferensbidrag (refereegranskat)abstract
- We address the optimization of joint source-channel coding schemes for iterative source-channel decoding of first-order Markov sources. Compared to the traditional design, we propose two novelties: (1) source encoders, providing code words with a minimum Hamming distance distance d(min) >= 2, realized by linear block codes, and (2) irregular channel encoders which are optimized for both the source characteristics and the conditions on the channel. Inner code rates Rc > 1 may be chosen in order to compensate for the additional source redundancy if required. Design examples for the AWGN channel and an overall code rate R=0.66 show that the proposed system is able to establish reliable communication within 0.3 dB of the capacity limit for an interleaver length of approximatively 200000 bits.
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