publications

preprints

  1. Learned Decimation for Neural Belief Propagation Decoders
    Andreas Buchberger, Christian Häger, Henry D. Pfister, Laurent Schmalen, and Alexandre Graell i Amat
    In Proc. IEEE Int. Conf. Acoustics, Speech and Signal Processing (ICASSP), Toronto, Canada, 2021
    [arXiv]
  2. End-to-end Autoencoder for Superchannel Transceivers with Hardware Impairment
    Jinxiang Song, Christian Häger, Jochen Schröder, Alexandre Graell i Amat, and Henk Wymeersch
    In Proc. Optical Fiber Communication Conf. (OFC), Virtual Conference, 2021
    [arXiv]

journals

  1. Pruning and Quantizing Neural Belief Propagation Decoders
    Andreas Buchberger, Christian Häger, Henry D. Pfister, Laurent Schmalen, and Alexandre Graell i Amat
    IEEE J. Sel. Areas Commun., 2021
    [PDF] [arXiv] [DOI]
  2. Model-Based Machine Learning for Joint Digital Backpropagation and PMD Compensation
    Rick M. Bütler, Christian Häger, Henry D. Pfister, Gabriele Liga, and Alex Alvarado
    J. Lightw. Technol., vol. 39, no. 4, pp. 949–959, 2021
    [PDF] [arXiv] [DOI]
  3. Physics-Based Deep Learning for Fiber-Optic Communication Systems
    Christian Häger, and Henry D. Pfister
    IEEE J. Sel. Areas Commun., vol. 39, no. 1, pp. 280–294, 2021
    [PDF] [arXiv] [Code] [DOI]
  4. Revisiting Efficient Multi-Step Nonlinearity Compensation with Machine Learning: An Experimental Demonstration
    Vinicius Oliari, Sebastiaan Goossens, Christian Häger, Gabriele Liga, Rick M. Bütler, Menno van den Hout, Sjoerd van der Heide, Henry D. Pfister, Chigo Okonkwo, and Alex Alvarado
    J. Lightw. Technol., vol. 38, no. 12, pp. 3114–3124, 2020
    [PDF] [arXiv] [DOI]
  5. Learning Physical-Layer Communication with Quantized Feedback
    Jinxiang Song, Bile Peng, Christian Häger, Henk Wymeersch, and Anant Sahai
    IEEE Trans. Commun., vol. 68, no. 1, pp. 645–653, 2020
    [PDF] [arXiv] [Code] [Video] [DOI]
  6. Approaching Miscorrection-free Performance of Product Codes with Anchor Decoding
    Christian Häger, and Henry D. Pfister
    IEEE Trans. Commun., vol. 66, no. 7, pp. 2797–2808, 2018
    [PDF] [arXiv] [DOI]
  7. Density Evolution for Deterministic Generalized Product Codes on the Binary Erasure Channel at High Rates
    Christian Häger, Henry D. Pfister, Alexandre Graell i Amat, and Fredrik Brännström
    IEEE Trans. Inf. Theory, vol. 63, no. 7, pp. 4357–4378, 2017
    [PDF] [arXiv] [DOI]
  8. On the Information Loss of the Max-Log Approximation in BICM Systems
    Mikhail Ivanov, Christian Häger, Fredrik Brännström, Alexandre Graell i Amat, Alex Alvarado, and Erik Agrell
    IEEE Trans. Inf. Theory, vol. 62, no. 6, pp. 3011–3025, 2016
    [arXiv] [DOI]
  9. Terminated and tailbiting spatially coupled codes with optimized bit mappings for spectrally efficient fiber-optical systems
    Christian Häger, Alexandre Graell i Amat, Fredrik Brännström, Alex Alvarado, and Erik Agrell
    J. Lightw. Technol., vol. 33, no. 7, pp. 1275–1285, 2015
    [PDF] [arXiv] [DOI]
  10. Improving Soft FEC Performance for Higher-Order Modulations via Optimized Bit Channel Mappings
    Christian Häger, Alexandre Graell i Amat, Fredrik Brännström, Alex Alvarado, and Erik Agrell
    Opt. Express, vol. 22, no. 12, pp. 14544–14558, 2014
    [PDF] [arXiv] [DOI]
  11. A low-complexity detector for memoryless polarization-multiplexed fiber-optical channels
    Christian Häger, Lotfollah Beygi, Erik Agrell, Pontus Johannisson, Magnus Karlsson, and Alexandre Graell i Amat
    IEEE Commun. Lett., vol. 18, no. 2, pp. 368–371, 2014
    [PDF] [arXiv] [DOI]
  12. Design of APSK Constellations for Coherent Optical Channels with Nonlinear Phase Noise
    Christian Häger, Alexandre Graell i Amat, Alvarado Alvarado, and Erik Agrell
    IEEE Trans. Commun., vol. 61, no. 8, pp. 3362–3373, 2013
    [PDF] [arXiv] [DOI]

conference

  1. End-to-End Learning of Geometrical Shaping Maximizing Generalized Mutual Information
    Kadir Gümüs, Alex Alvarado, Bin Chen, Christian Häger, and Erik Agrell
    In Proc. Optical Fiber Communication Conf. (OFC), San Diego, CA, 2020
    [PDF] [arXiv] [DOI]
  2. Pruning Neural Belief Propagation Decoders
    Andreas Buchberger, Christian Häger, Henry D. Pfister, Laurent Schmalen, and Alexandre Graell i Amat
    In Proc. IEEE Int. Symp. Information Theory (ISIT), Los Angeles, CA, 2020
    [PDF] [arXiv] [DOI]
  3. Decoding Reed-Muller Codes Using Redundant Code Constraints
    Mengke Lian, Christian Häger, and Henry D. Pfister
    In Proc. IEEE Int. Symp. Information Theory (ISIT), Los Angeles, CA, 2020
    [PDF]
  4. Benchmarking End-to-end Learning of MIMO Physical-Layer Communication
    Jinxiang Song, Christian Häger, Jochen Schröder, Tim O’Shea, and Henk Wymeersch
    In Proc. IEEE Glob. Communication Conf. (GLOBECOM), Taipei, Taiwan, 2020
    [arXiv] [Code] [DOI]
  5. Model-Based Machine Learning for Joint Digital Backpropagation and PMD Compensation
    Christian Häger, Henry D Pfister, Rick M. Bütler, Gabriele Liga, and Alex Alvarado
    In Proc. Optical Fiber Communication Conf. (OFC), San Diego, CA, 2020
    [PDF] [arXiv] [Slides] [DOI]
  6. Reinforcement Learning for Channel Coding: Learned Bit-Flipping Decoding
    Fabrizio Carpi, Christian Häger, Marco Martalò, Riccardo Raheli, and Henry D. Pfister
    In Proc. Annual Allerton Conference on Communication, Control, and Computing, Monticello, IL, 2019
    [PDF] [arXiv] [Code] [DOI]
  7. Learned Belief-Propagation Decoding with Simple Scaling and SNR Adaptation
    Mengke Lian, Fabrizio Carpi, Christian Häger, and Henry D. Pfister
    In Proc. IEEE Int. Symp. Information Theory (ISIT), Paris, France, 2019
    [PDF] [arXiv] [DOI]
  8. Revisiting Multi-Step Nonlinearity Compensation with Machine Learning
    Christian Häger, Henry D. Pfister, Rick M. Bütler, Gabriele Liga, and Alex Alvarado
    In Proc. European Conf. Optical Communication (ECOC), Dublin, Ireland, 2019
    [PDF] [arXiv] [Slides] [DOI]
  9. On Low-Complexity Decoding of Product Codes for High-Throughput Fiber-Optic Systems
    Alireza Sheikh, Alexandre Graell i Amat, Gianluigi Liva, Christian Häger, and Henry D. Pfister
    In Proc. Int. Symp. Turbo Codes and Iterative Information Processing (ISTC), Hong Kong, 2018
    [PDF] [arXiv] [DOI]
  10. ASIC Implementation of Time-Domain Digital Backpropagation with Deep-Learned Chromatic Dispersion Filters
    Christoffer Fougstedt, Christian Häger, Lars Svensson, Henry D. Pfister, and Per Larsson-Edefors
    In Proc. European Conf. Optical Communication (ECOC), Rome, Italy, 2018
    [PDF] [arXiv] [DOI]
  11. Deep Learning of the Nonlinear Schrödinger Equation in Fiber-Optic Communications
    Christian Häger, and Henry D. Pfister
    In Proc. IEEE Int. Symp. Information Theory (ISIT), Vail, CO, 2018
    [PDF] [arXiv] [Slides] [Code] [DOI]
  12. What Can Machine Learning Teach Us about Communications?
    Mengke Lian, Christian Häger, and Henry D. Pfister
    In Proc. IEEE Information Theory Workshop (ITW), Guangzhou, China, 2018
    [PDF] [arXiv] [DOI]
  13. Wideband Time-Domain Digital Backpropagation via Subband Processing and Deep Learning
    Christian Häger, and Henry D. Pfister
    In Proc. European Conf. Optical Communication (ECOC), Rome, Italy, 2018
    [PDF] [arXiv] [Slides] [DOI]
  14. Nonlinear Interference Mitigation via Deep Neural Networks
    Christian Häger, and Henry D. Pfister
    In Proc. Optical Fiber Communication Conf. (OFC), San Diego, CA, 2018
    [PDF] [arXiv] [Slides] [Code] [DOI]
  15. Decoding Reed-Muller Codes Using Minimum-Weight Parity Checks
    Elia Santi, Christian Häger, and Henry D. Pfister
    In Proc. IEEE Int. Symp. Information Theory (ISIT), Vail, CO, 2018
    [PDF] [arXiv] [DOI]
  16. Achievable Information Rates for Nonlinear Fiber Communication via End-to-end Autoencoder Learning
    Shen Li, Christian Häger, Nil Garcia, and Henk Wymeersch
    In Proc. European Conf. Optical Communication (ECOC), Rome, Italy, 2018
    [PDF] [arXiv] [Code] [DOI]
  17. Miscorrection-free Decoding of Staircase Codes
    Christian Häger, and Henry D. Pfister
    In Proc. European Conf. Optical Communication (ECOC), Gothenburg, Sweden, 2017
    [PDF] [arXiv] [Poster] [DOI]
  18. Density Evolution and Error Floor Analysis of Staircase and Braided Codes
    Christian Häger, Henry D. Pfister, Alexandre Graell i Amat, and Fredrik Brännström
    In Proc. Optical Fiber Communication Conf. (OFC), Anaheim, CA, 2016
    [PDF] [Poster] [DOI]
  19. Density Evolution for Deterministic Generalized Product Codes with Higher-Order Modulation
    Christian Häger, Alexandre Graell i Amat, Henry D. Pfister, and Fredrik Brännström
    In Proc. Int. Symp. Turbo Codes and Iterative Information Processing (ISTC), Brest, France, 2016
    [PDF] [arXiv] [Slides] [DOI]
  20. A Deterministic Construction and Density Evolution Analysis for Generalized Product Codes
    Christian Häger, Henry D. Pfister, Alexandre Graell i Amat, Fredrik Brännström, and Erik Agrell
    In Proc. Int. Zurich Seminar on Communications (IZS), Zürich, Switzerland, 2016
    [PDF] [Slides] [Code] [DOI]
  21. Deterministic and Ensemble-Based Spatially-Coupled Product Codes
    Christian Häger, Henry D. Pfister, Alexandre Graell i Amat, and Fredrik Brännström
    In Proc. IEEE Int. Symp. Information Theory (ISIT), Barcelona, Spain, 2016
    [PDF] [arXiv] [Slides] [Code] [DOI]
  22. On Parameter Optimization for Staircase Codes
    Christian Häger, Alexandre Graell i Amat, Henry D. Pfister, Alex Alvarado, Fredrik Brännström, and Erik Agrell
    In Proc. Optical Fiber Communication Conf. (OFC), Los Angeles, CA, 2015
    [PDF] [Slides] [DOI]
  23. Spatially-coupled codes for optical communications: state-of-the-art and open problems
    Alexandre Graell i Amat, Christian Häger, Fredrik Brännström, and Erik Agrell
    In Proc. Optoelectronics and Communications Conf. (OECC), Shanghai, China, 2015
    [PDF] [Slides] [DOI]
  24. Comparison of Terminated and Tailbiting Spatially Coupled LDPC Codes With Optimized Bit Mapping for PM-64-QAM
    Christian Häger, Alexandre Graell i Amat, Fredrik Brännström, Alex Alvarado, and Erik Agrell
    In Proc. European Conf. Optical Communication (ECOC), Cannes, France, 2014
    [PDF] [Slides] [DOI]
  25. Optimized Bit Mappings for Spatially Coupled LDPC codes over parallel binary erasure channels
    Christian Häger, Alexandre Graell i Amat, Alex Alvarado, Fredrik Brännström, and Erik Agrell
    In Proc. IEEE Int. Conf. Communications (ICC), Sydney, Australia, 2014
    [PDF] [arXiv] [Poster] [DOI]
  26. Constellation Optimization for Coherent Optical Channels Distorted by Nonlinear Phase Noise
    Christian Häger, Alexandre Graell i Amat, Alex Alvarado, and Erik Agrell
    In Proc. IEEE Glob. Communication Conf. (GLOBECOM), Anaheim, CA, 2012
    [PDF] [Slides] [DOI]

Patents

  1. Systems and methods for decoding forward error correction codes based on component codes
    Henry D. Pfister and Christian Häger (US 10,693,500 B2), filed: Sep. 17, 2018
    [PDF]

Thesis

  1. Analysis and Design of Spatially-Coupled Codes with Application to Fiber-Optical Communications
    PhD thesis, Chalmers University of Technology, May 2016
    [PDF] [Slides] [CPL]
  2. On Signal Constellations and Coding for Long-Haul Fiber-Optical Systems
    Licentiate thesis, Chalmers University of Technology, April 2014
    [PDF] [Slides] [CPL]
  3. Bidirectional Wireless Communication via Relay Nodes using Lattices
    Diploma thesis, Ulm University, July 2011
    [PDF]
  4. Turbo Equalization Performance: The Effect of Precoding and Application of Turbo Codes
    Study thesis, Ulm University, 2009
    [PDF]


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