Mitchell Coding Group

Welcome to David's website

David G. M. Mitchell received the Ph.D. degree in Electrical Engineering from the University of Edinburgh, United Kingdom, in 2009. He is currently an Associate Professor in the Klipsch School of Electrical and Computer Engineering at the New Mexico State University, USA. He previously held Visiting Assistant Professor and Post-Doctoral Research Associate positions in the Department of Electrical Engineering at the University of Notre Dame, USA. He is a Senior Member of the IEEE and his research interests are in the area of digital communications, with emphasis on error control coding and information theory. Dr. Mitchell holds 2 U.S. patents and has published over 50 peer-reviewed IEEE journal and conference articles gathering more than 1500 citations. He received the National Science Foundation CAREER award in 2022, the National Science Foundation's most prestigious award in support of early-career faculty, and the 2019 NMSU Early Career Award for Exceptional Achievements in Creative Scholarly Activity. He has received 3 best paper awards and is the recipient of the 2019 New Mexico EPSCoR Mentor Award. Dr. Mitchell serves as an Associate Editor for the IEEE Transactions on Information Theory.

Available positions
There are several open research positions in our group, including PhD and undergraduate opportunities. Please get in touch if you are interested in working in the exciting areas of data compression, machine learning, information theory, or quantum error correction!

Recent News

• 10/21/24: Traveling to the International Telemetry Conference with graduate student Andrew Cummins to present our paper "Spectrally Efficient LDPC Codes For IRIG-106 Waveforms via Random Puncturing" (co-authored with Erik Perrins).


• 07/07/24: Traveling to the IEEE International Symposium on Information Theory to present three papers "PAC Code Rate-Profile Design Using Search-Constrained Optimization Algorithms" (co-authored with post-doc Mohsen Moradi), "Generalized Quasi-Cyclic LDPC Codes: Design and Efficient Encoding" (presented by student Anthony Gómez-Fonseca, co-authored with Roxana Smarandache), and "Minimizing Distortion in Data Embedding Using LDGM Codes and the Cavity Method" (co-authored with post-doc Masoumeh Alinia)


• 06/02/24: Traveling to the IEEE International Conference on Communications (ICC) to present our paper "Cycle-Detection Based Decimation Policies for Lossy Source Encoding" (co-authored with post-doc Masoumeh Alinia).


• 04/19/24: US Patent 11,962,324 is issued: "Threshold-based min-sum algorithm to lower the error floors of quantized low-density parity-check decoders".
  
  


• 04/03/24: Traveling to the Munich Workshop on Shannon Coding Techniques to present our invited talk "Learning Sequential BP Decoding of Short Blocklength Codes" (co-authored with post-docs Salman Habib and Mohsen Moradi). Thanks very much to the organizers for the invitation!
  
  


• 01/31/24: Our new paper "Joint Learning and Channel Coding for Error-Tolerant IoT Systems based on Machine Learning" has been published in the latest IEEE Transactions on Artificial Intelligence.
  
  
  We propose a joint learning and channel coding (JLCC) scheme for IoT devices where the ML model is retrained to tolerate some channel errors, enabling a reduction in the required error correction. Simulation results show that, when employing JLCC with the proposed two retraining methods, an average reduction of 29.15% and 34.82% in the dissipated power is achieved.
  
  
• 01/06/24: Excited to begin work at my first stop on sabbatical leave to visit Dr. Pablo Olmos at the Signal Theory and Communications Department at the University Carlos III, Madrid. I will be working here on deep learning and generative AI.
  
  


• 12/01/23: Our new paper "An Efficient Strategy to Count Cycles in the Tanner Graph of Quasi-Cyclic LDPC Codes" has been published in the latest IEEE Journal on Selected Areas in Information Theory.
  
  
• 12/01/23: Our new paper "Error Propagation Mitigation in Sliding Window Decoding of Spatially Coupled LDPC Codes" has been published in the latest IEEE Journal on Selected Areas in Information Theory.
  
  
• 10/28/23: Had a great day representing the College of Engineering at the 2023 Las Cruces Spooky Science Festival! My team and I had fun explaining our research projects to over 500 talented future engineering students as well as creating some 3-D printed halloween decorations!
  
  
  
  
• 09/02/23: Congratulations to post-doc Masoumeh Alinia for our best paper award at the International Symposium on Topics in Coding for the paper "Optimizing Parameters in Soft-hard BPGD for Lossy Source Coding"!
  
  

In this paper, we have introduced a framework that leverages the cavity method to predict the values of softness parameters in the algorithm at which phase transition occurs. This framework can significantly reduce the need for time-consuming empirical searches to determine the best parameter values. Our approach has been found to deliver superior rate-distortion performance compared to conventional state-of-the-art approaches.


• 09/02/23: Traveling to the International Symposium on Topics in Coding to present four papers "Optimizing Parameters in Soft-hard BPGD for Lossy Source Coding" (co-authored with post-doc Masoumeh Alinia), "Reinforcement Learning for Sequential Decoding of Generalized LDPC Codes" (co-authored with post-doc Salman Habib), "A Low Complexity PEG-like Algorithm to Construct Quasi-Cyclic LDPC Codes" (presented by student Anthony Gómez-Fonseca, co-authored with Roxana Smarandache), and "Braided Convolutional Self-orthogonal Codes with Double Sliding Window Decoding" (co-authored with M. Zhu, A. Cummins, M. Lentmaier, and D. J. Costello, Jr.)


• 07/01/23: Our new paper "Optimizing Quasi-Cyclic Spatially Coupled LDPC Codes by Eliminating Harmful Objects" has been published in the latest EURASIP Journal on Wireless Communications and Networking.
  
  
  It is well known that some harmful objects in the Tanner graph of low-density parity-check (LDPC) codes have a negative impact on their error correction performance under iterative message-passing decoding. Differently from LDPC block codes, the design of spatially coupled LDPC codes must take into account the semi-infinite nature of the code. In this paper, we propose a general procedure, based on edge spreading, enabling the design of good quasi-cyclic spatially coupled LDPC (QC-SC-LDPC) codes.
  
  
• 06/11/23: Student Anthony Gomez-Fonseca presented our paper "On the Tanner Cycle Distribution of QC-LDPC Codes from Polynomial Parity-Check Matrices" at the 2023 IEEE International Symposium on Information Theory (ISIT).


• 04/01/23: Welcome to the group Dr. Mohsen Moradi! Mohsen obtained his PhD from Bilkent University in 2022 with Prof. Erdal Arikan. Before joining NMSU, he was a Postdoctoral Fellow at Bilkent University, advised by Prof. Tolga M. Duman. His main research interests include information theory, error correction coding, source coding, machine learning, and the analysis of algorithms.
  
  



• 03/01/23: Welcome to the group Dr. Salman Habib! Salman obtained his PhD in Electrical and Computer Engineering (ECE) at New Jersey Institute of Technology in 2021 with Prof. Joerg Kliewer. In 2022 he was at PetaIO Inc., Santa Clara, CA, where he developed techniques for determining the error-floor performance of high rate LDPC codes used for error correction in NAND flash storage devices. His research interests include coding theory, information theory, and machine learning.
  
  



• 11/11/22: Had a lovely trip to Brigham Young University to visit Dr. Willie Harrison and present the invited talk "Efficient Communication using Sparse Codes on Graphs" at the ECEN Colloquium.
  
  



• 09/30/22: Our new paper "A Unifying Framework to Construct QC-LDPC Tanner Graphs of Desired Girth" has been published in the latest IEEE Transactions on Information Theory.
  
  
  The performance of an LDPC code with parity-check matrix H depends on cycles in the associated Tanner graph. This paper presents a unifying framework to construct low-density parity-check (LDPC) codes with associated Tanner graphs of desired girth for which all existing designs must fit. Moreover, the derived necessary and sufficient conditions give rise to extremely efficient algorithms to construct such codes (as exemplified in the figure).
  
  
• 07/14/22: Traveling to the Coding Theory and Cryptography Workshop, ETH Zurich, held in honor of Joachim Rosenthal's 60th birthday. Dan Costello will be presenting our work "Modeling a Sliding Window Decoder for Spatially Coupled LDPC Codes". Happy birthday Joachim!


• 07/01/22: Welcome to the group Behrooz Mosallaei! Behrooz is currently pursuing his MSEE in the area of advanced wireless technologies in the smart grid.
  
  



• 07/01/22: Attending the 2022 IEEE International Symposium on Information Theory in Espoo, Finland, to present our paper "Systematic Doping of SC-LDPC Codes". PhD student Anthony Gómez-Fonseca (pictured) presented our other paper "Using Minors to Construct Generator Matrices for Quasi-Cyclic LDPC Codes". Great job Anthony!
  
  
  
  
• 07/01/22: Welcome to the group Dr. Masoumeh Alinia! Masoumeh obtained her PhD in Applied Mathematics (Coding and Information Theory) from Shahrekord University, with Prof. Mohammad Gholami. Her research interests are in the area of advanced error correcting codes, data compression, and machine learning.
  
  



• 04/15/22: Delighted to announce our new NSF project "RINGS: Resilient Edge Ecosystem for Collaborative and Trustworthy Disaster Response." Very excited to be a part of this unique public-private partnership.
  
  This project addresses networking and security challenges in next generation public safety and disaster response networks, where mission-critical emergency operations (e.g., search and rescue) need to be performed with limited surviving infrastructure, potentially augmented with diverse devices deployed by first responders. The project identifies the fundamental architectural and security challenges in fragmented networks, such as seamless multi-modal communications, resilient and verifiable computing, and trust management, and addresses them for viable deployment in disaster-response scenarios.
  
  
• 04/19/22: US Patent 11,309,915 is issued: "Efficient Implementation of a Threshold Modified Min-Sum Algorithm for LDPC Decoders".
  
  
  The proposed architecture introduces a novel lookup table based threshold attenuation technique, called threshold attenuated MSA (TAMSA). The TAMSA implementation (schematic above) is shown to improve bit error rate performance compared to conventional methods with no extra circuit power or circuit area compared to conventional AMSA, and only 0.07% extra leaf cells compared to conventional MSA.
  
  
• 04/11/22: Welcome to the group undergraduate student Yousif Yosif! Yosif is currently doing a double major Electrical Engineering and Computer Science. He is interested in research in the intersection of Information Systems and Machine Learning.
  
  



• 03/25/22: Thanks to NM EPSCoR for recognizing my CAREER award! Proud to be a part of this excellent team.
• 3/12/22: Nice write-up in the Las Cruces Sun-News about my NSF CAREER award! Check it out to find out more about our research projects and educational outreach.
  
  
  
  
• 02/18/22: Our new paper "Concatenated Spatially Coupled LDPC Codes With Sliding Window Decoding for Joint Source-Channel Coding" has been published in the latest IEEE Transactions on Communications.
  
  
  In this paper, we show that concatenated SC-LDPC codes display a notable performance improvement compared to existing state-of-the-art JSCC schemes based on LDPC codes with comparable latency and complexity constraints.
  
  
• 02/11/22: Enjoyed participating as a panelist in the HSI Stem Hub CAREER workshop. We fielded some great questions from early-career researchers working at Hispanic-Serving Institutions across the USA. Good luck to all!


• 02/01/22: Excited to announce that I am a recipient of the 2022 NSF CAREER Award for the project "Sparse Graph-Based Codes for Network Data Compression.". Many thanks to my current and former students, mentors, and colleagues.
  
  The proposed research significantly advances the state of the art in network data compression by employing ideas from network coding, graph theory, iterative information processing, machine learning, and circuit design. This promises a significant transformative impact on many critical applications employing reliable networked data compression, for example in the fields of healthcare, environmental monitoring, and finance.
  
  The project also includes an integrated education plan to increase participation in Science, Technology, Engineering, and Mathematics (STEM), particularly among minority groups. This objective is supported by several complementary initiatives, including targeted K-12 activities as well as related teacher training and mentoring.
  
  
• 01/31/22: Our new paper "Ternary LDPC Error Correction for Arrhythmia Classification in Wireless Wearable Electrocardiogram Sensors" has been published in the latest IEEE Transactions on Circuits and Systems.
  
  
  This system for improved arrhythmia detection presents a hardware-friendly LDPC encoder circuit. Simulation results show that the ternary LDPC codes can significantly improve classification accuracy in the presence of errors. For example, with an error probability of up to 21% in the sensor output bitstreams, the classification accuracy remains above 99% with the proposed error correction system.
  
  
• 12/11/21: Dan Costello presented our paper "Modeling a Sliding Window Decoder for Spatially Coupled LDPC Codes" at the 2021 IEEE Global Communications Conference (GLOBECOM).


• 12/09/21: Yanfang Liu presented (online) our research paper "Ternary LDPC Error Correction for Arrhythmia Classification in Wireless Wearable Electrocardiogram Sensors" at the 2021 IEEE International Symposium on Integrated Circuits and Systems (ISICAS). Great job Vivian!


• 11/03/21: Congratulations to Dr. Ahmad Golmohammadi for completing his doctoral thesis. Ahmad will be leaving us to join Bose Corporation.
  
  
  
  In his doctoral research, he showed several fundamental results related to spatially coupled codes for source compression, including that they have distortion performance very close to the rate-distortion (RD) limit as well as showing notable performance improvement compared to existing state-of-the-art joint source-channel coding schemes based on LDPC codes with comparable latency and complexity constraints (both published in the IEEE Transactions on Communications). Congratulations to Ahmad and good luck in your future career!


• 10/23/21: Had a great day representing the College of Engineering at the 2021 Las Cruces Spooky Science Festival. We had fun explaining our research projects to future generations of talented engineering students as well as creating some 3-D printed halloween decorations!
  
  
  
  
• 10/01/21: Good luck to Dr. Yanfang (Vivian) Liu, who is leaving us to join Innogrit Corporation to work on research related to LDPC codes for data storage! In her post-doctoral work, she published several important theoretical papers related to generalized LDPC codes, showing their suitability for URLLC in 5G communications, as well as multiple hardware implementation papers for LDPC decoders for communications and biomedical applications.
  
  
  
  


• 09/01/21: Congratulations to graduate students Andrew Cummins ("Iterative Threshold Decoding of Spatially Coupled, Parallel-Concatenated Codes") and Anthony Gomez-Fonseca ("Necessary and Sufficient Girth Conditions for LDPC Tanner Graphs with Denser Protographs") that both presented their first papers at the IEEE International Symposium on Topics in Coding 2021.
  
  
  
  


• 07/18/21: Attending the 2021 IEEE International Symposium on Information Theory (online) to present our research paper "Necessary and Sufficient Girth Conditions for Tanner Graphs of Quasi-Cyclic LDPC Codes".



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