Ken Duffy, M.A., Ph.D. Hamilton Institute NUI Maynooth. E-mail: ken.duffy@nuim.ie.

Research

I'm an applied mathematician whose main research interests are in applied probability and stochastic modelling.
I have a penchant for interdisciplinary applications, particularly within communication networks and immunology.
I am a member of the Institute's Applied Probability Group.

Drafts

• Guesswork, large deviations and Shannon entropy.
  Mark M. Christiansen and Ken R. Duffy.
  
• Tail asymptotics for busy periods.
  Ken R. Duffy and Sean P. Meyn.
  
• Decentralized constraint satisfaction.
  Ken R. Duffy, Charles Bordenave and Douglas J. Leith.
  For a real-time illustration of how the algorithm solves problems, see the applets
  for two problem classes, decentralized graph colouring and decentralized consensus identification.
  
• H-RCA: 802.11 collision-aware rate control.
  K. D. Huang, Ken R. Duffy and David Malone.
  

Journal papers by subject (journal papers by year)
Immunology; Communication Networks; Applied Probability and Stochastic Processes.

• Activation-induced B cell fates are selected by intracellular stochastic competition.
  Ken R. Duffy, Cameron J. Wellard, John F. Markham, Jie H. S. Zhou, Ross Holmberg,
  Edwin D. Hawkins, Jhagvaral Hasbold, Mark R. Dowling and Philip D. Hodgkin.
  Science, 335 (6066), 338-341, 2012.
  
• A minimum of two distinct heritable factors are required to explain correlation structures in proliferating lymphocytes.
  John F. Markham, Cameron J. Wellard, Edwin D. Hawkins, Ken R. Duffy and Philip D. Hodgkin.
  Journal of the Royal Society Interface, 7 (48), 1049-1059, 2010.
  The data used in this study is available for download from the Hodgkin Lab at WEHI.
  
• On the impact of correlation between collaterally consanguineous cells on lymphocyte population dynamics.
  Ken R. Duffy and Vijay G. Subramanian.
  Journal of Mathematical Biology, 59 (2), 255-285, 2009.
• Determining the expected variability of immune responses using the Cyton Model.
  Vijay G. Subramanian, Ken R. Duffy, Marian L. Turner and Philip D. Hodgkin.
  Journal of Mathematical Biology, 56 (6), 861-892, 2008.

• Decentralised learning MACs for collision-free access in WLANs.
  Minyu Fang, David Malone, Ken R. Duffy and Douglas J. Leith.
  Wireless Networks, to appear.
• The 802.11g 11 Mb/s rate is more robust than 6 Mb/s.
  K. D. Huang, David Malone and Ken R. Duffy.
  IEEE Transactions on Wireless Communcations, 10 (4), 1015-1020, 2011.
• On the validity of IEEE 802.11 MAC modeling hypotheses.
  K. D. Huang, Ken R. Duffy and David Malone.
  IEEE/ACM Transactions on Networking, 18 (6), 1935-1948, 2010.
• Mean field Markov models of wireless local area networks.
  Ken R. Duffy.
  Markov Processes and Related Fields, 16 (2), 295-328, 2010.
• Log-convexity of rate region in 802.11e WLANs.
  Douglas J. Leith, Vijay G. Subramanian and Ken R. Duffy.
  IEEE Communications Letters, 14 (1), 57-59, 2010.
• Existence and uniqueness of fair rate allocations in lossy wireless networks.
  Vijay G. Subramanian, Ken R. Duffy and Douglas J. Leith.
  IEEE Transactions on Wireless Communications, 8 (7), 3401-3406, 2009.
• On a buffering hypothesis in 802.11 analytic models.
  K. D. Huang and Ken R. Duffy
  IEEE Communications Letters, 13 (5), 312-314, 2009.
• Modeling the impact of buffering on 802.11.
  Ken Duffy and Ayalvadi J. Ganesh.
  IEEE Communications Letters, 11 (2), 219-221, 2007.
• Modeling the 802.11 distributed coordination function in non-saturated heterogeneous conditions.
  David Malone, Ken Duffy and Douglas J. Leith.
  IEEE/ACM Transactions on Networking, 15 (1), 159-172, 2007.
• Modeling 802.11 Mesh Networks.
  Ken Duffy, Douglas J. Leith, Tianji Li and David Malone.
  IEEE Communications Letters 10 (8), 635-637, 2006.
• Modeling the 802.11 distributed coordination function in non-saturated conditions.
  Ken Duffy, David Malone and Douglas J. Leith.
  IEEE Communications Letters, 9 (8), 715-717, 2005.

• Sample path large deviations of Poisson shot noise with heavy tail semi-exponential distributions.
  Ken R. Duffy and Giovanni Luca Torrisi.
  Journal of Applied Probability, 48 (3), 688-698, 2011.
• Estimating Loynes' exponent.
  Ken R. Duffy and Sean P. Meyn.
  Queueing Systems: Theory & Applications, 68 (3-4), 285-293, 2011.
• Sample path large deviations for order statistics.
  Ken R. Duffy, Claudio Macci and Giovanni Luca Torrisi.
  Journal of Applied Probability, 48 (1), 238-257, 2011.
• On the large deviations of a class of modulated additive processes.
  Ken R. Duffy, Claudio Macci and Giovanni Luca Torrisi.
  ESAIM: Probability and Statistics, 2011 (15), 83-109, 2011.
• Most likely paths to error when estimating the mean of a reflected random walk.
  Ken R. Duffy and Sean P. Meyn.
  Performance Evaluation, 67 (12), 1290-1303, 2010.
• Complexity analysis of a decentralised graph colouring algorithm.
  Ken R. Duffy, Neil O'Connell and Artem Sapozhnikov.
  Information Processing Letters, 107 (2), 60-63, 2008.
• The large deviation principle for the on/off Weibull sojourn process.
  Ken R. Duffy and Artem Sapozhnikov.
  Journal of Applied Probability, 45 (1), 107-117, 2008.
• Logarithmic asymptotics for a single-server processing distinguishable sources.
  Ken R. Duffy and David Malone.
  Mathematical Methods of Operations Research, 68 (3), 509-537, 2008.
• Loss aversion, large deviation preferences and optimal portfolio weights for some classes of return processes.
  Ken Duffy, Olena Lobunets and Yuri Suhov.
  Physica A, 378 (2), 408-422, 2007.
• Ambiguities in estimates of critical exponents for long-range dependent processes.
  Ken Duffy, Christopher King and David Malone.
  Physica A, 377 (1), 43-52, 2007.
• Some remarks on LD plots for heavy-tailed traffic.
  David Malone, Ken Duffy and Christopher King.
  ACM SIGCOMM Computer Communications Review, 37 (1), 41-42, 2007.
• Using estimated entropy in a queueing system with dynamic routing.
  Ken Duffy, Eugene A. Pechersky, Yuri M. Suhov and Nikita D. Vvedenskaya.
  Markov Processes and Related Fields, 13 (1-2), 57-84, 2007.
• How to estimate a cumulative process's rate-function.
  Ken Duffy and Anthony P. Metcalfe.
  Journal of Applied Probability 42 (4), 1044-1052, 2005.
• The large deviations of estimating rate-functions.
  Ken Duffy and Anthony P. Metcalfe.
  Journal of Applied Probability 42 (1), 267-274, 2005.
• Some useful functions for functional large deviations.
  Ken Duffy and Mark Rodgers-Lee.
  Stochastics and Stochastics Reports 76 (3), 267-279, 2004.
• Logarithmic asymptotics for unserved messages at a FIFO.
  Ken Duffy and Wayne G. Sullivan.
  Markov Processes and Related Fields 10 (1), 175-189, 2004.
• On Knuth's generalization of Banach's matchbox problem.
  Ken Duffy and W. M. B. Dukes.
  Mathematical Proceedings of the Royal Irish Academy 104A, 107-118, 2004.
• Logarithmic asymptotics for the supremum of a stochastic process.
  Ken Duffy, John T. Lewis and Wayne G. Sullivan.
  Annals of Applied Probability 13:2, 430-445, 2003.
• Distribution-free confidence intervals for measurements of effective bandwidth.
  Laszlo Gyorfi, Andras Racz, Ken Duffy, John T. Lewis and Fergal Toomey.
  Journal of Applied Probability 37:1, 224-235, 2000.
  

Conference papers (all Communication Networks)

• Modeling conservative updates in multi-hash approximate count sketches.
  Giuseppe Bianchi, Ken R. Duffy, Douglas J. Leith and Seva Shneer.
  24th International Teletraffic Congress, 4-7th September 2012, Krakow, Poland.
• Investigating the validity of IEEE 802.11 MAC modeling hypotheses.
  K. D. Huang, Ken R. Duffy, David Malone and Douglas J. Leith.
  IEEE PIMRC 15-18th September 2008, Cannes, France.
• Improving fairness in multi-hop mesh networks using 802.11e.
  Ken Duffy, Douglas J. Leith, Tianji Li and David Malone.
  Resource Allocation in Wireless Networks, 3rd April 2006, Boston, USA.
• Modeling 802.11e for data traffic parameter design.
  Peter Clifford, Ken Duffy, John Foy, Douglas J. Leith and David Malone.
  WiOPT 2006, 28-37, 3rd-7th April 2006, Boston, USA.
• Modelling 802.11 wireless links.
  Ken Duffy, David Malone and Douglas J. Leith.
  IEEE Conference on Decision and Control, 6952 - 6957, 12th-15th December 2005, Seville, Spain.
• On improving voice capacity in 802.11 infrastructure networks.
  Peter Clifford, Ken Duffy, Douglas J. Leith and David Malone.
  IEEE WirelessCom, 214 - 219, 13th-16th June 2005, Maui, Hawaii, USA.
• Modeling the 802.11 distributed coordination function with heterogeneous finite load.
  David Malone, Ken Duffy and Douglas J. Leith.
  Resource Allocation in Wireless Networks, 3rd April 2005, Trento, Italy.

• Modelling and simulation analysis of the 802.11/802.11e MAC layers.
  Qiang Ni, David Malone, Peter Clifford, Ken Duffy, Douglas Leith and Tianji Li.
  Advances in Wireless Networks: Performance Modelling, Analysis and Enhancement,
  Nova Science Publishers, edited by Geyong Min, Yi Pan and Pingzhi Fan, 2007.

Other articles

• John T. Lewis (1932-2004).
  Ken Duffy and Joe Pule.
  Markov Processes and Related Fields, 13 (1-2), 3-19, 2007.

Current graduate-students

• Mark Christiansen.
• Alessandro Checco (co-supervised with D. Leith).

Past graduate-students

• Kaidi Huang, Ph.D. (NUI Maynooth), 2010.
  
• Minyu Fang, M.Sc. (NUI Maynooth), 2010.
  
• Anthony Paul Metcalfe, M.Sc. (University of Dublin), 2004.
  
• Mark Rodgers-Lee, M.Sc. (University of Dublin), 2003.
  

Current Editorial Boards

• Forthcoming special issue of Queueing Systems on the Mathematics of Energy Networks, with James Cruise and Stan Zachery.
• PLoS ONE.

• 11th International Conference on Artificial Immune Systems, 2012, (ICARIS 2012).
• ACM CoNext, 2012, (CoNext 2012).
• 24th International Teletraffic Congress, 2012, (ITC 24).
• 1st International Workshop on Network Science, 2011, (Hamilton Institute-NS1).
• IEEE International Conference on Computer Communications and Networks, 2011, (ICCCN 2011).
• 23rd International Teletraffic Congress, 2011, (ITC 23).
• 3rd International Workshop on Systems Biology, 2010, (Hamilton Institute-SB3).
• 22nd International Teletraffic Congress, 2010, (ITC 22).
• 3rd International Workshop on Performance Analysis and Enhancement of Wireless Networks, 2008, (PAEWN 08).
• Valuetools workshop on interdisciplinary systems approach in performance evaluation and design of computer and communication systems, 2007, (Inter-Perf 2007).
• 1st Hamilton Institute Workshop on Applied Probability, 2007, (Hamilton Institute-AP1).

Oddities

I have had the unusual honour of having acknowledgements in at least eleven diverse places.

1. Christopher Fuchs thanks me for teaching him about magnalium in his article "On the Quantumness of a Hilbert Space",
   Quantum Information, Statistics, Probability: Dedicated to Alexander S. Holevo on the Occasion of His 60th Birthday,
   edited by O. Hirota (Rinton Press, Princeton, NJ, 2004).
2. In their O'Reilly book IPv6 Network Administration, the authors, Niall Murphy and David Malone, say the following:
   "Ken Duffy managed to resist the temptation to edit our manuscript, and we can only admire his restraint."
3. My academic grand-nephew, Stephen Wills thanks me for facilitating corrections to his paper
   "On the generators of operator Markovian cocycles", Markov Processes and Related Fields 13 (2007), 191-211.
4. In his CUP Monograph Control Techniques for Complex Networks, Sean Meyn thanks me for graphs generated by
   code that I wrote while attending a meeting organised by Serguei Foss, Takis Konstantopoulos and Stan Zachary.
5. In their article "Large deviation results on some estimators for stationary Gaussian processes", Statistics 44 (2), 129-144, 2010,
   Claudio Macci and Lea Petrella thank me for illustrating to them results from the literature on semi-exponential distributions.
6. In their article "A single-cell pedigree analysis of alternative stochastic lymphocyte fates", Proceedings of the National Academy of Sciences
   11, 106(32), 13457-13462, 2009, E. D. Hawkins, J. F. Markham, L. P. McGuinness and P. D. Hodgkin thank me, along with others,
   for critical reading of the manuscript and helpful suggestions.
7. In the article "The effect of correlations on the population dynamics of lymphocytes", Journal of Theoretical Biology,
   264 (2), 443-449 2010, by C. Wellard, J. Markham, E.D. Hawkins, P.D. Hodgkin, Cameron thanks me for discussions.
8. In the article "On Thresholds for Robust Goodness-of-Fit Tests", presented at the IEEE Information Theory Workshop, 2010
   by Jayakrishnan Unnikrishnan, Sean P. Meyn and Venugopal V. Veeravalli, the authors thank me for for initial discussions that
   motivated the problem studied in the paper.
9. In the article "Large Deviations Of Max-Weight Scheduling Policies On Convex Rate Regions", Mathematics of Operations Research
   35(4), 881-910, 2010, my pal Vijay G. Subramanian is overly kind in thanking me for suggestions that helped expand its scope.
10. In the article "Many Sources Large Deviations of Max-Weight Scheduling", IEEE Transactions on Information Theory 57(4),
    2151-2168, 2011, Vijay G. Subramanian T. Javidi and S. Kittipiyakul thank me, Ruth Williams, Milan Matejdes and the reviewers for
    "tremendously helpful suggestions". I don't know what Ruth, Milan and the reviewers said, but in my case you're overly generous.
11. In the article "How neurons migrate: a dynamic in-silico model of neuronal migration in the developing cortex" by Yaki Setty, Chih-Chun Chen,
    Maria Secrier, Nikita Skoblov, Dimitris Kalamatianos and Stephen Emmott BMC Systems Biology 5:154, the authors thank me for proof-reading duties.