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Research
Current Work
My main interests are algorithms and networking.
I am currently working with Brendan Mumey and Richard Wolff on an optical networking project. This research project considers agile constraint-based routing and wavelength assignment (RWA) strategies to mitigate physical layer impairments that affect the end-to-end performance of next generation all-optical networks. The RWA methods being developed take into account changing traffic patterns, resource availability, and the behavior of the underlying physical layer under transient conditions to minimize impairments and assure that Quality of Service (QoS) requirements are achieved. Physical layer network impairments that affect end-to-end path performance include switching transients, amplifier gain fluctuations, and channel cross talk. Temporal and geographic variations in network traffic can also affect network performance. A general framework for studying the cumulative effects of such impairments and traffic variations is being designed and conducted using the Montana State University optical network testbed. Based on this new framework, state-of-the-art physically aware RWA algorithms are being designed, implemented and tested.
I am also working with Brendan Mumey and Jian Tang on wireless networking. More specifically, we have been studying scheduling algorithms for multihop wireless networks with MIMO links. We have formally proved that this problem is NP Complete and are searching for good approximation algorithms. In the future, we hope to study joint routing and scheduling algorithms.
Past Work
During my Master's work at University of Nebraska at Omaha, I studied compilers under the direction of William Mahoney. We developed C++ Annotations for Improved Software Reliability (CANNISTR), based largely on Spark. The general idea is to add additional annotations to a language in the form of special comments. Then CANNISTR takes these annotations and inserts additional assertions into the source code.
I also received my Bachelor's degree from the University of Nebraska at Omaha.
Industry
From February 2005 to January 2007, I worked for Raytheon's Intelligence and Information Systems Division in Omaha, Nebraska as a Software Engineer. I worked on the National Polar Orbiting Environmental Satellite System (NPOESS), primarily for the CrIS sensor. We took a GUI based Visual Studio implementation of a scientific algorithm and ported it to run on the IBM AIX platform via a command line interface. We also spent time optimizing the code and validating the results.
Since October 2001, I have worked part-time for Russ Kaplan Investments. I am a Registered Investment Adviser. My various consulting and advising tasks for the company include: making investment recommendations, writing monthly articles in a newsletter, tracking performance of clients, and other miscellaneous tasks.
Publications
Conference Papers
- Brendan Mumey, Jian Tang, Timothy Hahn. "Joint Stream Control and Scheduling in Multihop Wireless Networks with MIMO Links." IEEE ICC 2008. [PDF]
- Trent Jackson, Matt Lee, Timothy Hahn, Wenhao Lin, Richard Wolff, Brendan Mumey, Kevin Repasky. "EDFA Transient Reduction Using Power Shaping." IASTED WOC 2008. [PDF]
- Timothy Hahn, Andrew Albers, Brendan Mumey, Richard Wolff. "RAPTOR: A High Performance Physically Aware Simulation Engine for Optical Networks." OFC 2010. [PDF] (in submission)
Journal Articles
- Wenhao Lin, Timothy Hahn, Richard Wolff, Brendan Mumey. "A Distibuted Impairment Aware QoS Framwork for All-Optical Networks." Optical Switching and Networking. [PDF]
- Trent Jackson, Timothy Hahn, Wenhao Lin, Richard Wolff, Brendan Mumey. "Bit Error Rate Reduction by Power Shaping in EDFA Networks." Optical Fiber Technology. [PDF]
- Timothy Hahn, Andrew Albers, Brendan Mumey, Richard Wolff. "RAPTOR: A High Performance Physically Aware Simulation Engine for Optical Networks." Optical Switiching and Networking. [PDF] (in submission)
Presentations
- Timothy Hahn, Brendan Mumey, Richard Wolff. "Modeling All-Optical WDM Networks." Optec 2007. (poster)
- Timothy Hahn, Shen Wan. "An Ant colony Optimization for Routing and Wavelength Assignment." MSU Student Research Celebration 2008. (poster)
- Timothy Hahn. "Joint Stream Control and Scheduling in Multihop Wireless Networks with MIMO Links." IEEE ICC 2008. [PDF]
- Timothy Hahn, Brendan Mumey, Richard Wolff."Routing and Wavelength Assignment (RWA) for Wavelength Division Multiplexing (WDM) Optical Networks." Optec 2008. [PDF]
- Timothy Hahn, "Physically Aware Routing and Wavelength Assignment (RWA) Algorithms for Next Generation Transparent Optical Networks," Ph.D. Comprehensive Examination, April 2009. [Presentation] [Paper]
- Timothy Hahn, Brendan Mumey, Richard Wolff."RAPTOR: A High Performance Physically Aware Simulation Engine for Optical Networks" Optec 2009. [PDF]
Selected Coursework
- Timothy Hahn. "C++ Annotations for Improved Software Reliability (CANNISTR)." July 2007. [PDF]
- Timothy Hahn, Chad Bohannan. "A Parallel Implementation of Branch and Bound to Solve Mixed Integer Linear Programs (MILP)." December 2007. [PDF] [Presentation] [Source Code]
- Timothy Hahn. "Optical Add-Drop Multiplexers (OADMS)." December 2007. [PDF] [Source Code]
- Timothy Hahn, Shen Wan. "An Ant Colony Optimization for Routing and Wavelength Assignment." May 2008. [PDF] [Source Code].
Source Code
- RAPTOR (Route Assignment Program for Transparent Optical Routes): A program still under develop to simulate optical networks for the purpose of evaluating Routing and Wavelength Assignment (RWA) algorithms. Last Updated: August 27, 2009
- MIMO Coloring: A program developed to simulate wireless MIMO networks. It was used to implement several of the coloring algorithms presented in our ICC 2008 paper. Last Updated: February 23, 2009 [SOURCE CODE]
- MIMO Stream Control: Another program developed to simulate wireless MIMO networks. It was used to implement the joint stream control and routing algorithms presented in our AAIM 2009 paper. Last Updated: February 23, 2009 [SOURCE CODE]