Dr.-Ing. Thomas Michel

Contact:

Email: michel@hhi.fhg.de

Dauer der Mitarbeit:

bis 2008

Thema der Arbeit:

Resource Allocation for Single and Multiple Antenna OFDM Uplink and Downlink Systems

Research interests:

• broadcast and multiple access channels
• (convex) optimization theory
• multi-antenna (MIMO) and multi-carrier systems
• adaptive scheduling and cross-layer design

Main research:

My main interest focuses on multiantenna systems for frequency selective channels, where for combating intersymbol interference orthogonal frequency division multiplexing (OFDM) is employed. In future multiuser systems, each user will be in need of a different QoS (quality of service) requirement according to the kind of service provided to him currently. Therefore, smart adaptive transmission strategies have to be developed, which exploit multiuser diversity and take into account the users' individual states. The optimal transmission schemes highly depend on the kind of channel feedback provided by the system, user mobility, channel properties, rate requirements, etc. A further challange is to take into account real world restrictions as limited feedback, limited computational ressources, etc.

To develop applicable algorithms for real world MIMO-OFDM systems, a broad understanding of the underlying fundamental information-theoretic problems for MIMO and OFDM and their problem structures is of great importance (this turned out to be true especially for MIMO systems, where the theoretic insights resulted in practical schemes such as e.g. BLAST). That is why our studies include quite theoretic topics.

Projects:

• "Entwurf von Mehrträger-Mobilfunksystemen mit kooperativen, verteilten Antennen (MOSKOVA)" funded by the Federal German Ministry of Education and Research (BMBF)
• industry project

Publications:

Journal Papers

• Delay-Limited Transmission in OFDM Systems: Performance Bounds and Impact of System Parameters
  G. Wunder, T. Michel, and C. Zhou, submitted to IEEE Transactions on Wireless Communications, accepted, 2009.
• Multiuser OFDMA Optimization: Algorithms and Duality Gap Analysis
  G. Wunder, T. Michel, and C. Zhou, submitted, 2009.
• Iterative Water-Filling Algorithms for Power Efficiency Optimization in MIMO Broadcast Channels
  T. Michel and G. Wunder, AEÜ-Archiv f. Elektronik u. Übertragungstechnik, 2008, to be published.
• Optimal Resource Allocation for parallel Broadcast Channels: Minimum rate constraints and sum power minimization
  G. Wunder and T. Michel, IEEE Trans. on Information Theory, vol. 53, no. 12, pp. 4817-4822, Dec. 2007.

Conference, Symposium, and Workshop Papers

• Multiuser OFDMA optimization: Algorithms and Duality Gap Analysis
  G. Wunder and T. Michel, Proc. ITG/IEEE Int. Workshop on Smart Antennas (WSA), Darmstadt, Feb. 2008.
• Utility Maximization for OFDMA systems over discrete sets
  C. Zhou, G. Wunder, and T. Michel, Proc. IEEE Int. Conf. on Communications (ICC), Glasgow, June 2007.
• Achieving QoS and Efficiency in the MIMO Downlink with Limited Power
  T. Michel and G. Wunder, Proc. ITG/IEEE Int. Workshop on Smart Antennas (WSA), Vienna, Feb. 2007.
• Throughput aware power-balancing for the MIMO Gaussian MAC
  T. Michel and G. Wunder, Proc. 8th IEEE Workshop on Signal Processing Advances in Wireless Communications (SPAWC), Helsinki, June 2007.
• Nonlinear Downlink Beamforming under QoS Constraints: Optimum Precoding Order and the Need for Time-Sharing
  T. Michel and G. Wunder, Proc. IEEE Int. Symp. on Personal, Indoor and Mobile Radio Communications (PIMRC), Athens, Greece, Sept. 2007, invited.
• On optimization of multiuser systems using interference calculus
  G. Wunder and T. Michel, Proc. Asilomar Conference on Signals, Systems, and Computers, Nov. 2007, invited.
• Utility Optimization based on MSE for Parallel Broadcast Channels: The Square Utility Optimization based on MSE for Parallel Broadcast Channels: The Square Root Law
  G. Wunder, I. Blau, and T. Michel, 45th Annual Allerton Conference on Communication, Control, and Computing, Sept. 2007.
• Delay-limited OFDM broadcast capacity region and impact of system parameters
  G. Wunder and T. Michel, Proc. IEEE Information Theory Workshop (ITW'06), Punta del Este, Uruguay, Mar. 2006.
• Minimum Rates Scheduling for OFDM Broadcast Channels
  T. Michel and G. Wunder, Proc. IEEE Int. Conf. on Acoustics, Speech and Signal Processing (ICASSP '06), May 2006.
• Approaching the delay-limited OFDM broadcast capacity with OFDMA
  G. Wunder and T. Michel, Proc. 7th IEEE Workshop on Signal Processing Advances in Wireless Communications (SPAWC '06), Cannes, France, July 2006.
• A Generic OFDM Downlink Scheduling Policy Incorporating Service Induced Rate Constraints
  T. Michel, C. Zhou, and G. Wunder, 15th IST Mobile & Wireless Communications Summit, Myconos, Greece, June 2006.
• A Framework For Resource Allocation in OFDM Broadcast Systems
  G. Wunder, T. Michel, and C. Zhou, Proc. 14th European Signal Processing Conference (EUSIPCO), Sept. 2006, invited.
• Sum Rate Iterative Water-Filling for Gaussian MIMO Broadcast Channels
  T. Michel and G. Wunder, Proc. 9th Intern. Symposium on Wireless Personal Multimedia Commun. (WPMC), San Diego, USA, 2006.
• Minimum Rates Scheduling for MIMO-OFDM Broadcast Channels
  G. Wunder and T. Michel, Proc. 9th IEEE Intern. Symp. on Spread Spectrum Techniques and Applications (ISSSTA 2006), Manaus, Brazil, Aug. 2006, invited.
• Minimum Delay and Buffer Length Bounds for Stable OFDM Broadcast Systems
  G. Wunder, C. Zhou, and T. Michel, IEEE Int. Symposium on Information Theory and its Applications (ISITA), Seoul, Korea, 2006.
• The low and high SNR behavior of the OFDM delay limited capacity
  G. Wunder and T. Michel, Proc. of Allerton Conference on Communication, Control and Computing, Monticello, USA, Sept. 2006.
• Optimal And Low Complexity Suboptimal Transmission Schemes For MIMO-OFDM Broadcast Channels
  T. Michel and G. Wunder, Proc. IEEE Intern. Conf. on Communications (ICC '05), Seoul, Korea, May 2005.
• A (not so) Many User Sum Capacity Analysis for the MIMO OFDM Broadcast Channel
  G. Wunder and T. Michel, International ITG/IEEE Workshop on Smart Antennas (WSA), Duisburg, Germany, Apr. 2005.
• Solution to the Sum Power Minimization Problem under Given Rate Requirements for the OFDM Multiple Access Channel
  T. Michel and G. Wunder, Proc. of Allerton Conference on Communication, Control and Computing, Monticello, USA, Sept. 2005.
• Interpolation and Noise Reduction in MIMO-OFDM - A Complexity Driven Perspective
  T. Haustein, S. Schiffermüller, V. Jungnickel, M. Schellmann, T. Michel, and G. Wunder, Proc. 8th International Symposium on Signal Processing and Its Applications (ISSPA 2005), vol. 1, Sydney, Australia, Aug. 2005, pp. 143-146.
• On the OFDM Multiuser Downlink Capacity
  G. Wunder and T. Michel, Proc. IEEE Vehicular Technology Conference (VTC Fall '04), Los Angeles, USA, Sept. 2004.

Unpublished

• Moderate complexity approximation to MMSE for MIMO-OFDM systems
  O. Henkel, T. Michel, and G. Wunder, 2005, Technical Report.