Contact:  RWTH Aachen  Chair of Communication Networks  Kopernikusstr. 16  D-52074 Aachen Germany phone:   +49 (0)241 80 27928 fax:   +49 (0)241 88 9085 mail: tim@comnets.rwth-aachen.de

Navigation: Research Interests HiWi Jobs and topics for diploma theses Publications

Chair of Communication Networks (ComNets), Aachen University of Technology (RWTH)

My research interests are:

• Performance Evaluation of relay concepts for future (B3G) multi-hop packet radio networks


• GPRS live network measurements and GPRSim validation


• Analytical models and dimensioning procedures for packet-switched mobile radio networks ((E)GPRS, UMTS)


• Realistic characterization and modelling of elastic (i.e., WWW, WAP, e-mail) and inelastic (Streaming applications) traffic considering the well-known self-similar property of recent Internet traffic.


• Modelling of TCP-based traffic and interaction of TCP with specific properties of the radio link and radio interface protocols


• Modelling and (mostly analytical) performance evaluation of
  • Quality of Service mechanisms for packet switched mobile radio networks
  • Scheduling algorithms for QoS support in packet-switched mobile radio networks
  
  
Currently I am evaluating several approaches for analysis of TCP-like flow control mechanisms sharing the bandwidth of a bottleneck link. Recently published research indicates that realistic modelling of the IP arrival process not only can be achieved by using powerful stochastic processes, but also needs to account for the elasticity caused by TCP flow control. I am looking for a way to combine both in one modelling approach.


• Algorithms, utilities and tools for traffic theory and performance analysis support


• Numerical convolution of probability functions (DF, CDF, CCDF)


• Numerical Laplace-Stiltjes transformation and inversion


• Curve-fitting and EM-fitting of phase type distributions to statistical data

Topics for diploma theses and student project theses, HIWI jobs:

• Diploma thesis:
  Dimitri Eges: Analytical Performance Evaluation of Real-time Applications in Packet-switched Mobile Radio Networks using the Fluid-flow Model
  Status: finished


• Diploma thesis:
  Verena Früh: Load-dependent Performance Evaluation of GPRS Data Services in Live Networks
  Status: finished


• Diploma thesis:
  Analysis of TCP performance over GPRS using ON/OFF-type models of self-similar traffic and a model for TCP flow control
  Status: unassigned (View detailed description)


• Diploma thesis:
  Concept and Specification of a Generic Procedure for Quality Assessment of Mobile Radio Networks
  Status: unassigned (View detailed description)(Deutsche Beschreibung)


• Diploma thesis/Student project thesis:
  Analysis of relay and multihop concepts for B3G networks
  Status: unassigned (View detailed description)


• HiWi job (8-12 h per week):
  Code, release and CVS repository management for our GPRS simulation environment GPRSim
  Status: unassigned (View detailed description)

Publications:

• Fluid-flow modelling of Internet Traffic in GSM/GPRS Networks
  In: Proceedings of the 2002 Symposium on Performance of Computer and Telecommunication Systems (SPECTS),
  San Diego (USA), July 2002.
  View abstract - View BibTex
• Analytical Performance Evaluation of Internet Access over GPRS and its Comparison with Simulation Results
  In: Proceedings of the 13th International Symposium on Personal Indoor and Mobile Radio Communication 2002 (PIMRC),
  Lisbon (Portugal), September 2002.
  View abstract - View BibTex
• GPRS Multiuser Performance with Heavy Traffic: Simulation and Reality
  Submitted to: 18th International Teletraffic Congress (ITC-18),
  Berlin (Germany), August 2003.
  View abstract - Download PS - Download compressed PS (compressed with bzip2)
• Delay performance analysis and simulation of real-time applications in GPRS networks
  2003 Symposium on Performance Evaluation of Computer and Telecommunication Systems (SPECTS 2003),
  Montreal (Canada), July 2003.
  View abstract - View BibTex
• Capacity of a Relaying Infrastructure for Broadband Radio Coverage of Urban Areas
  To appear at: VTC-Fall 2003
  Orlando, FL (USA), October 2003.
  View abstract