Christian Bettstetter

Professor, University of Klagenfurt, Networked and Embedded Systems

 

Research Portfolio

[Jump down to research activities]
 

Christian Bettstetter and his research group work on the design, modeling, and analysis of future networked communication systems, with focus on mobile and wireless networking (see figure below). Of particular interest are also interdisciplinary and theoretical aspects of self-organization and networked systems in general. Research expertise covers

  • distributed algorithms and protocols;
  • network theory;
  • modeling, simulation, and performance analysis; and
  • network and protocol architectures.

One goal is to design technology that will enable new applications going beyond classical applications of communication and computer networks, such as networked embedded systems with applications, e.g., in disaster management and automotive safety. Such systems require a different architectural thinking than usual telecommunication networks. We believe that four paradigms are especially important, and they are currently in the core of our activities:

  • self-organization in communication and computer networks;
  • multihop communications (ad hoc networking, relaying);
  • exploiting cooperation between network devices; and
  • exploiting the mobility of devices.

Research portfolio

The research methodology is theoretical, simulation-based, and experimental. Methods range from protocol engineering and system simulation over prototyping on real hardware platforms to a set of mathematical methods (mainly stochastic processes, random graph theory, and complex networks). Research is at the intersection of electrical engineering and information technology, informatics, and applied mathematics.

The group cooperates with researchers from Orange Labs, DOCOMO Euro-Labs, Soongsil University, University of Porto, TU Munich, the University of Passau, and the Max Planck Institute for Dynamics and Self-Organization. Funding is obtained from major international companies as well as national and European funding agencies. In particular, the group is part of the Erasmus-Mundus doctoral school ICE (2011-2018) and the ESF-funded research network MiNEMA (2005-2009).

Research Activities

 

Current research areas of Bettstetter and his team are the following:

These topics are addressed in the context of various projects funded by European and national funding agencies and by companies.

The group participates in the following research programs and clusters:

Completed projects include the following:

  • Self-organizing slot synchronization (Triple-S)
    Univ. Klagenfurt, 2009-2010, with Lakeside Labs
  • Middleware for Network Eccentric and Mobile Applications (MiNEMA)
    Research networking program funded by the ESF, 2005-2009
  • Cooperative spatial diversity in ad hoc networks
    Univ. Klagenfurt, 2006-2009, with and funded by Orange Labs, France
  • Modeling spatial node distributions
    Univ. Klagenfurt, 2007-2008, with Soongsil Univ., Seoul, Korea
  • Ad hoc networking with adaptive antennas (ADMIN)
    DOCOMO Euro-Labs, 2004-2005, with TU Munich
  • Distributed medium access control with QoS support in multihop networks
    DOCOMO Euro-Labs, 2003-2005, with TU Berlin
  • IP-based protocols for multihop radio access networks (MRAN)
    DOCOMO Euro-Labs, 2003-2004
  • Mobility modeling, connectivity, and adaptive clustering in ad hoc networks
    TU Munich, 2000-2003, funded by DFG
  • IP-based communication protocols in a car environment (IPcar)
    TU Munich, 1999, with and funded by BMW
  • Turbo decoding with tail-biting trellises
    University of Notre Dame and TU Munich, 1998

Self-Organizing Synchronization

 

Time synchronization is an essential building block in wireless communications and networking and is needed on various layers of the protocol stack. For instance, time is often divided into periods of fixed duration ("slots") and nodes throughout the network agree on a common start of a slot. Classical means of providing such a time slot structure involves centralized control. In cellular networks, for instance, in each cell, the base station broadcasts a reference signal ("beacon") on a dedicated synchronization channel. All mobile devices within the cell synchronize to the base station. The base stations are typically mutually synchronized using the Global Positioning System. In infrastructureless wireless networks, the state-of-the-art approach is to select a "master device" among a set of devices, whose task is to coordinate the time slots in its surrounding. Such centralized algorithms have some drawbacks, for instance, the need for re-selection of the master device if it switches off or moves away.

The overall objective of our research in this area is to design and assess solutions for slot synchronization that are completely distributed, i.e., they does not rely on any centralized master devices, neither a predetermined master device nor an elected master device. We believe that particularly in ubiquitous computing scenarios, where large number of tiny wireless devices are interconnected to meshed networks, such a distributed algorithm is preferable.

Our approach has been inspired by a phenomenon of self-organization occurring in nature: the synchronous flashing of fireflies. The idea is adapt and enhance a mathematical model for this phenomenon (Mirollo and Strogatz) to make it work in wireless networks. A simple one-to-one transfer of the model is however infeasible, due to the characteristics of radio communications.

Research topics include the following:

  • Synchronization with realistic assumptions of wireless communications
  • Synchronization in multihop network topologies
  • Robustness of self-organizing synchronization
  • Convergence proofs
  • Implementation on a wireless hardware platform and technology integration

People and collaborations

  • Christian Bettstetter (lead)
  • Wilfried Elmenreich
  • Johannes Klinglmayr
  • Alexander Tyrrell

The work has been done in cooperation with DOCOMO Euro-Labs (Germany), Lakeside Labs (Austria), and the Max Planck Institute for Dynamics and Self-Organization (Germany). Research is funded by the Austrian Research Promotion Agency (FFG) within the disseration fellowship project ROSSY from 2010 to 2013.

Publications

Patent applications

Cooperative Relaying in Wireless Networks

 

Cooperative relaying is a new wireless communication technique promising significant gains in throughput and energy-efficiency of mobile systems. It exploits the broadcast nature of the wireless medium and benefits from a new, distributed form of spatial diversity that mitigates the negative effects of signal fading and interference.

The basic building block of this emerging area is the "relay channel": A source node S transmits a signal to a destination D; a third node R overhears this transmission and relays the signal to D; finally, the destination D combines the two received signals to improve decoding. It was shown that the maximum achievable throughput of this channel can be increased compared to direct S-D transmission and non-cooperative S-R-D relaying. Alternatively, less power is needed to achieve the same throughput.

Although better understanding of cooperative relaying has been achieved during the past years, most research efforts have focused on information-theoretic and physical-layer aspects, not accounting for higher-layer protocols and networking issues. The goal of our research activities is thus to investigate the benefits and tradeoffs of cooperative relaying from a networking perspective and to develop and assess algorithms and protocols above the physical layer that will facilitate its use.

More specifically, Bettstetter's team works in the following areas:

  • Distributed protocols for relay selection
  • Medium access issues in cooperative relaying
  • Network capacity of cooperative relay networks
  • Overall system and protocol architecture
  • Implementation and measurements on a wireless hardware platform

If successful, these activities will provide building blocks and a new understanding for the design of cooperative wireless networks, with the expectation of large performance improvements over current approaches. Results can be applied in the context of self-organizing multihop networks and relay-enhanced cellular systems.

People and collaborations

The research projects in this area have been performed in cooperation with Orange Labs (France) and Lakeside Labs (Austria), who both have provided funding.

Publications

Patent applications

  • Apparatus and method for cooperative relaying in wireless systems using an extended channel reservation
  • Cooperative relay scheme having backward compatibility

Collaborative Microdrones

 

Microdrones are small-scale unmanned aerial vehicles (UAVs) carrying cameras and other sensors. A conventional microdrone can be regarded as an autonomous isolated system that flies in the air, senses the environment, and communicates with the ground station. It is typically manually controlled by a human operator using a remote control or using predefined routes. Such systems are used today for aerial imaging, police and fire rescue operations, and military missions. The use of a single microdrone has severe drawbacks, demanding for a system in which several microdrones fly in the air and cooperate to achieve a certain mission.

The Lakeside Labs project cDrones aims at advancing the current state-of-the-art in the cooperating networked microdrones. Our work addresses the following areas:

  • robot routing (path "planning");
  • image processing and interpretation;
  • system integration and user interface; and
  • application areas.

Although the developed technology should be of general applicability, the project focuses on networked microdrones for fire rescue scenarios.

People

  • Torsten Andre
  • Christian Bettstetter
  • Evsen Yanmaz
This is a joint activity of four research groups in Klagenfurt and a group at the University of Central Florida. Detailed information is available from the project Website.

Demonstrations

Publications

Flooding in Stochastic Networks

 

Flooding is a basic technique for information dissemination in several networking protocols. It is needed, for example, in route discovery, link state advertisements, autoconfiguration, and query propagation in ad-hoc and peer-to-peer networks. In its most simple form, flooding leads to redundant and unnecessary transmissions. The objective is to minimize the number of transmissions while achieving global outreach of the message sent. Finding an optimum scheme for disseminating a message in a given network with minimum overhead, i.e., finding the minimum connected dominating set, is however NP-complete. Approximation algorithms are needed.

We study various flooding algorithms in different kinds of networks. The major goal is to take a more formal approach than previous work, employing methods from graph theory and stochastic processes to draw conclusions for the design and parameterization of flooding algorithms. Networks under investigation include Erdös Rényi graphs, geometric random graphs, and small world networks. Algorithms under investigation include probabilistic flooding, multipoint relaying, and flooding based on network coding.

People and Collaborations

  • Sérgio Crisóstomo
  • Christian Bettstetter
  • Udo Schilcher

The work is done in cooperation with the the University of Porto (João Barros) and is partly funded by a scholarship from the Portuguese Science and Technology Fund (FCT).

Publications