Site visit in Espoo 11 June 2003

The coordination unit made a site visit at the Networking Laboratory at the Helsinki University of Technology in Espoo on 11 June 2003. Professors Jorma Virtamo and Pekka Orponen together with their research groups and the research group of Coordinator Patrik Floréen presented their research in their project Networking and Architecture for Proactive Systems (NAPS).

The aim of the project is to develop networking infrastructure in two areas, energy-aware algorithms for proactive systems and traffic management in ad hoc networks.

Jorma Virtamo's group has earlier studied routing and other traffic related issues of ad hoc networks in the Ahras project. In the NAPS project, they intend to extend their optimisation research into the dynamic setting characterised by the mobility of nodes, randomness of the traffic and scheduling. One particular problem to be addressed is the routing algorithms for finding a path across the network for delivering packages and with the aim of, e.g., minimising delivery delay or balancing the traffic in the network. Another problem studied, is capacity optimisation. An increasing number of nodes in the network usually implicates lower capacity. Applying a hierarchical network architecture may solve this problem. Of great importance is also the robustness of the network, i.e., connectivity between communicating nodes must be ensured.

As a result from the Ahras project, Henri Koskinen has just finished his Master Thesis on connectivity and reliability in ad hoc networks. The scope of his study has been k-connectivity: A k-connected network remains connected even after removing k-1 nodes from the network. Among his results are algorithms for 2- and 3-connectivity. Within the Ahras project, the group has also studied energy-efficient multicasting and developed simulation software for ad hoc networks.

Patrik Floréen's and Pekka Orponen's groups concentrate on algorithms for ad hoc networks. One particular problem here is maximising multicast time in energy-constrained wireless networks, where one node transmits to several recipient nodes and where the power of the nodes may be static or dynamically changing. The first promising solutions are just to be published in the DIALM-POMC Joint Workshop on Foundations of Mobile Computing 2003.The groups also intend to study clustering of ad hoc networks into smaller subnetworks that can be efficiently controlled but where the workings of the entire network is optimised. The clustering should also be flexible and adapt as the network is changed, e.g., if the nodes move.

More information
For more information, please contact the Coordinator of the project, Senior Research Scientist Patrik Floréen at HIIT or see the project's extensive web pages at http://www.cs.helsinki.fi/hiit_bru/projects/naps/ or the project's web pages at this site.

The research consortium consists of the following units

• Helsinki University of Technology, Networking Laboratory:
• Professor Jorma Virtamo, researchers Dr. Pasi Lassila, Henri Koskinen, affiliated researchers Samuli Aalto, Juha Leino, Laura Nieminen, Aleksi Penttinen
• Helsinki University of Technology, Laboratory for Theoretical Computer Science:
• Professor Pekka Orponen, researchers Petteri Kaski, Emil Falck, affiliated researcher Mikko Särelä
• Helsinki Institute for Information Technology HIIT, Basic Research Unit:
• Senior Researcher Patrik Floréen, researchers Jukka Kohonen, Johannes Ukkonen
• Affiliated research group: Helsinki University of Technology, Laboratory of Theoretical Computer Science:
• Professor Hannu Kari

Greger Lindén
Programme Coordinator
Greger.Linden@cs.helsinki.fi