Anchor-Free Distributed Localization (Testbed)

The Anchor-Free Distributed Localization-Algorithm (AFL) algorithm by  Priyantha et al. distinguishes two separate phases: initial fold-free graph embedding and mass-spring based optimization. In the first phase, a coordinate sytem for the network is created. Hop-count is applied as metric to select particular nodes that create the axis. All nodes are then asigned initial positions based on their location in the network topology. In the second phase, the nodes are considered to be connected by springs which apply forces to them. The power of these forces depend on the difference between the measured distances to the neighbors and the distances based on the positions in the coordinate system. The mass-spring algorithm “pushes and pulls” the nodes in the coordinate system to minimize the network-wide force.

We have already a running AFL implementation.  The implementation based on the DES-LOFT framework was developed as part of two Diploma theses. Additionally, we have gotten some experience from experiments in the testbed but several problems are still unresoved to create a final product for end user application.

For an introduction to AFL you may also have a look at some slides (german) prepared for the "Lange Nacht der Wissenschaft 2010".

Objectives

• Get familar with AFL
• Tryout the AFL implementation in the testbed of on our virtual networks
• Port the implementation from the stand-alone daemon into our routing framework, resp. provide a daemon based on DES-SERT
• Improve the implementation to handle multiple coordinate systems that have to be merged
• Improve the implementation to handle mobile nodes
• Use the RSSI data provided by DES-SERT for distance measurement
• Improve the (inaccurate) RSSI based distance measurement by other information, e.g., packet delivery ratio, corrupt frames, etc
• Run experiment series in the testbed and evaluate the measured data