Introduction

One of the key issues faced with ad-hoc networking is the provision of unique addresses for nodes within the network. Ideally these addresses should be auto-configured without the need for human intervention. The addressing scheme should work in all ad-hoc scenarios, such as the partitioning and merging of networks, preferably keeping traffic to a minimum.

We have developed a scheme based upon the election of a leader, to uniquely identify an ad-hoc group, and so this can be used as an indication of network merges. The scheme should also deal efficiently with the failure of a leader, and with partitioning of the network.


The Implementation

Many of our individual researchers have developed layers that work within our development environment. The implementation of this addressing work has been tested out with a number of these other layers:
  • We use a DSR layer, implemented by Tim Forde, to provide the ad-hoc routing required. The addressing layer provides the DSR layer with a unique address

  • To assist development and testing we use JEmu, a real-time emulation environment developed by Juan Flynn. This allows testing of various scenarios with real traffic. The sample clips below provide a sample of this emulator in action. For further details on JEmu see http://www.cs.tcd.ie/omahony/jemu-iei.pdf



  • Demo Samples

    A couple of movie clips of a demo of this scheme in operation are available using different compression schemes. These provide varying quality video, at the expense of download size and the requirement for non-standard codecs.

    File Notes
    Standard clip(indeo)4.6MB Quite large and fairly poor quality (uses Indeo 5.1 codec - should play in most media players without need for installation of a new codec)
    Divx clip1.9MB (Smaller and better quality but needs the popular divx codec installed)
    Techsmith clip- 1024x768 resolution1.27MB (Small, Excellent quality but needs the Techsmith codec installed)
    Techsmith clip- 800x600 resolution1.17MB (Small, Excellent quality but needs the Techsmith codec installed)
    All files are best viewed in Full-Screen mode!

    This example shows two ad-hoc groups forming separately, with nodes choosing a leader and obtaining unique addresses within each. This could represent a search-and-rescue scenario with different emergency services arriving at the scene. One of these groups partitions so a new leader must be elected, and then there is a merging of the networks, so the leaders must merge, and duplicate address detection should be done again. This is done in an efficient manner by the leader nodes.

    Key
    Black No address
    Blue Leader node
    Green Standard node
    White Node with duplicate address - obtaining new address
    Red Node in an election


    This auto-configuration functionality has now been tested with the 4GPhone application


    Future Work

  • Schemes will be examined to increase the efficiency of the table distribution.
  • Sometimes it may make sense to avoid merging networks completely, and simply allow relaying between them. Lazy merging schmes will be explored.
  • Interoperability between this ad-hoc network and the fixed network will also be examined.