An Adaptive Ad Hoc Routing Network for Mobile Wireless Devices, 10-9373

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Principal Investigators
Sandra G. Dykes
Ronnie L. Killough
Arthur N. Rasmussen
Victoria Zhou

Inclusive Dates: 01/01/03 - 12/31/03

Background - Ad hoc networks contain laptop computers, Personal Data Assistants (PDAs), embedded sensors or other wireless devices that self-organize into a multi-hop communications network. Devices are typically mobile and may enter or leave the network at any time. Ad hoc routing extends communication beyond the radio signal range by relaying data packets through intervening devices, enabling packets to "hop" across devices to the final destination. Because ad hoc networks do not depend upon a fixed infrastructure, they are ideal for disaster scenarios where cables and routers have been damaged, or for remote areas where no infrastructure exists. In addition to disaster response and military operations, ad hoc networks are being developed for applications as diverse as inter-vehicular communication, space networks, and environmental monitoring. Devices and applications vary greatly in communication patterns, mobility, and operational constraints such as battery size. No single routing algorithm is well suited to all situations. However, current designs build the ad hoc protocol into the operating system or custom hardware, thereby forcing all applications to use the same routing algorithm and adding complexity to protocol development and modification.

Approach - Our program offers two important advancements for ad hoc networks:

  • A design and prototype software that support multiple ad hoc routing protocols on each device, and that allow applications to select the most suitable protocol.
  • Use of off-the-shelf laptop computers and PDAs without special hardware or modifications to the operating system.

We achieve these goals by building an ad hoc routing (AHR) network layer on top of the IP network layer. The AHR layer replaces the IP interface to applications, and provides both packet forwarding and route discovery services. Each ad hoc routing protocol that plugs into our framework supplies its own algorithm for discovering routes and for maintaining the routing lookup tables. Our AHR framework deploys multiple ad hoc servers that run different plug-in protocols. An application selects its routing protocol by selecting the associated AHR server.

Accomplishments - An operational prototype of the AHR software layer has been developed and is installed on a heterogeneous testbed of six devices. The testbed consists of a Windows 2000® laptop computer, a Windows XP® laptop computer, and four Compaq iPAQ PDAs, each equipped with an IEEE 802.11b "Wi-Fi" network card in ad hoc mode (no access point is used). To demonstrate AHR operations, we developed interactive visualization software that, in real-time, probes the network, shows which devices are reachable from the visualization host, and displays the path between any source-destination pair.

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