Implementation With Mobile Ad-Hoc Network Routing Protocols |
This paper outlines our experience withthe implementation and deployment of two MANET routing protocols on a fivenode, four hop, network. The work was prompted by the lack of published resultsconcerning the issues associated with the implementation of MANET routingprotocols on actual wireless networks, as opposed to results of simulationexperiments. We examined implementations of two distance vector MANET routingprotocols and found a number of problems with both protocols during the courseof our experiments. The most significant was that neither protocol couldprovide a stable route over any multi-hop network connection. The routediscovery process of both protocols is fooled by the transient availability ofnetwork links to nodes that were more than one hop away. Packets transmittedover a fading channel cause the routing protocol to conclude incorrectly thatthere is a new one hop neighbor that could provide a lower metric (hop count)route to even more distant nodes. This can occur even when nodes arestationary, mobility resulted in even less route stability. Weimplemented a simple signal strength based neighbor selection procedure to testour assertion that fading channels and unreliable network links were the causeof the failure of the routing protocols. The result was that neighbor discoveryand the filtering for neighbors with which nodes could communicate reliably enablesthe creation of reliable multi hop routes. Based on our experiences, we outlineseveral recommendations for future work in MANET research.