Lessons from an Ad hoc Network Test-Bed: Middleware and Routing Issues

Although MANET research has been ongoing for some time, there are relatively few experiences with real ad hoc networks. Instead, a large portion of protocol development is done in (often unrealistic) simulation settings only. In this paper we discuss lessons learned from our experimental work. Specifically, we present results for a fully functioning prototype implementing a p2p middleware (FreePastry) on top of a multihop ad hoc network based on 802.11b technology. Recently, for this technology, [GLNT04] pointed out the existence of an ad hoc horizon (2-3 hops and 10-20 nodes) after which the benefit of multi-hop ad hoc networking vanishes. All the experiments we performed fall inside this ad hoc horizon. The aim is to identify solutions for this realistic setting and to quantify the Quality of Service (QoS) the system is able to provide to the users. Our measurements pointed out that also in this limited setting, several problems still exist to construct efficient multi-hop ad hoc networks. Cross-layering seems to be an effective approach to fix some of the problems identified in our analysis.