This demonstration concerns Geographic Forwarding (GF) as an effective solution for data dissemination (from sensors to a sink) in wireless sensor networks (WSNs). In particular, we focus on demonstrating the different degrees of resilience of a recent solution, ALBA-R [1], to localization errors, which are highly likely to occur in WSNs. GF routing protocols are based on the nodes knowing their own location information as well as that of the sink, which is the intended destination of a packet. When a node has a packet to send it attempts to forward it in the direction of the sink. Several forwarding methods have been proposed [2]. For instance, according to a typical GF routing protocol, like GeRaF [3], forwarding happens by the sender node s requesting which among its neighbors can relay the packet and provide a positive advancement to the sink. Nodes that receive this request, based on the distance from s to the sink carried by the request message, candidate themselves as relays. At this time, s chooses one of them that provides high advancement as relay, and sends the packet to it. Improvements can be obtained over this basic scheme by favoring relays which are less congested and enabling transmissions of bursts of packets back to back, as happens in ALBA [4]. With respect to these simple and effective forwarding methods, problems may arise when no nodes exist in the direction of the sink that can relay the packet for a given node. In this case the packet is stuck at a so called "dead end" node. For this problem, many solutions have been proposed, that range from planar graph traversal to flooding-based techniques, to cost-based techniques, where the cost is usually the distance from the sink [5]. One recently proposed solution, termed ALBA-R [1], for instance, enhances ALBA with a mechanism for guaranteeing the delivery of data packets even in presence of dead ends in the network. The aim of this demonstration is that of showing the capabilities of ALBA-R of efficiently performing GF, and in particular its resilience to localization errors. We demonstrate that, while in presence of both dead ends and localization errors ALBA packet delivery ratio suffers quite remarkably, ALBA-R is able to deliver all packets to the sink, even those from dead ends and even when the estimated location of a node is considerably distant from it actual position.
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