Aligned Virtual Coordinates for Greedy Geometric Routing in Wireless Sensor Networks

The performance of geographic routing protocols is impacted by physical voids and localization errors. Traversing voids is carried out by a complimentary algorithm, which requires high overhead and results in lower quality paths. Furthermore, localization errors lead to inefficient routes or even misrouting of packets. Accordingly, virtual coordinate systems (VCS) were proposed to be an alternative solution that is resilient to localization errors and naturally traverses physical voids. However, we show that VCS is vulnerable to different forms of anomalies and actually perform worse than physical coordinates. The goal of this paper is to increase the success of greedy forwarding in VCS, to avoid using the expensive complementary algorithm. We identify some of the reasons that cause anomalies in VCS and propose an aligned virtual coordinate system (AVCS) to address them. AVCS aligns the coordinates of nodes by taking into account the coordinates of their neighbors. With AVCS, greedy routing success is significantly improved, approaching perfect delivery for many scenarios. With our approach, and for the first time, we show that greedy routing on VCS out performs that on geographic coordinate systems even in the absence of localization errors. We compare AVCS against some of the most popular geometric routing protocols both on geographic and virtual coordinate systems and show that AVCS significantly improves performance over the best known solutions.