Aligned Virtual Coordinates for Greedy Routing in WSNs
  Geographic routing provides relatively good performance at a much lower overhead than conventional routing protocols such as AODV. However, the performance of these protocols is impacted by physical voids, and localization errors. Accordingly, virtual coordinate systems (VCS) were proposed as an alternative approach that is resilient to localization errors and that naturally routes around physical voids. However, we show that VCS is vulnerable to different forms of the void problem and the performance of greedy routing on VCS is worse than that of geographic forwarding. We show that these anomalies are due to the integral nature of VCS, which causes quantization noise in the estimate of connectivity and node location. We propose an aligned virtual coordinate system (AVCS) on which the greedy routing success can be significantly improved. With our approach, and for the first time, we show that greedy routing on VCS out-performs that on physical coordinate systems even in the absence of localization errors. We compare AVCS against some of the most popular geographical routing protocols both on physical coordinate system and the virtual coordinate systems and show that AVCS significantly improves performance over the best known solutions. 
Ke Liu and Nael Abu-Ghazaleh