Using virtual coordinates for wireless sensor networks: Proof-of-concept experimentation

Routing in a multi-hop wireless network with low- cost nodes is still a challenging task, and specific ultra-low power solutions need to be investigated for WSNs. Geographic routing protocols have been designed, analyzed and simulated. Yet, early experimental trials show that they fail dramatically when faced with real-world constraints such as lossy links. Experimental studies are needed as a complement to analysis and simulation. In this paper, we create a complete energy-efficient self- organizing communication architecture. This protocol stack consists of an ultra low-power MAC protocol based on preamble sampling and which avoids maintaining neighborhood tables, and a geographical inspired routing protocol using virtual coordinates. It can be implemented on existing commercial nodes, does not need them to be location-aware (no GPS), allows ultra-low power operation and is extremely robust. We show the validity of this architecture by analysis and simulation and present experimental results. In this experiment, we confront our architecture with the extreme case of a fast moving mobile sink by mounting the sink node on a radio-controlled airplane. This deployment serves as a proof-of-concept experiment, showing the efficiency and robustness of the virtual coordinate approach. Other main lessons learned from this real-world deployment are that experiments should be used in conjunction with simulation and analysis; results from all three approaches complement one another. This work also stresses the importance of the MAC layer when using low-cost nodes and lossy links.