Message-Efficient Beaconless Georouting With Guaranteed Delivery in Wireless Sensor, Ad Hoc, and Actuator Networks

Beaconless georouting algorithms are fully reactive and work without prior knowledge of their neighbors. However, existing approaches can either not guarantee delivery or they require the exchange of complete neighborhood information. We describe two general methods for completely reactive face routing with guaranteed delivery. The Beaconless Forwarder Planarization (BFP) scheme determines correct edges of a local planar subgraph without hearing from all neighbors. Face routing then continues properly. Angular Relaying determines directly the next hop of a face traversal. Both schemes are based on the Select-and-Protest principle. Neighbors respond according to a delay function, but only if they do not violate a planar subgraph condition. Protest messages are used to remove falsely selected neighbors that are not in the planar subgraph. We show that a correct beaconless planar subgraph construction is not possible without protests. We also show the impact of the chosen planar subgraph on the message complexity. With the new Circlunar Neighborhood Graph (CNG) we can bound the worst case message complexity of BFP, which is not possible when using the Gabriel graph (GG) for planarization. Simulation results show similar message complexities in the average case when using CNG and GG. Angular Relaying uses a delay function that is based on the angular distance to the previous hop. We develop a theoretical framework for delay functions and show both theoretically and in simulations that with a function of angle and distance we can reduce the number of protests by a factor of 2 compared to a simple angle-based delay function.