Date Added: Jan 2010
Link asymmetry is one of the characteristic challenges that wireless sensor networks pose in the design of network protocols. The authors observe, based on testbed experiments that a substantial percentage of links are asymmetric, many are even unidirectional. They also find that the reliability of synchronous acknowledgments is considerably higher than that of asynchronous messages. Thus, the norm of estimating link quality bidirectionally via asynchronous beacons underestimates the link reliability of asymmetric links. This leads one to investigate how to exploit asymmetric links in order to improve network functions such as convergecast routing in sensor networks via one-way link estimation.