Network-wide Consensus in Low-power Wireless Networks

In low-power wireless networking, new applications such as cooperative robots or industrial closed-loop control demand for network-wide consensus at low-latency and high reliability. Distributed consensus protocols is a mature field of research in a wired context, but has received little attention in low-power wireless settings. In this talk, we present A2: Agreement in the Air, a system that brings distributed consensus to low-power multi-hop networks. A2 introduces Synchrotron, a synchronous transmissions kernel that builds a robust mesh by exploiting the capture effect, frequency hopping with parallel channels, and link-layer security. A2 builds on top of this reliable base layer and enables the two- and three- phase commit protocols, as well as network services such as group membership, hopping sequence distribution and re-keying.

We evaluate A2 on four public testbeds with different deployment densities and sizes. A2 requires only 475ms to complete a two-phase commit over 180 nodes. The resulting duty cycle is 0.5% for 1-minute intervals. We show that A2 achieves zero losses end-to-end over long experiments, representing millions of data points. When adding controlled failures, we show that two-phase commit ensures transaction consistency in A2 while three-phase commit provides liveness at the expense of inconsistency under specific failure scenarios.

Olaf Landsiedel is an Associate Professor in Computer Science at Chalmers University of Technology, Sweden. His work focuses on Cyber-Physical Systems and the Internet of Things. From 2010 to 2012 he spent two years as Postdoctoral fellow at the Royal Institute of Technology (KTH), Sweden, and the Swedish Institute of Computer Science (SICS). He received his PhD from RWTH Aachen, Germany, in 2010.

Recent awards include the Best Paper Award at ACM SenSys 2013 and the "Lecturer of the Year 2014 Award” at Chalmers University of Technology.