Symbol-Synchronous Buses: Deterministic, Low-Latency Wireless Mesh Networking with LEDs

Abstract

Latency-sensitive applications for the Internet of Things often require performance guarantees that contemporary wireless networks fail to offer. The cause of this shortcoming lies in the inherent complexity and inefficiency of networking abstractions such as routing, medium access control, and store-and-forward packet switching, which coordinate multiple nodes across a wireless network. This research highlight describes a novel networking paradigm that aims to enable a new class of latency-sensitive applications by systematically breaking these abstractions. The paradigm, referred to as a symbol-synchronous bus, has nodes that concurrently transmit optical signals and thus delivers a wireless mesh network with a performance envelope resembling that of a wired bus in terms of deterministic latency and throughput. A physical prototype, called ZERO-WIRE, confirms that symbol-synchronous buses unlock a novel end-to-end performance envelope for wireless mesh networks: our 25-node test bed achieves 19kbps of contention-agnostic goodput, latency under 1 ms for two-byte frames across four hops, jitter on the order of 10s of ms, and a base reliability of 99%. These early results suggest a bright future for the under-explored area of optical wireless mesh networks in delivering ubiquitous connectivity through a low-complexity physical layer.