Implementation and Evaluation of the Reference Broadcast Infrastructure Synchronization Protocol

TLDR

RBIS is tailored for industrial and home automation networks, offering advantages over similar solutions in many application contexts. This paper presents RBIS, a clock synchronization protocol for IEEE 802.11 infrastructure wireless networks. RBIS relies on conventional, unmodified Wi‑Fi access points, uses a master/slave, receiver/receiver paradigm, and is implemented entirely in software with interrupt‑level timestamps, enabling a distributed hard‑real‑time control application across two PCs running RTAI over Wi‑Fi. The software implementation achieves a synchronization error below 3 µs and an actuation error on synchronous pulse generation below 13 µs.

Abstract

This paper describes reference broadcast infrastructure synchronization (RBIS), a clock synchronization protocol for IEEE 802.11 infrastructure wireless networks. The protocol is especially tailored for industrial and home automation networks, and in many application contexts, it offers several advantages compared with other solutions targeted at similar purposes. RBIS has been conceived to rely on conventional Wi-Fi equipment and, in particular, on unmodified access points. It is based on the master/slave approach and follows the receiver/receiver paradigm. An implementation of RBIS-carried out completely in software and based on timestamps taken at the interrupt handler level-has been developed, which achieves a synchronization error below 3 μs. Then, a simple distributed hard real-time control application has been setup, which consists in two PCs running real-time application interface for Linux (RTAI) and connected through Wi-Fi. The actuation error, measured on the generation of synchronous pulses, is strictly below 13 μs.