IMPROVING RELIABILITY WITH BIT VOTING IN SYNCHRONOUS TRANSMISSION-BASED IOT NETWORKS

Abstract

Emerging Internet of Things (IoT) applications like industrial IoT require ultra-high reliability, strict latency, and low energy consumption. Balancing these requirements is a considerable challenge for traditional low-power wireless protocols. Recently, there has been considerable interest in addressing these challenges by utilizing flooding-based protocols based on the notion of Synchronous Transmissions (STX), where packets can take advantage of certain physical layer properties such as non destructive interference and the capture effect. By fully embracing redundancy, such protocols offer a competitive edge over current flooding protocols– particularly in terms of dependability. However, STX-based protocols can suffer from the impact of the beating effect, a physical layer phenomenon caused by signal frequency offsets between simultaneously transmitting devices. This beating effect can corrupt packets and reduce reliability. The resulting errors can appear in isolation or in bursts, depending on the duration of the beating. Most physical layer (PHY) protocols employ error correction mechanisms, e.g., Forward Error Correction (FEC), or Direct Sequence Spread Spectrum(DSSS), but they are generally limited on how effective they are. Thus, we introduce STX-Vote, an error correction scheme that can handle both isolated and burst errors occurring due to the beating effect. The important observation is that, since STX protocols are by definition redundant, it makes sense to exploit the redundancy for the purpose of error correction, while avoiding additional on-air overhead. We implement STX-Vote on nRF52840-DK development kits as an extension of OSF, an open-source STX framework. Our evaluation was performed over networks that exhibited various beating effect patterns. The results confirm that STX-Vote improves the reliability of both Bluetooth Low Energy (BLE) version 5 and IEEE 802.15.4 PHYs, producing as much as a 8% improvement for BLE5.