Performance Evaluation of Parallel Wi-Fi Redundancy with Deferral Techniques

TL;DR

This work quantitatively evaluates deferred parallel redundancy for Wi-Fi in industrial real-time contexts, showing that deferring the secondary channel can dramatically reduce high-latency occurrences with modest spectral costs. By analyzing a large real-world dataset, the authors demonstrate that parallel redundancy (A+B) delivers substantial latency improvements, while deferral provides a tunable trade-off between timeliness and spectrum use. They further explore per-packet channel selection strategies, including Alternating and heuristic approaches, highlighting the potential of learning-based methods to optimize performance. Overall, deferred redundancy emerges as a practical technique to enhance reliability and timing in industrial Wi-Fi for soft real-time control loops.

Abstract

Wireless communication is increasingly used in industrial environments, since it supports mobility of interconnected devices. Among the transmission technologies operating in unlicensed bands available to this purpose, Wi-Fi is certainly one of the most interesting, because of its high performance and the relatively low deployment costs. Unfortunately, its dependability is often deemed unsuitable for real-time control systems. In this paper, the use of parallel redundancy is evaluated from a quantitative viewpoint, by considering a number of performance indices that are relevant for soft real-time applications. Analysis is carried out on a large dataset acquired from a real setup, to provide realistic insights on the advantages this kind of approaches can provide. As will be seen, deferred parallel redundancy provides clear advantages in terms of the worst-case transmission latency, at limited costs concerning the amount of consumed spectrum. Hence, it can be practically exploited every time a wireless connection is included in a control loop.

Figures (7)

• Figure 1: Experimental testbed for acquiring the dataset.
• Figure 2: CDF of latency for different redundancy approaches.
• Figure 3: Mean latency ($\mu_d$)
• Figure 4: Mean number of attempts per packet ($\mu_{a}$).
• Figure 5: 90-percentile of latency ($d_{p90}$).