• • • SMART BUILDINGS & IOT • • • No-strings networks for a better
IIoT: Wireless TSN is on the horizon By Dave Cavalcanti, principal engineer, Intel and Avnu Alliance Wireless TSN workgroup Chair
T
he Internet of Things has created the potential to optimize practically any environment through the collection of and response to real-time data. That value proposition is especially stark in the industrial segment, where the Industrial Internet of Things (IIoT) has led to more efficient operations, safer factories, and entirely new business models such as Equipment as a Service. The power of the IIoT can only be fully realized with a network that is reliable, deterministic, future-proof, and interoperable. This is why Time Sensitive Networking (TSN) is central to the future of Industrial Networks.
As part of the IEEE 802.1 family of standards, TSN is an intrinsic part of the most widely-used open LAN standard in the world. TSN offers time synchronization, guaranteed delivery, and strictly bounded latency, enabling the use of standard Ethernet in time-sensitive applications such as factory automation. The value of TSN adoption is clear to the industrial market: it offers a pathway to converged, interoperable networks. As wireless technologies have advanced alongside deterministic network capabilities, though, we have to ask: why should emerging industrial TSN- capable networks be tied down with wires? Wireless networks offer greater flexibility, higher mobility and reconfigurability, and lower maintenance costs than wired infrastructure. Wireless TSN links could be used to both extend the range of wired networks and enable wireless access to end devices and computing resources. Already, several IEEE 802.1 TSN capabilities can operate over both Ethernet and Wi-Fi. As Wi-Fi 6/6E and 5G network technologies bring typical latency requirements for deterministic networks within reach for wireless topologies, interest in extending TSN to wireless applications has expanded. As a technology based on an IEEE standard (802.11ax), Wi-Fi 6/6E comes with new scheduling capabilities baked in, significantly enhancing determinism over previous generations of Wi-Fi. Emerging 5G ultra reliable low latency communication services (URLLC) have motivated the development of interfaces, in 5G Rel. 16 specifications, that allow TSN-capable networks to connect to 5G systems as a “virtual” TSN bridge. Work on wireless TSN is already progressing. How, then, will wireless capabilities impact the ultimate adoption of TSN within the industrial segment? The Avnu Alliance, an organization dedicated to driving industry change and creating an interoperable ecosystem of networked devices using the foundational, open IEEE TSN standards, has formed a Wireless TSN Workgroup to assess market requirements and to test and prepare wireless TSN technology for the market. Their whitepaper, Wireless TSN – Definitions, Use Cases & Standards Roadmap, provides an overview of the
40 ELECTRICAL ENGINEERING • MAY 2021
AR/VR, which may be used to enable the remote maintenance and operation of industrial equipment and robots. Wireless TSN has a role to play here too, as AR/VR interface devices should ideally be wireless for usability/mobility purposes, and also have strict bandwidth, latency, jitter, and reliability requirements. As these applications roll out across the
industrial segment, how can we expect these emerging wireless TSN-capable networks to operate? It can be assumed that TSN networks will be protected domains where all devices are TSN-capable or meet TSN-defined
opportunities presented by wireless TSN, as well as the challenges that must be met to realize them. Their forthcoming market requirements document will analyze wireless TSN use case scenarios and KPIs across segments and set the guidelines for testing and certification specifications for Wireless TSN features.
INDUSTRIAL APPLICATIONS
The workgroup’s efforts thus far have created a portrait of where we can expect to see wireless TSN deployed in an industrial context: • Mobile Robots: a wireless TSN network could carry communication between mobile robots and control systems, including guidance control, process data exchange, video/image data, and emergency stop commands, without requiring those robots to be fixed in place. This use case encompasses sensor input from autonomous mobile robots, automated guided vehicles, or any other type of industrial robot. • Remote I/O and Human-Machine-
Interface (HMI): wireless TSN can enable remote I/O, such as video-based inputs into a control system. It can also carry HMI inputs triggered by remote human operators. This use case also encompasses remote actions and control guidance provided to industrial machines, including robots. • Closed Loop Control (Sensing-Control-
Actuation): the foundational use case for industrial processes; this is the synchronous communication between sensors, programmable logic controllers and actuators.
In all of these cases, it’s assumed that using wireless TSN, time-critical cyclic flows and events can operate on the same network infrastructure as other normal network traffic, including video, voice, FTP and TCP traffic. Though the area of service and anticipated devices per area will vary by use case, these scenarios share expected requirements for low bounded latency, high reliability and network synchronization accuracy, critical security requirements, and relatively small packet sizes for most industrial control applications. More data-hungry applications are bound to emerge from cross-segment use cases such as
requirements—meaning that they may be a subset of a larger enterprise network. In industrial networks, the network management will likely be centralized as defined in the IEEE 802.1Qcc specification. To avoid any issues arising from network
interference or security breaches, wireless TSN domains must be carefully planned and stringently managed. Coverage requirements and traffic profiles must be uncovered at the planning stage to allow network engineers to plan the proper number and locations of access points and base stations. Because Wireless TSN domains may be susceptible to malicious attacks impacting QoS, it is anticipated that TSN-capable wireless networks must be centrally managed with only authorized devices allowed access. Any authorized device must comply with all required TSN capabilities, even if the device itself doesn’t require time-critical performance, to preserve time synchronization and determinism across the domain. It is also expected that innovative solutions in terms of redundant communications, data monitoring and automation for anomalies and security threat will be key to managing Wireless TSN domains.
COLLABORATION
Wireless TSN is currently in a crucial exploratory phase. Extending seamless operation and interoperability from wired to wireless TSN domains is going to be a significant technological challenge; this work is currently being evaluated by Avnu and other industry consortia. Wireless networks themselves must increase in resiliency and reliability in order to meet anticipated market requirements for industrial and other use cases. In order to seize this opportunity, we need every stakeholder in the value chain, from manufacturers, to integrators, service providers, and system owners to take interest in the development of cross-market collaborative standards. Working together, we can untether the IIoT from its wired infrastructure.
AVNU ALLIANCE
avnu.org
electricalengineeringmagazine.co.uk
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