How single-pair Ethernet benefits IIoT architecture

Single-pair Ethernet (SPE) provides an enabling platform that allows the migration from various legacy networks to one universal physical layer.

By Stuart McKay May 20, 2021

The latest development in Ethernet data communications is extending its capabilities over single-pair cable. Single-pair Ethernet (SPE) allows legacy industrial networks to migrate to Ethernet network technology whilst delivering power and data to and from edge devices.

SPE provides an enabling platform that allows the migration from various legacy networks to one universal physical layer. Industry 4.0 comes a step closer to being delivered through a single technology from the edge sensor, plant floor to the corporate desktop.

SPE expands the resource of the Industrial Internet of Things (IIoT) providing the accelerator for organizations to migrate to Ethernet based operational technology (OT), offering common communications protocols compatible with the information technology (IT) network. This expansion encompasses end-to-end solutions including, switches, valves, cables and sensors, which have been developed by numerous organizations collaborating to effect the changes necessary to harmonize OT and IT operations, on the most effective protocol.

While Ethernet has gained share in the Industrial market and is available in a variety of forms, non-Ethernet protocols still prevail where application requirements are not yet met by Ethernet. This multiple protocol scenario continues to add cost and complexity to legacy environments, including the multiprotocol experienced installation and maintenance staff needed to service such diverse environments.

As more manufacturing and industrial equipment and devices are connected, OT networks have become a composite of Ethernet and legacy Fieldbus protocols. In terms of new installed nodes, recent research concluded that industrial Ethernet had surpassed traditional fieldbuses for the first time in 2018, and this progress continues. Industrial Ethernet continues with a steady growth rate of 20% and now makes up 65% of the global market, an increase of 8%. Globally, Profinet is the largest industrial Ethernet network with 18% of the market followed closely by EtherNet/IP at 17%

Speeding migration

The capabilities of SPE increases the commitment to an all-Ethernet networking solution. Advances are making the network easier for organizations to implement and manage. The single protocol network will provide for data transparency and increase security and the growth of the IIoT and its requirement to seamlessly connect to corporate information systems as well as industrial processes will drive the convergence onto the Ethernet platform.

The initial single-pair IEEE standard 802.3cg-2019, was announced early in 2020, when device chips were launched to support SPE applications. The reduced number of pairs used for communication, allows for a reduction in cable and connector size, while the technology delivers both power and data to edge devices within a single connection. The IP20 SPE connector is a small format module with half the footprint of a RJ45 port which features positive latch engagement for secure connections. Integrated power and data eliminates the need for local batteries or power supplies, and saves on transformers and circuit protection, while improves installation time and simplifies maintenance.

Compared with terminating 4-pair cable to TIA-568A/B standards, field terminating one-pair cable with the LC-style connector is fast and simple. Using common tools, a technician is able to perform an SPE termination in half the time taken for a 4-pair termination. It also utilizes 18 AWG cable offering lighter, smaller cables. The SPE connector termination will be less prone to error, minimizing rework. Given the decreased weight and size, more cable runs can be pulled together, simplifying implementation.

The importance of data and power over SPE to remote devices cannot be overstated. The IEEE 802.3bu standard provides for remote dc power over the SPE connection, called Power over Data Line, or PoDL. PoDL is akin to the Power-over-Ethernet (PoE) technology for standard Ethernet, which is transforming smart building electrical and data communications infrastructure.

A further positive attribute of SPE is the potential to reuse existing cable media. Many factories and plants have legacy single-pair twisted cable, that can possibly be reused as SPE cable media, subject to qualification. For instance, much RS-485 cable in use or redundant is 18 AWG gauge making it a viable alternative to new cable runs. The cables will need to be tested to ensure they meet electrical performance relative to the TIA-568.5 standard for 10BASE-T1L link transmission.

Bob Voss, senior principal engineer for Panduit Corporate Research and Development, and chair of the Single-Pair Ethernet Subcommittee at the Ethernet Alliance, recently stated gains in capability of Single-Pair Ethernet and its ability to support proven Operations Technology topologies in industry and manufacturing is bringing real value to organizations.

Consolidating on SPE environments reduces or eliminates non-Ethernet challenges while extending the advantages of Ethernet and IP-based networking. Ethernet networks are faster, offering enhanced techniques such as time-sensitive networking (TSN) and software-defined networking (SDN). And while four-pair Ethernet is already well established supporting higher levels in industrial networks, it is not cost-effective for many lower value edge devices. SPE is designed to be the solution at the right price point, providing the entry level for far wider implementation of price sensitive IIoT devices. Systems that currently use RS-485 serial communications can be upgraded with little change to the media and therefore brought into the Ethernet network.

Fast and friendly

SPE provides increased bandwidth allowing higher data rates at the edge, with up to 10 Mbps transmission speeds up to 1,000 m. Consider that against legacy protocols based on RS-485, where the link speed is only 31.2kbps for the same 1,000m – that is 300 times faster.

The convenience, cost and relative functionality of SPE provided low-cost access for either migration or incremental deployment of SPE within an industrial environment. The technology cost aligns with extending data capture capabilities out to multiple edge devices, where previous access was cost prohibitive.

Expected early applications for SPE include connecting the following:

  • Instrumentation devices for hazardous and less severe process automation environments.
  • Skid and machine I/O blocks to the OT network .
  • On-machine devices to an on-machine or cell area industrial network switch.
  • Field sensors and actuators to industrial network switches point-to-point or via structured cable link channels, both with lengths up to 1km far exceeding the current 100m limit.
  • Field devices connecting in a daisy-chain fashion with embedded 2-channel switches.
  • Remote I/O modules to one another, the network switch, or to the controller.
  • In-panel devices together over a single cable via the multi-drop topology (10BASE-T1S).

Expansion of IIoT is dependent on cost-effective technology, coupled with inexpensive sensors to drive scale. High volume automation products are likely to change first, while specialized legacy protocol devices will take longer to replace. Once organizations understand the market advantage they can gain from SPE the implementation of associated devices will increase dramatically, which in turn will reduce complexity of the network as it converges on Ethernet.

SPE is expected to be a key enabling technology for manufacturers and industrial plants to:

  • Achieve a seamless network with visibility from cloud to edge.
  • Increase bandwidth at the edge for implementing advanced diagnostics .
  • Simplify edge networks by eliminating protocol translation gateways.
  • Transform and simplify dc control power infrastructure.
  • Improve cybersecurity by extending manufacturing IT defense-in-depth technologies.
  • Connect miniaturized micro-IoT and otherwise constrained form factor devices.
  • Lower total cost of ownership (TCO) for the OT network.

SPE is a transformative technology for manufacturers and industrial plant facilities. For the manufacturing space and other market segments such as rail transportation and building automation will also begin to adopt SPE networks in the ensuing years.

This article originally appeared on Control Engineering Europe’s website. Edited by Chris Vavra, web content manager, Control Engineering, CFE Media,

Author Bio: Stuart McKay is business development manager at Panduit.