Single Pair Ethernet - Standardization landscape

With Single Pair Ethernet, a new physical layer is entering the world of Ethernet communication. Born out of the automotive industry, SPE is also developing into a key technology for the coming steps of digitization in industrial automation. Ethernet IP can finally be transmitted continuously from the cloud to the field level via just one pair of copper wires.

In industry, communication protocols and the infrastructure are subject to strict rules. To ensure interoperability and interchangeability, standardization is a high priority. This also applies to Single Pair Ethernet.

This article shows the work of international committees, the current status of standardization around the new physical layer SPE, and explains to users how and with which standards the path to the IIoT will be successfully taken.

IEEE802.3 specifies the primary transmission method and must also define the transmission channel, such as the transmission length and number of connectors. The cabling Application note: Single Pair Ethernet - standards landscape ISO/IEC and TIA consider the transmission channel and refer to the corresponding IEC groups for the cable and connector specification with regard to the connectors and cables. There is close cooperation between IEEE802.3 and ISO/IEC and TIA.

The origin

Due to the focus on in-vehicle applications, all SPE standards, with the exception of IEEE 802.3cg, do not specify specific MDI connectors. This allows users in the automotive industry in particular to use manufacturer-specific connectors.
IEEE 802.3cg was adopted in November 2019 and there the LC Style according to IEC 63171-1 and the T1 Industrial according to IEC 63171-6 are listed as optional MDI (wording: "...may be used..." = "can be used"). Other connectors, especially special types for automotive, or also PCB terminals are possible, provided they meet the defined requirements. However, for cabling in buildings, data centers and industry, the connectors selected in the ISO/IEC 11801 and TIA sets of standards are LC Style according to IEC 63171-1 and the T1 Industrial according to IEC 63171-6.
In March 2021, at the IEEE802 - Plenary Meeting, a working group was formed to extend the point-to-point protocols to add TSN functionality for 10BASE-T1L and to look at possible increases in transmission lengths. Furthermore, the IEEE802.3cy working group is working on SPE speeds above 10Gbps. Results in the form of approved standards for all these working groups are expected from 2023 to 2025, depending on the working group (See also: www.ieee802.org/3/index.html).

Note: IEC 63171-1 (LC Style) and IEC 63171-6 (Industrial Style) are complete standard documents with all necessary specifications and test sequences. All standards started later refer to the basic IEC 63171 standard and only include the different mechanical designs. 
The IEC 63171-6 for T1 Industrial is the first available standard for SPE connectors worldwide and includes versions from IP20 to IP 65/67. 

sPE CABLING STANDARDS

In parallel, the installation standards for industry as a basis for the cabling of automation solutions according to IEC 61918 (IEC SC65C) are also being adapted accordingly. To this end, work is being done on the addition of SPE to IEC 61918 Edition 4 AMD1. The publication is planned for 03/2022. To what extent this will then influence the automation profiles themselves remains to be seen. What is certain is that PI (with PROFINET according to IEC 61784-5-3) and ODVA (with EtherNet/IP™ according to IEC 61784-5-2) are actively involved in the further development and implementation of standards for SPE and are developing corresponding profile-specific standard documents. A similar approach will certainly be taken with Advance Physical Layer (APL), based on 10BASE-T1L, for the process industry, and a new profile will also be developed for this in IEC 61784-5-x. 
In conjunction with the component standards for connectors and cables, all users for SPE receive clear guidelines for the construction and testing of corresponding transmission links.

For the time being, these cabling systems are limited to a range of 40 m for 1 GBit/s SPE. For the 10 Mbit/s variant, ranges of 1,000 m and beyond will be realized. 
Other papers on SPE cabling relevant to the U.S. including Canada and Mexico, such as ANSI/TIA-568.5, are being prepared at TIA TR 42.9. In the TIA 42.9 papers this is realized via a revision: ANSI/TIA-1005-B (industrial cabling without SPE). In terms of content, all these supplements are largely congruent. 
These cabling standards provide the user with information on the structure of the cabling, the cabling components to be used to achieve the performance specifications and the limit values for checking the cabling. Thus, they are the most important tool for the construction and commissioning of SPE cabling systems. At the same time, they ensure compatibility between devices and cabling via the references to the component standards (e.g. connectors according to IEC 63171-6). This compatibility is a basic requirement for the function of networks and connections based on SPE and thus the basis for IoT/IIoT. The use of other cabling components is possible in principle, but then no longer compliant with the standard and carries the risk of incompatibilities and functional losses. 

OUTLOOK - INDUSTRIAL ETHERNNET USER GROUPS

In addition to the completion of the cabling standards at ISO/IEC and TIA, the focus of SPE standardization will now be on the integration of SPE into the Industrial Ethernet standardization groups such as PI (PROFINET International), ETG (EtherCAT), IDA (Modbus), CLPA (CC-Link IE), ODVA (EtherNet/IP™) and other user groups. 
However, depending on the strategic orientation and skill of these user groups, the implementation of SPE in the individual automation profiles will probably be more from the device side (sensor/actuator networks) and will not automatically affect communication in the automation network above. Fast Ethernet (e.g. PROFINET) and Gigabit Ethernet (e.g. EtherNet/IP™) will still predominate here for the time being.