Single pair Ethernet in the context of IIoT

In the foreseeable future, the sustained trend toward digitalisation and connectivity is set to impact all parts of the industrial sector, transport, building technology and many other applications. The cyber-physical system (CPS) enables information and software to be linked together with electromechanical components. Implementing a CPS requires the type of powerful and robust data infrastructure that can be built using Ethernet technology in accordance with the IEEE 802.3 standard.

The IEEE 802.3 working group has pushed Ethernet technology forward at a tremendous pace since the introduction of the first Ethernet 10BASE-T standard in the 1990s. The first Ethernet CAT 5 cables, based on TIA-568 A/B and with a transfer rate of 100 Mbps, were unveiled as early as 1995, followed by publication of the 1000BASE-T standard in 1999. 1,000 MHz cables in accordance with IEC 61156-5/-6 for 10GBASE-T are now state of the art in the cable industry.

Parallel to the technical development of the Ethernet technology – driven principally by the IEEE 802.3 (Institute of Electrical and Electronics Engineers) and the TIA (Telecommunications Industry Association) – the IEC (International Electrotechnical Commission) and the affiliated national committees work on compiling uniform standards for cables and connectors. Examples of successful efforts in this area are the IEC 60603-7 series of standards for the RJ45 detail specifications for shielded 8-pin connectors up to 2,000 MHz and the ISO/IEC TR 11801-9901 guideline for balanced cabling to support transmission speeds of up to 40 Gbps.

In order to fulfill the more stringent environmental and IP protection requirements in industrial environments, D-coded M12 data connectors for Fast Ethernet with two pairs of wires were included in the IEC 71076-2-101 standard for circular connectors in 2008. For higher data speeds up to 500 MHz, an X-coded 4-pair M12 standard conforming to IEC 61076-2-109 was published in 2014.

TSN, Time Sensitive Networking in accordance with IEEE 802.1 and IEEE 802.3, enables urgent and business-critical messages to be transmitted parallel to other data traffic. This permits defined response times – a prerequisite for use in industrial environments.

In order to implement end-to-end Ethernet technology from the cloud right through to the sensor, and replace existing field bus systems such as Profibus at process level, new technologies with cost-effective, miniaturised and standardised components are needed.

The new single pair Ethernet cables from Belden will play a crucial role in transmission technology. As well as being considerably lighter in weight and more compact, these single pair Ethernet cables are cheaper to manufacture.

SPE cables are suitable for use in offices as well as harsh and dirty industrial environments – as permanent or flexible connections. Belden manufactures LSZH (low smoke zero halogen) cables for applications in buildings. These cables provide enhanced safety in cases of fire and comply with the requirements laid down in the EU Regulation No. 305/2011. SPE cables with a PUR sheath are available for industrial applications. Thanks to their 80% shield coverage, Belden’s shielded SPE cables are ideally suited to applications where there is severe electromagnetic interference.

In order to comply with the requirements of IEEE 802.3, the guideline for Generic Cabling for Customer Premises was amended to include ISO/IEC TR 11801 Part 9906 – “Technical Report: Balanced 1-pair cabling channels up to 600 MHz”, which specifies the following three use cases:

• - 10BASE-T1 in accordance with IEEE P802.3cg: bandwidth 0.1 MHz – 20 MHz; reach up to 15/1000 meters
• - 100BASE-T1 in accordance with IEEE 802.3bw: bandwidth 0.3 MHz – 66 MHz; reach up to 15 meters
• - 1000BASE-T1 in accordance with IEEE 802.3bp: bandwidth 1 MHz – 600 MHz; reach up to 15/40 meters

Unshielded SPE cables of up to 15 meters in length may be used to cover short distances. At this point in time, cables of this kind are mainly used in automobiles.
IEEE 802.3bu specifies the standard for provision of data and power (PoDL) via a single twisted pair.

In order to reconcile the opposing requirements of high data speed and long transmission links specified by IEEE 802.3, new cable standards are needed. Standards for SPE cables are currently being elaborated by the SC 46C EC committee:

• - Transmission performance of up to 600 MHz and transmission length of up to 40 meters.

- IEC 61156-11 for permanent installation;
- IEC 61156-12 for flexible installation;

• - Transmission performance of up to 20 MHz and transmission length of up to 1,000 meters

- IEC 61156-13 for permanent installation;
- IEC 61156-14 for flexible installation;

Coupled with ISO/TR 11801-9906, the requirements defined in the SPE cable standards place high demands on the quality and construction of single pair Ethernet cables.

Single pair Ethernet connectors are needed to connect up SPE cables to devices. Connector types appropriate to the environmental classifications specified in ISO IEC TR 29106 for M1I1C1E1 (IP 20) and M2I2C2E2 / M3I3C3E3 (IP 67) must be taken into account in order to meet the different requirements in office and industrial environments.

The IEC SC 48B – PT 63171 project team is working on the specifications for connector variants 1 to 6.

In addition to pure single pair cabling configurations, it is also possible to set up a four-pair structure in order to simultaneously integrate four single pair Ethernet channels into a single cable.

This enables simpler cabling, particularly in industrial environments where large numbers of sensors are frequently located in small spaces. Tried and tested in industrial environments (M2I2C2E2 / M3I3C3E3), the design of the M8 and M12 circular connectors enables the implementation of this type of cable structure. All SPE connector variants need to comply with the fundamental single pair Ethernet specifications defined in the SPE connector basic standard IEC 63171 “General Requirements and Test”.

Belden is working with other experts in international and national standardisation bodies and user organizations to meet market requirements for standardized components and devices, and leverage the benefits of SPE for end users.

SPE technology is currently being driven by PROFIBUS & PROFINET International (PI), ODVA and the FieldCommGroup through specification of an Advanced Physical Layer (APL) for Ethernet, which can be used in process automation and instrumentation to enable access to field devices at remote locations and in areas with a high explosion risk. Power and data are transmitted to the field devices in this setup via a shielded twisted pair SPE cable. As a result, Ethernet to field level should be up and running by 2021/2022 as an alternative to existing field bus technologies.

A network from production process at field level to control level (PLC), process management (MES) and enterprise level (ERP) is now becoming a reality, in other words a network from the sensor to the cloud.

Single pair Ethernet is set to become the backbone of the fully digitalised factory. Thanks to affordable, reliable cables, connectors and devices that comply with the SPE standards, all systems within a factory can be designed on a smaller scale. Belden focuses on developing system solutions based on the plug&play principle, fast connection technology between connector and cable and between connectors and devices, a lightweight cable and systems for monitoring the entire network, which will speed up the use of IIoT in the near future.

Single pair Ethernet devices and components from Belden will have a significant impact on the automated, intelligent connected factory:

• - A network from sensor to cloud guarantees control across all network components
• - Thin, lightweight Ethernet cables open up new fields of application
• - Simple structured cable installation and use of several Ethernet channels in existing cable ducts
• - SPE connectors in the circular connector design proven in industrial environments
• - The SPE standard enables cable sharing (four SPE channels in one cable) and ensures simple and cost-effective passive cable distribution
• - Possibility to connect network components using multidrop bus technology, which allows up to eight network nodes to be connected to a cable
• - Increased reliability thanks to simpler cable and connector designs, since only one channel with one wire pair has to be taken into account.

A universally standard Ethernet network will exist in future for every sector and every field of application. A heterogeneous network infrastructure can continue to be used for specific system requirements. The common denominator, however, will be Ethernet. Fiber optic cable will continue to be needed for long transmission distances as well as shielded CAT 7 Ethernet cables made of copper with four pairs of wires for high data rates of 10 Gbps. The industrial sector will benefit if sensor, actuator and PLC data can be recorded without gateways and proprietary interfaces and forwarded to data highways.

Belden collaborates closely with other experts within the standardization projects, and in late 2018 was able to present SPE cables conforming to the IEC 61156-11 and IEC 61156-13 standard at two German trade fairs (electronica and SPS IPC Drives).

More standardisation work is still necessary, however. In the context of Industry 4.0, the need for higher data speeds and for robust and cost-effective connectors and cables demands further development and standardization efforts. In IEEE P802.3ch, a working group titled the Multi-Gig Automotive Ethernet PHY Task Force was set up with the aim of refining the IEEE 802.3 standard for speeds greater than 1 Gbps for Automotive Ethernet.

Combined with a simple connection technology, the advantages of SPE technology with regard to miniaturisation and weight reduction make it attractive for factory and process automation, building cabling, rail technology, the automotive industry and many other applications.