Leveraging PoE Technology to Power Next-Generation IoT and Other Devices in 5G Networks

The new generation of 5G technology can provide advanced mobile Internet connections with higher speeds, enabling various IoT and big data applications, thereby creating new business opportunities. These applications are driving the need to connect more types of powered devices (PDs) to Ethernet networks at unprecedented rates, including IP surveillance cameras, 802.11ac and 802.11ax access points, LED lighting, 5G small cells, and Other IoT appliances.

— Addresses interoperability challenges of delivering up to 90W over Power over Ethernet in existing switch infrastructure

Microchip Technology
PoE Marketing and Business Development Senior Manager
Galit Mendelson

The new generation of 5G technology can provide advanced mobile Internet connections with higher speeds, enabling various IoT and big data applications, thereby creating new business opportunities. These applications are driving the need to connect more types of powered devices (PDs) to Ethernet networks at unprecedented rates, including IP surveillance cameras, 802.11ac and 802.11ax access points, LED lighting, 5G small cells, and Other IoT appliances. Power over Ethernet (PoE) technology brings a number of advantages to powering these devices in 5G deployments. By setting the power limit for Power Sourcing Equipment (PSE) and Powered Device (PD) to 90W and 71.3W respectively, the latest IEEE® The 802.3bt standard makes this possible.

The challenge is how to deploy PDs that support this latest generation of PoE technology so that they can work with pre-existing IEEE 802.3bt 2- and 4-pair PDs, i.e. supporting earlier Universal PoE (UPOE) compliant with the previous standard and HDBaseT Power Delivery (POH) specification for PD. Today, the industry has bridged this interoperability gap, ensuring PDs compliant with the previous standard and the new IEEE 802.3bt-2018 standard can share the same Ethernet infrastructure without having to replace existing switches or cabling.

The road to IEEE 802.3bt

Since the first PoE standard was ratified in 2003, the range of applications for PoE has grown substantially, and progress continues to be made in new applications. PoE has huge advantages in simplifying installation, saving CAPEX and OPEX costs, and providing a uniform and secure power standard for global use.

The main limiting factor affecting the use of PoE in new applications is the amount of power available. While the 15.4W power supply is sufficient for most IP phones and 802.11a/b/g access points, it is not enough to power IP video phones, 802.11n and PTZ IP cameras. Therefore, the Institute of Electrical and Electronics Engineers (IEEE) released the IEEE 802.3at standard in 2009, specifying a PoE power supply with a power of 30W.

Today, higher power is required to power other Ethernet-connected devices such as PTZ surveillance cameras, kiosks, POS terminals, thin clients, 802.11ac and 802.11ax access points, small cells, and connected LED lighting support, and such devices can benefit from PoE. To meet this need, the new IEEE 802.3bt standard increases the maximum power available for PoE primarily by utilizing all four pairs of structured cabling. IEEE 802.3bt extends the power classification information exchanged during initial negotiation to enable efficient power management capabilities, support multiple PoE classes, and also be backward compatible. These enhancements address the challenges posed by higher power and more efficient PoE powered systems.

A Call for Intent (CFI) for the IEEE 802.3bt standard started in early 2013 and was formally approved in September 2018. Since the new standard expands the use cases of PoE by setting the power limits of PSE and PD to 90W and 71.3W, respectively, it not only meets the existing market demand, but is also widely regarded as the main driver of PoE market growth.

However, prior to the implementation of IEEE 802.3bt, there was also some simultaneous work to improve the power supply performance of PDs. Beginning with the IEEE 802.3af-2003 PoE standard, it is capable of delivering up to 15.4W of output power per device over two pairs of Category 5e (Cat5e) cables. The IEEE 802.3at-2009 standard (also known as PoE+) introduced a “Type 2” PSE/PD that supports 30W output power and 25.5W load power. The latter is mainly an extension to the first standard. Subsequently, the HDBaseT Alliance standardized the HDBaseT protocol, allowing HDMI links to be extended up to 100m through Cat5e or higher cables. In 2011, the HDBaseT Alliance created the Power-over-HDBaseT (PoH) standard, which extends the maximum power supply over a four-pair cable to 95W.

The following table summarizes the pre-IEEE 802.3bt standards:

type

standard

PSE minimum input power

The minimum input power guaranteed by the PD

Cable category

cable length

Power supply

Type 1

IEEE® 802.3af

15.4W

12.95W

Cat5e

100m

2 pairs

Type 2

IEEE 802.3at

30W

25.5W

Cat5e

100m

2 pairs

PoH

PoH

95W

72W-95W 1

Cat5e/6

100m

4 pairs

Note 1: Extended power capability enables up to 95W of PD input power if the channel length is known.

IEEE 802.3bt adds many features. In addition to introducing Type 3 and Type 4 PSE/PD and working over four-pair cables, the standard supports single-signature and dual-signature PD structures and adds Levels 5 to 8 to an improved two-way authentication process. As long as the channel length is known, automatic classification is added and the power capacity is extended. Finally, the standard includes low-power standby and support for 10G-BASE-T with PoE. The table below shows the PoE functions provided after the ratification of the IEEE 802.3bt standard.

type

standard

PSE minimum output power

PD minimum input power

Cable category

cable length

Power supply

Type 1

IEEE® 802.3af

15.4W

12.95W

Cat5e

100m

2 pairs

Type 2

IEEE 802.3at

30W

25.5W

Cat5e

100m

2 pairs

Type 3

IEEE 802.3bt

60W

51W-60W 1

Cat5e

100m

2 Pairs or 4 Pairs Levels 0-4
4 pairs of grades 5-6

Type 4

IEEE 802.3bt

90W

71W-90W 1

Cat5e

100m

4 pairs of grades 7-8

Note 1: Extended power capability enables up to 60W (Type 3) and 90W (Type 4) PD input power if the channel length is known.

One of the goals of the IEEE 802.3bt standard is to comply with the Limited Power Supply and Safety Extra Low Voltage (SELV) requirements as defined in ISO/IEC 60950. However, this compliance means that each port cannot exceed 100W. Despite this power cap, 100W per port is still sufficient for applications not previously supported under the legacy IEEE standard, thus expanding the potential number of PoE port deployments.

ensure interoperability

The IEEE 802.3bt specification ensures that IEEE 802.3bt systems automatically work with legacy Type 1 and Type 2 devices only if the PSE can support PD (in terms of power) and both are compliant. If the PD requires higher power (IEEE 802.3bt PD) and the PSE cannot support the PD (IEEE 802.3af/at PSE), then the PD will remain off, or go into an on state and consume only the available power from the PSE.

One of the first examples of solutions to provide such interoperability was Microchip’s PSE chipset, which enables interoperability between switches that conform to the previous standard and products that conform to the new IEEE 802.3bt-2018 standard. The chipset is based on Microchip’s earlier PSE chipset for implementing the widely adopted PoH four-pair power supply standard (for 95W PD). In addition, it is at the heart of IEEE 802.3bt-2018 compliant PoE injectors and midspans, bridging the interoperability gap for users.

By installing an IEEE 802.3bt-2018 compliant PoE injector and midspan between the PD and the existing switch, users can power any combination of previous compliant PDs and IEEE 802.3bt-2018 compliant PDs. Switches that comply with the new IEEE 802.3bt standard can also power PDs that meet the previous standard by using single-port and multi-port options.

For system developers, the IEEE 802.3af/at/bt PoE chipset provides the scalability to integrate the two- and four-pair systems required to support both previous and IEEE 802.3bt-2018 compliant PoE into Single board design. These chipsets must be able to balance cooling throughout the system and should contain all the manager and controller functions needed to build PSE devices that can deliver 90W to 99.9W per port while providing IEEE 802.3bt Type 3 (Class 1-6) and Type 4 (Class 7-8) applications provide support for up to 48 ports. As an additional consideration, systems based on these chipsets should have the ability to upgrade earlier standards to IEEE 802.3bt via software updates without changing hardware.

A final concern for developers is the ability to protect PDs from reverse polarity connections and reduce the power space and cost required to provide IEEE 802.3bt Type 4 Class 8 power. The latest IEEE 802.3bt solutions also solve this problem with full-bridge rectifiers used on the supply side of the PoE connection.

The new IEEE 802.3bt standard is capable of delivering 90W of power over four-pair Cat5e cables and higher. This PoE class is expected to be the highest defined, as higher classes may not be safe for existing cables and connectors deployed in today’s infrastructure. This standard will replace all existing solutions that currently offer 60W/75W/95W that comply with previous standards, such as UPOE or 4PPoE. PoE system and equipment vendors provide roadmaps for implementing these new standards, as well as support for early implementations that comply with previous standards, including those that support the UPOE and POH specifications. PDs compliant with the previous standard and PDs compliant with the new IEEE 802.3bt-2018 standard, when properly implemented, can share the same Ethernet infrastructure without replacing existing switches or cables.

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