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Power over Ethernet (PoE) Technology for the 5G Generation & Beyond

How to deliver up to 90 watts of Power over Ethernet wiring in an existing switch infrastructure

The Advancement of 5G and PoE

Galit Mendelson
Galit Mendelson Senior Manager of PoE Marketing & Business Development | Microchip Technology, (

As next generation 5G technology comes to the mainstream, it opens new business opportunities that rely on a variety of IoT and Big Data applications driven by higher data rates and power. There is a greater need to connect powered devices (PDs) such as 802.11ac and 802.11ax access points, 5G small cells, IP surveillance cameras, LED luminaires, and other IoT appliances to Ethernet networks. Power-over-Ethernet (PoE) technology works well to power these devices in 5G deployments, facilitated by the latest IEEE® 802.3bt standard that pushes the power limits of Power Sourcing Equipment (PSE) and Powered Devices (PDs) to 90W and 71.3W respectively. Ensuring that the PDs that support this latest generation of PoE technology can still work with existing pre-IEEE® 802.3bt 2-pair and 4-pair PDs that support legacy PoE standards is a challenge. This issue has now been resolved since pre-standard and new IEEE® 802.3bt-2018-compliant PDs can share the same Ethernet infrastructure and don’t require changes to existing switches or cabling.

The Road to IEEE 802.3bt

The first PoE standard was ratified in 2003. Since then, PoE adoption has picked up as it is finding its way into powering new applications. PoE offers several advantages such as ease of installation and lower CAPEX and OPEX costs. It has also emerged as a unified and safe power standard that can be used worldwide.

In the early years, the primary drawback with PoE was that the amount of power available wasn’t sufficient for devices such as IP video phones, 802.11n, and pan-tilt-zoom (PTZ) IP cameras, although it worked well for most IP phones and 802.11a/b/g access points. To address this, the Institute of Electrical and Electronic Engineers (IEEE) specified 30W at the PoE source when it released IEEE 802.3at-in 2009.

With devices such as PTZ security cameras, kiosks, POS terminals, thin clients, 802.11ac and 802.11ax access points, small cells, and connected LED lighting connected to the Ethernet network, there is demand for even higher power. Addressing this requirement, the new IEEE 802.3bt standard utilizes all four pairs of the structured wiring, thereby increasing the maximum PoE power. IEEE 802.3bt extends the power classification information exchanged during initial negotiation to allow meaningful power management capability, enabling support of multiple PoE classes, while also being backward compatible. In turn, this helps achieve higher power and more efficient PoE delivery systems.

The IEEE 802.3bt standard was ratified in September 2018, five years after the Call for Interest (CFI) activity started. The new standard facilitates the expansion of PoE use cases since it pushes the power limit of PSEs and PDs to 90W and 71.3W respectively. This makes it a major catalyst to PoE market growth. In the past too, efforts were taken to increase power delivery to PDs. First, the IEEE 802.3af-2003 PoE standard was launched and could provide up to 15.4W of output power to each device over two pairs of Category 5e (Cat5e) cables. Then, the IEEE 802.3at-2009 standard, also known as PoE+, which is an extension of the first standard, could support 30W output power and 25.5W load power through the “Type 2” PSE/PD. We then saw the emergence of the HDBaseT Alliance, which helped standardize the HDBaseT protocol. This standard allowed the HDMI links to be extended up to 100m over Cat5e or better cables. In 2011, the Power over HDBaseT (PoH) standard, which was created by the HDBaseT Alliance, could extend the maximum power deliverable to 95W over four pairs.

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

summarizesNote 1: Extended power capability allows PD input power to reach up to 95W if channel length is known.

IEEE 802.3bt not only introduces Type 3 and Type 4 PSEs/PDs and working over four pairs, but also supports both the singleand dual-signature PD constructions. It also adds class 5 to 8 as part of an improved mutual identification process. By bringing in the automatic class functionality, it extends the power capability as long as the channel length is known. It also supports 10G-BASE-T with PoE and provides low standby power support. Here are the PoE capabilities that were available once the IEEE 802.3bt standard was ratified:

tableNote 1: With extended power capability, PD input power can reach up to 60W for Type 3 and up to 90W for Type 4 if channel length is known.

The IEEE 802.3bt standard is also compliant with the limited power source and Safety Extra Low Voltage (SELV) requirements as defined in ISO/IEC 60950. Despite this, power cannot exceed 100W per port. However, the 100W per port supports applications that were not feasible under the prior IEEE standards, expanding the potential number of PoE ports deployments.

Ensuring interoperability

With the IEEE 802.3bt specifications, the IEEE 802.3bt system will work automatically with legacy Type 1 and Type 2 devices. However, to ensure this, the PSE needs to be capable (in terms of power) of supporting the PD and both must be standardcompliant. If the PSE cannot support it (IEEE 802.3af/at PSE), the PD will remain off or turn on and consume only the power available from the PSE.

The PSE chipset from Microchip is a great example of a solution that enables pre-standard switches to interoperate with new IEEE 802.3bt-2018-compliant products. It is based on an earlier PSE chipset from Microchip, which was widely adopted to implement the POH four-pair power standard for 95W PDs. It also forms the basis for IEEE 802.3bt-2018-compliant PoE injectors and midspans that bridge the interoperability gap for users. For system developers, IEEE 802.3af/at/bt PoE chipsets provide the scalability to incorporate, into a single board design, the two- and four-pair systems that are required for supporting pre-standard and IEEE 802.3bt-2018-compliant PoE. They also need to include all required manager and controller functionality for building PSE equipment while being able to balance thermal dissipation evenly across the system. The fact that systems based on these chipsets can be upgraded from legacy standards to IEEE 802.3bt via a software update with no hardware changes is an important factor.

The full-bridge rectifier devices that are used on the powered side of the PoE connection help address concerns around reverse-polarity connections for PDs. This can also help cut power space and the costs of delivering IEEE 802.3bt Type 4 Class 8 power.

With the new IEEE 802.3bt standard, 90W can be delivered over four pairs of Cat5e cables and above. Higher PoE levels than this are not recommended since they may not be safe for the existing cabling and connectors deployed in today’s infrastructures. This standard will replace all existing pre-standard PoE solutions that deliver 60W/75W/95W today, such as Universal PoE (UPOE) or 4PPoE. With the right implementation, organizations can continue to use both pre-standard and new IEEE® 802.3bt-2018-compliant PDs on the same Ethernet infrastructure without changing existing switches or cabling.

The Ultimate Solution To Powering 5G Technology With PoE

Microchip multi-Power over Ethernet (mPoE) technology powers any wired network device seamlessly and efficiently, making it the ideal solution for Ethernet-based applications. Addressing the 5G market demand for more power, more data and more speed, Microchip’s family of multigigabit multiport PoE midspans offer the easiest and most cost-effective way to install Wi-Fi 6 APs and 5G small cells. The ready-to-install PoE injectors not only solve the challenges of adequately powering these devices up to 90W, but also support their 10Gbps data rates across both, indoor and outdoor environments. These solutions make it easy for users and system engineers to transition to the latest IEEE® 802.3bt standard by supporting both pre-standard and IEEE-compliant PoE devices without having to change network switches or cabling infrastructure. With this, powering challenges will soon be a thing of the past.


BiS Team

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