Thursday, April 18, 2024
HomeTechPower over Ethernet (PoE)...

Power over Ethernet (PoE) – Explained

Power over Ethernet, or PoE, describes any of several standards or ad hoc systems that pass electric power along with data on twisted-pair Ethernet cabling. This allows a single cable to provide both a data connection and enough electricity to power devices such as wireless access points (WAPs), Internet Protocol (IP) cameras and voice over Internet Protocol (VoIP) phones.

Techniques

There are several common techniques for transmitting power over Ethernet cabling. Three of them have been standardized by the Institute of Electrical and Electronics Engineers (IEEE) standard IEEE 802.3 since 2003.

The three techniques are:

  • alternative A, which uses the same two of the four signal pairs that 10BASE-T and 100BASE-TX use for data in typical Cat 5 cabling.
  • alternative B, which separates the data and the power conductors for 10BASE-T/100BASE-TX, making troubleshooting easier.
  • 4PPoE, which uses all four twisted pairs in parallel, increasing the achievable power.

Alternative A transports power on the same wires as data for 10 and 100 Mbit/s Ethernet variants. This is similar to the phantom power technique commonly used for powering condenser microphones. Power is transmitted on the data conductors by applying a common voltage to each pair. Because twisted-pair Ethernet uses differential signaling, this does not interfere with data transmission. The common-mode voltage is easily extracted using the center tap of the standard Ethernet pulse transformer. For Gigabit Ethernet and faster, both alternatives A and B transport power on wire pairs also used for data since all four pairs are used for data transmission at these speeds.

4PPoE provides power using all four pairs of a twisted-pair cable. This enables higher power for applications like pan–tilt–zoom cameras (PTZ), high-performance WAPs, or even charging laptop batteries.

In addition to standardizing existing practice for spare-pair (Alternative B), common-mode data pair power (Alternative A) and 4-pair transmission (4PPoE), the IEEE PoE standards provide for signaling between the power sourcing equipment (PSE) and powered device (PD). This signaling allows the presence of a conformant device to be detected by the power source, and allows the device and source to negotiate the amount of power required or available while avoiding damage to non-compatible devices.

Standards development

Two- and four-pair Ethernet

The original IEEE 802.3af-2003 PoE standard provides up to 15.4 W of DC power (minimum 44 V DC and 350 mA) on each port. Only 12.95 W is assured to be available at the powered device as some power dissipates in the cable.

The IEEE 802.3at-2009 PoE standard also known as PoE+ or PoE plus, provides up to 25.5 W of power for Type 2 devices. The 2009 standard prohibits a powered device from using all four pairs for power. Both of these standards have since been incorporated into the IEEE 802.3-2012 publication.

The IEEE 802.3bt-2018 standard further expands the power capabilities of 802.3at. It is also known as PoE++ or 4PPoE. The standard introduces two additional power types: up to 51 W delivered power (Type 3) and up to 71.3 W delivered power (Type 4). Each pair of twisted pairs needs to handle a current of up to 600 mA (Type 3) or 960 mA (Type 4). Additionally, support for 2.5GBASE-T, 5GBASE-T and 10GBASE-T is included. This development opens the door to new applications and expands the use of applications such as high-performance wireless access points and surveillance cameras.

Single-pair Ethernet

The IEEE 802.3bu-2016 amendment introduced single-pair Power over Data Lines (PoDL) for the single-pair Ethernet standards 100BASE-T1 and 1000BASE-T1 intended for automotive and industrial applications. On the two-pair or four-pair standards, the same power voltage is applied to each conductor of the pair, so that within each pair there is no differential voltage other than that representing the transmitted data. With single-pair Ethernet, power is transmitted in parallel to the data. PoDL initially defined ten power classes, ranging from 0.5 to 50 W (at PD).

Subsequently, PoDL was added to the single-pair variants 10BASE-T12.5GBASE-T1, 5GBASE-T1, and 10GBASE-T1 and as of 2021 includes a total of 15 power classes with additional intermediate voltage and power levels.

- A word from our sponsors -

Most Popular

More from Author

Angola’s Billionaire Elite: Unveiling the Top 10 Wealthiest Moguls in 2024

Here's a look at Angola's wealthiest individuals in 2024, highlighting the...

Algeria’s Billionaire Elite: Unveiling the Top 10 Wealthiest Moguls in 2024

Algeria, with its significant oil and gas reserves, has a group...

Ethiopias’s Billionaire Elite: Unveiling the Top 10 Wealthiest Moguls in 2024

Ethiopia, known for its rich cultural heritage, is also home to...

- A word from our sponsors -

Angola’s Billionaire Elite: Unveiling the Top 10 Wealthiest Moguls in 2024

Here's a look at Angola's wealthiest individuals in 2024, highlighting the top entrepreneurs and business magnates who are shaping the country's economic landscape. This list is current for 2024 and excludes Isabel Dos Santos, focusing on the new and prevailing forces in Angola's billionaire circle.Angola’s Billionaire Elite:...

Discover the Ultimate Road Companion: Nissan Caravan Now Available in Mombasa, Kenya

Are you on the hunt for a vehicle that combines robust performance with spacious comfort? Look no further than the Nissan Caravan, currently on offer in the bustling city of Mombasa, Kenya. Ideal for businesses requiring cargo transport, groups seeking adventure, or families needing extra space, the...

Algeria’s Billionaire Elite: Unveiling the Top 10 Wealthiest Moguls in 2024

Algeria, with its significant oil and gas reserves, has a group of wealthy individuals whose influence spans across various industries including construction, manufacturing, food, and pharmaceuticals. Here is a table summarizing the top 10 wealthiest individuals in Algeria as of 2024:As of 2024, here is the latest...

Rising Icon of Sport: Kenya’s Talanta Stadium Set to Redefine African Athletics

Kenya's Pinnacle of Pride: Unveiling the Talanta Sports CityNAIROBI-KENYA | Amidst the bustling energy of Nairobi, a new landmark rises - the Talanta Sports City. A marvel of architecture that intertwines the spirit of Kenyan heritage with cutting-edge design, this stadium is poised to become a beacon...

Ethiopias’s Billionaire Elite: Unveiling the Top 10 Wealthiest Moguls in 2024

Ethiopia, known for its rich cultural heritage, is also home to some of the wealthiest individuals in Africa. These moguls have diversified their investments across various sectors including oil, mining, agriculture, and real estate, significantly contributing to the nation's economic development. Here's a look at the top...

Trailblazers of Wealth: Kenya’s Five Most Influential Women in 2024

Kenya's economic landscape is distinguished not only by its vibrant markets and industries but also by the formidable women who have risen to the top of these sectors. As of 2024, here is a detailed look at the five richest women in Kenya, highlighting their net worth,...