Power Over Ethernet: What It Is and Where is It Going

Technology is wonderful. Electronics allow people to do many things more quickly, thoroughly, and with less effort. Unfortunately, all those devices require power which may not always be easily accessible. A former mall undergoing renovation into a medical clinic may not have enough power outlets for all its new equipment. Or picture a business that’s going green. One of the ways it’s doing so is installing computer-controlled shades that rise and fall depending on the temperature. However, it’ll cost a fortune to hire electricians to rewire the numerous offices to power them. 

Power over Ethernet gives a solution to both examples which will be covered below.

Power over Ethernet: Terms You Should Know

Before diving deep into the workings of Power over Ethernet, here are a few terms you should know:

• PD – Powered Device. These are devices that are powered by Power over Ethernet. A well-known PD is a VoIP phone found in most offices.
• PSE – Power Sourcing Equipment. This is the device that sends power and data through the Ethernet cable to a connected PD. A common one is a PoE network switch. They have a maximum range of sending data around 300 ft. PSE are further broken down into “midspan” or “endspan”. 
• Midspan – When a non-PoE network switch is connected to a PD, it only sends data, not power. A midspan device like a PoE injector adds that power for use by the PD. 
• Endspan – This is the device that actually provides the power and data to the PD. Examples include a PoE network switch and PoE injector. In both, the data and power are sent out simultaneously. 
• PoE Injector – This is a device that adds the power component to the data streaming from a non-PoE network switch to a PD. Also called a midspan device. 
• PoE Splitter – This splits the data from the power running through an Ethernet cord. A splitter normally used when a PSE is being used to power a non-PoE PD that doesn’t have ready access to an outlet. 
• IEEE – The Institute of Electrical and Electronics Engineers. The governing body that creates standards for Ethernet, PoE, and other data communications. 
• Active PoE – These are PoE that meet with the standards established by the IEEE. They can automatically detect the power consumption status of each connected PoE PD and supply the required power. And if the connected device is non-PoE, it will not send power, protecting it. 
• Passive PoE – Does not meet any IEEE standard. Also known as an “always ON” device. Dangerous to PD since it continues to send low voltages which can cause damage especially to non-PoE equipment. 
• Energy Efficient Ethernet – Also known as EEE, this is technology designed to reduce switch power consumption by more than 50 percent during periods of low network traffic. It is also sometimes known as Green Ethernet. 
• PoE budget  –  This is found on multi-port PSE devices like network switches and injectors. Basically, this is the maximum amount of power the PSE can supply to all connected PDs. Exceeding that amount can cause the PSE to turn off power to one or possibly all the ports.

What is Power Over Ethernet

PoE is a way of powering electronic devices through the single network cord called the Ethernet cable. A non-PoE device like a digital security camera normally has two connections, one to receive power from an outlet so it can function, and one to transmit data or send the video feed over to a receiver. So if the above camera is PoE-enabled, there is no power cord and adapter. 

Devices that are powered by PoE are referred to as a powered device or PD. Common examples of PDs include VoIP phones, wireless access points, and IP cameras.

Devices to send power and data through the Ethernet cable to a connected PD are called Power Sourcing Equipment (PSE). PSEs include network switches, injectors, repeaters, and extenders.

Different Types / Standards of Power Over Ethernet 

Before we cover how PoE works, we need to discuss the IEEE.

The IEEE is a non-profit professional association primarily made up of electronic and electrical engineers and related professions. Formed in 1963, it is considered the world’s largest association of technical professionals. 

It’s the IEEE that sets the protocols for today’s standards followed by PoE device manufacturers. Starting in 2003, these are:

• PoE Standard: This is the most common rating. Can power up devices up to 15.4 watts. This is enough for internet protocol (IP) cameras, Voice over Internet Protocol (VoIP) phones found in most offices, wireless access points (WAP), switches, and powered audio systems.
• PoE Plus: Also known as PoE+, up to 30 watts is supported. Common PDs include IP telephones, alarm systems, pan-tilt-zoom (PTZ) cameras, motion tracking cameras, remote computer terminals, and biometric sensors.
• PoE ++ / PoE Type 3: Devices that use up to 60 watts. Video telephones, thin clients, and door access systems are supported.
• PoE ++ / PoE Type 4: Originally offering up to 71 watts of power, this standard recently increased to 100 watts as of 2018. PTZ thermal cameras, large display screens and monitors, and large LED lighting fixtures are just a few examples that use this cutting-edge technology.

Note each new standard is backwards-compatible. Thus you can plug a PoE Plus PD to a Type 4 port. 

How Power Over Ethernet Works 

So how does PoE work? Inside that cable, there are all these pairs of wires called twisted pairs. There are four pairs per cable. PoE uses two of these pairs to transmit data while the other two pairs are used to transmit power. PoE standards PoE and PoE+ use two twisted pairs for power and two for data. Other, newer PoE standards like Type 3 and 4 use all four twisted pairs for both power and data, allowing them to transmit power at higher wattages.

When a PSE is turned on, it leaves the Ethernet port unpowered, periodically checking to see if something has been plugged in. This is called the “Discovery” stage. When a PD is connected to the Ethernet port, it’s detected and the PSE moves on to the “Classification” stage.

In classification, the PSE determines whether the connected device requires PoE, and if so, what standard of PoE it requires. The process is also called “negotiation.” If the PSE doesn’t detect this negotiation, it doesn’t supply power. This makes it safe to plug non-PoE end devices into a PoE port and not experience any problems.

If a non-PSE switch is being used with a PD, a PoE injector is placed between the two. It connects to the switch to receive data while plugged into an outlet to get power. It then sends both through a single Ethernet cable to the PD. 

A PSE can also work with a non-PoE device. This is usually done so if the device doesn’t have ready access to an outlet or other source of power. In this case, a PoE splitter is used. Like the injector, it’s placed between the PSE and the device. Power and data are “split” within the splitter and transmitted into two different cables. Both are then connected to the non-PoE device.

Advantages of Power over Ethernet

PoE technology offers several benefits to businesses and consumers.

• PoE provides value for devices and networks that require power but also involve transmission of data. The main one is the delivery of data and power over a standard ethernet cable. This eliminates the need for separate AC/DC power supplies, bricks, and outlets. All you need is to run cat6 cables from the switch to the PD. In some cases like In-Vehicle Computers, the computer acts as the PoE switch. This means it can power other attached PDs like PoE cameras while handling vehicle conditions like ignition variability and road vibration. 
• There’s no need to hire an electrician to install new wiring and outlets. This lowers the costs of adding or installing a PD. Benefits of Power Over Ethernet Computers in Healthcare Settings goes at length over this advantage in a hospital, which can’t afford shutting down critical areas even temporarily just to rewire for more outlets. 
• Regular Ethernet cable itself is rather inexpensive and is often found already installed at a site. 
• In most locations, there are fewer regulations concerning the installation and placement of Ethernet cables and outlets.
• Since PDs don’t rely on electrical outlets, it’s far easier to move them about in a place. This is especially useful when dealing with monitors, security cameras, and wireless access points where placement is variable. Power outlets, for example, are rarely located in the ceiling. A manufacturing company, as part of its IoT initiative, could place a PoE mini PC and its two sensors far above its assembly line or warehouse. Power comes from the same Ethernet cable it’s sending data through, while the entire setup is protected from factory harsh conditions thanks to the PC’s rugged construction and fanless design. 
• PD are specifically designed to work with less power than conventional network devices without loss of quality. This reduces the amount of power drawn from outlets. This in turn cuts down the energy bills of companies. 
• A PoE switch can automatically detect power consumption by PDs to only supply the right amount of power. This minimizes waste and helps businesses save money.
• PoE technology usually has fewer points of failure in general. Compare this to the various electrical configurations typically powering even a small office building. Mission-critical applications on PoE can further be protected by simply being attached to an uninterruptible power supply (UPS). 
• Some PoE configurations allow users to remotely restart connected PDs. 

Power over Ethernet: Disadvantages / Limitations

Anyone looking to use PoE should know its shortcomings. This is especially true if they’re looking to roll it out across large networks like business enterprises, school campuses, hotels, or retail.

• The furthest distance a PoE switch can transmit data is 300 ft. This is because those two twisted pairs encounter resistance the further they carry the data signals. A PoE ethernet extender, however, can increase that distance up to 4000 ft. Chaining PoE injectors between the PoE and PD can greatly lengthen the reach of such cables.
• A PoE port provides a limited amount of power. The common PoE standard is 15W. Higher standards like PoE ++ / PoE Type 4 have an output of 71W. To access such greater output, the PSE must be configured to do so, especially the hardware. Note a typical computer consumes between 60W up to 250W per hour depending on the number of peripherals attached to it. 
• As mentioned earlier, a PSE has a power budget. Take, for example, a PoE network switch with 24-ports and a 200W power budget. Attaching a PoE IP camera rated at 7W will consume 7W of power. Attach 10 such cameras and power consumption jumps to 70W. Exceed that budget and one risks the PSE shutting down entirely.
• PoE switches cost more than ordinary switches.

• Non-standard PoE, called passive PoE, do not perform the negotiation or communication process. Such switches are “always-on,” sending a constant electric current out over the Ethernet cable at a certain voltage regardless of whether attached devices are PD or not. This may burn them out. 

The CyberMed M Series is a Power over Ethernet 12 and 22 in computer

Uses of Power over Ethernet

PoE may have been first used for VoIP phones, but it has definitely moved on for other uses. An example is the PoE-based patient monitoring system found at the University of Wisconsin Hospital (UWH). The facility, which is the flagship to the University of Wisconsin Health healthcare system, needed a way to quickly provide patient vitals in its long-term care ward to caregivers. This included any dietary restrictions, medication information, and who were fall risks to name a few. That information was displayed on wall-mounted computers outside each patient’s room.

Powering each unit with a separate power cord would have been prohibitive since it would have been expensive to install a new outlet and wiring for each one. Instead, each was a PD, drawing their power as well as their data from PoE. (As an aside, the hospital also liked that they were IP65-sealed to make cleaning easier for staff.)

Another example is the Sinclair Hotel. Based in Fort Worth, TX, the 164-room establishment that uses PoE to power and control lighting, window shades, and amenities like minibars.

Explains Farukh Aslam, Sinclair Holdings president and the hotel’s developer: “In a south-facing room in Texas providing an optimal temperature is essential to the guest experience. We can tell if a guest is no longer in the room and track them leaving the hotel. Once a guest has left the property, the system can automatically turn off lights and bring down the shades. Once the guest re-enters the hotel again the temperature quickly sets back to their preference.”

It’s more than optimizing a hotel guest’s experience, though. Use of PoE equipment cuts power consumption by 30 to 40 percent. Burnt-out lightbulbs are also a thing of the past as staff can quickly trace such eyesores through network connections. The futuristic setup was even inexpensive since electricians weren’t needed which saved thousands in labor costs.

Sinclair Holdings also worked with its vendors to develop more PDs like smart mirrors, AC units, and even exercise equipment.

Other applications of PoE include smart offices and smart cities.

Market Share of Power over Ethernet

The growth of Internet of Things is poised to grow explosively. Nearly 14 million units back in 2021, that figure is estimated to reach 30.9 billion units sold by 2025.

PoE will play a big part of that growth in IoT thanks to low costs and flexibility. Businesses are especially eyeing security devices like cameras as well as “smart lighting” systems. At the time of this writing, Global Industry Analysts Inc. estimates the demand for PoE will reach $1.2 billion by 2025. The US has the biggest share of the market at an estimated 43.3 percent. However, China looks to be adopting PoE the fastest at a compounded annual growth rate of nearly 13.8 percent by 2025 while the US is at 10.8 percent in the same time period.

Closing Thoughts

Much of the technology used in modern society requires power. Access to it is not always convenient due to lack of outlets, the right wiring, or the wrong room design. Power over Ethernet (PoE) resolves many of those thanks to its ability to power devices as well as transmit data simultaneously.

To learn more about how this is done, and if PoE is right for your company’s wants and needs, contact a representative from Cybernet. Also follow Cybernet on Facebook, Twitter, and Linkedin to stay up to date on this and other relevant topics.