PoE(Power over Ethernet) is a technology that allows data to be transmitted over Ethernet cables while providing Power to connected devices. Traditionally, network devices (such as IP cameras, wireless access points, IP phones, etc.) require independent power supplies, which can lead to complex wiring, high costs, and reliance on power outlets. The emergence of PoE technology solves these problems and provides greater flexibility and convenience for the deployment of network equipment.
History and Development of PoE
PoE technology was first proposed by Cisco Systems and standardized by IEEE in 2003, namely IEEE 802.3af standard. With the continuous popularization and development of network equipment, PoE technology has gradually been widely used and further developed. Later, IEEE proposed an updated PoE standard, the IEEE 802.3at standard, also known as PoE +, to provide support for higher power devices.
Role and advantages of PoE
- Simplified cabling: Because PoE technology can transmit data and power through a single Ethernet cable, no additional power lines are required, which simplifies the wiring process of network equipment and reduces cost and complexity.
- Increased flexibility PoE technology enables network equipment to be more flexibly deployed in various places, without being limited by the location of the power outlet, and is suitable for occasions that require mobile or temporary deployment.
- Reduce energy consumption: Traditionally, many network devices still need to be powered on when not in use, and PoE technology can flexibly control the power supply of the device as needed, thereby reducing energy consumption.
- Improve reliability: The power supply provided by PoE technology is stable and reliable, which can reduce the risk of network interruption caused by power failure.
Principle of PoE
In traditional Ethernet, network devices usually need two connections: one for data transmission and the other for power supply. This means that in addition to the network data lines, each device also needs a separate power supply line, which increases the complexity of wiring and requires more power outlets.
The core idea of PoE technology is to provide power supply to connected devices by transmitting DC power in Ethernet cables. This process involves two main components: Powered Device(PD) and Power Sourcing Equipment(PSE).
Powered Device(PD): PD refers to devices that need to receive power from Ethernet cables, such as IP cameras, IP phones, wireless access points, etc. PD devices usually contain a PoE interface for receiving power supply from PSE.
Power Sourcing Equipment(PSE): PSE refers to the device that provides power supply, such as a switch or injector. The PSE device sends current to the connected Ethernet cable to supply the PD device connected to it.
PoE technology utilizes unused wire pairs (usually data wire pairs) in Ethernet cables to transmit current. Before transmitting current, the PSE device sends a special signal (called a “detection” or “classification” signal) to identify whether the connected device supports PoE and determine the required power level. Once it is confirmed that the device supports PoE and the required power level is available, the PSE device will transmit current on the data line pair while maintaining the data line pair for data transmission.
Components of PoE
PoE power supply (PSE): The device responsible for providing power supply to the devices in the network, usually a switch or a dedicated PoE injector.
PoE device (PD): Devices that receive power supply from PSE devices, such as IP cameras, IP phones, wireless access points, etc.
PoE middleware: Software or hardware components used to manage and monitor PoE networks, which can be used to manage power supply equipment, monitor power consumption, etc.
Application scenarios of PoE
Enterprise Network
in enterprise networks, PoE technology is widely used in various network devices, such as IP phones, wireless access points, webcams, etc. Through PoE technology, enterprises can achieve simpler and more flexible network deployment, and reduce the management and maintenance costs of network equipment.
Home Network
in the home network, PoE technology can be used to connect smart home devices, such as smart cameras, smart speakers, etc. With PoE technology, users can deploy and manage various smart devices more conveniently, regardless of the location and number of power outlets.
Public Places
in public places, such as airports, shopping malls, hotels, etc., PoE technology can be used to deploy security monitoring systems, wireless networks and other equipment to provide users with safer and more convenient services.
Standard of PoE
IEEE 802.3af standard
IEEE 802.3af is a networking standard, commonly referred to as PoE(Power over Ethernet), that allows network devices to be supplied with Power over Ethernet cables. This standard was officially released in 2003, marking the beginning of a new era in web design.
The 802.3af standard provides the basis for powering a variety of devices, including IP cameras, VoIP phones, and WLAN access points, directly through network cables. It can provide up to 15.4 watts of power output for each port, but due to the power loss on the cable, the actual available power is about 12.95 Watts.
The introduction of this standard makes the deployment of network equipment more flexible and convenient, without the need for separate power lines, reducing cost and complexity. At the same time, PoE technology also brings higher reliability and energy saving. By transmitting power and data on Ethernet cables, it reduces the dependence on power outlets and reduces energy consumption.
IEEE 802.3at standard
IEEE 802.3at is a networking standard, also known as PoE +(Power over Ethernet Plus), which is an improvement and extension of the IEEE 802.3af standard (PoE). The 802.3at standard was officially released in 2009 to provide PoE solutions with higher power output to meet the needs of high-performance network equipment that requires more power.
The 802.3at standard extends the power output capability of PoE, allowing each port to provide a power output of up to 30 watts, compared with the 802.3af standard, which can only provide a power output of up to 15.4 Watts. This allows the 802.3at standard to support more types of devices, including devices that require higher power, such as dual-band wireless access points, PTZ (Pan Tilt Zoom) cameras, VoIP video phones, etc.
In addition to providing higher power output, the 802.3at standard also introduces some new features, such as power management and classification, to improve the efficiency and reliability of power transmission. These capabilities allow PoE + devices to manage power supply more intelligently, dynamically adjust power supply, improve energy efficiency, and pave the way for future network infrastructure development.
IEEE 802.3af vs 802.3at
IEEE 802.3af and 802.3at are two different PoE(Power over Ethernet) standards, and the main difference between them is the Power output capability and the type of equipment supported.
Power output capacity:
802.3af standard:
- Provides up to 15.4 watts of power output.
- The actual available power is about 12.95 Watts, because there is power loss during transmission.
802.3at standard(Also known as PoE +):
- Provides up to 30 watts of power output, which is twice the 802.3af standard.
- The device side provides at least 25.5 watts of power, more than the 802.3af standard.
Supported device types:
802.3af standard:
- Suitable for low-power devices, such as IP cameras, VoIP phones, wireless access points, etc.
- Due to power limitations, it is not suitable for some types of equipment that require more power.
802.3at standard:
- Customized for devices that require higher power.
- Support more types of devices, including dual-band wireless access points, PTZ (Pan Tilt Zoom) cameras, VoIP video phones, etc., these devices require more power to operate efficiently.
Introduction of other PoE standards
In addition to the IEEE 802.3af and IEEE 802.3at standards, there are several other PoE standards, such as the IEEE 802.3bt standard, also known as PoE ++ or 4 PoE(4 pairs of PoE). This New Standard provides higher power output, up to 60 watts or more, to meet the growing power demand of network equipment. The IEEE 802.3bt standard also introduces some new features, such as two different power supply modes (Type 3 and Type 4), and new types of high-power devices.