Power over Ethernet or PoE technology, which also called PoL (Power over LAN) or Active Ethernet, describes a system to transfer electrical power, along with data, to remote devices over a single Ethernet cable. This works great in areas where you may not have power and/or Ethernet easily accessible, like a roof. This also allows you to more easily place the AP closer to the antenna, thus reducing signal loss over antenna cabling. The result is lower cost, less downtime, easier maintenance, and greater installation flexibility than with traditional wiring.
 
Definedby IEEE 802.3,PoE technology has two common standards with different power abilities.

• IEEE 802.3af (June 2003) —— According to this standard, many IP phone sets, Wireless LAN access points and other IP DTEs are designed to receive operating power (up to 15.4W) through Ethernet interfaces.
• IEEE 802.3at (September 2005) —— The higher power (up to 25.5W or more) available with this standard make self-powered equipment with higher power requirements such as WiMAX transmitters, HD cameras, videophones and laptops possible.

Also, there’s another PoE standard called Passive Power over Ethernet or Passive PoE. In comparison with IEEE 802.3af, it uses no active electronic components for transmission. It is a simple way ofconnecting the cables in order to transfer the data and power supply along the same Ethernet cable at the same time.

In the near future, we’ll have PoE Access Points or Routers to support standard IEEE 802.3af PoE or Passive PoE. Standard PoE AP/Router can work with the PoE switch and passive PoE AP/Router will be equipped with independent PoE power supply for convenient installation.