Comparison with other integrated data and power standards

PoE provides both data and power connections in one cable, so equipment doesn't require a separate cable for each need. For equipment that does not already have a power or data connection, PoE can be attractive when the power demand is modest. For example, PoE is useful for IP telephones, wireless access points, cameras with pan tilt and zoom (PTZ), and remote Ethernet switches. PoE can provide long cable runs e.g. 100 m (330 ft) and deliver 12 W of galvanically isolated power.^[12] PoE-plus provides even more power.

There are competing data and power technologies. The Universal Serial Bus (USB) provides both data and power, but it is designed for short cables with a maximum length of 5 m (16 ft) and provides less than 2.5 W of non-isolated power. It is less expensive than PoE, and works well for low power peripherals such as a computer mouse, a headset/microphone or a serial port. Some peripherals, such as speakers, scanners and printers, need more power than USB can provide. IEEE 1394 (FireWire) is similar to USB but can provide substantially more power (45 W) at a distance of 4.5 m.

If a device already has power available but no data link, then PoE may not be attractive. A wireless data connection such as IEEE 802.11 may be more economical than running a data cable for the device. Alternatively, there are power line communication technologies that can use power cables for transmitting data. Using some power line modems may be more economical than running a cable.

When data rate and power requirements are both low, other approaches may be viable. Mobile phones, for example, use batteries for power and antennas for communication. Remote weather sensors use very low data rates, so batteries (sometimes supplemented with solar power) and custom wireless data links are used.

Depending on the application, some of the advantages with PoE over other technologies may be:

• Inexpensive cabling carries both data and power
• Power to equipment can be remotely cycled
• Fast data rate

[출처 : http://en.wikipedia.org/wiki/Power_over_Ethernet]