What's So Great About Ethernet?
By Daniel Feldman
A case is made for power over Ethernet providing the networking backbone for the digital home.

Ethernet cable has become the universal backbone for residential computing, communications, entertainment and home-control networks. With the advent of Power over Ethernet (PoE) technology that same Ethernet cable is increasingly being used to simultaneously deliver power to digital home devices, from WiFi wireless access points and notebook computers to video surveillance cameras, game consoles and other broadband entertainment products.

PoE improves consumer convenience and energy efficiency by enabling both power and data to be distributed over the same cable. With PoE, the home network's various devices can be located wherever the consumer wants to use them, and not just where power outlets are available.



The same PoE technology that has become the power backbone for business' Voice over IP (VoIP) and wireless data and security networks is now bringing benefits to the broadband digital home.

During 2009, the industry completed its work of enhancing PoE technology so it could support even more devices with higher-power needs. The previous industry-standard technology was limited to delivering 12.95 watts to any given device. However, devices such as video phones, 802.11n WiFi access points and pan-tilt-zoom cameras require 15 to 30 watts.

A group known as the IEEE 802.3at Task Force worked to enhance PoE so that it could power devices requiring up to 25.5 watts. The resulting IEEE P802.3at PoE+ standard also included extensions so powered devices could negotiate their own power requirements. With PoE's new capabilities, it became possible to power WiMAX Subscriber Stations (SS), fiber-to-the-home (FTTH) optical network terminators (ONTs), 3G pico and femto cells and even laptop computers.

Some of these applications require as much as 50 watts. This is also now possible because the latest PoE+ technology can deliver power over all four Ethernet Cat 5 pairs. Four-pair powering enables 60 watts to be delivered with a much more efficient, 600mA current, rather than the 1.2A required for two-pair PoE technology. As a result, for the same 60 watts at the source, 51 watts can be delivered over Cat 5 cable with a four-pair solution, compared with 42 watts for a two-pair solution.

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