802.3at: The Proposed New Standard for PoE
The IEEE has been listening to concerns expressed by the PoE user community and is currently working to define a new standard — often referred to as HiPoE, PoE+, or PoE Plus — that will support the needs of more advanced technologies.
The foremost difference from the current standard is the proposed near-doubling of power that can be distributed over the network to enable devices that require more current to benefit from PoE. In particular, the new 802.3at specifications call for delivering 30 watts of power via two twisted pairs — a significant boost from the previous standard. Even going beyond 30 watts using all four twisted pairs has been discussed as a potential future revision on the new standard.
Some of the other proposed improvements include backwards compatibility with 802.3af devices. 802.3at also proposes embedding intelligence via a newly defined data link layer (layer 2) protocol. This Link Layer Discovery Protocol (LLDP) will allow the power source equipment to discover devices on the network and communicate with those powered devices to enable dynamic allocation of power levels and even putting a device in sleep mode.
Interim Solutions for High-Power Devices
If you cannot wait for next year’s ratification of a new standard, several vendors currently offer a few options that can provide an interim solution to your power needs. Many of these solutions consist of midspan and splitter technology added onto the existing network switches and cameras respectively.
The midspan, which adds power to an Ethernet cable, is placed between a network switch and powered devices. Midspans often have 1, 6, 12, 24 or 48 ports. The splitter splits the power and data in an Ethernet cable into two separate cables, which can then be connected to a device that has no built-in support for PoE.
Projected impact of 802.3at
With ratification expected in 2009, analysts believe that the new 802.3at standard, like its predecessor, will further accelerate the adoption of network video by including substantial savings for PTZ and outdoor camera installations.
Fredrik Nilsson is general manager of Axis Communications, a provider of IP-based network video solutions that include network cameras and video encoders for remote monitoring and security surveillance.