High Tech Talk

What if the device requires more than 15.4W power?

The IEEE is working to enhance the 802.3af Power over Ethernet standard to give networked devices more juice. PoE provides a way to deliver electrical power over LAN cabling to networked devices, such as IP phones, wireless access points and IP security cameras.
The IEEE formed a working group to develop the 802.3at standard or PoE Plus, with the goal of boosting the amount of power that PoE can deliver.

The group is evaluating whether to continue to carry electricity on two wire pairs or move the electrical current onto all four Ethernet wire pairs. Each copper wire in a cable's bundle can take only so much power before being damaged. Likewise, the wires in an Ethernet bundle can carry only so much total wattage before the bundle overheats, creating cable life-expectancy concerns. The IEEE also must account for possible interference between higher-powered electricity and data signals. Cabling specialists are investigating what those limits are.

Once researchers determine the best delivery method, the working group will set the wattage limits. The current standard delivers as much as 15.4 watts; the goal for the new standard is to provide 30 watts or more. It's possible that PoE Plus could deliver as much as 60 watts, which is enough to power high-speed, dual-radio access points or almost any other mobile multimedia device.

As a part of the standard, PoE Plus will specify guidelines for Category 5 and higher Ethernet cable, as well as support power delivery with 10M, 100M, 1G and perhaps even 10Gbps data delivery.

In addition to boosting power, the IEEE is exploring new, improved power-management capabilities for PoE. These would make it possible for a switch to have more electricity available for more devices. The current 802.3af PoE standard delivers power at three levels: 4, 7 or 15.4 watts. PoE Plus will likely make it possible for a PoE-enabled switch to allocate exactly the amount of power a device needs and to adjust the power to the device automatically, such as when a device moves from standby to active use.

The industry must wait patiently for PoE Plus, however. Standards groups tend to move slowly, and the IEEE's 802.at working group is no exception. The most optimistic estimate for the first publication of the 802.3at standard is early 2007. If the group gets ambitious and wants to include more features into PoE Plus, it could take a bit longer, leaving the networking industry without the much-needed power boost. Either way, it is likely to be well into 2007 or 2008 before there is a ratified standard.

IEEE 802.3at forum have decided the classification will change and per pair deliver 720 mA current, feeding power through 2 pair only and add new layer 2 classify mechanism. It also changes the output voltage from PSE site from 44V to 50V.

The JetNet 4706 / JetNet 3706 series must apply DC 55V when it perform high power feeding as following diagram.

Korenix JetNet 4706 / JetNet 3706 support both of IEEE 802.3af and IEEE 802.3at standards with friendly Web user configure interface for different PoE power forwarding mode.