Implementing the New PoEPlus Standard

While many users took advantage of the cost-effective benefits of Power over Ethernet (PoE), 12.95W maximum of af is not enough power to serve all the applications and implementations. The IEEE 802.3at task force was formed to create an improved Power over Ethernet standard, building on the original IEEE 802.3af specifications. Designated PoEPlus, it will more than double the wattage available to powered devices, delivering up to 30W of power and possibly even 45W. If accepted as a new IEEE standard, PoEPlus will allow increased power to many more devices, enhancing their capabilities, such as those used for wireless multi-radio access points, Pan Tilt Zoom security cameras, streaming video, VoIP (define - news -alerts), and IP security applications.

The most recent focus of the task forces debate has centered on whether a two-pair solution is feasible, or if a four-pair solution will be necessary in providing enough power for high power applications such as multi-band access points and controllable security cameras. The greatest concern is rising temperatures in the cabling which can cause permanent deformity and eventual data degradation.

At the task forces January 12th meeting, a proposal was approved stating the groups objectives can most likely be met without having to resort to four-pair powering, and that the members would focus on developing two-pair solutions, which are lower in cost and easier to implement when compared to the alternative. The current proposal is to use a source voltage from the power sourcing equipment (PSE) of 5157V with 650mA on Category 5 or better wire. The drop per pair total in the worst case scenario of 100m cable and connectors is 12.5ohms. This will provide at least 30W at the power device with a voltage range of 4057. While these values are not final and still subject to additional thermal dissipation work being conducted by IEEEs cabling working group, what makes the two-pair solution both viable and preferable?

Why is PoE being implemented?

PoE technology offers an innovative solution to systems designers in eliminating the need for local power outlets or in getting power to a device without calling an electrician. PoE allows power and data to be carried over a single Ethernet cable, allowing for greater flexibility in office design, higher efficiency in systems design, and faster turnaround time in set-up and implementation.

To date, the most pervasive applications have been wireless access points and IP phones, for which PoE provides a single cable connection as well as a single point of backup for a UPS in case of power failure.

Some applications, however, require significantly more power, and the original IEEE802.3af specification limits the user to 350mA due to cable and patch panel limitations of Category 5 wiring systems. This was done as a safety precaution, even though several demonstrations showed drawing up to 750mA was possible with no safety hazard. Since that original specification was written, Category 5e and 6 cabling systems have become more common.

While manufacturers have been able to develop proprietary PoE products that meet the growing demand for higher power, users would prefer that all products meet a single interoperable standard that provides for those high power applications specifically.