I came across an interesting article by Joanie Wexler over at Network World about the power consumption of 802.11n. In a nutshell, the current generation of wireless access points (WAP) generally require more power than what is available with PoE implementations.

Excerpt from the article:

Today’s widely installed 802.3af power-over-Ethernet (PoE) switches and power injectors supply about 15 watts of power at the switch port. To comply with Ethernet standards, 12.95 watts of the initial 15 watts must be sustainable over 100 meters. The 802.3af “power budget,” then, is 12.95 watts; however, some 802.11n Draft 2.0-based access points consume up to 18 watts.

As a result of the highlighted power issue, manufacturers resort to various ways to make it work. According to her research, the following are some of the methods currently used:

  • AP only comes with a single 802.11n radio — single-radio devices are likely to operate within the power budget
  • Automatically disable certain AP services
  • Require two ports on your PoE switch (using either one cable or two)
  • Silently sacrifice range to stay within the power budget

The above power-saving methods will probably not bother most of us — although as IT professionals, it is still useful to know the score. And if you are a consultant or an infrastructure engineer, you will probably want to stay in the know.