Siemens Communications says its new 802.11n product line needs only the electricity available in existing power-over-Ethernet systems. That eliminates a problem faced by some early adopters of these power-hungry access points.

What' s more the Siemens announced this week that its 802.11n access points can run in both the 2.4GHs and 5GHz frequency bands at the same time using three send/receive antennas (dubbed a 3x3 configuration) for maximum performance. By contrast, some rival products limit 802.11n functions or need an extra Ethernet switch port, until PoE gear that supports the new, higher-power 802.3at standard is available.

By using existing PoE gear, the Siemens products make it easier for companies to deploy 802.11n sooner. (Learn more about available 802.11n products from our Enterprise Wireless LAN Buyers Guide.)

The enterprise products are the HiPath Wireless AP 3620, with external antennas, and the AP 3610, with internal antennas, and new software upgrades, one for the HiPath Wireless Convergence software on the company's companion wireless controller, and one for the HiPath Wireless Manager HiGuard, the vendor's wireless LAN (WLAN) management and security application. The access points have one 10/100/1000Mbps Ethernet port, and can be mounted on the same bracket used by the older 802.11a/b/g access points.

Siemens, like some other WLAN vendors, is using Atheros Communications' latest 802.11n chip. This silicon lets the two radios in the access points run on both bands at the same time and can support up to three antennas (Marvel also just unveiled a 3x3 802.11n chip). Depending on these configurations, 802.11n throughput can range from about 150M to 350Mbps, and soon 450Mbps (see our Clear Choice Test of 802.11n products for the small office/home office market).

But to date 802.11n products for the enterprise use more power than the 15.4 watts supplied by today's 802.3af PoE equipment. That's not a problem if you can plug the access point directly into an AC wall socket or run separate power cables to each device. The new 802.3at standard doubles the wattage available, but very few if any PoE products yet support it.

WLAN vendors with two-radio access points are tackling this challenge in various ways. Trapeze created new code that lets its 802.11n access point make use of existing PoE injectors, but there are tradeoffs in terms of performance. The 30-watt power need of Meru's 802.11n gear means that early adopters such as Morrisville State College have to consider a possible mix of solutions: upgrading their PoE system when new 802.3at equipment is available, or drawing an additional 15 watts of power from a second, unused Ethernet switch port, or using mid-span power injectors that pump additional wattage into the cable. Cisco's 1250 802.11n access point runs fine on existing PoE, if you only use one of its two radios. To use both, you need a wall outlet or a mid-span power injector.