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IEEE 802.11n and Architecture Redux at Interop: Page 3 of 7

Colubris surprised us when the company shared that it is aiming to power its new dual-radio AP, the Multiservice AP 625 or MAP-625, with a single 802.3af PoE feed. Colubris claims to be working closely with chipset manufacturer Atheros to tweak power consumption requirements so that both 802.11n and 802.11abg radios operating at full transmit power and functionality (40 MHz wide channel, three radio chains, two spatial streams and so on) can be powered. Atheros shared that, "we work closely with our customers and design partners to review and suggest design, and identify and select components that lend an efficient POE architecture. Components such as power supply, optimizing and tuning front-end radio chains are done by us with our partners to achieve lower power." Don't hold your breath, though: Any vendor with two 802.11n radios is not going to operate them with full functionality within an 802.3af power budget anytime soon.

Meru has built a pre-standard 802.3at port into its own AP300 AP. Will this pre-standard PoE implementation be anymore upgradeable than the pre-standard 802.11n chipset? While this remains an unknown, pre-standard PoE injectors are already available from vendors including Microsemi, so enterprises eager to deploy gear will have a viable method to power them. What Meru demoed to me in a private suite at the show used an external power adapter. And for those who noticed that Meru's AP300 has a second Ethernet port, it's used for bonding Ethernet traffic using LACP not as a second powering point.

Trapeze also supports pre-standard 802.3at with its pre-standard 802.11n AP, the MP 432. Trapeze was the only vendor to introduce a pre-standard 802.11n product at Interop. Mirroring some of its other products, this new AP includes two Ethernet ports. If only one Ethernet port is powered with PoE, a sub-set of the AP's capabilities will operate. But Trapeze engineers were clever enough to simultaneously use the second Ethernet port for power, which enables the AP's full features. Although customers like options, unless the second cable is already run or it's a greenfield site, it's significantly more cost effective to install a pre-standard 802.3at injector with the existing cable run.

Xirrus introduced its own proprietary PoE injector, which provides about 60 watts of power. When asked why the IEEE 802.3at standards committee wasn't able to achieve a higher level of power, company representatives could only point to the fact that most vendors are easily satisfied with the 30 watts currently proposed and that the IETF's involvement was stirring things up. Xirrus claims that its unique power requirements haven't been a deal breaker and its unique architecture more than compensates for this nonstandard network element.

Gigabit Edge Ports: One vendor I spoke with made it sound like enterprises will have to upgrade their edge switch ports to gigabit Ethernet with 802.3at or mid-spans at the same time they move to 802.11n. My advice is, don't present that purchase order to your CIO for signing the same week he's calculating your holiday bonus.