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IEEE 802.11n and Architecture Redux at Interop

All the major enterprise WLAN vendors made their way to Interop Las Vegas 2007 last week, and I had the opportunity to meet with the majority of them. Top on my list: IEEE 802.11n and enterprise WLAN architecture providers. While previous briefings sketched out the key issues, these one-on-one meetings fleshed out some of the details (live demos didn't hurt, either).

Since I wrote my last column less than two weeks ago, Aruba Networks released a white paper on 802.11n, marking the first enterprise WLAN vendor document on the topic. Author Peter Thornycroft discusses the technical aspects of this unfinished standard and provides some perspective and recommendations regarding implementation. Although not completely without vendor bias, it's the first vendor treatise on this subject and I hope the other vendors follow suit. The 802.11n standard is much more complex than the previous three 802.11 connectivity standards, and organizations looking to experiment or engage in early deployments would do well to enter in with both eyes wide open.

Chipsets: It seems that all the enterprise WLAN vendors, save Cisco perhaps, will bring products to market based on an Atheros chipset design. The features appear to be the same: Support for 3x3 MIMO, two spatial streams and compatibility with the 802.11n Draft 2.0 specification. Note that there is support for only two spatial streams, even though there are three antennas. According to one vendor, this is because of the additional processing (and cost) requirements. When asked, Atheros did not directly address the resource concern. Also, transmit beamforming will not be in the initial release(s).

From our conversations with vendors at the show, it appears that Atheros' first chipset is truly a 1.0 release. As such, some vendors are holding back until Atheros' second-generation 802.11n chipset, currently planned for general availability in July/August. Atheros confirmed that there would be better price points, especially in the consumer market, but other items such as product performance, link stability and power usage likely will come into play, too.

Antenna Placement: Simple two-stick antenna deployments are quickly fading into history, at least in the high-end consumer market. The pre-standard 802.11n consumer targeted APs (access points) from Linksys and NetGear come with three antennas positioned at a variety of angles. No doubt the antennas are used as a marketing tool for consumers (more antennas means better and faster transmissions, right?).

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