• 02/26/2008
    8:13 PM
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Cisco's 11n AP: Timing Is Everything

Pulling the trigger on a prestandard product is inherently risky, but sometimes, so is waiting.
Responsible IT decisionmakers are wary of prestandard technologies, having discovered the hard way that "prestandard" is often code for "proprietary, premature and/or prone to vendor lock-in." Still, sometimes you have to walk on the wild side. Occasionally a nascent technology provides enough of a competitive advantage that it's worth taking a chance, or events make us comfortable that vendors will stay on the standards path. 802.11n Draft 2.0 is a perfect example, so when Cisco offered to let us test an early version of its 1250 access point in our Syracuse University Real World Labs, we were excited to get a glimpse of the future of enterprise WLANs.

From a performance standpoint, our testing revealed speed increases of four to six times what an 802.11a/g infrastructure can provide. And using an 802.11n access point for even legacy a/b/g clients delivered a measurable performance advantage thanks to MIMO (Multiple Input, Multiple Output) technology's ability to maintain high-bandwidth data rates for a larger portion of an AP's coverage area. For a/b/g voice over WLAN phones this greater reliability translates into higher quality calls and fewer dead spots.

We believe that 802.11n's bug shakedown period will be a less rocky version of what occurred when 802.11g was an IEEE draft. Unlike 802.11n, 802.11g's Wi-Fi Alliance interoperability certification occurred after the standard was set in stone; in contrast, products based on 802.11n Draft 2.0 are being certified today, before the standard's ratification by the IEEE. That's great news for enterprise IT: As of this writing 225 products, albeit predominantly SOHO/consumer oriented, have received the seal of interoperability from the Wi-Fi Alliance. Notable names on that list include Apple, Aruba, Atheros, Broadcom, Cisco, Intel and Meru—all big businesses with an economic interest in ensuring that the current crop of 802.11n Draft 2.0 products are both backward and forward compatible.

This isn't to say maximum performance won't increase as subsequent versions of 802.11n are endorsed by the Wi-Fi Alliance. But it does mitigate the risk that current devices will be incompatible with future revisions. The truth is, companies don't buy WLAN devices based on an IEEE standard, but on the Wi-Fi Alliance's endorsement of interoperability and the independent certification that 802.11n Draft 2.0 has received. In addition, Cisco is a member of Intel's more exhaustive "Connect with Centrino" interoperability testing program, which gives an added comfort level.Setting A 5GHz Strategy

The 5GHz frequency has been underutilized compared with the more popular 2.4GHz band, but with the advent of 802.11n that's poised to change. In the early days of WLANs, light user loads and a focus on maximizing coverage made the superior propagation characteristics of 2.4GHz a clear choice over 5GHz's more limited range. Now that those WLANs have grown from scattered hotspots to pervasive coverage blankets with many microcells supporting a multitude of users and high-bandwidth applications, the focus has shifted from coverage to capacity. And when you're talking capacity, nothing beats the massive amount of spectrum available in the 5GHz band, which encompasses 21 nonoverlapping channels when an AP implements full DFS2 (Dynamic Frequency Selection 2) support, compared with 2.4GHz's modest three nonoverlapping channels.

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