I recently attended a live Cisco Mobility TV webinar co-sponsored by AirMagnet entitled "Designing and Deploying 802.11n Next-Generation Wireless." Apparently it was a big hit; according to the moderator, a record "thousands" of viewers logged in to watch it. Here’s what I thought were a couple of interesting takeaways.
Drop in Replacement or New Site Survey Required?
A Cisco representative started out by recommending a 1-for-1 access point replacement of legacy APs giving priority to performance over coverage. In other words, swap in a Cisco dual band 1250 AP to handle both legacy 802.11bg devices with the same coverage pattern as before while providing 802.11n access (in the 5 GHz band) for new 802.11n clients.
I thought this was a bit strange since 802.11bg does not like reflections whereas 802.11n using MIMO thrives on it. APs must be relocated accordingly. Later in the Webinar, the AirMagnet guy noted that an active site survey using a laptop with a live 802.11n client adapter is required to figure out the optimal 802.11n AP placement to take advantage of multipath. This seemed to contradict the Cisco 1-for-1 forklift strategy.
AirMagnet also recommended surveying with more than one 802.11n client adapter type if you are supporting more than one brand. I think this is a good idea since, unlike 802.11bg, Cisco does not provide a client side adapter.
Upping the Power Requirements
Perhaps the most controversial aspect of an 802.11n wireless LAN upgrade is the additional power requirements for dual band APs. Cisco claims that their enhanced PoE is the only viable single port solution for dual radio operation. They stated that dual PoE is twice the cable cost, 4x the cost to pull the cable, and uses more switch ports. They also noted that competitors supporting dual band operation over standard 802.3af PoE do so at reduced transmission power.
Luckily, CPUs are not the only chips going green. Witness the recent announcement from Siemens that generated a flurry of online articles discussing the 802.11n power controversy. Siemens managed to cut 3W off a full 802.11n MIMO (roughly 600 Mbps using transmission over 3 antenna with 3 streams each) AP running at maximum radio output in both the 2.4 GHz and 5 GHz bands simultaneously and yet operate over standard PoE.
Audience Survey
Having a captive audience of thousands, Cisco conducted three polls during the Webinar. Here are the questions and results.
"How do you expect to benefit from the use of 5 GHz with 11n?"
No surprises here. Only 5% claim that they will not use 5 GHz for 11n, vindicating the use of 5 GHz in the enterprise.
"What do you see as the biggest inhibitor to 11n adoption?"
Is the undetermined business need from those not deploying wireless whatsoever or are their needs currently met by 802.11bg? Also note the lack of a warm fuzzy for the current 802.11 draft 2.0 standard.
"How do you plan to power your 802.11n access points?"
Not much to add here. Looks like the largely Cisco audience prefers enhanced PoE.
So there you go. Some inside info and survey results from a wildly popular wireless webinar.
802.11n definitely a big improvement to WLAN. Finally we see progress.
Posted by: 802.11n | March 26, 2008 at 12:16 PM