802.11n: 5 Reasons to Go For It!

802.11n: 5 Reasons to Go For It!

By CWNP On 11/14/2007 - 4 Comments

1.  The technology works.  

With all of the vendors racing to be first, there's already a significant number of successful enterprise 802.11n deployments that prove that the technology actually works.  This is, of course, on top of all of the certification testing completed by the Wi-Fi Alliance.  I've tested a number of client adapters (Mini-PCIe, CardBus, USB, etc) and a small number of enterprise 802.11n APs.  They work.


2.  Longer Shelf Life

Let's face it, users aren't clamoring to use LESS bandwidth.  More and more applications are finding their way onto the WLAN.  Some of these applications are bandwidth hogs, and others are latency sensitive.  Any time you're installing a new network, so long as the technology is stable and you can afford the price premium, it makes sense to go with the devices that will give you the longest shelf life.  The real expense to 802.11n will be installation and infrastructure upgrades.  Due to the fact that most users will still be 802.11a/g for quite some time to come, you will undoubtedly still have quite a while before you have to worry about larger WLAN controllers and gigabit ethernet (GE) AP connections.  10/100 Ethernet and the controller(s) you're using today (that already supports your user traffic) will likely do the trick for a while.

3.  802.11n Makes Indoor Mesh a High Value Proposition

Indoor mesh has been plagued by multiple hops and decreased bandwidth since day one.  With new dual-band 802.11n APs, we have enough backhaul bandwidth to support many clients.  Since the backhaul can be greenfield (pure 802.11n, running at 300 Mbps), many AP's worth of mixed mode client traffic could be supported on the mesh backhaul.  This means that so long as you have an AC power source near where you want to place your mesh node, you're in good shape.  One option there is to have single port PoE injectors (with enough power to fully power the 802.11n AP of course) plugged into AC adapters within 100 meters (max length of a Cat5e cable) of the location where you want to place the mesh AP.  You could use PoE to power the AP, but the AP wouldn't use the Ethernet cable for data transport.

4.  High Multipath Environments

Have you ever spent countless hours at a customer site where they required VoWiFi and you just couldn't get it to work?  You brought in the spectrum analyzers and the site surveying applications.  You did predictive modeling.  You used directional antennas and turned down the power on APs.  You enabled TPC and monitored every statistic you know of to see if you could get VoWiFi to work...and it just wouldn't run reliably.  Damn you multipath!  Well now there's an answer.  A system that eats multipath for lunch - heck, it even thrives on it!  802.11n.  Yes, that MIMO is some cool stuff.  Finally a solution that will work well in those auto part manufacturing plants!

5.  802.3af Now, 802.3at Later...Maybe.

Since most WLAN deployments don't come close to maxing out the 10/100 Ethernet pipe behind APs, it's safe to say that after 802.11n APs are installed, the same will be true - at least for a while.  Since the number of clients, number and type of applications, and client use won't change overnight, that 10/100 pipe should be fine for a while.  That means there won't be any cost to upgrading the Ethernet infrastructure for a while, and it means that 802.3af will still be available to our new 802.11n APs (providing you have it now).  Most new 802.11n APs will run on 802.3af - some in a limited (2x3 or 2x2) capacity and some in a full 3x3 capacity.  Some 802.11n APs are compliant with the 802.3at draft standard.  Certainly those manufacturers are aiming to upgrade only firmware at a later time in order to remain compliant.  Choose your PoE solution carefully.

4 Responses to 802.11n: 5 Reasons to Go For It!

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11/20/2007 at 10:32am
Hi Glenn,

In 802.11n, there are 20 MHz mode, 20/40 MHz mode, and PCO mode. In the case where 802.11a/b/g and 802.11n stations are present in any form, the AP will be using the Mixed Mode PPDU frame format (mandatory) and likely be using 20/40 MHz mode. PCO mode is an option, but one that we're not likely to see for a little while I suspect. If the 802.11n stations are using 40 MHz channel widths, then they can do so while the 802.11a/b/g stations are using 22 MHz (802.11b) or 20 MHz (802.11a/g) channel widths. All of this will happen simultaneously in 20/40 MHz mode.

There's more info about PCO in some of my other posts. There's also two really good Aruba Networks whitepapers on 802.11n I suggest that everyone read.

You are right in that the best scenario is greenfield (pure 802.11n), but that's not going to be possible about 95% of the time. Certainly everyone should try diligently to get 802.11b off their network entirely. 802.11a/g will cause enough degraded throughput by themselves without adding 802.11b poison into the mix. :)

11/20/2007 at 04:26am
I would personnally not encourage the use of b and g phones on the 11n AP. We all know the effect of 11b on 11g systems where your 11g client gets almost less bandwidth than your 11b client due to the protection mechanisms. Adding the L-SIG header will mean again more overhead thus less time to use for data communication. Furthermore, the b and g clients will require the 11n AP to go to 20MHz channel mode instead of 40MHz killing your throughput by 50%! I don't dare to say if Phased Coexistance will make this change completely dynamic and if it will avoid too much penalty (does anyone have more information?) but until then, I would suggest keeping the standards seperated. Of course, if bg is not working in your envirnment and 11n does and the only thing you are interested in is voice and not high throughput data, then I can completely agree on this standpoint.

11/19/2007 at 21:32pm
Uh, it's 2 down from this article. :)

11/19/2007 at 21:19pm
I read "802.11n: The Top 5 Reasons To Wait" article only couple of weeks ago. I don't remember where!

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