The Rush To 802.11ac


Things seem to be moving quickly in the wireless world.  In January, many presenters at Wireless Field Day 2 were discussing the future of client-side wireless.  It all revolves around 802.11ac, the specification that leads to gigabit-speed wireless connections.  A 5 GHz-only specification, 802.11ac uses wider channels and more spatial streams to create more throughput for client devices.  Whereas a single spatial stream in 802.11n can create about 150 Mbit of bandwidth at a 20 MHz channel bandwidth, the default single spatial stream for 802.11ac can deliver almost three times that at 433 Mbits across an 80 MHz channel.  The numbers just keep climbing from there when you include the ability to use 160 MHz wide channels and up to 8 spatial streams.  No wonder people are salivating over the idea of this new generation of wireless.  So much so that vendors have already started coming out with hardware to support 802.11ac even before the specification is fully ratified.  After Broadcom announced support for 802.11ac in forthcoming chipsets, Buffalo announced an 802.11ac home router and media station.  Cisco has even gotten in on the 802.11ac game with a new module designed to extend the 3600 series AP to support 802.11ac.  The times, they are a changing.  However, for those of you that like to live on the bleeding edge of technology, there are some things to keep in mind as you race out to Best Buy to make your Wi-Fi super fast.

1.  There are no 802.11ac client devices today.  All the horsepower in the world on the infrastructure side of things won’t matter one whit if the clients connecting to the devices don’t have support to interface with these blazing fast speeds.  It wasn’t that long ago at Wireless Field Day 1 that Cisco was telling us the 3×3:3 support in an AP was a bunch of hooey because most laptops on the market don’t have support for three spatial streams.  Of course, a year later and almost all consumer laptops now have the requisite support.  Coincidentally, now so do the newest Cisco APs.  And that’s just the laptop side of things.  Look around right now at the majority of devices that are using the wireless in your house or at the office or even at Starbucks.  Odds are good that those devices are phones or tablets of some kind.  Those present huge issues for 802.11ac adoption.  Take the iPhone and iPad as an example.  The iPhone is a 2.4 GHz-only device.  With 802.11ac being a 5GHz-only protocol, your iPhone won’t even be able to talk to your 802.11ac router.  You’re going to need to keep 2.4 GHz connectivity.  Odds are good that Apple and other phone manufacturers will eventually build 5 GHz radio support into their hardware, but that’s unlikely to happen until there is a way to shrink the size of the antennas and provide better battery life for the throughput.  Even the iPad, which supports 5 GHz radios, had to make some battery life concessions.  It’s a 1×1:1 device, so even on 802.11n it can never use more than 150 Mbits of bandwidth.  It can’t even support the use of 40 MHz channels on 802.11n.  If these devices don’t see hardware changes in the future, it’s going to be difficult for 802.11ac to see much adoption when the majority of “post PC” BYOD devices won’t come close to supporting the new standard.

2.  802.11ac throughput is nice.  In theory.  When you look at the high-end specs for 802.11ac, the amount of data that can be transferred is downright sexy.  However, the same can be said for 802.11n.  There is support for up to four spatial streams in 802.11n, although I’ve never seen APs that support more than 3.  Hitting the top end of 802.11n capabilities requires you to use 40 MHz channels, reducing the number of available channels by 50%.  That’s not a huge concern in the 5 GHz range today due to a larger number of non-overlapping channels.  However, 802.11ac is going to create bigger issues.  The default channel bandwidth in 802.11ac is 80 MHz, so we’ve already reduced the number of available channels by another 50%, so we’re working with a quarter of what we were before.  If you want to really cook on 802.11ac at those sexy data rates, you’re going to need to enable 160 MHz-wide channels.  Now we’re looking at something like 3 or 4 non-overlapping 160MHz channels instead of the 23 that are available by default in the 5GHz range.  Sounds pretty crowded to me.  You also need to realize that 5 GHz doesn’t penetrate walls as well as 2.4 GHz.  A typical 5 GHz deployment today has to have APs clustered a lot closer together to provide the same coverage as a 2.4 GHz setup.  Add in the fact that those wanted to pump out the data are going to want to be as close to the AP as possible to get the best signal and throughput, and you’ve got a real interesting scenario unfolding.  There’s a real possibility of a log jam of frequencies in a given area.  A lot of this can be sorted out by doing proper site surveys and planning.  Hope you’ve been doing them all along because you are definitely going to have to do them before you order your first 802.11ac AP.

3.  802.11ac isn’t a final standard yet.  All that wonderful gigabit wireless goodness is a nice idea, but right now it’s not much more than just that – an idea.  We’re still technically working from the 0.1 draft spec approved in January of 2011.  The finalization of the draft specification isn’t expected to happen until sometime at the end of 2012, and the 802.11 Working Group isn’t expected to give their approval until 2013.  Even after that, it’s going to take quite a while for the devices to really permeate the market.  The 802.11ac devices you can buy today might not even support the final standards.  This is exactly what happened before with 802.11n.  I can remember going into my local office supply company and seeing these new fast Wi-Fi devices based on the 802.11n Draft 1 spec.  The device in question was from Belkin.  Of course, there was a lot that changed from Draft 1 to Draft 2, so those Belkin Draft 1 devices only really work with the Belkin cards that were sold to go with the routers.  When the Draft 2.0 and the finalized 802.11n devices came out later, you basically had to repurchase everything to make it work correctly.  This bit more than a couple of people that I know, and in some cases I got to remind them of that fact when I was pulling out the old Draft 1 equipment and replacing it.  I can see this same thing happening with the current crop of SOHO devices from companies like Buffalo.  There may not be a whole lot that changes between the 802.11ac 0.1 spec and the final draft, but if there is you are going to have to toss out your bleeding edge gear and buy something new.  Larger enterprise vendors like Cisco are more than happy to offer you upgrade protection for your 802.11ac modules if you buy them now to be on the cutting edge.  Of course, because you are buying enterprise-grade APs, you’re going to be paying more up front for them.  Either way, being an early adopter of 802.11ac is going to cost you in the long run, either from buying upgrade protected devices or from buying a whole new kit when the final 802.11ac specs are released.

Tom’s Take

The only two sure things in information technology are death (of products) and upgrades.  Just like the plain jane 802.11 spec and the hopefully-departed 802.11b spec, everything eventually gets old and needs to be replaced by something newer and better.  When you think about the amazement of being able to use a computer without being connected to the network just a few years ago at a staggering 11 Mbits to the ability on the near horizon to pump out more than 1 Gbit of traffic over the airwaves it is almost mind boggling.  However, with any new standard coming out, you need to be careful that you don’t jump on it at the wrong time.  Everyone wants to be the first person on the block to get something new.  Whether it be the first generation iPhone or the newest Intel octo-core chips, there are always going to be those people that want to be on the upward slope of the early adopter curve.  On the other hand, there are people like me that want to take a little extra time to be sure that what is coming out is going to work.  I’m one of those people that tends to wait a few days before upgrading to a new software release before installing it to make sure the bugs are worked out.  I tend to wait to upgrade to a new version of Windows until the first service pack is on the horizon.  When it comes to 802.11ac, I’m going to wait out this first round of products.  I don’t have anything that can take advantage of all that extra speed and I likely won’t have anything in the near future.  I don’t want to go out and spend money today that I’m likely going to have to go back and spend again later. Add in the fact that I really prefer my devices to be based on some sort of standard protocol that other things can interoperate with and you can see that 802.11ac 0.1 is going to be a “pass” in my book.  I know that there are great things on the horizon and I can see them getting closer all the time.  It just takes a little patience to get there.  And if I can learn to have a little patience then so can everyone else.

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12 thoughts on “The Rush To 802.11ac

  1. Tom,
    Good article. A few comments:

    An iPad only supports 20MHz 1×1:1 MIMO, and no SGI, so it’s max raw data rate is 65 Mbps (not 150 Mbps).

    High bandwidth with 80 or 160 MHz channels and up to 8 spatial streams is sexy. But many devices won’t ever be able to take advantage of that (e.g. phones and tablets). Wi-Fi is all about compatibility. In homes, it may be feasible to crank it up to 160 MHz for a few laptops on a single AP. But in enterprise environments, this is unrealistic. Density demands, channel planning, and the diverse set of clients make 20 MHz much more realistic.

    The story gets even worse than you describe. Assuming that we can or are willing to use DFS channels, there are 24 channels at 20 MHz, 9 channels at 40 MHz, 5 channels at 80 MHz, and 1 channel at 160 MHz (possibly 2 if using discontiguous frequencies). It gets way worse if we take DFS channels out of play for network stability precautions with 9 channels at 20 MHz, 4 channels at 40 MHz, 2 channels at 80 MHz, and definitely only 1 channel at 160 MHz.

    See this graphic (but note that the TDWR Weather Radar highlight is wrong, it only affects ch 120-128 in the U.S., not ch 132). Those 3 channels are NEVER available in the U.S., even when DFS support is enabled and certified by the FCC.

    The primary benefit, in my opinion, of 802.11ac will be the forced adoption of 5GHz by mobile devices. This will increase overall network capacity. The higher raw speeds of 802.11ac, even at 20MHz 1×1:1, will also translate into better battery life for mobile devices. So, I expect mobile adoption to be very quick.

    Also, it’s worth noting that enterprise class 11ac APs, although recently announced, still won’t be available until 1H2013. So we have some time before they’re even out on the market.

    Consumer devices will be available before then, but who uses that stuff anyways :P

    Cheers,
    Andrew

  2. Tom Good article and I agree with you on the timing of upgrading as your equipment you are using will also need upgrading if possible or replacement which can be quite costly. Depending on the age of your laptops or devices they may make an add on which would be hardware and software updates. This will probably half work causing frustration. It will be interesting to see how this unfolds in the future.

    Big John

  3. A good article, pointing out the flaws in the rush to 802.11ac, but you’ve missed the obvious one for me – what about back-haul from the AP? If you’re going to have any serious number of connections at 1Gbps over wireless, how fat does the connection back to your fixed infrastructure have to be? My guess is that for enterprise APs, you’ll be looking at 10Gbps uplinks as a minimum, with 40Gbps probably more realistic for proper back-haul, and 10G still ain’t cheap.

    • Funny you should mention that, Neil. I had a conversation with someone yesterday about the exact same problem. They were told that the 3600 add-on module has a 10 Gig interface for backhaul. I’m not sure how prevalent 10 Gig UTP cabling is right now, but I haven’t done any of it. When I’m at Cisco Live, I plan on hitting the wireless BU engineers about this module and finding out all about the backhaul oversubscription issues.

  4. Not being a wireless guy, this may be a stupid question, but would it make more sense to use the ultrawideband configs in concert with a high-gain antenna as a wireless backbone, rather than a client-facing technology? You could sidestep the issue of overrunning other frequencies if you had enough gain, couldn’t you?

  5. I am looking into wireless routers, and I am looking at a few 11ac routers that were just released.

    I started reading some reviews and they mentioned that these products are not WiFi certified 802.11ac products, since the certification won’t start until early next year. From what I could tell, they are definitely not WiFi Certified.

    I read that this could cause problems with devices that are released after the 11ac certification, so I am thinking of waiting, or getting a 11n router.

    Can anyone tell more about this issue?

    Should I only buy a 802.11ac router that has WiFi Certification?

  6. I am looking at 802.11ac routers, and I read this from Qualcomm:

    http://qca.qualcomm.com/thewire/qualcomm-atheros-bringing-forth-a-new-paradigm-for-11ac/

    What caught my eye is that they were talking about the 802.11n launch, and the upcoming 802.11ac products, “As a result, this rush to market diminished interoperability and performance in the first products to hit the market.”

    So, if there was a problem with people launching 802.11n early, and the 11ac certification will not be ready till next year, why are these several router makers jumping the gun and releasing 802.11ac routes now?

    Do these few manufactures think we are dumb enough to buy their non certified 802.11ac routers? Oh wait, the answer is ‘yes’!! That is why you can buy them now.

    If this was a problem with 11n, why won’t it be a problem with 11ac?

    Do you think it is better to wait till early next year to get a WiFi Certified router?

  7. Pingback: 802.11ac Wireless Routers To Replace 802.11n Ones, Boasting To Have 3 Times The Traditional Wireless Speed! | EssayBoard

  8. People get excited about the speed of n, ac… that is not the point. The point is: reliability and security. Bandwidth is good for marketing purposes. 802.11n on a basic Linksys router will give you 6MBps, more than you need for watching HD TV or downloading a file from a server.

    • You are ignoring another benefit of this technology ( and “N”) as well. When the underlying communications media supports higher rates ..the amount of time that a client has to transit is shrunk … allowing more users to transmit data … leading to possible greater AP/user density.

  9. Pingback: Death to 2.4GHz! | The Networking Nerd

  10. Pingback: 802.11ac Wi-Fi Hotness from Wireless Field Day 3 – @SFoskett – Stephen Foskett, Pack Rat

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