802.11ac: 533Mbps Over WiFi

Haswell isn’t all that’s new with the 2013 MacBook Air, Apple also integrated support for 802.11ac. I wrote a primer on 802.11ac last year, but I’ll provide a quick recap here. 802.11ac is a 5GHz-only WiFi standard, with support for wider channels (80/160MHz vs. 40MHz in 802.11n) and better spatial efficiency within those channels (256QAM vs. 64QAM in 802.11n). Today, that means a doubling of channel bandwidth and a 4x increase in data encoded on a carrier, which are responsible for the significant increase in bandwidth. Usable bandwidth should also see improvements on 802.11ac as high-end access points are all expected to ship with beam forming enabled.

The first 802.11ac implementations we saw were on the smartphone side with HTC’s One and Samsung’s Galaxy S 4. Both of these devices were single antenna/single spatial stream implementations with 80MHz channels and 256QAM, resulting in a max PHY rate of 433Mbps. In his review of the HTC One, Brian documented peak performance using iPerf and a TCP transfer. In a smartphone, such high bandwidth from WiFi is really useful for improving battery life (race to sleep). In a notebook, you get the same potential improvement in battery life but there’s one more: a wireless alternative to Gigabit Ethernet.

In a 3-stream configuration given what’s available today, we’re talking about a 1.33Gbps PHY rate. Assuming better link efficiency on a notebook compared to what we’ve seen in smartphones thus far, we could be talking about a real alternative to Gigabit Ethernet - at least close to an AP. While wired GbE is always going to give you a more consistent experience, the vast majority of homes aren’t pre-wired with Gigabit Ethernet. In living situations where you can’t just run a bunch of Cat6 everywhere, but still want high speed networking, 802.11ac could be a real alternative.

The 2013 MacBook Air adds support for 802.11ac via Broadcom’s BCM4360. The controller is capable of supporting up to 3 spatial streams, but in its implementation in the MacBook Air we see a maximum of 2 used. I fully expect the 2013 rMBPs to use a third antenna to leverage all 3 streams. BCM4360 supports 80MHz channels, 256QAM and short guard intervals. The result is a max PHY rate of 867Mbps.

ASUS sent me its RT-AC66U based on the same BCM4360 silicon (coincidentally the same controller that’s in the new Airport Extreme), which I promptly used for testing the new MacBook Air. The ASUS router and MacBook Air combination worked perfectly. In the same room as the AP, I had no issues seeing the maximum 867Mbps PHY rate (above).

Within about 5 - 8 feet of the AP, I saw an average of 533Mbps using iPerf. That’s real data sent over TCP:

WiFi Performance

A 3-stream solution could definitely rival wired GbE, at least for short distances.

I then went about characterizing 802.11ac performance vs. distance to get an idea for how performance fell off as I moved away from the AP. My desk and test area is in the corner of my office, which is where I put the ASUS 802.11ac router. Performance around my desk was always up around 533Mbps.

Move around 18 feet away but remain in the same room and measured performance dropped to 450Mbps. One set of walls and another 10 - 15 feet dropped performance to between 250Mbps - 340Mbps. Another set of walls without moving much further and I was looking at 200Mbps. When I went one more set of rooms away, or dropped down to a lower level, I saw pretty consistent falloff in performance - dropping down to 145Mbps. Note that my setup is pretty much the worst case scenario for longer distances. The AP isn’t centrally located at all. If I were setting up an 802.11ac network for max coverage, I’d probably see 300 - 400Mbps in most immediately adjacent rooms.

So 802.11ac on the new MacBook Air is pretty awesome, there's just one issue...

PCIe SSD Performance Real World 802.11ac Performance Under OS X
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  • airmantharp - Monday, June 24, 2013 - link

    I'd prove that LG makes a better screen than Samsung- but it's already been proven. Reply
  • Malih - Monday, June 24, 2013 - link

    The laptop focuses on being lightweight, thus thin, thus limited battery capacity,
    and limited battery capacity doesn't play well with high res display,

    They could choose to increase resolution with haswell and keep the same battery life, but seeing as they chose battery shows where they are focusing with Air.

    That means if you want high res display, then get Retina MBP instead.
    Reply
  • airmantharp - Monday, June 24, 2013 - link

    Your iPhone would like to have a talk with you. Reply
  • seapeople - Tuesday, June 25, 2013 - link

    And tell you about what? It's similar display resolution? Reply
  • abazigal - Monday, June 24, 2013 - link

    You can always pay more to have the air ship with more ram. Reply
  • darwinosx - Monday, June 24, 2013 - link

    Or faster procs or more sad. Reply
  • Strulf - Monday, June 24, 2013 - link

    Yep, 8 GB are possible. In the generation before already. Reply
  • MatthiasP - Monday, June 24, 2013 - link

    The resolution is quite OK if you consider the battery life and weight you get. Also both displays still offer a higher DPI than what you can get on the best desktop displays. What is really disappointing is the lack of an IPS panel. There is no excuse for that on a mobile device. Reply
  • Exelius - Monday, June 24, 2013 - link

    8gb is available as a BTO option. I have a 11" 2012 MBP with an i7-3667U and 8gb RAM and it's more than enough for running a VM and even for doing some database work. Honestly, the machine is still mostly bound by the speed of the SSD for every workload I use it for. I love the size of the 11".

    The only complaint I have is that the GPU is a bit anemic, which the Haswell update seems to have addressed. I find that the 2012 Air has some noticeable jerkiness driving a 1080p display in OS X, which I suspect is a large part of the reason that the Airs haven't had a larger display. Hopefully, with that limitation removed, Apple can start to put some higher resolution displays in these machines over the next year or two.
    Reply
  • darwinosx - Monday, June 24, 2013 - link

    Read the article you are commenting on. 1400 X 900.
    You can get this laptop with 8 GB of you want.
    1600 X 900 is to high for a 13 inch for most people. Tiny icons and text. Thats why Apple goes all the way to retina display on their higher end laptops instead of some half measure that won't satisfy anyone.
    Dell makes junk and fails to support it. People looking at Mac's aren't going to consider a Dell with Microsoft's latest mediocrity of an OS.
    This is of course a premium product in build quality, quality control, service and support, custom components like the ssd and battery. Not some plastic Dell with the cheapest possible parts they could get out of China this week.
    Despite that retail starts at $1099 and they can be found cheaper online. Show me a PC laptop even close to this price, build, customizations and certainly service and support. How about a PC laptop with a working trackpad...
    If you want a higher res screen and 8 GB out of the box thats the 13" retina. A new version of it is coming shortly and will be thinner and lighter than the current model.
    Reply

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