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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  • malcolmcraft - Thursday, October 9, 2014 - link

    MacBook Air is absolutely fantastic! It is also interesting that it's the highest rated laptop among consumers (see http://www.consumertop.com/best-laptop-guide/)... I would not trade mine for anything. Reply
  • darwinosx - Monday, July 8, 2013 - link

    If you read the review you are commenting on you would know its not a terrible display. Reply
  • Subyman - Monday, June 24, 2013 - link

    Did you even read Anand's article? He explains why. Reply
  • sigmatau - Monday, June 24, 2013 - link

    Yes, apparently it is good to have a long battery life so you can be able to stare at a horrible display for as long as possible. I'd rather have that display in a $400 laptop. Actually, not even at that price point. Reply
  • designerfx - Monday, June 24, 2013 - link

    exactly. I laugh when people look at GPU performance when they forget that it's at 1366x768. You can get better (and AMD does) in IGP. Reply
  • josef195 - Tuesday, August 20, 2013 - link

    I laugh when people complain about good GPU performance at 1366x768 when it's actually 1440x900 Reply
  • jmmx - Monday, June 24, 2013 - link

    hardly a horrible display! Have you ever seen one? Not only are they very fine - though admittedly not as high resolution as others, but according to one monitor expert - only Apple displays have a consistency and an out-of-the-box color setting that is very close to professionally calibrated. Reply
  • sigmatau - Tuesday, June 25, 2013 - link

    OK, I will say that Apple offers some of the best displays, but the best 1366x768 display is still terrible even on a 13" display. Not sure why Apple didn't go with a 1080p display with haswell since any increase battery waste from the display should be more than mitigated by the increased efficiency of the CPU/GPU. It's not like anyone does any serious gaming on these laptops so a higher resolution display will not be affected there either. Reply
  • KitsuneKnight - Tuesday, June 25, 2013 - link

    The display is 1440x900 on the 13", not 1366x768 (that's the 11"). It's also one of the damn nicest displays I've ever had the pleasure of using (even the viewing angles doesn't bother me, maybe because it's the only laptop I've used with a decent henge).

    Personally, I'd opt for a 12 hour battery life over a retina-class display. Ideally, I'd have both, but it'll be quite a while before that becomes a possibility in any machine like the Air.
    Reply
  • ThreeDee912 - Monday, June 24, 2013 - link

    I'm not sure if it's the same panel, but the 2010 and 2011 reviews tested the LCD, and the panels had some of the best contrast ratios and black/white levels out of any TN panels at the time. It's no IPS, but they're still pretty darn good compared to everything else. While it would be nice if Apple made the panels IPS, I think the current panel resolution is fine.

    http://www.anandtech.com/show/3991/apples-2010-mac...
    http://www.anandtech.com/show/4528/the-2011-macboo...

    Also, I'm not sure why some people want to run an unscaled UI on super high-res panels, especially on laptops of this size. Yes, some smartphones have higher resolutions screens, but they scale things up so it's easier to read. Just stuffing in a high-res panel for the heck of it isn't the way to do things.
    Reply

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