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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  • vol7ron - Wednesday, June 26, 2013 - link

    I'm sorry, have you ever owned an MBA? You don't want to be doing any heavy development on this device, it will get hot fast.

    This device should be the Traveler's Laptop: good enough to carry with you, more productive than an iPad, full keyboard, longer battery life than a regular laptop, lighter weight, and a few ports to maybe support what you need. It would be perfect for a plane or train, maybe to lounge by the pool, but should not be considered as a desktop or MBP replacement.

    The shame of it is that it's so portable, that it leaves you wanting to do more with it. It almost has done it's job too well. In that regard, you are right, it is lacking the things that would put it over the edge, that would make it a replacement of the desktop/MBP, which again it's not. But be conscious that [I think] this has no fans, and from when I used it, got hot really fast -- horrible for any extreme development, or even long-term gaming.
    Reply
  • darwinosx - Monday, July 8, 2013 - link

    Hah! Lots of developers use Airs without issue. Reply
  • cscordo - Thursday, August 8, 2013 - link

    What a ridiculous comment from someone who clearly doesn't develop software.

    I'm still on a 13" MBA from two gens ago and run multiple IDE's and SQL Server 2010, and it doesn't skip a beat.

    What type of "heavy" software development do you perform that it can't handle? I'd be very interested to know.
    Reply
  • josef195 - Tuesday, August 20, 2013 - link

    So, you're saying the Macbook Air isn't for pro users? I must say, if only they had some Macbook for professional users; they could even call it a Macbook Pro. Reply
  • Calista - Thursday, June 27, 2013 - link

    I agree with your ideas of adding the option of 16 GB of RAM and 4G support. Virtualization is growing all the time, the memory usage can grow very quickly if starting to run a few VM in parallel. And not having the option of 4G in this day and age is just embarrassing. For a machine *built* to be used on the go, with every component (battery life, weight, size) adopted to this task not adding 3G/4G just doesn't make sense. Reply
  • Dave DeCo - Saturday, June 29, 2013 - link

    I have never given much thought to the 4G thing. But now that it's brought up I too wonder why the MBA doesn't offer it. My incredibly portable iPad has it. iPhone too of course. Why not the wafer thin MacBook Air? Oh Apple. Always dangling that carrot on the longest stick possible while telling us we don't need carrots. If that last line makes sense to anyone please tell me. Because I don't know what the Helsinki I just said. Reply
  • australianm8 - Saturday, July 6, 2013 - link

    A few considerations for everyone fussing about 4g support.
    1. Apple likes to keep a simple product line
    2. Look at a teardown, not much room in there for much more to add. (already pushing it's thermal limits)
    3. There are a plethora of cell carriers that offer 4g USB sticks
    Reply
  • darwinosx - Monday, July 8, 2013 - link

    That was a childish and ignorant display of petulance. Obviously a particularly immature teenager. Reply
  • jaycee1970 - Saturday, August 24, 2013 - link

    "Dump your apple stock now, it will bounce back"

    Wow, that's fantastic financial advice, genius. I'll definitely sell something that will go up in value. The rest of your post was just as intelligent. Thank you.
    Reply
  • othernet - Monday, November 4, 2013 - link

    Uhm... there are hybrid notebook/tablets out there. Did you buy one? I don't know of anyone that did.

    Apple sells Retina 4, 10, 13 and 15 inch products. Soon, an 8 inch product too. You must have missed the keynotes.

    Wireless charging? Wait, do you still need to plug the wireless charger somewhere to make it work? When it doesn't have to sign me up!
    Reply

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