The 2013 MacBook Air Review (13-inch)
by Anand Lal Shimpi on June 24, 2013 12:01 AM EST802.11ac: 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:
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...
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sunman42 - Tuesday, June 25, 2013 - link
"Until OS X Mavericks arrives, you'll have to make sure to pay attention to things like background web browser tabs running Flash from killing your battery life." Or you could just do without Flash, or use Click to Flash, and avoid many very nasty bugs, constant security patches, and battery vampirism. Just, as they say, sayin'.jcbottorff - Tuesday, June 25, 2013 - link
The use of a 64K TCP window may be a feature not a bug. I say this because there often is a need to minimize latency of small packets, like used for Voip or other streaming media. With a TCP window size of 64K, on a 6 Mbps DSL connection, a packet queue of 64Kb takes about 85 milliseconds to drain. This means if you did a 64K TCP send (which optimally is one request to the NIC, with the NIC doing TCP segmentation), followed by a Voip UDP packet, it could be 85 milliseconds before the Voip packet goes out the DSL modem. If the TCP window were 256K, the latency would climb to 85*4=340 milliseconds, an unacceptable delay for Voip. It is possible to use varying TCP window sizes based on the current mix of network activity. Like for example, if you have a Voip call active and you have a TCP connection to a server on the Internet, over DSL modem, you may want to limit the TCP window size. If you only have a file sharing connection to a server on the local subnet, you can use a large window size. It's a lot more complex than just changing one number, unless you don't care about things like streaming media working correctly. OS designers often have to compromise, such that nobody is totally happy, but nobody is really upset either. I think the real question is how well the OS dynamically adjusts things under varying conditions to always give the most optimal user experience possible.SimonO101 - Tuesday, June 25, 2013 - link
Can we expect even greater battery life once OS X Mavericks comes online?darwinosx - Tuesday, July 9, 2013 - link
Yes. But if I said I knew this for sure I might be violating an NDA.trip1ex - Tuesday, June 25, 2013 - link
Also they should let you sync your MBA to a Mac/PC like an iOS device to help mitigate the 128gb storage in the base model. Or even let you sync to an external drive. I would love an elegant way to offload media particularly.darwinosx - Tuesday, July 9, 2013 - link
There are MANY ways to do this.niico - Tuesday, June 25, 2013 - link
I run Windows 8 in a Parallels VM on Mac OS 10.8 - this is my usual setup. If you're looking for a more strenuous battery test I suggest a VM. This often keeps the CPU at 30-50% even when both OS's are idle.It is an increasingly common use case - and many users would be interested to see the battery performance, specially on Haswell.
ctwise - Monday, July 1, 2013 - link
I run Windows 7 in VMWare Fusion on OS/X 10.8 as a SQL Server provider for development. I'm not sure if it's a difference between use cases for VMs or a Parallels vs. VMWare, but I rarely see even a single percentage of usage by my Windows VM.Oscarcharliezulu - Wednesday, June 26, 2013 - link
Good review, usual d$&khead comments from apple haters. I love hardware, all brands and watching it improve, it never gets old. Have recently switched to OSX on a 27" iMac at home for the fun of it and have to say now I'm familiar with it I prefer it to windows. Might switch my work laptop to a MBA, use it rather than my iPad+keyboard that I generally also carry around.akdj - Thursday, June 27, 2013 - link
Lol...exactly how it started for me...some 8 years ago now. Twenty years on PC (first computer was actually an Apple IIe)--& my wife was graduating with her masters degree. She'd been talking about a friend's MacBook for a few months...for her grad gift, I got her one of the old, plastic white MacBooks...my 8 year old son is still using that computer...in stock form daily!That first month...it was hard for me to give it up to her. I loved it. Loved OSx. Within six weeks I'd bought my own 15" MBP. Haven't bought a Windows machine since. For a couple years, I used bootcamp as there were a couple of programs that were only on Windows that I needed. They've since been ported to OSx and I've no need any longer for anything other than OSx
Kinda bums me out I waited as Long as I did. It's amazing having a house full of computers that NEVER need support!