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802.11ac: Better Coverage, But Won't Hit Advertised Speeds
New submitter jcenters writes "Apple's new AirPort routers feature the new 802.11ac protocol, promising Wi-Fi speeds in excess of 1 Gbps, but Glenn Fleishman of TidBITS explains why we are unlikely to see such speeds any time soon. Quoting: 'When Apple says that its implementation of 802.11ac can achieve up to 1.3 Gbps — and other manufacturers with beefier radio systems already say up to 1.7 Gbps — the reality is that a lot of conditions have to be met to achieve that raw data rate. And, as you well know from decades of network-technology advertising, dear reader, a “raw” data rate (often incorrectly called “theoretical”) is the maximum number of bits that can pass over a network. That includes all the network overhead as well as actual data carried in packets and frames. The net throughput is often 30 to 60 percent lower.'"
Another issue is these routers are probably going to barf all over the spectrum, so as soon as you get a few of them operating in one area, performance will go to hell for everybody.
This has already happened on 2.4GHz in some areas, and is starting to happen on 5GHz too. Greater speeds require more spectrum.
The term "theoretical" is not just standing in for "raw" data rate. In complex data communication, it also covers whether all frequency sub-bands, spacial directions, etc. are also available.
Use ethernet. Cables don't have these kinds of problems. I just wish somebody made lighter ethernet cables though, my iPhone cable backpack is killing me.
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I occasionally have someone ask me why their internet is so slow when there router says up to 300mbps or a gigabit all I can do is reply "yes but the internet is coming through your dsl modem at a much lower 6mbps".
I'm sorry, but since the advent of marketing (the new wheel, now travel up to 1000x faster than walking!) the speeds we actually get *very* rarely ever approach the advertised "up to" speeds. Even the summation says this: "And, as you well know from decades of network-technology advertising, dear reader, a “raw” data rate (often incorrectly called “theoretical”) is the maximum number of bits that can pass over a network. That includes all the network overhead as well as actual data carried in packets and frames. The net throughput is often 30 to 60 percent lower.'" So...... why bother mentioning it, let alone headlining it? Is it just to attract us grumpy old trolls? The advertised wireless network speeds are very much like gas mileage, wildly inaccurate in the real world.
The school curriculum should be amended so that every school child graduates school knowing that physcial layer rate > MAC layer throughput.
I should use this sig to advertise my book ISBN-13 : 978-1501515132.
The advertised speeds are used by normal people to estimate performance compared to other products. If this was the only product that advertised "raw" data then a distinction would be necessary. Using the same speed measurement conventions as the rest of the industry allows for an accurate performance comparison against other available hardware.
No one is going to exclude the new AirPort from their short list because it can't transmit 1 GB within a certain amount of time. The choice will be based on if it transmits the data faster than other routers.
DECT 6.0 phones work on the 1900MHz band and more or less act like short-range cell phones with their protocols and compression. They work quite well, have decent penetration through walls, and are outside of the range used for computers.
I cannot fathom that any reader of /. would be unaware of theoretical vs real world performance, particularly in the networking space. This post is almost insulting.
So many injustices..so little time..
I have 802.11ac gear, and I'm getting about 8MB/sec whether on the 2.4GHz or 5GHz band. It's nothing anywhere near the pie-in-the-sky claims of 300mbps or 800mbps, but it is significantly faster than the 2.3MB/sec I was getting on 802.11g.
Wire based Ethernet is spec'd at MAC layer throughput. It is talking about the data rate of Ethernet frames, the 8b/10b encoding overhead is already accounted for and all that. So you discover that, particularly with Jumbo Frames, you get real near that speed in actual throughput.
Wireless Ethernet, not so much. You find that effective throughput, even under basically ideal conditions, are way less than the listed speed.
So it leads to confusion for people. Basically wireless is over advertising the speed.
Well, not all AC devices will do 5GHz, like not all N devices do 5GHz. It's the difference between 802.11abgn and 802.11bgn devices (the 'a', representing 802.11a, only works on 5GHz, and there isn't a 5GHz N device that doesn't support A as well)
The reason for the letters is because they're the substandards - 802.11 is WLAN (1/2Mbps on 2.4GHz or IR). a is 54Mbps over 5GHz, b is 11Mbps over 2.4GHz, ... g is 54Mbps on 2.4GHz, etc. etc. etc.
Each committee gets a new latter, and they already used a-z, and aa, ab was also used for something. This new spec is thus 802.11ac.
Since the naming scheme generally follows standards order, it would be
802.11abgnac, and 802.11bgnac (2.4GHz only).
Or, add slashes - 802.11a/b/g/n/ac and 802.11b/g/n/ac
Hello,
The problem with the current crop of 802.11ac adapters is that most of them have USB 2.0 interfaces (Edimax and Zyxel each offer a USB 3.0 adapter, and Asus has a PCIe card). With 480Mbit/s of bandwidth (and that's theoretical, since it does not include serialization, 8b/10b conversions, other overhead from peripheral bus communications, etc.) no one is is going to be getting anything near a Gbit/s of bandwidth over the bus even if they do have a strong signal. They may get better data rates due to technological improvements over previous generations of Wi-Fi (fatter channels, more MIMO streams, beamforming, etc.)
That will change as more adapters enter the market (probably in the form of MiniPCIe cards inside laptops), but consumers are not going to be much better off, bandwidth-wise, then going with 802.11n gear at home until the market for 802.11ac wireless adapters matures.
Regards,
Aryeh Goretsky
Dexter is a good dog.
So to clear up the confusion 802.11n rate specification should be "180mbps unless its higher, up to 300 or less".
I think you underestimate just how much I just dont care.
I'm not an Apple fanboi but do own a 2011 Macbook Air (2gb). The only real reason I still have a Desktop PC at home for web and video is because 802.11n cannot stream 1080p (at least not consistently in VLC over SMB). I do not want to buy an overpriced Apple Display for Gigabit Ethernet connectivity. So I'm stuck. I have an Ultrabook (docked to a 24" monitor) I'd like to solely use that's fast enough but it doesn't support the bandwidth I need.
Once the new Macbook Pro's are out I'll finally be able to upgrade to one of them and pair it with a new Airport Extreme (if 802.11ac can do 1080p in my apartment).
Sadly, I think at that point I will probably be masked as a fanboi even though I was really only looking for a powerful Ultrabook platform. None of which was previously possible unless I missed the marketing brochure from a boutique hardware provider (Sony) where they also started shipping 802.11ac.