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.'"

Comments

wasteful on spectrum

[ZorinLynx]

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.

Re:wasteful on spectrum

[phizi0n]

5GHz doesn't penetrate well so you won't get much interference from neighbors except maybe in very small apartments, the real problem is other devices within your home that use 5GHz such as cordless phones.

Re:wasteful on spectrum

[SJHillman]

My apartment is in a cellular dead spot. My landline only has two ports... one in the kitchen and one in the master bedroom. It would really suck if I couldn't use the phone in the living, garage, basement or office without having a long-ass cord getting tangled on everything. So maybe cordless phones do have a purpose after all.

Re:wasteful on spectrum

[MightyYar]

And "landline" (or internet) phones are still waaaaay cheaper than cellular. Free, even.

Re:wasteful on spectrum

[adri]

The 802.11ac spec lets you do that.

You can use 40, 80, 80+80 or 160. Right now I think everything is shipping 80 only, but I could be wrong. But the chip is allowed to transmit on whichever channel is free. If the primary 20MHz channel is free, it transmits on that. If the Primary and Extension 20Mhz channel are both free (ie, the "HT40" channel in 802.11n parlance) it transmits on that. If all 80MHz is free, it transmits on that.

It's pretty nifty stuff.

Re:wasteful on spectrum

[exodus2]

I got a notice today from Sprint that they are canceling my Air rave which gives me an indoor cell tower

Simple solution

[ArcadeMan]

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.

Re:Simple solution

[Anonymous Coward]

Gigabit ethernet doesn't have a practical throughput of 1 Gb either.

Yes it does, I've never seen any problems with pushing 1gig either at home or at work.
Perhaps you're having problems with the backplane capacity of your router, or issues with your NIC or computer. But it's not the connection between the ports at fault, unless you've got the cable wound around a source of powerful RF emissions.

Re:Simple solution

[Bengie]

I get 960Mb one direction and 1.6Gb bi-directional with my consumer-grade network at home. I also get 110MB/s+ over SMB with sub 1% cpu usage. 1Gb is not hard.

Teach the Little Children

[TechyImmigrant]

The school curriculum should be amended so that every school child graduates school knowing that physcial layer rate > MAC layer throughput.

Irrelevant knit picking

[Anonymous Coward]

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.

These days phones are going to 1900MHz

[Sycraft-fu]

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 don't even..

[Rytr23]

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.

The problem is that you see different ones spec'd

[Sycraft-fu]

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.