Max 802.11ac speed per radio?

[stu17323]

Hi, I am getting quite confused with all the theoretical speed limits for AC. Some people say 400 some say 1.3Gbps and some say 7Gbps?

What is the maximum theoretical AC limit for one radio and one antenna?

Thanks, Dylan.

 

[dderbowka]

The more antennas the more faster the speed would be. (Likely anyway)
7Gbps wouldn't likely be possible - well I mean "Anything is possible" but not likely on 802.11AC just yet.

I haven't got experiance much with the 802.11ac area yet, but I would want to say you should get 433Mbps. I have a small (Just like a wireless mouse chip) size 802.11ac adapter and It tops at 433Mbps when I last used an AC network.

 

[boosted1g]

Wireless AC spec covers a wide range of speeds.

And the previous statement that "more antennas = faster speed" is an inaccurate generalization.
More antenna can mean more bonded frequencies (which means more speed) but could also mean that it is a tri-band router, or could just mean that some OEM decided that 9 antennas "looks cool"

7gbps is not possibly on any wireless AC radio, period.
The wireless AC speeds are made difficult by the router manufacturers.
So my router is an AC1900 meaning it has a combined speed of 1900 mbps. Now 600 is for the 2.4 ghz band and 1300 is the 5ghz band.
Anything that is beyond 2400 is a triple or quad band router, usually meaning 1 2.4 ghz band and multiple 5ghz bands.
So an AC3200 with 1 600mhz 2.4ghz band and 2 1300 mbps 5 ghz bands wont actually perform any faster then my AC1900 does, it just has 2 5ghz bands.

The is no wireless AC router with a single antenna so I cant directly answer your quesiton.
The fastest on the market I have seen is a 1024 QAM (which requires 4 antennas) and it gets a max of 2167 mbps. Now given the nature of 5ghz and this ultra high speed connection, even throwing 1 interior wall into the mix and speeds are going to drop drastically (hard wired ethernet is still faster and much more reliable).

 

[BFG-9000]

AC is theoretically 433Mbps per antenna @80MHz wide and "Wave 2 AC" is 866Mbps each @160MHz wide.

Note this speed requires 256-QAM modulation which means a signal of at least -52dB at 80MHz, and -48dB at 160MHz so you can see it's only good for a very short distance of around 10-15' before it drops to 64-QAM and throughput drops 33%. But they can still advertise the large number on the box as that's all that matters to them, even if it has no practical use.

 

[boosted1g]

FYI the 7gbps routers are a different spec called wireless AD.
It is a very high frequency good for very short range transfers with line of sight (think VR goggles to computer).
This would not even be able to penetrate 1 interior wall (and I am talking hallow sheetrock).

 

[stu17323]

Thanks so much for the replies!

So do WAP's that advertise a max 867Mbps at 5Ghz use wave 2 AC?

 

[boosted1g]

An 867mbps Wireless Access Point will use 2 antennas to get 867 on a total of 2 433mhz frequency channels.

Now FYI most everything outside of the newest top of the line devices will be using 867mbps wifi cards so the 867 is the max theoritcal for that device, doesnt matter if the router can do 1300 1700

 

[stu17323]

An 867mbps Wireless Access Point will use 2 antennas to get 867 on a total of 2 433mhz frequency channels.

Now FYI most everything outside of the newest top of the line devices will be using 867mbps wifi cards so the 867 is the max theoritcal for that device, doesnt matter if the router can do 1300 1700

When you mentioned 5Ghz bands before, is that the same as "433mhz frequency channels"? Also if you can get dual band 2.4/5 antenna's, why can't you use multiple bands/frequency channels on one antenna?

Thanks.

 

[BFG-9000]

Dual-band antennas do tend to be less optimized for either band. Not sure why that is as if you look closely at them they have both long (for 2.4GHz) and short (for 5GHz) antenna stubs and the mismatch in impedance is supposed to make the wrong length part invisible to the other frequency. You only see those antennae on those dual-band but not simultaneous routers and APs where you have to select either 2.4 or 5, but they are often found on the client side especially in laptops, tablets and phones.

So if space is available and you want to be able to use both frequencies at the same time, separate antennae are better.

 

[stu17323]

Ok, so I did some more googling and I think I understand that each band has it's own radio, antenna and it's own SSID. So do radios that use multiple channels for faster speeds always need seperate antenna's for each channel? Also what does the client need to use the multiple channels the radio is using?

 

[BFG-9000]

Yep, if you want the speed increase it will need an antenna for each channel you want to use. Note however that some 2-channel devices can have three antennas because the extra antenna is used for diversity or MIMO, which improves reception but not speed when the signal is strong.

In practice, even 3-channel clients are pretty rare and are mostly seen in wireless bridges. But the number of 4-channel routers and APs keeps increasing because again, it helps put a big impressive number on the box. Some of the most expensive routers today essentially have two separate 5GHz APs in the same casing, and while that would indeed support more devices simultaneously (but offer no more speed for any one device), I'd rather have two APs at distant ends of the house because of the 5GHz range issue.

 

[stu17323]

Yep, if you want the speed increase it will need an antenna for each channel you want to use. Note however that some 2-channel devices can have three antennas because the extra antenna is used for diversity or MIMO, which improves reception but not speed when the signal is strong.

In practice, even 3-channel clients are pretty rare and are mostly seen in wireless bridges. But the number of 4-channel routers and APs keeps increasing because again, it helps put a big impressive number on the box. Some of the most expensive routers today essentially have two separate 5GHz APs in the same casing, and while that would indeed support more devices simultaneously (but offer no more speed for any one device), I'd rather have two APs at distant ends of the house because of the 5GHz range issue.

Thank you so much, you've helped me a lot!

 

[stu17323]

So would a 1200mbps AP with two antenna's, use one as both 2.4ghz and 5ghz and one as another 5ghz on a different channel?

 

[BFG-9000]

AC1200 devices are 2-channel on 5GHz, and usually any external antennas are both for 5GHz. With 2.4GHz, range is far less of an issue so it tends to use internal antennas, sometimes even printed right on the circuit board.

 

[boosted1g]

So you have frequency radio, frequency channel and speed.
2.4 and 5ghz (5.8 to be specific) is a frequency radio, the radio can see the entire frequency band . The entire 2.4ghz band goes from 2.412 to 2.484 ghz (2.484 is channel 14, USA though has only used 11 channels since wireless G).
So channel 1 is 2.412ghz, and each additional channel is approximately 22mhz apart, thus channel 6 is 2.437 and 11 is 2.462.
Now the 22mhz channel width is not sufficient, so while in USA there is 11 channels, you really only get 3 because you really need roughly a 2.5 channel gap to not have interference, so channel 6 for example actually bleeds over on channel 4-8. This is why 2.4 band gets so saturated in concentrated environments like apartment buildings. 5ghz band solves a big portion of this problem because it has many more channels and as a result of the frequency being double, its ability to penetrate solid objects (and thus its range in your home) is less. Due to 5ghz band having less range, its downside is that a single router is not able to provide solid 5ghz coverage in a larger home.

Max speed is determined by two factors, first of all the wifi standard (G, N, AC, AD, etc). For N you could only get 150mbps per antenna but AC can do a max of 433. The second factor is the number of bonded frequency channels your router has (which will be determined by antennas). AC1200 will have 2 antennas, AC1900 has 3, etc.

As BFG said though, many router companies have started putting multiple 5ghz radios (not just bonded channels) into the same box so they can put a bigger number on the box. These wont actually give you more speed, just allow you to have more simultaneous devices. These ultra speed routers are pretty much fluff marketing because you would need a > 100mbps internet connection, 20+ 5ghz wifi devices, and be in a 1500 sqft or smaller home to actually make full use of a tri or quad radio router.

Also as BFG said, 2 AC1200 or AC1900 routers with the second one setup as an Access Point on the other side of the house will be far more usefull.

Just an extra FYI:
Most residential grade WiFi repeaters are single radio devices and thus use the same radio to communicate with both the router and the devices connected to the repeater. This means that it has to split its bandwidth in half, so if the repeater is getting a real speed of 100mbps then it has 50mbps to share across all devices connected to it.
This is why a router + access point with an ethernet connection between them is way way faster (and more reliable).