Do wireless n devices slow down a wireless ac network?

[KeitaRR]

I heard that if you have a mix g/n network and then a device joins which runs at wireless g, it slows the network down to g speed. My first question is that true? If yes then does this also apply to n devices joining an 802.11ac network?

[minibois]

802.11n and ac work on different wave lenghts (2.4 and 5GHz respectively) and pretty much all access points have their N and AC speeds listed separately, so I assume it won't (at least I have never heard of that). G and N both work on 2.4GHz so yeah I can see where that first thing you said comes from.

[Gaub]

No it won't! 2.4 GHz and 5 GHz are handled by different radios. Now some access points even have multiple radios per frequency to make sure that doesn't happen.

[KeitaRR]

wireless n is compatible on both 2.4 and 5ghz. maybe i should be more specific in my original question. assume both wireless n and wireless ac devices are connected to the same 5ghz network.

[Donut417]

To my understanding your wireless network works as fast as the slowest device. So technically yes, a slower device can slow it down. I tend to run all slower devices on 2.4 Ghz and leave faster devices on 5Ghz. 

[beavo451]

6 hours ago, KeitaRR said:

I heard that if you have a mix g/n network and then a device joins which runs at wireless g, it slows the network down to g speed. My first question is that true? If yes then does this also apply to n devices joining an 802.11ac network?

I have a mix of different 2.4 and 5.0 N and AC devices on my WiFi. Each device shows a different connection speed and there are no performance issues.

[Guest]

Yes - if you're using wireless N devices and using wireless AC devices on the same 5Ghz radio, the radio will finish one communication before moving onto the next device. Hence if this first communication is to a wireless N device while the 2nd is to a wireless AC device, the N device will be slower to do the same communication versus the AC device.

 

This is changing moving forward with the support of AC Wave 2 - this allows for what is called MU-MIMO - meaning multi user at one time. This will allow for the AP to talk to multiple devices at the same time.

[LAwLz]

Yes, a wireless N device on the same network as a wireless AC device will slow the AC device down. It will NOT however, slow down all AC devices to N speeds.

The same is true for a G device on an N network.

 

The reason is fairly complicated and I might post an explanation for it later (unless someone beats me to it), but it has to do with how WiFi avoids collisions.

AC devices will only drop to N-levels while the N device is fully saturating the N standard (which shouldn't happen that often). If the N device is just sending a normal amount of data then it will have a slight impact on the AC devices, but it should not be that big. The same is true for G devices on N networks.

[dalekphalm]

23 hours ago, Minibois said:

802.11n and ac work on different wave lenghts (2.4 and 5GHz respectively) and pretty much all access points have their N and AC speeds listed separately, so I assume it won't (at least I have never heard of that). G and N both work on 2.4GHz so yeah I can see where that first thing you said comes from.

That's not inherently correct.

 

Wireless N provides specs for both 2.4GHz and 5GHz frequencies. If a Wireless N 5GHz device connects to a Wireless AC 5GHz network (One that allows mixed mode), it may indeed affect performance of the network. How much of a performance loss you see depends on many different factors, so there's no set rule about it.

[KeitaRR]

ok, if i'm understanding this correctly it slows down the ac device in the sense that ac and n devices have to take turns communicating to the router, and sometimes the ac device has to wait until the n device finished its communication (which is in wireless n speed). but when it's the ac device's turn it'll run in ac speed. if that's the case then the real world speed of the ac device would be running somewhere between wireless n speed and wireless ac speed (assuming there's a wireless n device connected in the same network)? Please correct me if i'm wrong

 

and the follow up question would be how big or how long is one "communication" between the device and the router? im thinking if the size of one "communication" is fairly small then it won't impact the speed as much

[dalekphalm]

15 minutes ago, KeitaRR said:

ok, if i'm understanding this correctly it slows down the ac device in the sense that ac and n devices have to take turns communicating to the router, and sometimes the ac device has to wait until the n device finished its communication (which is in wireless n speed). but when it's the ac device's turn it'll run in ac speed. if that's the case then the real world speed of the ac device would be running somewhere between wireless n speed and wireless ac speed (assuming there's a wireless n device connected in the same network)? Please correct me if i'm wrong

 

and the follow up question would be how big or how long is one "communication" between the device and the router? im thinking if the size of one "communication" is fairly small then it won't impact the speed as much

It's more complicated then that.

 

But if you're concerned, you should just test it yourself:

Do one test with an AC device and no other devices connected.

Do one test with an AC device and an N device (over 5Ghz) connected.

Do one test with an N device and no other devices connected.

Compare how the AC device performance differs between the two.

 

I would suggest simulating network traffic on the N device by doing something like a looped ping command to Google ("ping google.com -t"), or script a web browser to refresh the page every 5 seconds.

 

Then on the AC device, you can check Internet Speeds with a Speedtest, or you can perform a File Transfer/IO test to a wired computer on the network - run the test both with and without the N device connected.

[LAwLz]

On 2/24/2017 at 0:06 AM, KeitaRR said:

ok, if i'm understanding this correctly it slows down the ac device in the sense that ac and n devices have to take turns communicating to the router, and sometimes the ac device has to wait until the n device finished its communication (which is in wireless n speed). but when it's the ac device's turn it'll run in ac speed. if that's the case then the real world speed of the ac device would be running somewhere between wireless n speed and wireless ac speed (assuming there's a wireless n device connected in the same network)? Please correct me if i'm wrong

 

and the follow up question would be how big or how long is one "communication" between the device and the router? im thinking if the size of one "communication" is fairly small then it won't impact the speed as much

Yes that is the gist of it. There are a lot of other things to take into consideration too. For example, a wireless N device can be faster than a wireless AC device. This might happen when a wireless N device is really close to the access point, but the AC device is really far away and has to change to a lower data rate to get a clean signal. In those situations, it will be the AC device that is slowing down the N device.

 

In order to create some kind of fairness, most access points will try and let slow and fast devices send an equal number of frames over the same period of time. So if both devices want to send 20 frames, they will be interleaved so that device1 sends its last frame just before or just after device2 sent its last frame. In those situations, wireless N really will bring down an AC device to the same speed. But it will only be that way for the duration where both devices want to send data.

 

Some access points have a feature called "airtime fairness", but since there isn't any real standard for how it is implemented it is usually only implemented for sending data from the AP to devices, and not for when devices want to send data to the AP.

What airtime fairness does is that instead of saying "each device should send the same amount of frames in a given time", it says "each device will get equally long time slots". So if your AC device can send 4 frames in the same period of time the N device can send 1, your AC device will receive data 4 times as fast as the N device even though both want to receive data at the same time.

 

There are a ton of different scenarios where N/AC mixed networks will behave differently and it will impact performance. That's why it is so hard to say "having an N device will reduce the speed of your AC network by Y%".

 

But in simple terms you can say that while an N device is transmitting data on your network, your AC device will perform somewhere between N and AC speed.

Where in-between N and AC does it land? Nobody knows. It depends on your equipment, environment, how much data each device want to send/receive, how long that will take and a lot of other factors. I would not be too worried about it though.