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Airtime Fairness Explained: Why You Should Cut Down on “Smart” Wi-Fi Devices

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I’ve recently gotten a lot of questions about issues with Wi-Fi connection involving Smart Home devices and then some on the Airtime Fairness (ATF) setting of a router. As it turns out, the two are closely related.

I’ll explain in layman’s terms this setting here and why I never think it’s a good idea to use (a lot of) “Smart” Wi-Fi Internet of Things (IoT) devices in your main network.

Note: We’re talking about standard Wi-Fi devices here, not those IoTs with any other type of wireless connection.

Let’s start with Airtime Fairness.

The Airtime Fairness setting of a TP-Link router
The Airtime Fairness setting of a TP-Link router

Airtime Fairness and Smart Home devices: It’s not that fair

Airtime Fairness is a familiar setting dating back to Wi-Fi 4 (probably even earlier).

It ensures that each client in the network has equal access to air time with the broadcaster (Wi-Fi router, access point), no matter their operating system, Wi-Fi standard, operating mode, or signal strength.

“Equal” is the key here. We’ll find out how “fair” it is.

It’s very complicated to convey “air time” since Wi-Fi is a dynamic environment. That’s not to mention other related features, including MI-MO, MU-MIMO, and ODFMA.

So, everything you’re about to read has been simplified to show an idea of how things work.

Airtime Fairness turned off: First come, first served

By default, when Airtime Fairness is turned off — the case of most broadcasters — this is generally the norm:

The relationship between the Wi-Fi receivers (clients) and a broadcaster is first-come-first-served. On top of that, many broadcasters might take the slowest client’s speed as the effective rate of all connected clients on the same band (5GHz or 2.4GHz).

When an access point reaches its capacities in the amount of simultaneous active clients it can handle, a newly active client will need to wait for its turn. (Hundreds of clients can stay connected to a broadcaster but only so many can be active simultaneously.)

This wait time depends on how slow the currently active ones are and how much data they need to transmit. But in any case, bad efficiency is inevitable when you have a lot of slow devices. That’s because the access point will not do anything about a new (possibly much faster) client until it’s done with one of those it has at hand.

Again, that’s first-come-first-served.

Here’s an analogy of first-come-first-served:

You might have experienced long checkout lines in a big store like Costco. Everybody might have same-size shopping carts, but some are full of small items while others are half-full or even close to empty.

If you have just one or two items in your cart, behind a person with a full cart, you’ll have to wait for a long time before your turn. And when it’s your turn, it takes you just a fraction of the time to pay and get out.

If only you were allowed to cut in line.

Airtime Fairness turned on: Equal air time

With Airtime Fairness turned on, the access point now allots a dynamically determined equal amount of time for each client, regardless of how fast or slow they are.

The Airtime Fairness setting of an Asus router
The Airtime Fairness setting of an Asus router

So, for example, if the equal amount of time is determined at 5 seconds, a slow client that needs 20 seconds to finish transmitting its data will have to pause after 5 seconds, wait for the access point to deal with one or more clients, each for 5 seconds. And then it’ll get back to its turn. So on and so forth.

That said, with ATF turned on, fast clients get benefits at the expense of slower ones. How efficient this pans out depends on the situation: how many slow or fast devices are involved, how big the performance gaps between them are, and how much data each needs to transmit. It’s super unpredictable.

But as a whole, in terms of the total data being moved, this method is better than first-come-first-served when there are one or a few fast clients involved.

Back to the Costco analogy: ATF is like when the cash register spends no more than one minute for each customer.

As a result, those with a full shopping cart, who might need five minutes to be processed, will have to wait for five turns to be fully processed, during which a few of those with one or two items can get out first.

But carts that need only slightly more than one to two minutes to process will also need to do multiple turns. It gets touchy and complicated.

Airtime Fairness: How to be “fair,” for real

So Airtime Fairness is a “cheat” way for an environment with mixed clients. It’s more applicable to public Wi-Fi or in situations where you can’t avoid slow, legacy clients.

That includes modern IoT clients using special low-power protocols, such as Constrained Application Protocol, a.k.a CoAP.

While it might improve things in certain situations, it’s not ideal and might cause unexpected issues.

At the very least, this Airtime Fairness requires extra processing power from the router and, if you have lots of “smart” Wi-Fi devices, might cause the broadcaster to stop working properly after some time. If you choose to use ATF, it’s a good idea to restart your router — or schedule it to restart — every couple of days.

In a home where you have more control over the hardware, it’s best to avoid having slow and fast clients mixed in the same Wi-Fi network.

That said, here are a few ways to deal with them, without using ATF.

Avoid legacy and Smart Home Wi-Fi devices

The best way is to, well, remove all slow, dated, legacy clients from your network.

Again, if you have a modern (Wi-Fi 5 Wave 2 and newer) network, clients of older standards (Wi-Fi 4 or earlier) slow everything down.

Things can get very bad when you use many Wi-Fi Smart Home IoT devices — we’re talking about a device that uses Wi-Fi to connect directly to a home network here. That’s because most, if not all, of them, are equipped with dated, cheap, or buggy Wi-Fi adapters.

Right off the bat, you might have a hard time getting them connected, and when you succeed, the result can be bad news for your network. To put things in perspective, using these devices is like riding bicycles on a freeway, that’d hinder the traffic a great deal.

Yes, you should turn on Airtime Fairness in this case, but that only means these devices might get even slower or not work correctly. The result will vary, but it’s never ideal.

But removing all low-quality or slow devices from a network can be cost-prohibitive. In this case, the next best thing is to create a separate network for them.

Segmenting your devices

Generally, it helps to put similar (slow) devices in a group so that they will not affect the performance of other (faster) parties. You can do so by making different Wi-Fi networks (a.k.a SSIDs.)

If you have a dual-band router, name the 5GHz band and 2.4GHz band differently. If you have a tri-band, separate the band and designate one for a specific group of clients.

Some routers (or mesh systems) don’t allow you to separate these bands. In this case, you can create a Guest network for them.

Alternatively, you can also get a separate access point — preferably of an old standard or standard design specifically for low-power IoT devices.

Getting a separate AP might not be ideal in all cases since that can cause unnecessary interferences when not set up properly. But dealing with Wi-Fi is always about nuance — I talked more about that in this post on Wi-Fi troubleshooting.

This is similar to having “express” checkout lanes for customers with few items and regular ones for those with a full cart. You can find these and most stores and groceries.

Arlo Pro Hub
The Wi-Fi Hub of the Arlo security camera uses a network cable to connect to an existing network.

Opt for non-Wi-Fi smart home devices

Due to the low bandwidth, high-quality IoT devices tend to use Zigbee or Matter, two popular types of wireless standards.

They use these standards to connect to a central device — the Smart Home hub. This hub, each can handle dozens of LoT devices, is the only device that connects directly to the home network via Wi-Fi or a network cable, reducing or eliminating the negative impact.

Another example is the case of the Arlo Wi-Fi security camera. Its high-end (Pro) versions use proprietary Wi-Fi to connect to a hub, which uses a network cable to be part of a local network.

In other words, good and modern IoT devices are designed not to mess with a Wi-Fi network directly for a good reason. So, avoid those that do.

Alfred Connect Bridge Mount
Here’s a Wi-Fi Smart Home hub that hosts a bunch of non-Wi-Fi smart locks.

The takeaway

Not all Wi-Fi Smart Home devices are bad, but cheap no-brand-name ones almost always are.

Generally, if you buy a new device today and it supports Wi-Fi 4 (802.11n) or older (802.11g/a/b), or only the 2.4GHz band, that’s a telltale sign it’s bad.

Just because a device supports Wi-Fi doesn’t mean it supports it fully or uses an up-to-date standard/specifications. Sure, physically, you can ride a bicycle or take a stroll on a freeway, but there are many reasons you shouldn’t do so.

As you upgrade the broadcaster side of your Wi-Fi network to a faster, better standard, it’s always a good idea to use clients of the same or similar hardware specifications.

To put it in somewhat of a pun, just because a device has “smart” in the name doesn’t mean it’s a smart decision to use them.

Sure, you can make them work, but things can get complicated, and you might end up finding your top-notch router not worth your hard-earned cash. If so, keep in mind that it’s not necessarily its fault.

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20 thoughts on “Airtime Fairness Explained: Why You Should Cut Down on “Smart” Wi-Fi Devices”

  1. Hello Dong, 3 quick questions….

    I have Ring doorbell, 5 Ring security cameras, 2 Ring Motion lights that connect to the Ring bridge and 1 Ring Chime.
    When installing these I understood they work exclusively with the 2.4 GHz band.

    All TV’s, computers, phones, tablets inside the house connects to the 5Ghz band.

    1) Can I assume I have β€œnatural” band selection although I run one single SSID on my Orbi RBR50 with 1 satellite?

    Will be upgrading to Asus GT-AXE16000 with one wired ET12 as soon as the AXE becomes available (or maybe two wired ET12 if I get tired of waiting).

    2) Is it safe to assume that the β€œnatural” selection will remain with the Asus mesh?

    Currently using ADT wired alarm with 29 window/doors contacts, 3 motion sensors, 10 smoke sensors, 2 heat rise sensors & 2 sirens/speakers. Planning to migrate all to Ring alarm.

    3) Will this be too much for either of the two Asus mesh mentioned above? Keeping all other Ring items mentioned above.

    Best,
    Luis

    Reply
  2. So I’ve been suspecting this for a while. I’m thinking about using my TP-Link AX4400 as an access point with a separate SSID and connect it to my ASUS AX89x. Let the smart plugs, printer, and webcam fight it out on the β€œkids table” AP and the adults will sit at the ASUS table. Thoughts? Besides the fact this is overkill. (My tplink gear has yet to sell on Facebook marketplace)

    Reply
  3. Hello and thanks for this information/advice. Sadly, I already have a fair investment in IoT/Smarthome devices that employ wifi (all on the 2.4Ghz band) so just getting rid of them is not a likely solution. I do have a few more modern phones that connect via 5Ghz and 3 ethernet devices (TV, Chromecast, and an Android computer used mostly for Smarthome purposes).

    My main router is a Netgear R6400 v2 – which has a 1Ghz, 2-core processor and 128 flash/256RAM and “fairness” enabled. I have been finding that connecting more and more 2.4Ghz devices directly to this causes issues: (a) devices to “disappear” – they do not show on the router’s connected devices although they often can still be pinged and (b) the connection to the device may just be dropped entirely. The box for the R6400 clearly says supports 25 devices. But it is not clear if this refers to wifi devices, ethernet devices, or both. It is also not clear if this is per wifi band or both wifi bands. I do not have an exact count, but I am sure I was pushing 25 devices including ethernet.

    So I first responded by turning off several of the 2.4Ghz devices bringing the total number connecting to the R6400 directly down to about 15 on both wifi bands. And this “addresses” the issue but is obviously not a long term solution.

    In an effort to “solve” the problem, I took an old TP-Link WR841ND with a single-core 400Mhz processor, 4M flash, and 32M RAM and configured it using OpenWRT as an access point with its own2.4Ghz SSID and on a different channel which is connected via ethernet to the R6400. I then started moving many but not all 2.4Ghz devices onto the new SSID. I found that after about 8-9, similar issues arose.

    Now, I am not sure if this is because the TP-Link is just too limited to handle the load or if this is an issue with the R6400. Indeed, it is not clear if the issue in total is due to not enough CPU – where a faster or higher core processor would do the trick, not enough RAM – where doubling to 512M would do the trick, or something else entirely.

    I had considered going to a mesh system but your write up strongly suggests that they address mostly range and bandwidth issues and I really do not seem to have either of those problems. Perhaps I misunderstand…

    Agreeing with you that having a single broadcaster would be better since range/bandwidth is not an issue for me, I have been looking at alternatives to the R6400. But it is just not clear to me how much CPU and/or RAM is needed to address these problems (if that will address them at all). So I have little idea where to turn.

    Thanks

    Reply
    • The 2.4GHz has very limited bandwidth, David, so if your smart devices constantly upload information, that will kill the Wi-Fi bandwidth on that band fast. In your case, as you described in the email, having multiple broadcasters using different channels is the only way to go. A Wi-Fi 6 mesh system with wired backhauling will help, but how much will depend on the situation, only you will find out. Like I said, those “Smart” devices are evil.

      Reply
      • Evil they may be. But I have a lot of them and now, with a new GS-AX3000 in hand and configured, I have them all connecting to the one router on the 2.4Ghz. That’s 27-28 total devices with 22 of them being on 2.4Ghz. They have stayed put and worked well so far. I have also noted that the signal strength of the 2.4Ghz at the farthest point on my LAN is greatly improved using this router. I am sure my issue was not signal strength related, but this is a nice side-effect of the change. I do not know what it is about the new router that makes the difference over my old Netgear. But it does have a faster CPU with an additional core plus 256M more RAM. The performance graphs built into the stock firmware show it is not even breaking a sweat: core 3 is almost never used – however RAM usage is above 60% and that exceeds the total available on the Netgear. Cheers and thanks!

        Reply
  4. I have 20 lifx lightbulbs, 2 nest cams, 5 smart speakers running on 2.4ghz and zero issues. Maybe not enough to cause a problem in a small home.

    Reply
  5. Hi Dong, I admit to having already fallen into this trap. I have 15 devices that are exactly as you describe: economical, obscure brand WiFi Smart Home devices. Fortunately when I most recently replaced my router I bought a Tp-Link AX90 so I have separated out the 3 bands and all these devices are on the 2.4GHz band. They are all working ok so far. The only device other than the Smart Home devices on that network is my elderly, circa 2010, Kindle Keyboard. That works ok too, which is good because it is still the best device I have for book reading in good light.

    Reply
    • The Kindle doesn’t connect much, Gordon, and it actually has decent Wi-Fi specs. Looks like you’re in good shape! πŸ™‚

      Reply
  6. One thing you forgot to mention is that IoT devices tend not to work well in WiFi 6 environments.
    As for Matter, it’s an IP based framework that was created by the Zigbee Alliance, together with Google, Apple and Amazon, and it’s first implemention (and likely the most popular one) will run on WiFi.

    Reply
    • I did, Dror. “Wi-Fi 5 Wave 2 and newer” includes Wi-Fi 6, 6E and 7. πŸ™‚

      As for Matter, it’s Wi-Fi-based but proprietary — the clients don’t connect to a home’s regular Wi-Fi network directly — similar to the case of the Arlo I mentioned.

      Reply
      • It’s more than a slow down – these devices tend to intermittently disconnect from the network, rendering them unusable.
        The only way to overcome this is to disable WiFi 6 on the band or guest network they connect to – or setup a dedicated WiFi router for them on a different channel.

        Reply
  7. I have a netgear mr60, so I cant split 2ghz and 5ghz and there is no mixed wpa2/3. I tried to make my main network wpa3 and guest network wpa2.
    And placed my IOT devices on the guest network, however following that the devices stopped working on homekit.

    Reply

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