Tuesday, January 18, 2022 • Welcome to the 💯 No-Nonsense Zone!

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

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.

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 matters 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 mount of simultaneous active clients it can handle, a newly active client will need to wait for its turn. (Many clients can stay connected, but only so many can be active at the same time.)

This wait time depends on how slow the currently active ones are and how much data they need to transmit. But in any case, when you have a lot of slow devices, bad efficiency is inevitable. 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.

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 the 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”

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.

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

The best way to deal with this is to, well, remove all slow, dated, legacy clients from your network. And if you can’t do that, create a separate Wi-Fi access point for them.

If you have a dual-band router, name the 5GHz band and 2.4GHz band as two different Wi-Fi networks (a.k.a SSIDs). If you have a tri-band, separate the band designate one for specific 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 like Wi-Fi 4, though this is not ideal, either, since that might cause unnecessary interferences.)

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.

And that brings us to why Smart Home Wi-Fi devices are generally not good to have, especially in a large number.

Read this  Quick Wi-Fi Add-On: TP-Link's Unveils Low-Cost Adapter Trio
Arlo Pro Hub
The Wi-Fi Hub of the Arlo security camera uses a network cable to connect to an existing network.

Why you should avoid legacy and Smart Home Wi-Fi devices

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 — again, 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.

Non-Wi-Fi Smart Home devices are the way to go

For this reason, high-quality IoT devices tend to use Zigbee or Matter, two popular types of low-power, low-bandwidth Smart Home wireless standards.

In this case, the Smart Home hub is the only standard device that connects directly to the home network, via Wi-Fi or a network cable, and that reduces or even eliminates the negative impact. By the way, each hub can handle dozens of IoT devices.

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.

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 right now 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 that it’s bad.

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

The takeaway

Just because a device supports Wi-Fi doesn’t mean it supports it fully or uses an up-to-date standard/specifications.

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 then you might find your top-notch router not worth your hard-earned cash. And it’s not its fault.

☕ Appreciate the content? Buy Dong a Ko-fi!

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

  1. 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.

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

  2. 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.

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

      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.

      • 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.

  3. 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.


Leave a Comment