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.
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, 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.
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.
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. (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. 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 (virtual) network 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 and 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, or standard design specifically for the low-power IoT devices. Note that this approach might not ideal in all cases since that might cause unnecessary interferences. But dealing with Wi-Fi is always about nuance.
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.
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 — 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
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, reducing or eliminating 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.
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 then you might find your top-notch router not worth your hard-earned cash. And it’s not its fault.