I've recently gotten a lot of questions about issues with Wi-Fi connection involving Smart Wi-Fi devices and then some on the Airtime Fairness (ATF) setting of a router. As it turns out, the two are closely related.
In naked truth, this post is more about why it's, well, "dumb" -- pun intended -- to use more than a few particular "smart" Wi-Fi devices. Having hard feelings? Feel free to unring that bell!
I'll explain ATF, in simple terms, and why I never think it's a good idea to use many "Smart" Wi-Fi Internet of Things (IoT) devices in your main network and what you can/should do about them. And I speak from (harsh) real-world experience.
Note: I'm talking about standard Wi-Fi devices here, not those IoTs with any other type of wireless connection, such as Zigbee, Z-Wave, or Thread.
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 earlier).
It ensures that each client in the network has equal access to air time with the broadcaster (Wi-Fi router, access point), regardless of 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 hard to define 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 -- a giant chain grocery store anyone with a family in the US would know. 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, and 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 to have a well-performing network is to remove slow, dated, legacy clients.
A single slow client may cause the broadcaster to lower its Wi-Fi bandwidth of a particular band -- it has to support the lowest denominator -- reducing the connection speeds of all clients or the number of concurrent clients it can support.
Keep in mind that, unlike fast modern clients -- phones, laptops, etc -- that are active periodically, "smart" IoT devices tend to be working all the time, permanently hindering the broadcaster. Three reasons:
- They are designed that way. For example, an IP camera uploads footage constantly to a server.
- They are slow and need more time to finish transmitting a small amount of data.
- They are designed, by the vendor, to do more than just the intended functions.
Generally, you should not use them at all, but if you have to, use no more than a few. I'd say no more than five in a home network, though sometimes two are already too many.
Wi-Fi and parenting
There's a prevalent Wi-Fi bandwidth assumption that's the root of so many connection problems.
Folks tend to assume that if something works well with one, it will work equally well with many simultaneously. That's almost never true and definitely untrue regarding Wi-Fi.
Specifically, just because you can connect one unit of a specific device to your Wi-Fi router successfully doesn't mean you can go ahead and buy ten and expect them all to work the same.
I'd liken this to parenting. Just because you can raise one child or two children successfully doesn't mean you can do five, definitely not simultaneously. Take my word for it!
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 -- those that use Wi-Fi to connect directly to a home network. That's because most, if not all, of them are equipped with dated, cheap, or buggy Wi-Fi adapters.
To put things in perspective, using these devices is like riding bicycles on a freeway, that'd cause even the even fastest race car to slow down.
Yes, in this case, you should turn on Airtime Fairness to improve the general performance, but that only means these devices might get even slower or not work correctly. The result will vary, but it's never good.
However, removing all low-quality or slow devices from a network can be cost-prohibitive. 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 -- this network almost always uses the 2.4GHz band.
In my experience, it's best to get a separate access point (or Wi-Fi router) -- preferably of an older standard and use it specifically for low-end, dated Wi-Fi IoT devices.
Getting a separate AP can cause unnecessary interferences when not set up properly -- you need to put its SSID in different channels from those of the primary network. 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.
Opt for non-Wi-Fi smart home devices
Due to the low bandwidth, high-quality IoT devices tend to use Thread, Z-Wave, or Zigbee, 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 multiple IoT 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.
Here's a general idea: Not all Wi-Fi Smart Home devices are bad, but none are good for the network -- at best, they are OK. And cheap no-brand-name ones are almost always terrible.
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. But if you get one that supports the 5GHz, it's not necessarily good, either. Chances are it'll still slow the entire band down to a degree.
Just because a device supports Wi-Fi doesn't mean it supports it fully or uses up-to-date standards/specifications. That's similar to the fact while, physically, you can ride a bicycle or take a walk on a freeway, there are plenty of 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. If keeping slow clients is a must, use a separate broadcaster for them.
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. You can make them work, but things can get complicated, and you might end up finding your top-notch router or mesh system not worth your hard-earned cash. If so, keep in mind that your hardware is not to blame.