In recent years, I've received many questions about issues with Wi-Fi connections involving smart Wi-Fi devices. The increasingly widespread use of IoT (Internet of Things) gadgets that hook directly to your Wi-Fi network has its consequences.
Despite the "smart" notion in the name, it can be a bit, well, "dumb" to use these devices willy-nilly — they may cause all sorts of connection issues for traditional Wi-Fi devices, such as computers or smartphones. It's all in how Wi-Fi broadcasters handle their signals, as described in a setting called "Airtime Fairness".
I'll explain, in simple terms, Airtime Fairness, why it's never a good idea to use many "Smart" Wi-Fi devices in your primary network and what you can/should do to best handle them.
Note: We're talking about standard Wi-Fi devices and not IoT devices with any other type of wireless connection, such as Zigbee, Z-Wave, Thread, or the low-power Wi-Fi HaLow.
Airtime Fairness: How it’s not the best way to deal with IoT smart Wi-Fi devices
Internet of Things (IoT) is a different name for a smart Wi-Fi device.
Once upon a time in the tech world, these devices either didn't exist or lacked wireless connection capability. In recent years, their latest generations have emerged with built-in Wi-Fi, enabling them to connect to the Internet and exchange data with other devices. They can do much more than their older cousins or ancestors, which is where the "smart" notion comes from.
Everyday Wi-Fi-enabled gadgets in the home are examples of these IoT devices, including security cameras, printers, door locks, doorbells, power switches, lights, ovens, refrigerators, grills, and more. Nowadays, it's hard to find any type of home appliances that don't have Wi-Fi-enabled options.
At the gist of it, IoT smart devices are Wi-Fi clients — they are network devices — with limited functionality compared to traditional clients, such as computers or smartphones. They join the growing list of Wi-Fi devices that has created the need for a particular setting in Wi-Fi broadcasters (access points or routers) called Airtime Fairness.
So, what's Airtime Fairness?
It's a familiar network setting dating back to Wi-Fi 4 (probably earlier) that ensures each client in the network has equal airtime with the broadcaster, regardless of their operating system, Wi-Fi standard, operating mode, or signal strength.
IoT or not, all devices connected to a Wi-Fi broadcaster will need some time to finish transmitting data. That duration is called the "airtime".
Still, it's hard to define airtime since Wi-Fi is a dynamic environment, 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 or, well, don't work.
Airtime Fairness turned off: First come, first served
When Airtime Fairness is turned off — the default case of most modern broadcasters — this is generally the norm:
The relationship between the Wi-Fi receivers (clients) and a broadcaster is on a first-come-first-served basis.
A broadcaster can handle multiple clients at a time -- up to a certain number. During this time, it generally takes the slowest client's connection rate as the effective rate of all connected clients on the same band (5GHz or 2.4GHz).
When a broadcaster reaches the maximum number of simultaneous active clients it can handle, a newly active client must 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 inefficiency is inevitable even when you have just one slow device involved — it determines the connected speeds for the rest of the pool within the same band. That's because the broadcaster 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.
A crude analogy of first-come-first-served: You might have experienced long checkout lines in a big store. 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.
Airtime Fairness turned on: Equal airtime
With Airtime Fairness turned on, the access point now allows a dynamically determined equal amount of time to each client, regardless of performance grade or the amount of data they need to transmit.
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 Airtime Fairness 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 significant the performance gaps between them are, and how much data each needs to transmit. It's complicated and 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.
The retail store analogy: Airtime Fairness is like when the cash register spends no more than one minute on 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: Why it’s not ideal to handle lots of IoT smart devices
As you can imagine, 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 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 can cause unexpected issues, such as the slow real-world connection rates of low-end devices. This becomes severely problematic when you have more than a few IoT smart devices on the same frequency band. Things can get slowed down to a crawl.
Additionally, Airtime Fairness requires extra processing power from the broadcaster, which can cause the high-end clients connected to a different band to underperform or the broadcaster itself to crash after a while.
For this reason, if you choose to turn on Airtime Fairness, it's a good idea to restart your router — or schedule it to do so — every couple of days.
Three ways to best handle IoT smart devices
The point here is that in a home where you have complete control over the hardware, it's best to avoid having slow and fast clients mixed in the same Wi-Fi network. Again, most IoT smart Wi-Fi devices are slow clients.
That said, here are a few ways to effectively use smart devices without using Airtime Fairness.
1. Cut down the number
The best way to have a well-performing network is to remove all slow, dated, legacy devices.
A single slow client may cause the broadcaster to lower the Wi-Fi bandwidth of a particular band — it has to support the lowest denominator — reducing the connection speeds of all connected clients.
Keep in mind that, unlike traditional clients — phones, laptops, etc. — which 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 to do more than the advertised functions.
Generally, it's best not to use these devices or have more than a handful in your home — I'd say no more than five in a home network.
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 a Wi-Fi router works well with one particular device, it will work equally well with many units simultaneously. Specifically, just because you can successfully connect one unit of a specific device to your Wi-Fi router doesn't mean you can get 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. I speak from experience.
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. To put things in perspective, there are reasons why freeways are closed off to cyclists and pedestrians -- even one of them can cause a traffic jam.
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.
2. Segmenting your network
Generally, it helps to put similarly slow devices in a group so that they will not affect the performance of higher-performing parties. You can do so by making different Wi-Fi networks (a.k.a SSIDs) for them.
If you have a dual-band router, name the 5GHz and 2.4GHz bands as two separate SSIDs and use the latter for slow devices — Tri-band or Quad-band broadcasters give you even more options for network segmenting.
Some routers (or mesh systems) don't allow you to separate theirbands. In this case, you can create a Guest Wi-Fi, preferably with intranet access — this network almost always uses the 2.4GHz band. Additionally, if the broadcaster has an option of creating a separate IoT Wi-Fi network, use it for your IoT smart devices.
No matter the situation, you can always 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.
When upgrading your network by replacing the router, you can keep the old router and use it in the AP mode as a separate network to host existing (and new) IoT devices.
Using a separate AP can cause unnecessary interferences when not set up correctly — you need to put its SSID in different channels from those of the primary network. But dealing with Wi-Fi is always about nuance.
Real-world example: Segmenting your home network is similar to having "express" checkout lanes for customers with a few items, leaving the regular lanes for those with a full cart. You can find this practice at many grocery stores.
3. Opt for non-Wi-Fi IoT smart devices
Due to the low bandwidth, many high-quality IoT devices tend to use a separate wireless standard — such as Thread, Z-Wave, or Zigbee — for their connectivity.
Specifically, they use one of these wireless standards to connect to a central device — often called a Smart Home hub. Each hub can handle multiple IoT devices, and it 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 Arlo Wi-Fi security cameras, which use a proprietary Wi-Fi link to connect to a hub, which connects to the network via a network cable.
In other words, modern IoT devices are designed not to interact directly with a Wi-Fi network. You can use these instead of those with built-in Wi-Fi.
As mentioned at the beginning, there's a new Wi-Fi standard for low-bandwidth devices called Wi-Fi HaLow. When widely adopted, it'll be an appropriate wireless standard for IoT. We'll still have to wait to see how that pans out.
Here's a general idea: Not all IoT Wi-Fi devices are bad, but none are good for the network — at best, they are OK. 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 isn't good. 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 the latest standard or uses up-to-date specifications. That's similar to the fact that while you can physically 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, 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 SSID or, better yet, a different broadcaster for them.
To put it in somewhat of a pun, just because a device has "smart" in the name doesn't necessarily mean it's always a smart decision to use it. You can make them work, but things will get complicated, and you might end up inadvertently hindering your top-notch router or mesh system and everything else in your home network.
Dong's note: I first published this post on January 8, 2022, and last updated it on January 25, 2024, to add the latest relevant information.