Why does my device stick to the wrong Wi-Fi router?

You may never have heard the term Extended Service Set Identifier (ESSID), and why should you have? It’s a mildly esoteric term in the Wi-Fi world for how multiple routers with the same name form an extended network. In fact, it’s not even a protocol; it’s just a name, which makes it even more confusing.

So why would I bring it up? Because the notion of an Extended Service Set affects how we connect to Wi-Fi networks, and why you sometimes have a rotten connection when you’re bathing in the soothing high-speed waves of a nearby router.

The problem is easily stated: your device connected over Wi-Fi has poor throughput, even though it’s close to a Wi-Fi gateway or extender, while other devices nearby experience terrific data rates.

I’ve got an explanation and some solutions that may help you overcome a common problem readers have asked about many times over the years, plus a question that is coming from inside my house.1

The name is the same

This question is brought to you by my spouse and her home office. Because we have an aged house—that’s pronounced EH-jed—it is nearly impossible to run new wires through it except at great expense. While having some basement renovation done a decade back, we managed to get Ethernet strung from one end of the house to the other and to our connection point, also in the basement. We should have done more!

Hold down Option and click the Wi-Fi menu to reveal a host of technical detail you definitely usually don’t need to know.

Due to a lack of network wiring, we’ve had to use powerline networking, which generally works fine, but can perform erratically at times because of some of the eh-jed electrical wiring in our home. Our kitchen was apparently accidentally (?) designed to be a Faraday cage, so we had to add a repeater in there over powerline.

We have wound up with an embarrassing number of Wi-Fi access points in the house: six, if you count the one that the ISP provided because of the fiber-optic setup they use; we only use that router’s Wi-Fi connection to check when something is wrong.2 (Did I mention our house is not a mansion, but a small two-bedroom?)

The way we unify a network like this to allow our devices to roam seamlessly is the same as in a million-square-foot convention center: all the Wi-Fi gateways or access points have the same broadcast name. Here’s where it gets a little tricky:

The broadcast or network name is the Service Set ID (SSID). It’s human-readable and meant to be seen in a list of Wi-Fi networks.

Underlying the SSID is a Basic Service Set ID (BSSID), which is a unique numeric tag that is the same format and used in the same way as in Ethernet. Called the Media Access Control (MAC) address—an unfortunate overlap—it’s is a series of six two-digit hexadecimal numbers separated by colons.3 The uniqueness allows a bazillion devices to be on the same network without fear of collision, or two devices having the same network ID.4

Now, you wouldn’t want to select a Wi-Fi network by MAC address; even if you did so, you wouldn’t want to be stuck associated with that base station when you were moving around with your mobile device. You would like the device to connect to the best signal it can find.

And that’s the problem: Mobile devices define what’s they think is the “best signal.” Apple offers a full description of how its devices make this decision,5 but we have no control over that process. I can, however, give you advice for troubleshooting and improving your setup if you find yourself having poor throughput when you know you could do better.

A slow, strong connection prevails

Any device that uses Wi-Fi swims in a sea of BSSIDs. We see just the tip of this, even when it seems like we’re drowning in Wi-Fi names. You can get a better sense by examining a WiFi Explorer Pro scan from my home Mac, where my network and some near me have many base stations.

Open up WiFi Explorer Pro, and see the hidden Wi-Fi environment around. Particularly note how one network name, like Portage Airbasestation, can have oodles of networks in multiple frequency bands.

Each device you use has a unique formula for selecting among available BSSIDs that share the same network name. That’s true of a home sensor, like an alarm component, or an iPhone, Mac, Android, game platform, or other devices.

Generally, the strongest network signal with the highest data rate gets picked. If you’re relatively near within a building or have a good line of sight to an access point, the 5 gigahertz (GHz) or 6 GHz band is chosen. These bands can carry hundreds of megabits to multiple gigabits per second due to the breadth of frequency available.6 Modern Wi-Fi devices have a variety of tricks to work around overlaps in usage in the same area that produce high throughput rates even in crowded environments.

However, the 5 GHz and 6 GHz bands have relatively short wavelengths—the “length” of the signal. They can be readily absorbed by walls, ceilings, and floors, as well as other materials. (This is why you shouldn’t put a Wi-Fi router inside cabinets or behind furniture, as you’re decreasing range.)

When a high-frequency network can’t be used at its higher speeds, your device may opt for 2.4 GHz, the original “home” of Wi-Fi. With narrower ranges of frequencies and heavier use, 2.4 GHz nonetheless penetrates objects better, and thus can have a higher net throughput at a distance than the comparable 5 or 6 GHz network.7

As you roam around, your device may choose to maintain a lower-speed connection with a more distant or more obstructed router, even as you approach or are standing next to one that could offer 10 or 50 times as much throughput.

You can improve the situation, typically only in three ways:

Check your routers’ channel/band/signal strength configuration. Every router is different, but many let you pick preferred channels or use a reduced signal strength. Read up in the manual on whether a particular channel or setting will help increase range or tune performance.

On your device, turn Wi-Fi off and back on. You can use Settings/System Settings > Wi-Fi, and toggle the switch. (Airplane Mode on an iPhone or iPad won’t necessarily work because you can set it to leave Wi-Fi on.)

Break up one big ESSID into two or more smaller ones, either by location or by frequency band.

Toggling Wi-Fi causes your device to evaluate its network environment afresh and typically makes the “right” choice. It’s the least-frustrating option, but it gets old.

Reconfiguring your network requires some planning. I recommend this only when you’re having persistent problems and can’t move routers to improve roaming. If that’s the case, one of the following could help:

Create zones: Name routers the same in clusters. Maybe you have one set downstairs and another upstairs.

Separate by band: Most routers have at least two separate radio systems, letting you name 2.4 GHz and 5/6 GHz networks separately. Some have three bands, separating 5 and 6 GHz or offering two distinct 5/6 GHz networks with differently configurable features. This lets you force some devices onto slower but more reliable networks if they have weak radios or are far away from an access point.

Add specialized guest networks: Most routers let you set up additional network names under “guest networking.” You can keep these networks’ traffic private from the rest of your network, or allow it to bridge, so the guest networks just work like additional networks.

At one point, I discovered that some of my smart home devices that were limited to 2.4 GHz networking were having trouble consistently connecting. I realized they were often choosing a more distant access point, which caused their connections to drop. To fix the problem, I set up a 2.4 GHz guest network on the router closest to all of them and had them connect to it.

This is a lot of work to get consistent Wi-Fi. However, if you’re like those of us in our home, the frustration of having to manage and tinker with your device’s connection is enough that some rethink of your configuration could make for a happier household.

For further reading

Would you imagine I wrote a book about Wi-Fi? Yes! In fact, I’ve had at least one Wi-Fi book in print for over 20 years, since Adam Engst and I wrote The Wireless Network Starter Kit. My latest up-to-date title is Take Control of Wi-Fi Networking and Security.

[Got a question for the column? You can email glenn@sixcolors.com or use /glenn in our subscriber-only Discord community.]

I’m writing this just before Halloween. By the time you read it, that will just sound weird. ↩

The fiber-optic terminal requires a modem that handles VLAN tagging and PPPoE. The former used to be an expensive option, and they gave me the modem at no cost when I signed up. ↩

The Wi-Fi Alliance, the trade group that came up with the Wi-Fi moniker and handles certification of devices complying with the industry’s IEEE 802.11 set of standards, was originally called the Wireless Ethernet Compatibility Alliance due to its close relationship to Ethernet (IEEE 802.3). ↩

Some operating systems, like those from Apple, let you create “private” MAC addresses on each Wi-FI network, which are randomly generated MACs that prevent third-party software operating on a given network from associating you across sessions in different locations. ↩

Only a network engineer can decipher “For macOS, the candidate BSS needs to have an RSSI that’s 12 dB stronger than the current BSS, whether the Mac is idle or transmitting data.” That RSSI is the Relative Signal Strength Indicator, a formula that provides a basis for comparing strong and weak network signals. ↩

Like broadcast TV channels, Wi-Fi and all wireless gear are designed around ranges of frequencies. Roughly speaking, with the same amount of signal power, the wider the range of frequency, the greater the potential throughput. I’m leaving out lots of provisos! ↩

Companies testing Wi-Fi penetration may use sacks of tubers to simulate human beings. That led to one of my all-time great headlines for an article I wrote for the Economist about tests Boeing was doing: “Coach Potatoes.” The illustration was also excellent. You’re welcome. ↩