If you are wondering why your WiFi is slower than if you plug into your router with an ethernet cable, look no further. WiFi is a technology that trades performance for convenience. People want to walk around with devices that don’t need to be plugged in for internet access. To make this possible, WiFi has to make a number of compromises that really start to add up.
If you wanted a simple answer, It’s because it’s never going to match a wire for performance & reliability, and wireless devices aren’t typically made with top of the line wireless chips. This is completely normal.
Look at my speed test results between wired and wireless using the same computer. My contracted ISP speed is 600mbps down, 40mbps up.
This is the Ethernet Result from my desktop.
As you can see, even with the gaming of the speed test servers all the ISPs do, the Ethernet results are fairly respectable. This is an Intel dedicated NIC to a CISCO Catalyst 2960x, to a Maxxwave x86 built Mikrotik router. This is several thousand dollars in networking equipment all in.
This is the wireless result for the same computer, with excellent signal reception.
This is with the exact same computer a minute or so later, after I enabled the wireless card and disabled the Ethernet. The wireless card is the onboard one on my ASROCK Taichi X370 Motherboard, which has an Intel 3168 chipset. The access point in a Ubiquiti Unifi UAP-HD. An 802.11AC Wave 2. Basically top of the line for Unifi. Not that it matters for this client, which can only negotiate at 433mbps tops. Besides that, there is a wireless N printer and echo dot in the mix, which doesn’t help matters, but is very realistic to the typical home.
As you can see, there is a marked difference in the speed between wired and wireless, even on the same PC. In practice you aren’t going to see anything near what is advertised on the box of these products. If I went out and bought a nice $120 wireless card to install in my desktop, I could expect better performance, but still wouldn’t see the advertised rates. If I was using this desktop wirelessly I would have built the PC with such a wireless card, but since I wired everything, I don’t need to worry about that.
If you want to know why wireless doesn’t work as well as wired…
Consider the Humble Wire Cable
Wires are ideal for carrying data. They are a little universe unto themselves that we send very clear impulses down, whether light or electricity.
You don’t have to worry much about interference or signal loss. Both are definitely a thing in cabling, but nowhere near the trouble it is in Radio Frequency technology like WiFi.
Because each one is self contained, wires scale extremely well. So long as you have the appropriate networking equipment on the back end, the total number of devices is irrelevant to the performance of any given device along the way. It’s backhaul, the cable providing it’s connection back to network resources like the internet or a local server, is individual to that one client.
A Shared Resource
People like to envision WiFi networks as if there are invisible wireless ethernet cables between the wireless access point and client devices. This is fine if we are making a logical network diagram or something, but it’s FAR more accurate to envision WiFi as one ethernet cable all attached client devices share. Every device added to the WiFi network shares the same backhaul to the router. This matters little when it’s just a device or two, but when you try and scale up, you quickly run into bandwidth issues. Every AP services clients is a round robin fashion. They all get in line and then take turns talking with the AP alone, kinda like a bank teller or cashier. Then they get back in line and wait their turn for the next chunk of data.
Access Points serve up requested data to client devices, who wait in a circular queue for more data. This goes on many times a second.
The more clients, the more users in line waiting for their turn (literally a slice of time they get to talk to the access point), the worse the performance for everyone. Furthermore, it’s also a lowest common denominator thing, so if there is one device working at a really bad data rate, every device on the band has to slow down to match it, so they can all play nicely together. Like adding an old lady in a walker to this queue diagram above; Everyone is waiting on this old lady, every circuit.
And that’s just how it’s a shared resource in a vacuum, to your usage of it. When you have to compete with other RF sources that’s called interference.
Interference
In the real world, everyone is using all sorts of wireless technology everywhere. There is only so much radio spectrum to go around. It’s a shared resource on this level too. If you were to magically teleport an urban building out to a rural area, it’s wireless performance would no doubt improve simply because there aren’t a lot of neighbors your devices have to shout over anymore. A wire is it’s own little universe for the most part in terms of RF, but wireless devices have to share theirs.
Even within your home there are numerous competing wireless technologies, and even stuff like microwaves which hum along at a frequency similar to WiFI because everything runs in the same limited consumer band dictated by government. Your cordless home phone system runs at the same frequency as WiFi for instance. Lots of things you wouldn’t think of do.
All this stuff just makes it harder to get good real world performance out of your hypothetically high performance equipment.
Marketing Math
The number on the outside of a wireless router box is almost certainly wrong in a practical sense. This number derives from adding the maximum speed of the router at 2.4ghz to the maximum speed of the router at 5.0ghz. This is wrong is a number of ways, but since if you don’t play along on your box and put this number down like everyone else, your equipment will look inferior.
An AC1900 device is typically a 600 @2.4/1300 @5.0 device, so even theoretically, which you won’t get, it can only do 1300mbps in a best case scenario, not the 1900 on the box.
First off, you can’t actually use both the 2.4ghz and the 5.0ghz bands at the same time, so adding their bandwidths up makes no sense.
Next, it doesn’t matter how fast the router can serve up data to a client device if the client device can’t also handle that speed. Lowest common denominator wins.
Finally, those numbers only hold true if there is only one device connect to the router, which is such an impractical scenario, it’s hard to take seriously.
Manufacturers Cut Corners
While people tend to buy technology devices on features, some features are more paid attention to than others. In device sales, for networking, the only important aspect is to mention the 802.11 revision it’s compatible with. Details after that aren’t important to most consumers. Most don’t even care past mention of “WiFi”.
If you are a manufacturer, the only sensible thing to do is as little as you can get away with.
A device with the most basic 802.11AC profile sells about as well as a much more expensive 802.11AC profile chipset that does higher performance connections. As a result most devices cheap out on the wireless chip to keep costs down. In my example at the beginning of this post, ASROCK’s motherboard didn’t build in the nicest wireless AC chipset they could buy, because most people wouldn’t have seen that as a valuable selling point. The people who know enough about wireless are probably hardwired, and the people who would benefit don’t know any better in the place to see it as desirable.
I do have to give credit to Apple here. All of their devices generally have very nice wireless chipsets in them. Much nicer than they could probably get away with given their market share and dominance. Everyone else is considerably worse about it, since the market doesn’t punish them for cutting that particular corner.
Conclusion
Wireless speeds are never going to be as advertised, and all that is really important is to keep enough bandwidth available for key applications like laptops and cell phones. If you are worried about a computer’s network performance, a wired connection is the gold standard. What are you going to do with more than 50mbps on a cell phone anyway? That’s two 4K media streams on a handheld device. If you are getting 150mbps, I don’t even know what application would benefit from more than that.