How does a Wi-Fi extender work? Let’s say if a certain location has a signal of -50dBm, how does adding an extender at that exact location boost the signal around it?
In: Technology
It’s a repeater. Every WiFi signal it receives, it broadcasts again. So, you put it at the end of your range, and your device transmits as “loud” as it can and it gets as far as your repeater, but the signal dissipates before it gets as far as the access point. That’s fine, because the repeater then transmits the signal again, and since it’s much closer to your access point, the original message reaches the destination. The reverse occurs when the access point transmits it’s response.
The problem with repeaters is that it generates more signal traffic. Understand that there is ONLY 1 electromagnetic spectrum. Every device using the 2.4 GHz band HAS TO TAKE TURNS, because if two devices transmit at the same time, it’s like two people talking at once – the receiver, WHICH IS EVERY DEVICE IN RADIO RANGE, all hear garbled noise and you can’t tell one signal from the other. The more devices in range, the slower everyone goes. It doesn’t matter if you divide things up by network, you’re still all using the same radio frequencies. If you’re close to your neighbors, then ALL your devices are picking up their noise, it’s just silently dropping the data because it’s not meant for them. WiFi, is a shared medium, it’s like if every device were wired, and sharing the same wire – you all have to take turns.
So a repeater is just one more participant, one more device vying to take it’s turn, meaning everyone has to wait that much longer to send their next packet. And more devices means more chance for collisions, meaning everyone has to wait even longer as data has to be resent.
The better thing to do is wire in all the devices you can. I recommend Cat-5e or Cat-6 STP with the proper grounded connectors. The thing is all conductors are antenna, so a long run of copper can pick up a lot of RF noise, so by shielding your runs, you’ll get far better performance. Anything you wire in means you free up the air waves, making your whole WiFi network, and that of all your neighbors, that much faster. It also cuts out the need for this repeater.
Barring that, the next best thing is to change your antenna to something with higher gain. This makes the most sense for stationary devices, like desktops or televisions, which may have an external antenna. A higher gain antenna simply means a directional antenna pointed directly at the access point. Instead of wasting electromagnetic energy sending your signals in all directions – all directions your access point ISN’T, you can direct all that energy to where your access point IS. This is a “passive” solution, in that it doesn’t require additional electronics or power. You’re not repeating your signal, you’re concentrating the energy and sending it in a focused beam. This solution isn’t practical for things like laptops or cellphones, especially since these devices almost universally don’t have external antenna. You can still prop the thing in front of an old DirectTV dish – which is the right size for WiFi, but that would be cumbersome.
Barring that, I would recommend moving your AP closer to where you use it most, and consider how to configure your home network more efficiently for your most common use cases.
WiFi isn’t one radio channel, it’s several. The Extender listens on one channel, with a very sensitive receiver, and transmits on another, with a powerful transmitter. This makes the same network available on two radio channels. Since devices have algorithms to choose the most powerful signal, they will connect to the strong extender rather than the weak primary. For devices that are constrained in their radio antenna geometry, like a cell phone, this can be a big improvement.
The way I understand it is, the extender acts as a radio repeater. It receives the signal from the router or access point. From there, it re-transmits the signal on a different channel that is capable of being received further out.
You add it before the signal drops, then it repeats the signal so it can be accessed further away.
going on your example, say your location has a path attenuation of -50dBm, and the repeater (which is really just an amplifier) has a gain of 30dBm, and it’s placed at the location where the signal of the original signal reaches -25dBm (not actually physically halfway due to the inverse square law). the signal attenuates -25dBm from the router to the repeater, gets amplified back up to +5dBm, and then travels from the repeater to the target, losing 25dBm, and arriving with -20dBm, a saving of 30dBm. This is significant because most coding schemes scale non-linearly in efficiency against SNR.
As for how they work, they essentially create a new network with the identical SSID of the router, so that any connected devices can’t tell the difference between the router and repeater. it accepts traffic as if it were the router, and just passes the messages over to the router.
The equipment in the extender is better quality than a standard device. It might have a more sensitive receiver and/or powerful broadcaster. While a phone might have trouble receiving signal to the router and broadcasting back, the extender can. The extender then broadcasts a network with the same SSID as the router. This identifies it as the same network as the router. Your phone then connects and transmits to the extender, which relays those packets through its link to the router.
If you move closer to the router or a different extender so much that your original link weakens, your device will swap over and send to whichever endpoint with the same SSID can receive. This gives you a seamless experience as you move around as if it were one big signal.
It’s like if you got your friends to stand in a line 50 metres apart
A friend at one end can yell something loud enough for the second friend in the line to hear, they can then yell it to the next person in line
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