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I'm trying to set up a simple "wall wart" WiFi extender, a DLink DAP-1520. The setup is straight forward enough, but there seems to be no option for choosing a channel/frequency, so the extender will compete for bandwidth with the main AP. Is this normal? I would expect it to avoid the frequency used by the main AP. Am I missing something?

For context, I have been trying to learn a bit about extending WiFi networks (my expertise starts above TCP, I'm a bit lost when it comes to the lower layers). As far as I understand, the DAP-1520 is not a repeater. It's an AP with a second WiFi device that it uses to connect to the main AP. At least, that's what I gather from the fact that the configuration wants me to specify an SSID and password for the back-haul as well as for the extender itself. And they suggest to pick a different SSID. (Edit: the extender supports 2.4 OR 5 GHz for the back-haul, and dual 2.4 AND 5GHz for the use by clients).

Using the same frequency in this arrangement doesn't make sense top me. So I have a few questions:

  • Does a repeater necessarily re-transmit on the same frequency? Why would it not be possible to re-transmit on a different frequency?
  • Does a repeater need a WiFi password?
  • When setting up multiple APs, should the all operate on different frequencies? Especially if they use WiFi for the back-haul? Why would an extender be hard coded to operate on the same frequency?
  • When setting up multiple APs, should they all share the same SSID? If not, why not? Why would the instructions for the DAP-1520 suggest using a different SSID?

I have read How does a WiFi range extender work?, but it doesn't really help with my confusion...

brightbyte
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1 Answers1

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Simple, it only has one radio. One radio === one channel. If it has two (or more) radios, then it can use one for the mesh, and the others for clients.

If your WLAN employs security, then every device on the WLAN needs the correct settings (i.e. password) to connect.

Note: Dual-band does not mean "dual radio". And it only has two internal antenna.

Ricky
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    Dual-band devices usually do have two radios - one for 2.4GHz and one for 5GHz. Also, many dual-band devices end up with more than two antennas (MIMO, diversity, spatial multiplexing). – Yosef Gunsburg Jan 21 '16 at 22:29
  • Wait; now I see what point you're trying to make. Just because it is dual-band, does not mean it can operate at two 2.4GHz frequencies simultaneously (or two 5GHz frequencies). – Yosef Gunsburg Jan 21 '16 at 22:31
  • Thanks. So using a different frequency would definitely be better, but it would require more hardware (a third radio)? And they just skipped that for the cheapo wall-wart? Do I understand that right? – brightbyte Jan 22 '16 at 06:49
  • Also, you say that every device on the WLAN needs to have the same encryption/password. This is obviously true for any kind of AP. But would it also be true for a plain repeater? Doesn't a repeater just re-transmit frames without modifying or even reading them? – brightbyte Jan 22 '16 at 12:04
  • NO. A repeater is a client and an AP. – Ricky Jan 25 '16 at 05:44