Is it possible for a single (802.11 b,g,n,ac) WIFI radio to act as both an Access Point and Access Point client simultaneously – if so how, and are there examples of software that allow this (I'm particularly interested in Linux, but any OS that does it would evidence it can be done, and thus valuable to me). If not, why not?
For the sake of clarity, I'm not talking about a radio acting as either one or the other, and switching roles at different times, nor am I talking about 2 radios on different frequencies doing different jobs. I'm also not interested in ad-hoc mode unless this can be leveraged to appear as an AP and AP client to other AP's and AP clients respectively.
Best Answer
Modes of operation
The access point, providing WiFi is usually called AP, while the client is called STA.
It's possible to configure your device as a repeater or as something I will call a wireless-wireless router, since I can't find a consensual name.
The wireless-wireless router will need more configuration, but will only transmit packet as needed.
Hardware compatibility
Some wireless adapter are not able to use STA and AP mode at the same time (some adapters even can't serve as AP).
If you've got an adapter at hand,
iw list
can be used to establish if it is able to do act as an client and access point at the same time. As said in this question, you must look for thevalid interface combinations
part of theiw list
command.About the single 802.11 a/b/g/ac radio
Since 802.11 b/g/n uses 2.4 GHz and 802.11 a/ac uses 5 GHz, the adapter will need at least 2 phy, and will probably need to be configured as 2 separate access point, from the Linux point of view.
About the software
They are plenty of dedicated Linux distribution targeting small computers and WiFi routers, here are some examples:
All the previously listed distributions have their own flag on superuser.
About the WRT name
Interestingly, a lot of router-targeted Linux distributions contain the WRT word, since they started as an alternative firmware for the venerable LinkSys WRT54G.