I would say this guide is a good place to start. However, this is assuming when you say "wifi-like" you mean very similar to authentication using WPA2.
Cracking WPA2 is a little more complex than WEP, for example. The initialization code for WPA2 uses a four-way handshake to properly initialize all of the vectors that are used in the actual encrypting. So in order to properly break it you need to sniff the traffic that gets sent back and forth during a session initialization. However, because this is a WiFi it's not uncommon for packets to not be sniffed properly. So you should be aware that you may have to initialize the connection more than one time. Again, see the link I posted.
As for not knowing the carrier frequency there are a few ways to approach the issue. As the link pointed out they suggest getting an antenna. This is the best option when you're doing anything with WiFi. However, if you have reason to believe the access point is on a standard frequency discovering it could be as simple as an App on a smartphone to search for networks. But if you're doing this with any kind of frequency you should get an antenna and look for some guides on how to interact with it; they're all over the place.
Another approach would be to look at the client. Since you asked this question on an RE forum I'm assuming you have access to at least one of the access points so you can attack it from that angle and try to trace what happens when the connection is initiated.