[nuand]

Cellphones are half duplex but the basestation is generally full-duplex. A half-duplex basestation could probably handle no more than one cellphone. OpenBTS and YateBTS, as well as most commercial basestations, have design patterns that require tight timing capabilites that in turn lend themselves to running on full-duplex basestations.

[danellis]

Ah, yes, you're right, of course. I don't know why I was thinking of the phone side. (You can use two HackRFs, though.)