Multilateration with TOA using lowcost transceivers (like NRF24L01) and uCs
Why does everyone try to do this digitally with modules NOT designed for precision timing? 

Think mixers, filters and oscillators, not computer datacomms, there will probably be a computer in there somewhere but the high speed timing and phase shift measurement should be in hardware.

I would be looking at modules from MiniCircuits not Nordic.