gr-ntnisac: An Open GNU Radio Testbed for NTN-ISAC
gr-ntnisac is an open GNU Radio testbed that simulates a LEO satellite channel applied to a 5G New Radio downlink sent through two cabled USRPs. It scores the receiver's performance against commanded delay and Doppler values for every path. The tool helps compare simulation results with real hardware, revealing discrepancies between the emulator and actual system limitations.