The library can use different methods to measure the distance between devices:
Multi-carrier phase difference:
IFFT of spectrum
Average phase-slope estimation
It does also provide the following features:
TX power and RSSI for both the remote and the local devices
When using round-trip timing (RTT), the library measures the distance between nodes based on the transmission delay of the wave between them. Knowing the time it takes to transmit a message, the library can estimate the distance between the nodes.
Multi-carrier phase difference
When using multi-carrier phase ranging, the library measures the phase difference in RF signals between two devices as a function of the frequency. See the following example:
The initiator transmits a signal to the reflector.
The reflector measures the phase difference to its local reference.
The reflector transmits a signal back to the initiator on the same frequency.
The initiator measures the phase difference to its local reference.
The initiator and reflector jump to a new frequency and repeat the measurement.
The library then calculates the distance between devices based on the measured phase differences as a function of the frequency.