The library can use different methods to measure the distance between devices:

  • Round-trip timing

  • Multi-carrier phase difference:

    • IFFT of spectrum

    • Average phase-slope estimation

    • Friis-path-loss formula

  • Link loss

It does also provide the following features:

  • Quality indicator

  • TX power and RSSI for both the remote and the local devices

Round-trip timing

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:

  1. The initiator transmits a signal to the reflector.

  2. The reflector measures the phase difference to its local reference.

  3. The reflector transmits a signal back to the initiator on the same frequency.

  4. The initiator measures the phase difference to its local reference.

  5. The initiator and reflector jump to a new frequency and repeat the measurement.

  6. The library then calculates the distance between devices based on the measured phase differences as a function of the frequency.