delay (path delay)

{
  "id": "MLC-T-CYB-001301",
  "term": "delay (path delay)",
  "field": "Cybersecurity",
  "definition": "The [signal] delay between a transmitter and a receiver. Path delay is often the largest contributor to time transfer uncertainty. For example, consider a radio signal broadcast over a 1000 km path. Since radio signals travel at the speed of light (with a delay of about 3.3 µs/km), we can calibrate the 1000 km path by estimating the path delay as 3.3 ms and applying a 3.3 ms correction to our measurement. Sophisticated time transfer systems, such as GPS, automatically correct for path delay. The absolute path delay is not important to frequency transfer systems because on-time pulses are not required, but variations in path delay still limit the frequency uncertainty.",
  "references": [
    "NISTIR 8323 [Superseded] from NIST T&F Glossary (Adapted); NIST IR 8323r1 from NIST T&F Glossary (adapted)",
    "NIST CSRC Glossary"
  ],
  "url": "https://mlchart.com/terminology/cybersecurity/delay-path-delay/"
}