What's FHSS and the advantages ?

Frequency-hopping spread spectrum (FHSS) is a method of transmitting radio signals by rapidly changing the carrier frequency among many distinct frequencies occupying a large spectral band. The changes are controlled by a code known to both transmitter and receiver. FHSS is used to avoid interference, to prevent eavesdropping, and to enable code-devision multiple access (CDMA) communications.

The available frequency band is divided into smaller sub-bands. Signals rapidly change ("hop") their carrier frequencies among the center frequencies of these sub-bands in a predetermined order. Interference at a specific frequency will only affect the signal during a short interval.

FHSS offers three main advantages over a fixed-frequency transmission:

  • FHSS signals are highly resistant to narrowband interference because the signal hops to a different frequency band.
  • Signals are difficult to intercept if the frequency-hopping pattern is not known.
  • FHSS transmissions can share a frequency band with many types of conventional transmissions with minimal mutual interference. FHSS signals add minimal interference to narrowband communications, and vice versa.