Frequency-hopping spread spectrum

Frequency-hopping spread spectrum (FHSS) is a method of transmitting radio signals by rapidly changing the carrier frequency among many frequencies occupying a large spectral band. The changes are controlled by a code known to both <a href="/facts/Transmitter/nFYghtKv">transmitter</a> and <a href="/facts/Receiver_(radio)/5olDTxkg">receiver</a>. FHSS is used to avoid interference, to prevent eavesdropping, and to enable <a href="/facts/Code-division_multiple_access/o2RLKE4M">code-division multiple access</a> (CDMA) communications.
The 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 determined order. Interference at a specific frequency will affect the signal only during a short interval.
FHSS offers four main advantages over a fixed-frequency transmission:

<ol><li>FHSS signals are highly resistant to <a href="/facts/Narrowband/76nBsRml">narrowband</a> <a href="/facts/Interference_(communication)/BVce5g8d">interference</a> because the signal hops to a different frequency band.</li>
<li>Signals are difficult to intercept if the frequency-hopping pattern is not known.</li>
<li>Jamming is also difficult if the pattern is unknown; the signal can be jammed only for a single hopping period if the spreading sequence is unknown.</li>
<li>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.</li></ol>

Frequency-hopping spread spectrum open-in-new

Frequency-hopping spread spectrum