What is Frequency Hopping Spread Spectrum (FHSS)?

Frequency Hopping Spread Spectrum

If there is anybody who hates the prospect of interceptions more than Peyton Manning or Tom Brady, it is anyone attempting to transmit radio signals and hoping to avoid narrow band interference and having their signals "picked off" the way a larcenous defensive back going for the pigskin does in a football game.

Keeping Your Transmission Safeguarded

If you want your radio signals to be less susceptible to interception, Frequency Hopping Spread Spectrum transmission is the way to go. Defined as "a means of transmitting radio signals by shifting a carrier across a number of channels with a pseudorandom sequence that the sending and receiving station knows beforehand," Frequency Hopping Spread Spectrum (FHSS) is employed as a multiple access process in the Frequency Hopping Code Division Multiple Access transmission scheme. Repeatedly switching frequencies when transmitting a radio signal makes it harder to jam or mess with that signal by any agent with potentially malicious intent.

The Benefits of FHSS

FHSS provides several clear-cut advantages. First, the likelihood of narrow band resistance is slim with FHSS because an interfering signal gets relegated to the background with the spread signal. Second, when a narrow band receiver detects FHSS signals, the signals give the appearance of an increased level of background noise, making their interception unlikely because the pseudorandom transmission hopping sequence has to be known. Military radars are harder to target with FHSS than radars on a single frequency. Third, FHSS transmission signals cause very little interference, maximizing the use of the bandwidth so they can share frequency bands with a number of other types of conventional transmissions.

Reflections, noise and other external factors in the environment have a minimal influence on this technology, which is well-suited for installations that cover large areas where several co-located systems might be required.

When the military uses the FHSS Algorithm, it uses cryptographic techniques that encrypt communications and generate the channel sequence to be used during the communications session.