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What is Frequency Hopping Spread Spectrum


What is Frequency Hopping Spread Spectrum

What is Frequency Hopping Spread Spectrum

Frequency-hopping spread spectrum (FHSS) is a method of transmitting radio signals by rapidly switching a carrier among many frequency channels, using a pseudorandom sequence known to both transmitter and receiver. ... Signals rapidly change ("hop") among these in a predetermined order.

As the name implies, FHSS works by quickly moving from one frequency to another according to a psuedorandom pattern.The frequency range used by the frequency hop is relatively large (83.5 MHz), providing excellent protection from interference.The amount of time spent on any given frequency is known as dwell time and the amount of time it takes to move from one frequency to another is known as hop time.

FHSS devices begin their transmission on one frequency and move to other frequencies according to a pre-defined psuedorandom sequence and then repeat the sequence after reaching the final frequency in the pattern. Hop time is usually very short (200 to 300 µs) and not significant relative to the dwell time (100 to 200 ms). In general, the longer the dwell time, the greater the throughput and the more susceptible the transmission is to narrowband interference.

The frequency hopping sequence creates a channel, allowing multiple channels to coexist in the same frequency range without interfering with each other.

A variation of frequency hopping spread spectrum is adaptive frequency hopping spread spectrum that improves resistance to radio frequency interference by avoiding crowded frequency in hopping sequence.

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