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Frequency hopping spread spectrum (FHSS) is a method of transmitting radio signals by shifting carriers across numerous channels with pseudorandom sequence which is already known to the sender and receiver.
Frequency hopping spread spectrum is defined in the 2.4 GHz band and operates in around 79 frequencies ranging from 2.402 GHz to 2.480 GHz. Every frequency is GFSK modulated with channel width of 1MHz and rates defined as 1 Mbps and 2 Mbps respectively.
Frequency hopping spread spectrum is a robust technology with only very little influence from reflections, noise and other environmental factors. The active system numbers in same geographical areas is higher than an equivalent number for direct sequence spread spectrum systems. Thus it is suited well for installations designed to cover large areas where numerous co-located systems are needed. They are also used in cellular deployments for fixed broadband wireless access where direct sequence spread spectrum cannot be used. 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.