FH-PHY – Frequency Hopping Physical Layer
The Frequency Hopping Physical Layer was developed for IEEE 802.11 to enable multiple networks to coexist in the same frequency band yet minimize the effect of interference. The system operates by switching the frequency upon which data is transmitted in a pseudorandom manner. Hence the term Frequency Hopping. Should one frequency suffer from interference, it will only effect a very small percentage of the total information since that frequency will only be utilised occasionally in the hopping sequence. To support frequency hopping, the 2.4GHz ISM (Industrial Scientific and Medical) band is divided into 95 channels, each separated by 1MHz. Unfortunately these channels may not all be available, as different regulatory bodies have allocated different portions of the ISM band.
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