CCNA Wireless 640-722 Official Cert Guide

FHSS

Early wireless LAN technology took a novel approach as a compromise between avoiding RF interference and needing complex modulation. The wireless band was divided into 79 channels or fewer, with each channel being 1 MHz wide. To avoid narrowband interference, where an interfering signal would affect only a few channels at a time, transmissions would need to continuously “hop” between frequencies all across the band. This is known as frequency-hopping spread spectrum.

Figure 1-25 shows an example of how the FHSS technique works, where the sequence begins on channel 2, then moves to channels 25, 64, 10, 45, and so on, through an entire predetermined sequence before repeating again. Hopping between channels has to occur at regular intervals ...