What is the width of direct sequence spread spectrum (DSSS) channels and how far apart are their center frequencies spaced?

• A. 20 MHz wide and 5 MHz apart.
• B. 22 MHz wide and 5 MHz apart.
• C. 24 MHz wide and 2.5 MHz apart.
• D. 30 MHz wide and 10 MHz apart.

Answer: (B)

DSSS channels in the 2.4 GHz band occupy about 22 MHz of bandwidth, and the center frequencies are spaced in 5 MHz increments across the band. That means each channel sits roughly 11 MHz on either side of its center, so adjacent channels’ spectra overlap somewhat, which is why in practice we often use non-overlapping selections like channels separated by more than that overlap, such as choosing channels that are 25 MHz apart in center frequency to avoid interference. The pairing that matches these facts is a 22 MHz-wide channel with center frequencies 5 MHz apart.