Definition - What does Guard Band mean?
A guard band is a narrow frequency range that separates two ranges of wider frequency. This ensures that simultaneously used communication channels do not experience interference, which would result in decreased quality for both transmissions.
Guard bands are used in frequency division multiplexing (FDM).
Techopedia explains Guard Band
A spectrum's unused portion is intended to prevent crosstalk, or noise or interference from other modulated signals on the same transmission medium, such as AM or FM radio.
The guard band concept applies to wired and wireless communications. It also simplifies the process of signal filtering for hardware, software or both.