Narrowband

Narrowband is a term used in telecommunications to describe signals or channels that occupy a relatively small portion of the spectrum around a carrier frequency. It is used for both analog and digital communications and is contrasted with broadband, where signals cover wide spectral ranges. In practice, narrowband bandwidths are typically on the order of a few hertz to a few tens of kilohertz, depending on regulatory definitions and the application.

Narrowband systems generally enable simpler and cheaper receivers and filters, and can achieve longer range or lower power for the same data rate. They often exhibit good selectivity in crowded bands and facilitate efficient channelization. Limitations include relatively low data throughput and capacity compared to broadband systems, and vulnerability to narrowband interference and coexistence issues with nearby channels.

Common applications include land-mobile radio and professional two-way communications (public safety, utilities, transit), where channel spacing of 12.5 kHz or 25 kHz is common in VHF/UHF bands. Narrowband digital technologies, such as NB-IoT, use narrow carrier bandwidths (e.g., 180 kHz) to enable long-range, low-power data transmission for the Internet of Things. In audio, narrowband is sometimes used to describe low-deviation or speech-focused modulation schemes, in contrast with wideband or full-band approaches. The term ultra-narrowband is used for even tighter spectral confinement in certain sensor networks.