Limitedband

Limitedband is a term used in communications to describe systems that operate within a deliberately restricted frequency spectrum. The aim is to minimize interference, maximize spectrum efficiency, and comply with regulatory limits. The term can apply to both hardware and software controls that enforce a maximum channel bandwidth, as well as to signaling and coding schemes optimized for narrowband operation.

Technical characteristics: Typically, limitedband systems maintain a narrow spectral occupancy by using bandwidth-efficient modulation and tight filtering. Common approaches include frequency shift keying (FSK), phase shift keying (PSK), or quadrature phase shift keying (QPSK) at reduced symbol rates, coupled with emission masks that limit out-of-band leakage. Designers often implement duty-cycle controls and adaptive gain to meet licensed bandwidth allocations within a given frequency band.

Applications: Limitedband concepts appear in public safety radio, telemetry and remote sensing networks, and some Internet of Things deployments that require long range or low power. They are also favored in legacy links and satellite or terrestrial channels that must share spectrum with other services, where higher data rates are unnecessary or impractical.

Regulation and standards: Spectrum use for limitedband systems is governed by national authorities and international bodies such as the ITU, which define allocation, emission limits, and performance criteria. Compliance typically involves adherence to specified bandwidth caps, power limits, and interference margins.

History and development: The idea of limiting bandwidth arose from early radio engineering to cope with scarce spectrum. Advances in digital modulation and filtering have enabled more reliable narrowband communications without excessive spectral leakage.

See also: Narrowband, Bandwidth, Spectral efficiency, Modulation, Emission mask.