What is OBW?
OBW (Occupied Bandwidth) is a spectrum measurement that defines the frequency bandwidth containing 99% of the total integrated mean power of the transmitted signal, centred on the assigned channel frequency. OBW is a mandatory RF conformance parameter for both 5G NR base stations and user equipment, ensuring that transmitters confine their emissions within the allocated spectrum and do not spread energy beyond their authorised bandwidth.
How Does OBW Work?
OBW is measured by computing the power spectral density of the transmitted signal and then finding the frequency span that contains 99% of the total signal power (0.5% of the power lies below the lower frequency limit and 0.5% above the upper limit). The measurement is performed using a signal analyser with sufficient span and resolution bandwidth. For 5G NR, the OBW must not exceed the channel bandwidth — for example, a 100 MHz NR carrier should have an OBW of less than 100 MHz. OBW is related to but distinct from SEM (Spectrum Emission Mask) and ACLR, which measure out-of-band emissions rather than total signal containment.
Use Cases
5G NR transmitter conformance testing, spectrum utilisation efficiency assessment, regulatory compliance verification, manufacturing quality control, and interference investigation.
3GPP / Standards Reference
3GPP TS 38.104 (NR BS radio transmission — occupied bandwidth), 3GPP TS 38.101 (NR UE radio transmission), ITU-R SM.443 (Bandwidth measurement at monitoring stations)
Related Terms
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This glossary entry is part of the 5GWorldPro Complete 5G Glossary. To go deeper into 5G architecture and technology, explore our 5G Training courses.
