Occupied Bandwidth
Occupied Bandwidth (OBW) refers to the portion of the spectrum that contains a defined percentage—typically 99%—of the total transmitted signal power. It is a key measurement in regulatory compliance for wireless devices to ensure efficient spectrum use and minimal interference.
Scope and Application
Occupied Bandwidth is used across various wireless technologies to characterize the spectral footprint of a signal. It is relevant in both unlicensed and licensed bands and is part of regulatory requirements in regions governed by ETSI, FCC, ISED, and others.
Typical use cases include:
Wi-Fi (2.4 GHz, 5 GHz, 6 GHz)
Bluetooth and other short-range devices
Licensed systems such as LTE, satellite, and fixed wireless
Definition and Measurement Conditions
Measurement Definition: OBW is the bandwidth within which 99% of the total mean power of the signal is contained, centered around the occupied carrier frequency. While 99% is the most common definition, some standards may use alternative thresholds (e.g., 70%) depending on the technology and application context.
Measurement Method: Measurements are typically performed using a spectrum analyzer with defined settings, such as a Gaussian or RMS detector and a resolution bandwidth of 30 kHz or less, depending on the standard. The signal’s power spectral density is integrated to determine the occupied range.
Relation to Bandwidth: OBW must not exceed the channel bandwidth declared by the manufacturer or permitted by the relevant standard.
Example:
If a Wi-Fi device operates on a 20 MHz channel, the measured OBW must typically be ≤ 20 MHz, depending on regional and normative constraints.
Certification and Compliance
Regulatory standards specify OBW as a required measurement:
FCC: OBW must be reported for devices under Part 15 (e.g., §15.247, §15.407)
ETSI: EN 300 328 and EN 301 893 require OBW measurements during emissions testing
ISED: RSS-247 includes OBW criteria for 2.4 GHz and 5 GHz devices
Non-conformance (e.g., exceeding the allowed OBW) can lead to rejection of test results or denial of market access.