Occupied Bandwidth (OBW) Measurement Description
Last updated: January 16, 2009
How is the occupied bandwidth measurement made?
As defined by 3GPP TS 34.121 section 5.8 Occupied Bandwidth (OBW) is the bandwidth containing 99% of the total integrated power of the transmitted spectrum, centered on the assigned channel frequency. The test set allows the percentage of total integrated power to be adjusted from 70.0 to 99.0%.
During this measurement, a Gaussian filter with a bandwidth greater than 10MHz and a resolution bandwidth (RBW) of 30 kHz or less is used to measure the distribution of the power spectrum.
First, the total power found in the measured frequency range is calculated. Then, starting at the lowest frequency in the range and moving upward, the power distributed in each frequency is summed until this sum is 0.5% of the total power. This gives the lower frequency value. Next, starting at the highest frequency in the range and moving downward, the power distributed in each frequency is summed until 0.5% of the total power is reached. This gives the upper frequency value. The bandwidth between the 0.5% power frequency points is the occupied bandwidth.
Input Signal Requirements
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For this measurement the test set's receiver uses autoranging to adjust for the level of the signal being measured; therefore the expected signal level does not need to be specified during measurement setup.
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The frequency of the signal being measured must be in the range of 800 MHz to 1000 MHz, or from 1700 MHz to 1990 MHz.
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The level into the test set's RF IN/OUT connector must be in the range of +5 dBm to +28 dBm, in a 3.84 MHz bandwidth.
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The uplink must be of constant in-channel power for the duration of this measurement. This requirement has implications for correct power control configuration, and uplink dynamics in HSDPA and HSUPA.
Trigger Source
The trigger source defaults to
Auto
and tries to use protocol triggering if the UE is synchronized to the test set. Immediate triggering is used if the UE is not synchronized.
If you want to measure the occupied bandwidth for a specific timeslot, use the trigger delay parameter.
Measurement Calibration
This measurement should be calibrated using the Calibrate Measurements function (see
CALibration:MEASurements?
) when the temperature has changed by ± 10° C or more since the last calibration. If this situation exists, the integrity indicator value is changed to 19 and a message is displayed indicating "Uncalibrated Due to Temperature".
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