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Last updated: October 28, 2004
The TROLPC measurement is a power versus time measurement that analyzes the output power of a mobile station for the 100 ms period following an abrupt (step) change (+/- 20 dB) in output power from the test set.
This measurement is made while the mobile station is in a loopback connection at full data rate transmission (see Operating Considerations ).
When you initiate the test set's TROLPC measurement, cell power either increases or decreases by 20 dB depending upon whether you initiate an up or down step change. When the cell power changes, the mobile station reacts by decreasing or increasing its power, according to the open loop equation. The test set automatically sends alternating up and down closed loop power control bits while the measurement is executing (that is, the the Rvs Power Ctrl (reverse power control) mode is temporarily set to Alternating (up/down) bits), so the mobile station's response is determined solely by the open loop equation, and not influenced by closed loop power control. (On the TROLPC graph, the alternating power control bits appear only as "ripple" on the measured trace.)
Two softkey selections are provided for triggering TROLPC measurements:
When the F2 ( Start Meas Up
) or F3 ( Start Meas Down
) softkey is selected, the Cell Power
( F7 ) setting will automatically step up or down 20 dB. The START SINGLE hardkey will also begin a TROLPC measurement, defaulting to the last measurement choice of stepping up or down 20 dB.
As soon as the new cell power level is received by the mobile station, the test set begins measuring the mobile station output power and continues to measure power for the 100 ms period following the change in cell power . The test set measures power at 371 data points over the 100 ms following the step change in cell power. The test set will automatically range its measuring receiver to the expected value from the mobile station as the test is performed.
After the TROLPC measurement has completed, the test set returns closed loop power control to the mode it was set to before the measurement was initiated.
TROLPC test results include a pass/fail indication determined by the mobile station's conformance to test standard amplitude mask limits. If a TROLPC test fails, the display will show the first point that the trace crossed the amplitude mask. See TROLPC Measurement Results )
By standard definition the TROLPC test process consists of a series of measurements. Before these measurements are made, the Cell Power parameter is set to -60 dBm/1.23 MHz. Then, to test the mobile station over the operating range of interest, the following sequence of tests is performed:
Refer to Time Response of Open Loop Power Control for an example of the display after performing step 1 from the sequence above.
Pass/Fail limits are determined by comparing the mobile station response with an amplitude mask derived from the test standard TIA/EIA IS-98D, 4.4.2 Time Response of Open Loop Power Control. When analyzing the results of time response to open loop power control programmatically, a comparison between the trace (see FETCh:TROPower:TRACe? ) and the mask can be made using the following formula:
The upper pass/fail limit line is made up of three line segments. In the following formulas, p is mobile station power delta, in dB, and t is equal to time in milliseconds. Note: These formulas are derived from test standard TIA-EIA IS-98D and apply to a cell power step size of 20 dB only.
The lower pass/fail limit line is made up of one line segment and a curve. In the following formulas, let t1 equal:
The TROLP measurement meets or exceeds specifications when the following requirements are met:
The TROLPC measurement is automatically calibrated during a channel power calibration. Follow the channel power calibration schedule and the TROLPC measurement will be properly calibrated. Refer to Calibrating the Test Set for a description of channel power calibration.
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Measuring Time Response of Open Loop Power Control (TROLPC)
Programming a TROLP Measurement
Time Response of Open Loop Power Control (TROLPC) Troubleshooting
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