How is a TROLPC Measurement Made?
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 in output power from the test set (+ or - 20 dB).
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 access terminal reacts by decreasing or increasing it 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, so the access terminal's response is determined solely by the open loop equation, and not influenced by closed loop power control (the alternating power control bits appear only as "ripple" on the measured trace).
The test set begins measuring the AT power as soon as the test set's source begins its transition to the new cell power setting (this transition is very rapid), and continues to measure power for the 100 ms 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. Data point 0 reports the average power from 0 ms to ~0.270 ms after the power transition. Data point 1 reports the average power from ~0.270 ms to ~0.540 ms, and so on, up to data point 370 which reports the average power from ~99.730 ms to 100 ms. (Each data point reports the average power over a period of ~270 µs, within the 1.23 MHz measurement bandwidth.)
Before the test set's source begins its transition, the test set begins sending alternating closed loop power control bits. The test set then transitions its source such that the power control bit sent at the power transition is opposite in direction to the transition (the bit sent at the power transition is an "up" bit when the cell power transition is -20 dB, and a "down" bit when the cell power transition is +20 dB).
The test set automatically ranges its measuring receiver to the maximum expected value from the AT as the test is performed.
When the measurement is complete, the test set returns closed loop power control to the mode it was set to before the measurement was initiated.
You must establish an RTAP (for Subtype 0 Physical Layer) or RETAP (for Subtype 2 Physical Layer) connection to perform the TROLPC measurement (see
Measuring Time Response of Open Loop Power Control (TROLPC)
for detailed procedure).
C.S0033 specifies that the R-ACK Channel is not transmitted by the access terminal for the test 4.3.2 Time Response of Open Loop Power Control. If the R-ACK Channel is transmitted during this test, the access terminal's power may fall outside of the mask specifications. To make your access terminal not transmit the R-Ack Channel, you should set ACK Channel Bit Fixed Mode Attribute (Rev TAP) (See
ACK Channel Bit Fixed Mode Attribute
for details.) to off and
AT Directed Packets
to 0% for this test.
No other measurements can be running while the TROLPC measurement is active. If any measurements are running, they are closed when TROLPC is initiated, and a message is displayed indicating that a measurement has been closed. Activating another measurement inactivates the TROLPC measurement.
TROLPC Measurement Parameters
TROLPC Measurement Results
-
Integrity Indicator - (see
Integrity Indicator
).
-
Pass/Fail: An overall pass/fail indicator is displayed on the measurement screen and is available via GPIB commands (see
FETCh:TROPower:MASK[:FAIL]?
). Fail is returned if the access terminal's power does not stay within the amplitude mask as defined in C.S0033 3.1.2.3.2 (see
4.3.2 Time Response of Open Loop Power Control
).
-
Power Versus Time Data Points: The 371 data points that describe the access terminal's power versus time behavior are available from the measurement screen marker, and via GPIB commands (see
FETCh:TROPower:TRACe?
).
-
First Fail Point: If the measurement result is "Fail," the measurement screen displays the first point that the access terminal output power crossed the amplitude mask.
The TROLPC Measurement Screen
The TROLPC measurement screen includes two softkeys to initiate the measurement for either a +20 dB or -20 dB step change (
Start Meas Up
(
F1
) or
Start Meas Down
(
F2
)). A graphical display is provided to show the measurement result, which you can navigate with the marker.
-
The y-axis on the graphical display is fixed at -5 dB to +30 dB. There are no polarity indicators on the y-axis, in accordance with the test standard specifications. All changes in mobile station output power are displayed as absolute values.
-
The x-axis on the graphical display is fixed from 0 ms to 100 ms.
-
The directions of cell power and access terminal power level changes are displayed in text above the grid.
-
The amplitude mask is displayed as green lines on the display. (The access terminal power trace is shown in yellow.)
-
The marker can be positioned on each of the 371 power versus time data points. The access terminal power level for that data point is then displayed.
Key C.S0033 Tests Performed using the TROLPC Measurement
Calibrating the TROLPC Measurement
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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