Power versus Time Measurement Description

How is a Power versus Time (PvT) measurement made?

PvT measurements determine if the mobile station's transmitter power falls within specified power and timing ranges. Refer to the Typical GSM PvT Measurement .

During a PvT measurement, the test set makes a narrowband point-by-point measurement of the instantaneous power received during the signal burst. The number of individual samples measured across the burst is 2220. A pass or fail result is returned based on a mask comparison (defined in "ETSI GSM 05.05 Ver 8.2.0, 7.2.0, 6.6.0 Annex B").

Included with the narrowband point-by-point measurement is a broad-band PvT carrier power measurement, labeled as Transmit Power on the Summary screen. The PvT Transmit Power measurement is synchronized to the burst midamble as recommended in 3GPP 51.010 (formerly ETSI GSM 11.10). (The test set also provides a faster transmit power measurement that is synchronized to the burst's amplitude. See Transmit Power Measurement Description ).

The dynamic range of the PvT measurement is approximately 70 dB.

This measurement conforms to 3Gpp 51.010 (formerly ETSI GSM 11.10), section 13.3. This is based on ETSI GSM 05.05 Ver 8.2.0, 7.2.0, 6.6.0 Annex B.

Types of Signals Power vs. Time Can Measure

The following list summarizes the input signal attributes and mobile station operating modes for which PvT can be measured with the test set.

1. Normal GSM TCH burst with mobile station in active cell mode.

2. Normal GSM TCH burst with mobile station in test mode (no protocol).

3. GSM RACH burst with valid midamble with mobile station in active cell mode.

Power vs. Time Input Signal Requirements

The PvT measurement will complete and meet the PvT measurement accuracy specifications when the signal meets the following input signal conditions.

1. Input signal level is between -15 dBm and +43 dBm.

2. Transmit power is within +/-3 dB of expected input level.

3. Input signal frequency is within +/-10 kHz of expected input frequency.

Trigger Source

Triggering choices available for the PvT measurement are RF rise, protocol, immediate, and auto. In most cases, auto triggering provides the optimum measurement triggering condition for the PvT measurement.

When auto triggering is selected, the test set chooses a trigger source based on the optimum trigger source available. For example, PvT measurements will automatically be triggered by a protocol trigger if a call is connected or call processing events provide the protocol trigger source.

In situations where no protocol trigger is available, the test set will choose RF rise triggering for the PvT measurement. An example of this situation might be when the test set is in test mode operating mode.

For more information on measurement triggering, refer to Triggering of Measurements .

Typical GSM PvT Measurement

Burst Synchronization

The PvT measurement provides you with a choice for the time reference setting (burst synchronization). (See Burst Synchronization of Measurements ).

Related Topics

Programming a Power versus Time Measurement

Test Adherence to Standards

Power versus Time Troubleshooting

Power versus Time Measurement Results

The primary result of a PvT measurement is the pass/fail result. The pass/fail result that the test set returns indicates whether the entire multislot configuration fell within power and timing ranges determined by a point-by-point comparison of the power versus time measurement mask.

The PvT measurement examines the multislot configuration to determine the points which have failed the most, or the points which are closest to failing the upper and lower limits. These worst case points provide the upper and lower limit margin results. A negative value, along with the offset time, is returned for the result if the multislot configuration fails the mask. A positive value indicates the multislot configuration is within the mask. The command FETCh:PVTime[:BURSt[1]]:MASK:ALL? FETCh:PVTime:BURSt2:MASK:ALL? is used to return these values for the burst you specify.

For statistical analysis, the test set allows you to set up to 12 time markers per burst. These markers do not define the mask, but are merely used to get results from specified points on the mask. To set these markers you use SETup:PVTime[:BURSt[1]]:TIME[:OFFSet][:SELected] SETup:PVTime:BURSt2:TIME[:OFFSet][:SELected] . Note that these points are a subset of those used in the point-by-point comparison which determines the pass/fail result.

The following lists show the results available for single measurements, multi-measurements and statistical measurements:

• Results for a single PvT measurement are listed below. Results one through four can be obtained using the query FETCh:PVTime[:BURSt[1]][:ALL]? FETCh:PVTime:BURSt2[:ALL]? . Results 5 through 8 can be obtained using the query FETCh:PVTime[:BURSt[1]]:MASK:ALL? FETCh:PVTime:BURSt2:MASK:ALL? .

  1. PvT measurement integrity indicator for each burst in the multislot configuration

  2. PvT multislot mask pass/fail result (0 = Pass, 1 & NaN = Fail)

  3. Transmit carrier power with midamble synchronization (average power during the burst) for each burst in the multislot configuration

  4. PvT maximum power at up to 12 time offsets

  5. PvT mask error code (this indicates which parts of the multislot configuration are causing failure). For more details on the mask error code result see FETCh:PVTime:MASK[:FAIL]:SEGment? .

  6. Upper limit timing margin worst case for each burst in the multislot configuration (the time offset where the signal came close to or exceeded upper timing limit)

  7. Upper limit power margin worst case for each burst in the multislot configuration (how close to or where the signal exceeded upper power limit)

  8. Lower limit timing margin worst case for each burst in the multislot configuration (the time offset where the signal came close to or exceeded lower timing limit)

  9. Lower limit power margin worst case for each burst in the multislot configuration (how close or where the signal exceeded lower power limit)

• In addition to the results you can obtain for a single measurement the following results are also available for multi-measurements . These results can be obtained using the query FETCh:PVTime[:BURSt[1]]:TXPower:ALL? FETCh:PVTime:BURSt2:TXPower:ALL?

  1. Average of transmit carrier power measurements (average of averages) for each burst in the multislot configuration

  2. Minimum transmit carrier power measured across each burst

  3. Maximum transmit carrier power measured across each burst

  4. Standard deviation of transmit carrier power measured across each burst

• Statistical PvT measurement results, calculated from measurements taken at each of the active time offset markers or across a subset of the markers and available only through programming commands are listed below. These results can be obtained using the FETCH:PVTime[:BURSt[1]]:POWer and FETCH:PVTime[:BURSt[2]]:POWer queries.

  1. Average Power (in dBc) measured at the marker(s) relative to transmit power (carrier power)

  2. Maximum power (in dBc) measured at the marker(s) relative to transmit power (carrier power)

  3. Minimum power (in dBc) measured at the marker(s) relative to transmit power (carrier power)

  4. Standard deviation of power (in dBc) measured at the marker(s) relative to transmit power (carrier power)

• The measurement integrity indicator is another result available for any completed PvT measurement. This result provides information about error conditions which occurred and may have affected the accuracy of the most recently completed measurement. For more information about measurement integrity, refer to Integrity Indicator .

• The measurement progress report is a feature that allows you to periodically see how far a multi-measurement cycle has progressed. When the multi-measurement count is greater than 1, the progress report indicates the number of individual sub-measurements that have been completed, n , out of the total number to be completed, m . "n" is referred to as ICOunt remotely. "m," the total number of measurements to be made, is based on the PvT settings you make and the input signal attributes.

  The progress report is displayed on the test set's screen in an "n of m" format. The number of measurements completed, n , increases from zero to the total number of measurements which need to be made, m .

Typical GPRS PvT Mask for a Two Burst Multislot Configuration