Power versus Time Measurement Description

Power versus Time Measurement Description

Last updated: November 25, 2010

The Power versus Time Measurement is applicable to GSM/GPRS/EGPRS lab application and a test application with the required license.

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

PvT measurements determine if the mobile station's transmitter power stays within specified power and timing ranges. Refer to the Typical GSM PvT Measurement and Typical PvT Mask for a Two Burst Multislot Configuration .

During a PvT measurement, the test set makes a narrowband point-by-point measurement of the instantaneous power received during the signal burst as it varies across a single burst or up to six adjacent modulated TDMA bursts. The Burst Capture Range parameter determines the maximum number of TDMA bursts that the PvT measurement can measure. When the Burst Capture Range is set to Single , the PvT measurement can measure up to 2 adjacent modulated TDMA bursts. When the Burst Capture Range is set to All , the PvT measurement can measure up to 6 adjacent modulated TDMA bursts. A single pass or fail result is returned for the entire multislot configuration. This means that if any part of the multislot configuration fails the multislot mask, the result is a Fail. Additional information is provided to indicate which segments of the multislot configuration have failed.

Included with the narrowband measurement are broad-band carrier power measurements, labeled as Transmit Power on the Burst Numeric Results 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 ).

You can also control the modulation and coding scheme (either GMSK, 8PSK or 16QAM modulation) used by the data connection to be measured using CALL:(PDTCH|PDTChannel):MCSCheme . Additionally, you can manually control what modulation should be expected for individual bursts using CALL:MODulation[:FORMat]:CONTrol:AUTO . See Modulation Format Control (EGPRS only) for more information.

This measurement conforms to ETSI GSM 05.05 (Ver 8.2.0, 7.2.0, 6.6.0), section 4.5 and Annex B. It will also conform with 3GPP 51.010 (formerly ETSI GSM 11.10) if used as part of a type approval system.

Types of Signals Power vs. Time Can Measure

The following list summarizes the input signal attributes for making PvT measurements.

  1. A Single normal burst, or up to 2 normal bursts when Burst Capture Range is set to Single.
  2. A Single normal burst, or up to 6 normal bursts when Burst Capture Range is set to All.

  3. GSM RACH burst when Burst Capture Range is set to Single.

  4. CW signals.

For details on the multislot configurations which the test set supports, see CALL:(PDTCH|PDTChannel):MSLot:CONFig .

Typical GSM PvT Measurement

Typical PvT Mask for a Two Burst Multislot Configuration

Operating Consideration

You can perform the PvT measurement in all operating modes except Cell Off and Fast Device Tune . However, you must set the modulation format and the expected power correctly in order to get the accurate power result of the measured bursts. See "Expected Power Control" on page 6 and "Modulation Format Control (EGPRS only)" on page 10 to find how to set the modulation format and the expected power.

In the Active Cell mode, the test set automatically passes the Training Sequence Code (TSC) to the measurement with no action required by you. However, you must specify the TSC manually in the test mode.

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

Power vs. Time Parameters

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 falls 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? and FETCh:PVTime:BURSt2|3|4|5|6:MASK:ALL? are 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 can use SETup:PVTime[:BURSt[1]]:TIME[:OFFSet][:SELected] and SETup:PVTime:BURSt2|3|4|5|6: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 Power versus Time measurement allows you to use the ETSI mask specification or define up to two custom masks of your own. For more information refer to Mask Type .

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

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 +37 dBm for GMSK modulated signal.
  2. Input signal level is between -15 dBm and +33 dBm for 8PSK modulated signal.
  3. Input signal level is between -15 dBm and +30 dBm for 16QAM modulated signal.
  4. Input signal level is within +/-3 dB of expected input level.

Related Topics

How Do I Make a Power Versus Time Measurement?

Programming a Power versus Time Measurement

Test Adherence to Standards

Power versus Time Troubleshooting