How is a phase and frequency error (PFER) measurement made?
The PFER measurement performs a narrow-band (<200 kHz) measurement of the modulation quality and frequency accuracy of the mobile station's transmitter. The test set measures frequency error, rms phase error and peak phase error over the useful part of the burst.
The PFER measurement demodulates the data and compares the measured wave form with the "ideal" waveform that was expected for the data received. The frequency error is the difference in frequency, after adjustment for the effect of the modulation and phase error, between the RF transmission from the mobile station and the test set. The phase error is the difference in phase, after adjustment for the effect of the frequency error, between the mobile station and the theoretical "ideal" transmission. This measurement conforms to ETSI GSM 05.05; and ETSI GSM 11.10, section 13.1.
The PFER measurement demodulates the guard bits according to the Tail Bit Demodulation parameter setting. This parameter determines how the PFER measurement performs demodulation on the guard bits, which in turn impacts the demodulation of the tail bits. For details on the settings available for this parameter, see
SETup:PFERror:TBDemod
.
You can measure one of the six adjacent uplink bursts of the multislot configuration at any one time. You can specify the burst to measure using
CALL:(PDTCH|PDTChannel):MSLot:MEASurement:BURSt
. The relative power level is within 30dB according the data sheet.
For GPRS mobiles, this measurement conforms to ETSI GSM 05.05 (Ver 8.2.0, 7.2.0, 6.6.0), section 4.6.1. It also conforms with 3GPP 51.010 (formerly ETSI GSM 11.10) if used as part of a type approval system.
For EGPRS mobiles, the Phase and Frequency Error measurement conforms to 3GPP 51.010 (formerly ETSI GSM 11.10), section 13.16.1. You can control the modulation and coding scheme (either 8PSK or GMSK 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.
The PFER measurement is controlled by the DSP in the test set. No calibration is required by the user, the DSP gets calibration information during test set power up. PFER measurements can be initiated with any measurement made by the test set.
Single or Multi-Measurements
The DSP demodulates the data and compares the measured waveform with the "ideal" waveform created by the DSP.
A single burst for a PFER measurement calculates the following:
-
peak phase error
-
rms phase error
-
frequency error
A multiple burst PFER measurement is made when the multi-measurement state is on and calculates the maximum, minimum and average values for the following:
-
peak phase error
-
rms phase error
-
frequency error
-
worst frequency error (worst frequency error is the frequency furthest from zero.)
All of these results are available using the FETCh command. If the most positive and the most negative frequency error are the same value, the most positive frequency will be returned. Worst frequency error is only accessible through GPIB. The test set always has an integrity indicator available regardless of whether it is a single or multiple burst measurement.
Types of Signals PFER can Measure
PFER measurements can be made on these types of input signals.
-
Normal GSM TCH or GPRS PDTCH burst with mobile station in active cell mode.
-
Normal EGPRS PDTCH burst when the operating mode is set to active cell mode and the serving cell is set to EGPRS.
-
Access (RACH) burst with mobile station in active cell mode.
-
Normal GSM TCH or GPRS PDTCH burst with mobile station in test mode.
-
Normal EGPRS PDTCH burst when the operating mode is set to EGPRS BCH+PDTCH.
-
Access (RACH) burst with mobile station in test mode.
-
Bursted signal with GMSK modulation without a valid midamble.
Input Signal Requirements
The PFER measurement will complete and meet its accuracy specification of:
-
Frequency error measurement accuracy of +/-12 Hz + timebase reference (+/-18 Hz for RACH bursts).
-
rms phase error measurement accuracy of less than +/-1 degree.
-
Peak phase error measurement accuracy of less than +/-4 degrees.
under these conditions:
-
Level is between -15 dBm and +43 dBm.
-
Level within +/-3 dB of the expected input level.
-
Frequency is within +/-100 kHz of expected input frequency when serving cell is set to GSM or GPRS. The capture range is +/-1 kHz when the serving cell is set to EGPRS. See
Serving Cell
for more information about the different serving cells.
Trigger Source
Auto triggering is the recommended trigger source for each measurement allowing the test set to choose the preferred trigger source. However, you may want to select the trigger source. Immediate trigger source is not recommended for PFER measurements.
Recommended Trigger Source settings
|
Input Signal Type
|
Recommended Trigger Source |
|
Normal GSM TCH or GPRS PDTCH burst with mobile station in active cell mode
|
Protocol or RF Rise |
|
Normal EGPRS PDTCH burst with mobile station in active cell mode and modulation coding scheme set to MCS1, MCS2, MCS3, or MCS4
|
Protocol or RF Rise |
|
RACH burst with mobile station in active cell mode (GSM only) |
Protocol or RF Rise |
|
Normal GSM TCH or GPRS PDTCH burst with mobile station in test mode
|
RF Rise |
|
Normal EGPRS PDTCH burst with mobile station in test mode and modulation coding scheme set to MCS1, MCS2, MCS3, or MCS4
|
RF Rise |
|
RACH burst with mobile station in test mode (GSM only)
|
RF Rise
|
|
Bursted signal with GMSK modulation but no valid midamble
|
RF Rise |
|
Non-bursted (CW) signal with a manual frequency offset of +/- 67.7083 kHz
|
Immediate |
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