Modulation accuracy is a measure of how much a real 8PSK or 16QAM modulated signal differs from an ideal 8PSK or 16QAM signal carrying the same information.This measurement is used to measure the modulation accuracy of an 8PSK or 16QAM modulated signal in a single timeslot. For multiple uplink multislot configurations, bursts are measured from a single timeslot that you specify.
The measurement assumes that the specified burst in the multislot configuration is 8PSK or 16QAM modulated, but it is tolerant of occasional GMSK bursts present in the signal. In real mobile calls, GMSK bursts carrying control information occur during an 8PSK or 16QAM data transmission. If the specified burst is found to be GMSK modulated, it is discarded and the measurement is re-armed. This will result in an apparent increase in measurement time.
You can measure one of up to 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 most important measurements returned are Error Vector Magnitude (Peak and RMS), Frequency Error, Origin Offset Suppression, and 95th Percentile EVM. The AM-PM timing offset result for a polar modulation is returned when the AM-PM Timing Offset Calculate State is set to ON,
The measurement must know the training sequence code (TSC) to be able to synchronize to the burst's midamble. In an active cell mode, this information is received from the protocol processor. When using a test mode, you must manually specify the TSC using the CALL:BURSt:TYPE command (see
for more information) or from the front panel by accessing the
screen and selecting the
The modulation accuracy measurement does not trigger unless an uplink burst using 8PSK or 16QAM modulation is present. You can control the modulation and coding scheme (either 8PSK, 16QAM 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. If the test set is not configured properly, the measurement returns an "Unsupported Configuration" integrity indicator.The affected test set configuration parameters are:
Active Cell (EGPRS)operating mode.