About Summary Table Data (GSM/EDGE/EDGE Evolution)

Menu Path: Trace > Data > Summary

The following subjects are discussed in this topic:

Averaging and Error Summary Data

When averaging is on, averaging is applied to the numeric error data in the Summary table with the following exceptions.

Averaging is not applied to TSC, Slot Index, or Time Offset.

These data results only support Peak Hold/Continuous Peak Hold averaging:

95% EVM accumulates results from scan to scan, even when averaging is off. The accumulation is done the same regardless of whether averaging is set to Off, RMS (Video), RMS (Video) Exponential, or Continuous Peak Hold.

For more information see Averaging with Digital Demodulation.

Error data from the current scan is not included in the average when any of these conditions exist:

Error Information at Symbol Times

All data results in the Summary trace except Phase Err and Mag Err are computed only at the symbol times (the instant in time when symbols are detected). The VSA does not use points taken between symbols when computing these data results.

In contrast, error traces (such as Error Vector Time, IQ Phase Error, and IQ Mag Error) display the error at the symbol times and at all points between symbols.

All Modulation Schemes are demodulated using one point per symbol except for GMSK, which is demodulated using 10 points per symbol.

Using Band Power markers to Calculate Error Information for a Specific Region

If IQ magnitude or phase error information is desired for points in a specific region, use the band-power markers on IQ Mag Error or IQ Phase Error.

For example, to compute the phase error for all points within a region. Click Trace > Data > Channel 1 > IQ Phase Error to display the IQ Phase Error trace, then click Markers > Calculation and select the Band Power check box to turn on the band-power markers.

Now position the band-power markers to select the region of interest and then click Markers > Calculation > Calculate and select Rms to display the phase error for the selected region in the marker readout.

At this point, simply click Trace > Data > IQ Mag Error to display the magnitude error for the same region since the band-power marker's region does not change when another trace is selected.

How EVM and Magnitude Error Data is calculated (%RMS)

On the Summary trace, the VSA displays the error-vector magnitude and magnitude error as a percentage. Before computing these data results, the VSA normalizes the measured I/Q and reference I/Q signals by the RMS average of the IQ Ref Time trace (which contains the ideal points for the demodulated Timeslot).

The VSA then computes the error-vector magnitude and magnitude error at each symbol time.

Next, the VSA takes the rms average of the error over all symbol times. For example, to compute the rms average for the magnitude error, the VSA takes the square root of the sum of the squares of the individual magnitude-error values at each symbol time.

Finally, the VSA shows the error vector magnitude and magnitude error on the Summary trace. Since the measured I/Q and reference I/Q signals have been normalized, the rms average of the error is expressed as a percentage.

The overall, percent error is computed only at the detection decision-points (symbol locations). Other points are not included in the calculation.

Points per Symbol and Summary trace calculations

In the GSM/EDGE/EDGE Evolution demodulator, all modulation schemes are analyzed using one point per symbol, except GMSK which is analyzed using 10 points per symbol. The number of Points / Symbol is fixed and cannot be changed as in Digital Demodulation.

Traces in the GSM/EDGE/EDGE Evolution demodulator display all points, but Summary Table measurements are always calculated using only the values at the symbol points.

Querying summary table data results programmatically

To programmatically query the Trace Summary Table data results using the Summary() and SummaryUnit() methods in the MeasurementData object.

See the How To Query Summary Table Data Results topic for more information.

See Also

Available Summary Table Data (GSM/EDGE/EDGE Evolution)