Channel Error Summary Data (cdma2000/1xEV-DV)

When cdma2000/1xEV-DV demodulation is enabled, selecting the Syms/Errs trace data shows the symbol table and error summary trace data for the specified Walsh Code Number and Walsh Code Length. The bottom section of the display shows the symbol table data and the upper section shows the error summary data. This topic discusses the code channel error summary data, the Symbol Table trace data is discussed in the About the Channel Symbol Table topic.

This topic provides additional measurement and analysis information unique to Channel Error Summary trace data and cdma2000/1xEV-DV modulation analysis. This topic contains the following measurement, analysis and programming information:

Available Channel Error Summary Data
Selecting Chan Error Trace Data
Averaging and Error Summary Data
Using Band Power markers to limit Error information
How EVM Error vector magnitude (EVM): A quality metric in digital communication systems. See the EVM metric in the Error Summary Table topic in each demodulator for more information on how EVM is calculated for that modulation format. and Magnitude Error data results are calculated (%RMS)
.NET API 1) Access Preamble Indicator, or 2) Application Programming Interface Programming Information

Available Channel Error Summary Data

A list of the available channel error data is provided in the Available Channel Error Summary Data topic, which also links to detailed descriptions for each error result.

Selecting Chan Error Trace Data

The Chan Error Summary Data display shows the error data for the specified Walsh Code Number and Walsh Code Length. These parameters are entered in the Despread Channel Walsh Code Number and Walsh Code Length text boxes, located in the Channel/Layer tab of the cdma2000/1xEV-DV Demod Properties dialog box (MeasSetup > cdma2000/1xEV-DV Demod Properties > Channel/Layer tab).

Use the Copy Mkr to Despread Chan marker feature to automatically enter the Despread Channel Walsh Code Length, Walsh Code Channel and IQ Branch settings.

Averaging and Channel Error Summary Data

If averaging is on, averaging is applied to most numeric error data in the error Summary data with the following exceptions. The peak data values, such as peak EVM, peak Magnitude and peak Phase error are averaged only for the Peak Hold/Continuous Peak Hold averaging types. The PCG (or slot) number is never averaged. For more information see Averaging with Digital Demodulation.

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

CARRIER LOCK?
DATA? (if caused by a temporary condition like partial data record)

Using Band Power markers to limit Error information

If you want channel error information for all points over a selected region, you can use the band-power markers with an error trace.

For example, here's how you could compute the phase error for all points within a region. Click Trace > Data > Channel 1 Chan > 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 select Rms from the Calculate dropdown menu to display the phase error for the selected region.

At this point, simply click Trace > Data > Channel 1 Chan > IQ Mag Error to display the magnitude error for the same region.

How EVM and Magnitude Error data result are calculated (%RMS)

In the channel error summary data, the VSA shows the error-vector magnitude and magnitude error as a percentage. Before computing this percentage, the VSA normalizes the constellation diagram such that the outer-most, ideal states have a magnitude of one.

The VSA computes the overall, percent error by first computing the error-vector magnitude and magnitude error at each symbol time.

Next, the VSA derives the rms average for each parameter. 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.

Since the magnitude of the constellation diagram's outer-most state has been normalized to one, the rms average is the overall percent error.

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.