About Channel Error Summary Data (1xEVDO)
When 1xEV-DO Demodulation is enabled, selecting the Chan 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 under About the Channel Symbol Table. The following information is discussed as listed:
These data results only apply to reverse link direction signals.
The following subjects are discussed in this topic:
- Available Channel Error Summary Data
- Selecting Chan Error Trace Data
- Averaging and Error Summary Data
- Using Band Power markers to limit Error information
- 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., Magnitude and Phase Error data results (%rms)
- .NET API 1) Access Preamble Indicator, or 2) Application Programming Interface Programming Information
Available Channel Error Summary Data
Available Channel Error Summary Data
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 1xEV-DO Demod Properties dialog box (tab) Despread-Channel Walsh Code Number and Walsh Code Length text boxes.
You can use the marker feature to automatically enter the , , and 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 averaging types. The slots (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 either 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 to display the IQ phase-error trace, then click and select the check box to turn on the band-power markers.
Now position the band-power markers to select the region of interest and select from the Calculate text box to display the phase error for the selected region.
At this point, you could simply click to display the magnitude error for the same region.
EVM, Magnitude and Phase Error data results (%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.
Because the magnitude of the constellation diagram's outer-most state has been normalized to one, the rms average is the overall, percent error.
Additional Error Summary Data
1xEV-DO Demodulation also provides these additional Error Summary Tables:
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
