Error Vector Spectrum (Pre-5G)
Pre-5G trace shows the OFDM Orthogonal Frequency Division Multiplexing: OFDM employs multiple overlapping radio frequency carriers, each operating at a carefully chosen frequency that is Orthogonal to the others, to produce a transmission scheme that supports higher bit rates due to parallel channel operation. OFDM is an alternative tranmission scheme to DSSS and FHSS. symbol and subcarrier Error Vector Magnitude (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.) vs. subcarrier (frequency) and Symbol (time). There is separate trace for each measurement channel. The Error Vector Spectrum trace allows you to easily attain information about the signal modulation quality as a function of the subcarriers.
Error Vector Spectrum trace provides the following data results: the subcarrier EVM and the RMS average subcarrier EVM. Unused subcarriers are blanked and not included in the measurement analysis. There is also a plot (default White liner) of the RMS average subcarrier EVM for all subcarriers and symbols in the measurement analysis.
| Marker Results | Description |
|---|---|
| carrier | specifies the marker subcarrier index. |
| sym | specifies the marker OFDM symbol number. |
| This is the subcarrier EVM (%) result for the marker subcarrier. Subcarrier EVM is the EVM between the measured (IQ Meas) subcarrier vector and an ideal (IQ Ref) subcarrier vector. |
|
| This is the RMS subcarrier EVM (m%) result for the marker subcarrier. RMS Subcarrier EVM is the computed RMS average of the subcarrier EVMs at a particular subcarrier for all OFDM symbols in the measurement analysis region (see RMS Error Vector Spectrum trace data). |
You can limit the number of symbols included in the measurement analysis data results using the Result Length, Measurement Interval, and Measurement Offset parameters.
Trace Color coding Scheme
A multi-color coding scheme is used to make it easy to visually identify common symbols, subcarriers, and data results within various OFDM Traces. This makes cross trace data comparisons and analysis easy to accomplish. Different colors are assigned to symbols representing a common subcarrier type including: Preamble, Pilot, Data, and Null subcarrier types. Some common color scheme Traces include: Error Vector Spectrum, Error Vector Time, and IQ Meas trace data.
You can also customize and re-assign Trace colors schemes, see the Display Preferences Color tab (click tab and select a new color for the active Mod Type element).
See Also
