Error Vector Time (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. Symbol (time) and Subcarrier (frequency). There is a separate trace for each measurement channel. The Error Vector Time trace enables you to easily attain information about the signal modulation quality as a function of the OFDM symbols.
The Error Vector Time trace provides the following data results: the subcarrier EVM and the RMS average symbol EVM. The trace analysis data includes preamble and payload data including all Preamble, Pilot, and Data subcarriers for the measurement burst. Unused subcarriers are blanked and not included in the measurement analysis. There is also a plot (default white line) of the RMS average symbol EVM for each symbol in the measurement analysis.
| Marker Results | Description |
|---|---|
| specifies the marker OFDM symbol number. | |
| specifies the marker subcarrier index. | |
| 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 symbol EVM (%) result for the marker symbol. RMS Symbol EVM is the computed RMS average of the subcarrer-symbol EVMs for a particular OFDM symbol for all symbols within the measurement analysis region, see RMS Error Vector Time. |
Traces like Error Vector Time or All Subframes may show"0 Subframes" on the X-Axis, which is relative to the Subframe Offset value. Even though the axis shows Subframe 0, it is displaying the correct result for the Assigned Subframe, which may be non-zero depending on the Signal Radio Frame Offset and Analysis Region Subframe Offset settings.
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
