Error Vect vs. Sample (Sym overlay) (Custom OFDM)

Error Vect vs. Sample (Sym overlay) trace shows the value of the error vector for each point in the pre-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. time grid (sample x OFDM symbol). The value shown is usually 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., but you can also choose other Trace Formats.

Each location on the x-axis corresponds to a sample in the OFDM symbol's time data (the data before the FFT Fast Fourier Transform: A mathematical operation performed on a time-domain signal to yield the individual spectral components that constitute the signal. See Spectrum. is performed). When Measurement Interval is greater than 1 symbol, the points for all symbols are overlaid on each sample location. For example, when there are 10 symbols in the Measurement Interval, there would be 10 points overlaid on each sample location.

This trace allows you to see the performance of individual samples within an OFDM symbol, rather than just the performance of whole OFDM symbols as in the Error Vect vs. Sym (Carrier overlay) trace.

In addition to the individual points drawn on the trace, there is an average line (white by default) that shows the RMS average for each x-axis location (over all z-axis points for that x-axis location).

This trace is computed from the input to the N-point FFT, as compared to the other Error Vect traces. See Error Vect vs. Sym (Carrier overlay) for a diagram, and notice the N-point FFT block ("N-FFT").

To see the Error Vector data for the points after the FFT is performed, use the Error Vect vs. Carrier (Sym overlay) trace.