Getting Started : "LTE/NR5G EVM Measurement"

This getting started presents an example of LTE / NR5G waveform generation and measurement settings to achieve EVM measurements.

This getting started will be focussed on NR5G waveforms.

To run LTE and/or 5G-NR module in IQSTAR Matlab Runtim (MCR) version R2022b (9.13) is mandatory. Matlab Runtime installer can be install from https://fr.mathworks.com/products/compiler/matlab-runtime.html. If the Matlab Run Time is not installed following error message will appear:



1) Waveform generation / optimization

Standard NR5G waveforms have a lot of points and are very ressources consuming. In a case where DPD is enabled, waveforms needs to be oversampled :

Generated waveform is around 5 millions points with a classic configuration of 10 Sub-frames. To reduce the number of points of the waveform without decreasing the EVM accuracy, the number of subframes can be reduced. The following graph is showing the impact of the number of subframes on the EVM :

Reducing the number of subframes doesn't change the value of the EVM. The new waveform has now less than 500 000 points:

To achieve good results on ACP measurements, Low-Pass Filter need to be used. As shown with the figure below, ACPR are improved and EVM has not been significatively decreased:

Another source of EVM during the waveform generation is the Crest Factor Reduction. As shown below, as the PAPR of the waveform is reduced, the EVM will be increased. In the case of this example, we will work with a waveform of 8 dB of PAPR.


The final waveform is now the following :

2) IQ Settings for EVM Measurements

IQSTAR IQ tab enables EVM Measurements with generated waveforms from Waveform Generator. For LTE / 5G waveforms, IQSTAR allows to measure and compute only a few part of the generated waveform (at least one sub-frame) to improve measurement speed without decreasing results quality.



This guide was done with a FSW Spectrum Analyser. An advanced option enables the custom driver Auto-Level which achieve to faster results with better EVM compared to R&S Auto-Level, and comparables EVM to R&S EVM options.

With this setup, measurements will be fast enough to perfom some power / frequency sweep without any issues and loss of accuracy. One thing to consider is to have a computer enough powerfull to handle a big amount of datas.

During the measurement, EVM datas are available throught the real time viewer such as Constellation, EVM vs Sub-carrier, EVM vs Symbol, EVM vs Ressource bloc:



Post-Measurement Demodulation

Selecting "Perform waveform demodulation" allows to demodulate "PSK / QAM / LTE / 5GNR" waveforms in real time during measurement, making the measurement time longer.

If the "Perform waveform demodulation" is disabled, thanks to the Whiteboard or the I/Q viewer, it possible to demodulate waveforms post measurement.