RMS Error Vector Spectrum (5G NR/5G-Advanced)

There are two types of traces in the Trace > Data > Demod and MIMO Multiple Input, Multiple Output: A physical layer (PHY) configuration in which both transmitter and receiver use multiple antennas. menus that display component carrier data: CCn (component carrier is fixed), and Selected Display CC (component carrier is dynamically selected using the Display parameter). See About Per-Carrier Trace Types for more information.

RMS Error Vector Spectrum is a plot of the "RMS subcarrier EVM" data results for the component carrier. The results provide a single overlaid line per active numerology. When multiple overlaid lines are visible, they are distinguished by color as well as marker annotation, and support per-trace filtering behavior. This trace uses units specified by “Error Vector Freq unit”.

In VSA version 2020 Update 1, the RMS Error Vector Spectrum and RMS Error Vector Time traces were redesigned and improved to support multiple numerologies in separate layers. The legacy traces have been deprecated, but they are still available for compatibility when using pre-2020 Update 1 setup files or API 1) Access Preamble Indicator, or 2) Application Programming Interface code. To quickly distinguish if you are viewing the deprecated trace or the newly improved trace, the legacy traces are titled "RMS Err Vect Spectrum" and "RMS Err Vect Time," and the improved traces are titled "RMS Error Vector Spectrum" and "RMS Error Vector Time," respectively.

This trace does not participate in Measurement averaging.

The results generally map to the average line presented on the Error Vector Spectrum trace.

The results are always RMS averaged of the Error Vector Spectrum results (independent of the Average selection for the Measurement).

When more than one carrier is defined in the Aggregation Table, "(CCn)" will appear in the title of this trace, where "n" is the number of the component carrier whose data is displayed in the trace. Select the desired component carrier number using the Configuration > Carriers > Display parameter.

Trace Annotation	Description
xRMS: n	Indicates the maximum number of active time intervals included in any of the frequency domain points in the trace. The complex OFDMA allocations in 5G NR means there is not typically a uniform layout of active symbols/subcarriers. We allow disabling different physical channels to provide a more restricted Error Vector measurement (which makes the allocations even more sparse). We have Error Vector units for Frequency and Time, which determines the subcarriers and symbols that are used for the measurement. Performing an RMS calculation across “time” dimension for each element in the “frequency” dimension leads to a different number of active elements included in each RMS calculation. The largest count is shown as “xRMS:”

Trace Annotation

Description

xRMS: n

Indicates the maximum number of active time intervals included in any of the frequency domain points in the trace.

The complex OFDMA allocations in 5G NR means there is not typically a uniform layout of active symbols/subcarriers.
We allow disabling different physical channels to provide a more restricted Error Vector measurement (which makes the allocations even more sparse).
We have Error Vector units for Frequency and Time, which determines the subcarriers and symbols that are used for the measurement.
Performing an RMS calculation across “time” dimension for each element in the “frequency” dimension leads to a different number of active elements included in each RMS calculation. The largest count is shown as “xRMS:”