Troubleshooting (5G NR/5G-Advanced)

Trace displays CARRIER LOCK? indicator

Part or all of the component carrier may be outside the measurement span. When the CARRIER LOCK? indicator is visible, the component carrier is not included in the measurement.

If the occupied bandwidth of the component carrier does not fit within the selected span, adjust the Carrier Center frequency or Freq. Offset, or adjust the occupied bandwidth size using the component carrier's Bandwidth settings.

3D trace(s) not rendering correctly

The VSA software requires a video card and driver that support OpenGL 2.1 or higher for rendering of 3D trace data.

Make sure your video card and driver support OpenGL 2.1 or higher.

PUSCH/PDSCH Demodulation fails with multiple antenna ports

If there is no other channel used for synchronization (e.g., SSB), the PUSCH reference antenna port / PDSCH reference antenna port must be active on the reference input channel because it is used for the initial synchronization.

Make sure the reference antenna port is active on the reference input channel.

Missing measurement data in trace

The set of physical channels contributing to the Channel Frequency Response depends on the measurement configuration.

Check that measurement region includes the desired physical channel allocation definition.

Trace filtering may be incorrectly applied.

Check that trace filtering includes the expected physical channel definition (Trace > Digital Demod > Filtered Channel Types).

Modulation Analysis fails for PDSCH, with zero PDSCH-DMRS resources listed

The generated signal may have an invalid configuration. For example, some PDSCH Physical Downlink Shared Channel scenarios require the use of DMRS Mapping Type B (according to the standard). If DMRS Mapping Type A is used for the generated signal, the generated signal is left without PDSCH-DMRS when the analysis configuration expects to see it.

Verify the Slot Format, First Symbol, Last Symbol and X Symbols parameters are consistent with the DMRS settings for PDSCH. See TS Technical Specification 38.214 5.1.2.1 for specified interaction of these parameters in defining a valid signal.

Unexpected empty or different trace

"Layer1" was removed from the data names of the following traces to reflect multilayer trace support starting in VSA 2018 Update 1.0:

• OFDM Meas
• OFDM Ref
• Error Vector Spectrum
• Error Vector Time

• Detected Allocations Time

For some traces, the layout of the Y data array was also changed, which may affect automation code that retrieves and post-process the vector data.

Re-save the .setx file after mapping the desired trace, or edit automation code to use the new DataName.

Unexpected measurement results with N7631C Signal Studio generated signals using PDSCH puncture

The signal was generated using a version of N7631C prior to 1.1.8.0.

Try one of the two possible solutions:

• Update the N7631C Signal Studio software to version 1.1.8.0 (or newer).
• Use a side-by-side installation of VSA 2018 to make the measurement.

Unexpected high EVM in some symbols when multiple numerologies are defined

If a measurement is attempted with multiple numerologies present within the same symbol, the configuration is allowed, but elevated 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. will be observed.

Make separate narrowband measurements of SS/PBCH instead of a wideband measurement. This does not provide simultaneous PDSCH/PDCCH analysis with the SS/PBCH, but it does provide more accurate SS/PBCH EVM and Power/Phase results when transmitted at the same time as PDSCH using a different numerology. See Multiple Numerology Limitations for more information.

Scaling is different between measurement and traces

The VSA measurement scales everything by the smallest numerology defined in the signal; however, the traces' drawing engine necessarily scales everything by the largest numerology in the signal.

Convert from trace symbols to measurement symbols by dividing by the (maxSCS / minSCS) ratio. See the Impact on Measurement Interval and Measurement Offset for more information.

Demodulation fails to lock on signal

Signal not present.

Check test setup connections.

Carrier too far from center frequency.

Enable Extend Frequency Lock Range and adjust center frequency to within the extended frequency lock range for your selected subcarrier spacing (extended frequency lock range is +- 2.5 * subcarrier spacing). For example:

• If the subcarrier spacing µ = 1:30kHz, the extended frequency lock range is +-75kHz.
• If the subcarrier spacing µ = 4:240kHz, the extended frequency lock range is +-600kHz.

Input is over-loaded or under ranged.

Adjust input range.

Frequency span is too narrow.

Increase frequency span.

I/Q misaligned using I+jQ receiver.

Ensure that trigger delays for the hardware channels assigned to I and Q are correct.

The constellation symbol shape, such as dots, is not properly displayed on traces.

The display driver is not functioning correctly.

Contact your PC manufacturer to see if a newer version of the display driver is available. If not, try decreasing the hardware acceleration. See the Windows documentation for instructions.