Test Mode (5G NR/5G-Advanced)
- When enabled, pre-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. 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. minimization is automatically performed to estimate and compensate carrier frequency offset, time offset and sampling frequency offset for downlink, and carrier frequency offset, time offset, sampling frequency offset and carrier leakage for uplink. Post-FFT equalization covering Tracking, Equalizer Training and EVM Window and Symbol Timing parameters are configured. Both pre-FFT minimization and post-FFT equalization follow the standard 38.104/38.141 for Downlink and 38.521 for Uplink. The affected parameters are grayed out and not editable while 3GPP Conformance Test is enabled, and the Tracking Source is automatically set to 3GPP with phase tracking enabled when PTRS is present in the transmitted signal.
Default: Enabled
Choices: Enabled, Disabled
- This mode triggers specific synchronization algorithm and demodulation processing for use when the input signal is very noisy (e.g., receiver sensitivity tests, where the signal to noise power ratio can be around 0dB).
You can also use Low SNR Signal-to-Noise Ratio Mode for troubleshooting when EVM is unexpectedly high and the PDSCH/PUSCH RB Number is small (e.g., 2 or 3).
The Low SNR Mode synchronization and demodulation process is different from the normal measurement. This parameter is not coupled with any other parameters, but when the signal is very noisy, any tracking or channel estimation based on data is not accurate. To get the best performance of low SNR receiver test, set these parameters as follows:
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Turn off 3GPP Conformance Test.
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Enable Low SNR Mode.
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Enable Freq Moving Avg. Filter. Increasing the number of RSs may achieve better results.
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Turn off all tracking (Time/Phase/Amplitude).
The tracking options are grayed out by default. To activate them, the Tracking Source must be changed to RS+Data or RS.
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Change the EQ Signal Source to RS.
If the data modulation format is QPSK Quadrature phase shift keying and the SNR is not too low (> 0dB), setting the Signal Source to RS+Data may achieve better results.
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Change the EQ Time Basis to Per Frame.
If multiple slots are allocated to users and the channel frequency response remains constant over time, setting the Time Basis to Per Frame may achieve better results. However, if the channel frequency response varies across slots, particularly in the uplink (UL Up Link (reverse link: from cell phone to base station)) where data is transmitted on a per-slot basis, using Per Slot may achieve better results.
For TDD Time Division Duplex: A duplexing technique dividing a radio channel in time to allow downlink operation during part of the frame period and uplink operation in the remainder of the frame period. (uplink), if contiguous slots are allocated–to single or multiple users–and mapped to the same resource blocks (RBs) with constant channel frequency response over time, setting the Time Basis to Contiguous Slots may achieve better results.
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Change the Symbol Time Adjustment Mode to EVM Window Center.
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Turn off Compensate Symbol Clock Offset.
Default: Disabled
Choices: Enabled, Disabled
See Also
