Understanding 5G NR Auto Detection

5G NR auto detection is available for uplink or downlink within the PUSCH and PDSCH parameter settings. In Auto Detection Mode, the VSA attempts to demodulate the signal and return EVM results. It does not detect or return any signal parameters. You must enter all parameters in the Carrier panel and BWP panel correctly before Auto Detection Mode can work.

In Power Based 5G NR signal auto detection, the DMRS sequence or pseudo-DMRS sequence is detected.

The symbol boundary is detected through synchronization.
Each symbol is transferred from time domain to frequency domain.
In the frequency domain, the delta phase of two adjacent carriers is calculated to determine the DMRS Config Type (Type1 or Type2). The DMRS Config Type is important because it identifies the number of DMRS groups per RB (Type1 = 3 DMRS groups/RB; Type2 = 2 DMRS groups/RB, where 2 adjacent DMRS is a DMRS group).
Calculate the valid DMRS group number based on the knowledge that the delta phase between DMRS groups is n*pi/2.
The total DMRS group number is calculated based on the RB length (e.g., if RB length = 100 and DMRS Config = Type1, the total DMRS group number is 300).

When Power Based auto detection is used, switching between uplink and downlink signals can cause auto detection to not demodulate properly. Be sure to start a new VSA session or perform a Preset > All before switching directions.

Since DMRS is QPSKQuadrature phase shift keying modulation, if data is QPSK, it is not possible to distinguish between data and DMRS.