H35-481_V2-0 practice question 3 of 15

Which of the following statements about PDSCH DMR5 is incorrect?

Full set: 60 questions

Answer options

A: The start symbol of a front-loaded DMRS of a type B PDSCH is always the first symbol of PDSCH. Correct answer

B: The front-loaded DMRS is mandatory, and the additional DMRS is optional.

C: The overhead of type 1 DMRS is less than that of type 2 DMRS.

D: The start symbol of a front-loaded DMRS of a type A PDSCH can be symbol 2.

Correct Answer:

A. The start symbol of a front-loaded DMRS of a type B PDSCH is always the first symbol of PDSCH.

Explanation

For PDSCH mapping type-B, 3GPP specifies that the first front-loaded DM-RS symbol may be any of symbols {0,1,2,3} relative to the PDSCH start, not necessarily the first symbol. Therefore statement A is wrong. Front-loaded DM-RS is compulsory while additional DM-RS is configured only when required, and DM-RS type-1 uses two REs per RB versus four for type-2, hence lower overhead. Mapping type-A normally starts its DM-RS in symbol 2.

Why Incorrect

B. Front-loaded DM-RS is mandatory; additional DM-RS is optional – matches 38.211 specification.
C. Type-1 occupies 2 REs/RB; type-2 occupies 4 REs/RB, so overhead is smaller – statement correct.
D. For mapping type-A the first DM-RS symbol index is 2 (normal CP) – statement correct.

References

1. 3GPP TS 38.211 v16.3.0, §7.4.1.1.2, Table 7.4.1.1.2-1 (front-loaded DM-RS symbol indices).

2. 3GPP TS 38.211 v16.3.0, §7.4.1.1.3 (DM-RS type-1 vs type-2 overhead).

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