SSB and PDSCH coexistence

5G NR
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1

Hello everyone,

I have a, maybe, silly doubt about SSB and PDSCH, but I want to be sure about it.
In the downlink resource grid of a standard 5G link, does the PDSCH happen to be transmitted also on the same slots and OFDM symbol of the SSB? Clearly on different subcarriers.

Side question: if yes, how can it be implemented in hardware the case of having different SCSs for the two? I guess that if we want to change all the blocks and channels SCS (e.g. from 15kHz to 30kHz) it takes a simple sampling rate upscale, but what happens when having diffent SCSs on the same OFDM-symbol?

Thanks in advance,
Andrea

2

SSB is always 20 Resource blocks wide (240 Subcarriers) and occupies 4 OFDM symbols, within those same OFDM symbols it doesn’t share resources with PDSCH.
Maybe this example from Spectral analyzer will help:

image
image895Ă—502 61.2 KB

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3

Okay, so also if we had, e.g., 106 PRB, when an SSB symbol is transmitted there is no other information transmitted at that time, but we would have mute REs. Correct?
I am asking this because i found some graphics that make me think the other way, but not very sure. I’ll attach one.

SSB_image
SSB_image690Ă—761 104 KB

Here are some symbols that transmit both SSB and PDSCH.

It’s taken from this article: Fuentes, Manuel & Carcel, Jose & Dietrich, Christiane & Yu, Lang & Garro, Eduardo & Volker, Pauli & Lazarakis, Fotis & Grondalen, Ole & Bulakci, Omer & Yu, Jian & Mohr, Werner & Gomez-Barquero, David. (2020). “5G New Radio Evaluation Against IMT-2020 Key Performance Indicators”. IEEE Access. 8. 110896. 10.1109/ACCESS.2020.3001641.

Though, in many other images online, the PDSCH are not mentioned when the SSB is represented, leaving some kind of uncertainty.

4

Hi , it is possible via allocating pdsch above or below ssb in freq domain.
image
Not only but also in trs slots we can schedule pdsch.
image
BR

1 Like
5

Thanks!

And do you think there is some limitations in case of using different SCSs for SSB and PDSCH when allocating them in the same OFDM-symbol?

P.S. where are those image from? just to read something more about

6

No this is not correct. Frequency division multiplexing is possible between SSB and PDSCH

Should not be theriotically because allowed different SCS are of multiples of 2

A general limit will be imposed bt RBG boundaries and Coreset 0 location

7

Do you mean that we can apply OFDM modulation with different SCSs inside the same symbol? Do you refer to some kind of symbol repetition (in freq domain) or an actual DFT-like that take into account different SCSs inside the same symbol?

8

@djtandrea
Implementation is not standardized by 3GPP and is open for proprietary solutions

There are alot of research papers discussing this specially in the context of BWPs with mixed numerology

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