What is the benefit of flexible position of SSB in 5G?

5G NR
1

GSCN define the center frequency of SSB(PSS,SSS& PBCH) and it can be any where in defined channel BW as per the table and calculation given by 3gpp but in legacy technologies it was fixed at the center of the channel BW.

Question is -> What is the benefit of flexible position of SSB in 5G then fixed at the center of the channel? what is the need to introduce GSCN in 5G?

2

Let me know my views.

  1. SSB closer to start of bandwidth will save SSB detection time and hence accessibility time reduced, mainly in case of high BW scenario (400M)
  2. For PDSCH scheduling flexibity (i read it somewhere, how exactly i am not aware)
3

Agree.

Can you please share some more details of PDSCH scheduling flexibility and one is to use different SSB position used in BWP?

4

What do you mean by ?

5

That different BWP configuration can use different SSB position.

6

Ok, go it.

7

In BWP part no linking with SSB seen.

8

For example in one cell has 4 BWP configured, then each has different SSB frequency based on the application.

9

It is linked.

10

I have some disconnect here.
I am under impression that at a time only 1 SSB will be transmitted.
Position of that can be changed as per BWP configuration.

Please correct me if wrong…

11

Ok :+1: seems in initial BWP.

12

I think so:

It is necessary to identify center frequencies for both:
Channel Bandwidth
Set of SS/PBCH Blocks.
Initial deployments are likely to use a single set of SS/PBCH Blocks requiring a single center frequency.
More advanced deployments may use multiple sets os SS/PBCH Blocks requiring multiple center frequencies, e.g. when a channel bandwidth is configured to use multiple BWP.

Question is: what are the benefit to introduce GSCN other then larger raster compare ARFCN?

13

Do you mean location and bandwidth seen under BWP which indicates RIV?

14

So currently many operators use more than one BWP.
So those many SSBs will be transmitted you mean?

15

Yes; I think so different SSB in different BWP.

16

And for measuring neighbor cells, SSB associated with default/initial BWP will be used, like this?
If SSB based measurement are configured?

17

Inter cell HO with different BWP always use initial BWP; so there wil not be jumping between the BWP of 2 different cells.

That is my understanding…

18

Yes, correct.

19

Yes same understanding here
Even at the time of SgNB addition, SSB of initial BWP will be used.

But one more question, SSB configuration (Periodicity, Bitmap) will be same for all SSBs right?
Only earfcn will be changed?

20

Not sure but should be same and center frequency of SSB should change, not ARFCN.
ARFCN will be same.