SSB beam index 0 overlapping for different cells

5G NR
1

Hi Experts,
Ffor 5G need to check if there are 2 cells of same frequency facing each other and overlapping for FR1 having 8 SSB beams per cell.
Let’s user latch on SSB beam index 0 for cell 1.
For cell 2, there’s 8 SSB beam as well.
Below queries:

  1. Does cell 1 SINR will dip?
  2. SSB beam index 0 for cell 1 collide with SSB beam index 0 for cell 2 or not?
2

I don’t think SSB beam index 0 for cell 1 will overlap with SSb beam index 0 for cell 2, neither in space nor in time.

3

It means interference not there between 2 overlapping cells of same frequency at SSB beam level, correct ?

4

I mean SSB boradcast beams will be like this:

image

But PDSCH beams may interfere from 2 different cells if there are 2 UEs at same location (one served by a cell one served by another cell) but probably won’t be served in the same time.

So little chance of interference, I think.

5

Like in 4G we have RS RS, RS to PDSCH interference.
I’m not sure how it work in 5G.

Any guy working on 5G commercial network can comment…

6

I’d try to change user feedback to csi-rs instead of SSB and monitor this behavior.
Reporting SSB would bias entire clusters of users in case of interference while CSI-RS would allow gNB to perform more refined scheduling.
Also configure TRS properly.

7

Hi @ankgitm, we have deployed a small commercial network and we have never faced such issues. The reason is following…

Huawei product implement a randomized pattern which is static in terms of cell PCI MOD3,
So if you look at left to right beam indexes they will be positioned differently for each cell with different PCI MOD3, this avoids interference as you mentioned there since PCI MOD3 is already taken care while PCI planning of overlapping cells.

Hope this helps.

BTW, how Ericsson and Nokia implements it, would be interesting to know, anyone can suggest For these two vendors please…

Thank you.

8

Hi, we have also recently discovered this issue where different PCIs of Huawei base stations determine the arrangement of different SSB beam IDs. Could you provide relevant official documentation or reference materials? Specifically, we are interested in the SSB ID distribution for more PCI MOD 3 in different AAU. Thank you!