What can be the reason of high PDSCH BLER >30% in 5G SA?

Hi All.

What can be the reason of high PDSCH BLER >30% in 5G SA?

How is your SINR and CQI?

Interference is the first thing I have in mind.

Watch out in 5G there are 3 SINR: SSB SINR, CSI-RS SINR and PDSCH SINR.

You have to check all 3.

SNR is fluctuating from 0 to 8.
CQI is around 8-9.
SS RSRP is -90 to -95 dBm.

Ok, so you have some interference. But which SINR is that one? SSB? CSI-RS/ PDSCH?

Do you see retransmissions?

Initial bler may be 30% but residual bler should be 0%.

Yes, I’m checking this… SINR, PDSCH.

I am the single user latched on to site and avg PRB allocation is around 220.

But still average throughput is less than 50 Mbps.

How many other PCIs you see?

Interference from other cells is still present since your sinr fluctuates from 0 to 8.

Move in a better position where no other PCI is detected and then your sinr should jump to 20-30 dB.

Please check Preallocation, Rank, MCS as well.

2 more PCI are there, but RSRP difference is more than 8 dB between Serving cell and Nbr cell.

Well, your SINR is also 8 dB. So you have the answer.

You must get rid of the other 2 PCIs, find another location for test where you do not overlap with other PCIs.

And test there.

Are you on 100 MHz spectrum?

You should get 273 PRBs.

If 90 MHz you should get 245 PRBs and so on.

I am on 100 MHz spectrum.

Ok so you are probably on n78 TDD 30 kHz SCS.

Yes, right.

On Ookla I am getting around 600 Mbps in same scenario.

And while testing throught ftp script in DT tool I am getting around 50 Mbps.

Did you configure FTP to have multiple parallel streams?

This is what Ookla does.

10 streams in FTP.

Then try to test with HTTP, not with FTP.

Which FTP server are you using? That might be the bottleneck.

FTP has to be from inside the MNO, not some public ftp server.

FTP from MNO side.

And I have tried from HTTP as well but still throughput is same.

If it works on Ookla with 600 Mbpsec then you have no issue with network.

Just your test procedure something is wrong, don’t know what maybe not optimized PC, are you trying on laptop or mobile?

I am testing on mobile.

I am suspecting issue with testing tool. As same procedure works fine on TEMS.