Radio conditions OK, BLER 80 and CQI 1, but still call dropped

Hi Dears.

I have this case in LTE Huawei: Radio conditions are OK, BLER 80 and CQI 1, but call dropped.
and have drop.

What can be the reason?

LTE Huawei

And what is meaning NACK RATE DL %?

Other similar event:

This is the process:

  1. Network → UE: Data transmission through PSDCH
  2. UE receive PSDCH
  3. UE check CRC error for PDSCH
  4. Two possibilities
    4.1 UE has data to transmit and send CRC check result (ACK/NACK) through PUSCH
    4.2 UE has no data to transmit then send CRC result through PUCCH
  5. Network check CRC result sent from UE and do the following
    5.1 If ACK, next data is transmitted
    5.2 If NACK, data is retransmitted through HARQ process with different version

You can understand the NACK rate.

Yes, but in this case retransmition are very high because NACK is high.

CQI Adjustment

Yes and your MCS is at 0.


But in second picture if SINR and RSRQ are OK CQI is low.

What is a reason of drop call?

And to have very high retrasmitions?

It can come from differents issues:

  • Synchronization
  • Load

Load, the sector have 7 users

Synchronization, I don’t know how I can check this. Can you help?

Need to check with IP team.

Is it recurrent?

Yes, it is.

Means you have a TX issue.

Because retransmission should not exceed 2% in IP side.

In the same drive test I have 8 events in the sector.


Can you check the Packet loss?

Unfortunately no. I don’t have access to KPIs.

Maybe someone can comment.

You have cross sector…

Check Co PCI.


Only have two sites in the zone.
I reported cross sectors to installation group.

Your BLER is very high…

Yes, 100.

That should not be more than 10.

I think that for this reason have retransmitions. Because BLER is very high.