Troubleshooting Throughput limitation on one site

Hi Experts.

we have one challenge. There is throughput limitation on one of the site its not going beyong 130-40 Mbps.

Vendor = Huawei , 5G / NSA / ENDC / N78 / 100 Mhz / TDD /8:2

Following things have been checked:

  1. Transmission Capacity: OK
  2. Transmission Congestion: OK
  3. All parameters i.e pattern, DL leg switching, DL CA: everything is OK
  4. From DT UE is not getting full grant of RBs and PDCCH downlink grant which indicates something is wrong at upper layer.
  5. Interestingly statistical throughput is not degraded: Stats are fine
  6. 2/10 speed test will show good results otherwise mostly max 120-130 Mbps is appearing.
  7. X2 links: OK.
  8. RF Conditions perfect, Modulation: 256QAM, Multiple UEs with same issue but random.
  9. AMBR: no issue.
  10. No Abnormal Alarms.

Any idea / suggestion?

Admin note: this post was updated with image below.

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Check sim card.

Problem with other users as well. (Rest of sites OK, only one site issue)

Are you testing on laptop or on UE? I suggest multiple treads in DL, like 10 of them.

How is speedtestnet showing?

Testing on mobile. (2 to 3 speed test will show good results).

The problem is not speed test actually, other users are also complaining for low 5G speed.

But if not enough data is coming from higher layers how do you want to achieve 800 Mbpsec per second?

You’re right, but same results with FTP testing.

Checked UDP/TCP.

Also multi threads.

But unable to find any issue in radio / transmission.

Major throughput impacting parameters are OK.

But how many users per cell?

Maybe time to time too many users.

Can you look at gNodeB OSS online traces?

Have you checked if there is any license limitation as compared to other sites?

Also what about Uplink? Same limitation issue observed for Uplink on this site?

And no interference issue on this site?

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Just adding some points.

If there is no radio resources limitation, do parameters comparison with normal site and seems the main issue here due to DL grant which is not full 1600.

How much grant UE has in this case?

As per experience, TX issue could be one of the reasons, like TX port limited. Check how many bw 1Gbps or 10Gbps, is it the same as the normal site?

Faulty base band also can be a factor.

RIM configurations also can be a factor as well in this case need to check.

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Average of PDCCH Downlink Grant Count Current:

Average of MR-DC DRB PDCP DL Throughput Total (kbps):

Average of PDSCH Average RBs per Allocated Slot: AVG CNT SB = Serving Beam 1:

Parameter comparison with normal site OK, no such ambiguity. (Txn Also verified its OK).

What do mean by RIM Configuration?

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RIM basically, in Huawei, there are 2 adaptive options and forced if I’m not mistaken.

If by mistake forced is enabled then some symbols muted in this case could trigger a low grant.

Like normally with your current setting it is supposed to be 1600 but once forced enabled it will be 1400 only.

The question is how many grants you got for this site? How many TX port bw are you using?

Do you know the name of that parameter(s)?

Better find it in HEDEX, it is mentioned clearly.

Found it, thanks.

Yes, but those are related to adaptive.

Check with forced as well.


Your Grant counts and RB/slot is very low

Peak standard:
Grant: DL 1600/UL 400 times (8:2 Frame Structure)
RB: 265 RBs (100MHz)

Possible factors:

  1. Insufficient data supply;
  2. AMBR rate limitation;
  3. Downlink DCI missing detection;
  4. PDCP/RLC/MAC problem;
  5. Multi-user scheduling;
    6)LTE GAP

Also to rule out radio please check from same throughput testing these indicator:

  • CQI
  • DL BLER%
  • DL MCS Avg
  • DL 16QAM%
  • DL 256QAM%
  • DL 64QAM%
  • DL QPSK%
  • Rank 1
  • Rank 2
  • Rank 3
  • Rank 4

Also maybe you are checking backhaul from gNB to RTN which maybe 10G but from RTN-IIB connectivity has limitation of 1G, for this you need to involve TXN / Transport team.

Is there any packet loss? you can check rate from OSS.

Also check SCTP retransmissions of all SCTP links of the site // reflect to transport congestion.

Also explain the genre of your problem is it a UE or area specific, more importantly issue is with a moving ue(like your drive test results) or static (more of a complaint based)?

Reason is NSA some parameter setting will favour static UE instead of moving UE and vice versa due to different channel estimation algorithm / settings

Regarding Grant count limitation, you can check:

  • NRDUCellPdcch.UlMaxCcePct: If this parameter is set to a too small value, there is a high probability that uplink services are restricted. If this parameter is set to a too large value, there is a high probability that downlink services are restricted.

  • UL_DL_CCE_RATIO_ADAPT_SW: After this function is enabled, the ratio of available uplink CCEs to available downlink CCEs is adaptively adjusted based on factors such as required uplink and downlink CCEs and CCE usage, and the setting of the NRDUCellPdcch.UlMaxCcePct parameter no longer takes effect. Adaptive configuration is enabled by default.