UL Throughput drop and DL/UL imbalance in LTE Drive Tests

4G LTE
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Hello Experts,

I have a question regarding LTE performance. Is it normal for my UL throughput to drop to 0 when DL RSRP levels reach -117 dBm, along with UL MCS averaging near 0?

Interestingly, the first instance of UL throughput dropping to 0 occurs when DL RSRP is at just -110 dBm, which seems unusual. Could this indicate a significant imbalance between DL and UL, possibly caused by a weak UL due to low receiver quality at the base station?

From what I know, a DL RSRP of -124 dBm might already suggest that UL is essentially non-functional. Does this align with what you’ve observed?

This scenario is from drive tests using Qualipoc devices, and the vendor is not Huawei, Ericsson, or Nokia.

Looking forward to your insights!

2

When evaluating UL throughput, path loss is often a more meaningful metric than RSRP.

If the UL MCS is dropping to 0, it could indicate that you are reaching the cell edge limit. However, this also depends on how BLER is being managed within that RSRP range.

  • If BLER is not well-maintained, then it’s likely you are indeed hitting the limit.

  • If BLER is maintained or remains very low, there might still be room for optimization, possibly by setting more relaxed targets.

1 Like
3

It’s expected for UL throughput to decrease as DL RSRP deteriorates, but a complete drop to zero at -110 dBm is unusual.

This might point to issues such as a weak UL receiver at the base station or other network-related factors.

A DL RSRP of -124 dBm is extremely low, making it highly likely that UL performance would be severely degraded or entirely lost at that level.

4

Thank you all for your ideas!

I’m considering adjusting the BLER settings to address the issue. Do you think implementing a TMA could help resolve the DL/UL imbalance?

5

It will depend on the link budget calculation.

What are the values for UL PUSCH RSSI? And how is the UL SINR performing?

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PUSCH RSSI is not available for that equipment.

UL SINR is propably not available as well.

Is it possible to measure it with TEMS or similar SW?

7

That’s not possible - UL SINR is measured at the eNodeB, so TEMS cannot measure it.

On the UE side, you can only estimate UL SINR indirectly by analyzing the UL Tx Power on PUCCH and PUSCH.

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Assuming PUSCH Tx power reach 23dBm and high PUSCH TB allocations, I would check B883; RB #, RB location, HARQ ReTx rate, …