Hi Experts, how are you?
We are having a weird problem in our LTE network.
Radio Nokia FW2PC and CORE ZTE.
We have been troubleshooting for a few days, but no success: The phone attaches, but navigation is poor.
When doing speed test it shows a few kbps DL while UL shows Mbps as expected.
We have checked all physical installation, APN, IP pool, link, BTS database…
It’s weird because it has happened since last week, it worked before.
We have 37 sites with other vendor but only the 4 Nokia BTS have problem.
It is 3 different provinces.
Has anybody seen something like this?
DL poor and UL good?
I would suggest to quickly compare the dump of 2 sites.
Then it will quickly pop-up the issue.
Have you checked in good RF condition and still not good speed?
I suggest check the Tx parameters and any other throughput parameters.
Check the units as well.
Sometimes between vendors, parameters are wildly different so check the units.
I had similar issue with poor DL & good UL even in good radio conditions few years back. Issue was related to Transmission.
Suggest to do Ping tests from eNodeB.
Check S1 interface, check for any issues on the S1-MME and S1-U links.
Problems in S1-U could specifically affect Downlink traffic.
This is my guess as well…
In most cases if all looks OK then it’s Tx parameters.
In multi vendor cases some time one vendor has back haul defined in Mbps and other in Kbps.
Huge impact if same value is in both eNB.
Update here:
Problem solved!
Last friday we applyed iPerf test set from phone to internet gateway (PGW).
UDP tests were successful, but TCP tests failed.
Due to heterogeneous backhaul the BTS would guess backhaul failures were congestion and started to apply QoS.
Once every packet from CORE came with Best Effort BTS put it into low QoS and restricted resources to applications such as http.
We changed QoS factors for best effort and activated a BTS feature + reduced MAX PDU. It worked!
Thanks for all suggestions!
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