What could be issue of low TCP throughput in DL 5G SA?

[LordGm]

Check bler, collect trace and compare at wireshark expert view, select packts per second versus time and filter tcp.streams.

If I were you, i’d compare both cell config once again.

And focus on TX backhaul!

[tjoo]

@Ryan

Actually it’s like this: I have 2 5G SA cells, both same are identical on all configs .

• Cell1 connected to Core 1
• Cell2 connected to Core 2

Cell1 - udp in DL is 950 Mbps, DL tcp around 900 Mbps. (It’s working fine)

Cell2- udp in DL is 950 Mbps, DL tcp around 700 Mbps.

Both cells has mcs 26, 273 RBs, everything is same in terms of RAN configs.

On cell2 (problematic cell) I see that initially there is on tcp like 950 Mbps, then after little timestamps it downgraded to 700 Mbps in tcp DL.

If both cells have the exact same config & setup, results are strange.

HARQ retx does not explain much lower cell2 TCP Tput.

For OTA, dramatic RF condition change could cause degrade when testing cell2 TCP.

So I would double check if UL Tput (MAC/RLC/PDCP) show such discrepancies.

And conduct longer test to check the distribution (SNR/SINR, BLER, MCS, RB utilization) from both UE log and DU counters.