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srsran / srsRAN_Project

Open source O-RAN 5G CU/DU solution from Software Radio Systems (SRS) https://docs.srsran.com/projects/project
https://www.srsran.com
GNU Affero General Public License v3.0
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Very low throughput with RAN550 #737

Closed melkael closed 4 months ago

melkael commented 4 months ago

Hello!

Issue Description

We are trying to run SRS with a Benetel RAN550. We manage to attach the UE reliably. However the throughput is extremely low (downlink around 1.5mbps and uplink around 5mbps, see the attached iperf screenshots). The issue reminded us an issue we had of too high transmitted power so we tried playing with the gain (varying it to several values between 4 and 24db) but it did not help. We also tried modifying downlink_scaling which did not help either.

Setup Details

ru_ofh: t1a_max_cp_dl: 500 # Maximum T1a on Control-Plane for Downlink in microseconds. t1a_min_cp_dl: 450 # Minimum T1a on Control-Plane for Downlink in microseconds. t1a_max_cp_ul: 350 # Maximum T1a on Control-Plane for Uplink in microseconds. t1a_min_cp_ul: 290 # Minimum T1a on Control-Plane for Uplink in microseconds. t1a_max_up: 360 # Maximum T1a on User-Plane in microseconds. t1a_min_up: 300 # Minimum T1a on User-Plane in microseconds. ta4_max: 200 # Maximum Ta4 on User-Plane in microseconds. ta4_min: 0 # Minimum Ta4 on User-Plane in microseconds. is_prach_cp_enabled: true # Configures if Control-Plane messages should be used to receive PRACH messages. compr_method_ul: bfp # Uplink compression method. compr_bitwidth_ul: 9 # Uplink IQ samples bitwidth after compression. compr_method_dl: bfp # Downlink compression method. compr_bitwidth_dl: 9 # Downlink IQ samples bitwidth after compression. compr_method_prach: bfp # PRACH compression method. compr_bitwidth_prach: 9 # PRACH IQ samples bitwidth after compression. enable_ul_static_compr_hdr: false # Configures if the compression header is present for uplink User-Plane messages (false) or not present (true). enable_dl_static_compr_hdr: false # Configures if the compression header is present for downlink User-Plane messages (false) or not present (true). iq_scaling: 4.5 # IQ samples scaling factor applied before compression, should be a positive value smaller than 10. cells:

cell_cfg: dl_arfcn: 640000 # ARFCN of the downlink carrier (center frequency). band: 78 # The NR band. channel_bandwidth_MHz: 20 # Bandwith in MHz. Number of PRBs will be automatically derived. common_scs: 30 # Subcarrier spacing in kHz used for data. plmn: "00101" # PLMN broadcasted by the gNB. tac: 1 # Tracking area code (needs to match the core configuration). pci: 1 # Physical cell ID. nof_antennas_dl: 2 nof_antennas_ul: 2 prach: prach_config_index: 159 # PRACH configuration index. prach_root_sequence_index: 1 # PRACH root sequence index. zero_correlation_zone: 0 # Zero correlation zone. prach_frequency_start: 2 # Offset in PRBs of lowest PRACH transmission occasion in frequency domain respective to PRB 0. preamble_trans_max: 50 power_ramping_step_db: 4 tdd_ul_dl_cfg: dl_ul_tx_period: 10 # Optional INT (10). Sets the TDD pattern periodicity in slots. The combination of this value and the chosen numerology must lead to a TDD periodicity of 0.5, > nof_dl_slots: 7 # Optional INT (6). Number of consecutive full Downlink slots. Supported: [0-80]. nof_dl_symbols: 6 # Optional INT (0). Number of Downlink symbols at the beginning of the slot following full Downlink slots. Supported: [0-13]. nof_ul_slots: 2 # Optional INT (3). Number of consecutive full Uplink slots. Supported: [0 - 80]. nof_ul_symbols: 4 ssb: ssb_block_power_dbm: -20 pdsch: mcs_table: qam64 pusch: p0_nominal_with_grant: -76 log: filename: log.log # Path of the log file. all_level: warning f1ap_level: info # Optional TEXT (warning). Sets F1AP log level. f1u_level: info

* ru_config.cfg:

Config file for Benetel RANx50 radio units

Please place this file in /etc

MIMO mode - the radio can operate in 1_3, 2_4, 1_2_3_4_4x2 or 1_2_3_4_4x4 mode

Variable name : mimo_mode

Valid options : 1_3

2_4

1_2_3_4_4x2

1_2_3_4_4x4

mimo_mode=1_2_3_4_4x2

FPGA downlink scaling in steps of 6 dB (0, 6, 12 and 18 can be set)

Variable name : downlink_scaling

Valid options : 0

6

12

18

downlink_scaling=6

PRACH format

Variable name : prach_format

Valid options : short

long

prach_format=short

Short form PRACH compression settings (note uncompressed mode is not supported when RU is in 4x2 or 4x4 mode)

Variable name : compression

Valid options : static_uncompressed

dynamic_uncompressed

static_compressed

dynamic_compressed

compression=dynamic_compressed

Long form PRACH compression settings

Variable name : lf_prach_compression_enable

Valid options : true

false

lf_prach_compression_enable=false

C-Plane per-symbol workaround

Variable name : cplane_per_symbol_workaround

Valid options : enabled

disabled

cplane_per_symbol_workaround=disabled

CUPLANE dl couplling sectionID

Variable name : cuplane_dl_coupling_sectionI

Valid options : enabled

disabled

cuplane_dl_coupling_sectionID=disabled

FlexRAN PRACH workaround

Variable name : flexran_prach_workaround

Valid options : enabled

disabled

flexran_prach_workaround=disabled

DL_special slot tunning

Variable name : dl_tuning_special_slot

Valid range : 0x0:0x13bc

dl_tuning_special_slot=0xfd00000


* Uplink throughput
<img width="637" alt="Capture d’écran 2024-07-17 à 4 53 26 PM" src="https://github.com/user-attachments/assets/f15db942-8c49-4438-946c-91cfe81402d3">

* Downlink throughput
<img width="601" alt="Capture d’écran 2024-07-17 à 4 54 04 PM" src="https://github.com/user-attachments/assets/31e64438-884f-4a2e-b3bf-4e6fb58c2046">

Thank you
andrepuschmann commented 4 months ago

Hey - can you share console traces please? I assume timing is good - so it's very likely a power calibration matter.

melkael commented 4 months ago

Sure, please find the whole file for a DL test attached: log.log. I tried varying various power parameters on both SRS and the benetel, but no success for now.

The benetel indicates TX power of around 15-17dBm currently (with 24dB gain and the attenuation parameter in /etc/ru_config.cfg set to 0).

Also, I think the environment is not the issue because we have a Foxconn radio which works fine in the same room.

EDIT: And yes the timing is good.

Here are the traces:

Capture d’écran 2024-07-18 à 4 02 38 PM
ismagom commented 4 months ago

Hi @melkael, it seem the tx power is too low or DL signal is very low. You can see it by the CQI=2 reported by the UE. The UL power is also very low, but you should look at it later. Can you try the following?

1) If you set 4x2 mode in the RU, set 4 DL antennas in the gNB config too 2) Try increasing iq_scale until you see dBFS ~-15/-13 dB in the oru_stats command in the RU

melkael commented 4 months ago

Thank you guys for your help, the issue was that the TDD pattern was wrong.