srsRAN gNB Handover

[apperezG]

Issue Description

Good morning! I am trying out the tutorial https://docs.srsran.com/projects/project/en/latest/tutorials/source/handover/source/index.html#hardware-and-software-overview. My setup is very similar to the one given in the tutorial except that I am working with the srsUE. My problem is that the UE does not connect to the gNB but I do not see any errors or strange behavior in the gNB log file.

The gNB deploys without problem with the two cells and I don't get any errors, either on the terminal or in the logs. On the part of the srsrUE I am running it in the same way as in another deployment I have with a gNB with only 1 cell in a B210 and in that setup it works without problem. I attach the configuration I am applying in case you see something that does not make sense to you.

Thank you very much!

Setup Details

gNB configuration (I tested both the n3 and n50 bands -> I can't use the n78 due to frequency limitation):

        gnb_id: 411
        gnb_id_bit_length: 32

        amf:
          addr: 10.100.0.9                  
          bind_addr: 10.100.0.8          

        ru_sdr:
          device_driver: uhd
          device_args: type=x300
          tx_gain: 20
          rx_gain: 15
          srate: 23.04
          lo_offset: 45
          clock: internal
          sync: internal
          time_alignment_calibration: 0

        cell_cfg:
          dl_arfcn: 294900 #368500                                              # ARFCN of the downlink carrier (center frequency).
          band: 50 #3                                                      # The NR band.
          channel_bandwidth_MHz: 20                                       # Bandwith in MHz. Number of PRBs will be automatically derived.
          common_scs: 30 #15                                                   # Subcarrier spacing in kHz used for data.
          plmn: "00101"                                                   # PLMN broadcasted by the gNB.
          tac: 7                                                          # Tracking area code (needs to match the core configuration).
          nof_antennas_dl: 1
          nof_antennas_ul: 1

        cells:
          -
            pci: 1
            prach:
              prach_root_sequence_index: 0
          -
            pci: 2
            prach:
              prach_root_sequence_index: 64

        cu_cp:
          mobility:
            trigger_handover_from_measurements: true
            cells:
              - nr_cell_id: 0x19B0
                periodic_report_cfg_id: 1
                ncells:
                  - nr_cell_id: 0x19B1
                    report_configs: [ 2 ]
              - nr_cell_id: 0x19B1
                periodic_report_cfg_id: 1
                ncells:
                  - nr_cell_id: 0x19B0
                    report_configs: [ 2 ]
            report_configs:
              - report_cfg_id: 1
                report_type: periodical
                report_interval_ms: 480
              - report_cfg_id: 2
                report_type: event_triggered
                a3_report_type: rsrp
                a3_offset_db: 3
                a3_hysteresis_db: 0
                a3_time_to_trigger_ms: 100

        log:
          filename: ./gnb.log            # Path of the log file.
          all_level: debug

        pcap:
          mac_enable: true
          mac_filename: /tmp/gnb_mac.pcap
          ngap_enable: true
          ngap_filename: /tmp/gnb_ngap.pcap
          f1ap_enable: true
          f1ap_filename: /tmp/gnb_f1ap.pcap
          gtpu_enable: true
          gtpu_filename: /tmp/gnb_gtpu.pcap
          e1ap_enable: true
          e1ap_filename: /tmp/gnb_e1ap.pcap

UE configuration (I tested both the n3 and n50 bands):

      [rf]
      freq_offset = 0
      tx_gain = 30
      rx_gain = 20
      srate = 23.04e6
      nof_antennas = 1

      device_name = uhd
      device_args = type=b200, serial=31D4A7B
      #,num_recv_frames=64,num_send_frames=64
      time_adv_nsamples = 300

      [rat.eutra]
      dl_earfcn = 2850
      nof_carriers = 0

      [rat.nr]
      bands = 50 #3 
      nof_carriers = 1
      max_nof_prb = 106
      nof_prb = 106

      [pcap]
      enable = none
      mac_filename = /tmp/ue_mac.pcap
      mac_nr_filename = /tmp/ue_mac_nr.pcap
      nas_filename = /tmp/ue_nas.pcap

      [log]
      all_level = info
      phy_lib_level = none
      all_hex_limit = 32
      filename = /tmp/ue.log
      file_max_size = -1

      [usim]
      mode = soft
      algo = milenage
      opc  = 63BFA50EE6523365FF14C1F45F88737D
      k    = 00112233445566778899aabbccddeeff
      imsi = 001010123456780
      imei = 353490069873319

      [rrc]
      release = 15
      ue_category = 4

      [nas]
      apn = internet
      apn_protocol = ipv4

      [gw]
      # netns = ue1
      # ip_devname = tun_srsue
      # ip_netmask = 255.255.255.0

      [gui]
      enable = false

Expected Behavior

UE conects with the gNB.

Actual Behaviour

The UE does not connect to the gNB but I do not see any errors.

[pgawlowicz]

Hi, Band 50 uses TDD, srsUE supports only FDD.

[apperezG]

I tested both the n3 and n50 bands (the n3 with the values commented, which is FDD) and the result is the same in both cases.

[apperezG]

I attached the logs of the gNB and the UE (in n3 band) in case they are helpful: gnb.log ue.log

[pgawlowicz]

could you increase UE tx gain? the gnb did not receive any PRACH

[apperezG]

By adjusting the gain value so that I can see the tx of the gNB on the B210 that has the srsUE I get the following:

gNB

UE

Logs: logs.zip

I already ran the srsran_performance script as well just in case. Besides the gain can you think of anything else to try changing in the configuration file @pgawlowicz ?

Thank you!

[pgawlowicz]

CFO seems to be high, do you use external clock source?

[apperezG]

Not in this case. Do you recommend me to set a specific value or add an external sync generating a 1 Hz signal that will serve the x310 as a reference for the clock?

[pgawlowicz]

you should connect both to a single clock source, if it works then you can try if connecting only b200 (srsUE) is enough

[apperezG]

I am generating a sync signal with the following configuration:

  Function: Pulse
  Frequency/Period/Delay Menu
  Frequency: 1 Hz
  Amplitude/Level Menu
  High Level: 2V5
  Low Level: 0V
  Pulse Parameter Menu
  Duty cycle: 25 %

I am connecting this signal to the PPS port of the SDRs and configuring the sync as external in the conf files. Still the result I get is the same as before. What sync signal do you test with? Can you think of anything else to change in the setup?

Thank you so much for all the help and quick responses!

[pgawlowicz]

you also need to connect 10MHz clock

[apperezG]

Hi! I tried putting in an octoclock that would generate a 1 PPS signal and a 10 MHz clock signal for each USRP. I no longer have the problem of the UE giving me sync failure but, with the same configuration as before I only get Overflows and the UE does not connect. Attached are the logs --> logs.zip

I have the UE and the gNB on two (quite capacious) different servers and I already ran the srsran_performance.sh just in case it was processing problems but I don't think it could be from that.

[pgawlowicz]

could you share your current configs? could you try to run 5MHz cell and set srate to 5.76 in both gnb and srsue configs?

[pgawlowicz]

@apperezG any update on this issue?

[apperezG]

@pgawlowicz I couldn't go any further with this issue at the moment, if I make any progress I'll let you know!