[srsran-users] UE disconnecting SA when another PRACH is created

Wed Aug 31 09:43:16 UTC 2022

Hello all!!

Following the 5G SA COTS UE Application Note
<https://docs.srsran.com/en/latest/app_notes/source/5g_sa_COTS/source/index.html>,
after running srsENB the UE successfully connects to the network and gets
an assigned IP and access to the internet.
But after a few seconds or minutes the UE disconnects from the network.

Setup Details

   - Operation System: Ubuntu 20.04
   - srsRAN (last version)
   - RF: USRP B210 (UHD driver)
   - Asus ZenBook intel Core i7
   - UE: Galaxy S21 FE 5G Sysmocom USIM
   - Third Party 5G Core: Open5GS

The B210 is connected to a GPS antenna (clock= GPSDO in enb.config file)
The B210 is connected to external power and usb3.0. The laptop is also
connected to power-source.
The CPU governor of the PC is set to performance mode.

enb output:

[2022-08-31 11:18:08.018597711] Active RF plugins: libsrsran_rf_uhd.so
libsrsran_rf_blade.so libsrsran_rf_zmq.so
[2022-08-31 11:18:08.019614233] Inactive RF plugins:
[2022-08-31 11:18:08.020493476] ---  Software Radio Systems LTE eNodeB  ---
[2022-08-31 11:18:08.021239493]
[2022-08-31 11:18:08.022201553] Reading configuration file enb.conf...
[2022-08-31 11:18:08.047178857]
[2022-08-31 11:18:08.048211004] Built in Release mode using commit
ce8a3cae1 on branch master.
[2022-08-31 11:18:08.049021063]
[2022-08-31 11:18:08.112477909] Opening 1 channels in RF
device=default with args=clock=gpsdo, master_clock_rate=11.52e6,
sampling_rate=11.52e6, recv_frame_size=1024
[INFO] [UHD] linux; GNU C++ version 9.4.0; Boost_107100;
UHD_4.2.0.0-0ubuntu1~focal1
[INFO] [LOGGING] Fastpath logging disabled at runtime.
[2022-08-31 11:18:08.115658911] Supported RF device list: UHD bladeRF zmq file
[2022-08-31 11:18:08.116465257] Trying to open RF device 'UHD'
[2022-08-31 11:18:08.117174866] NG connection successful
[INFO] [UHD RF] RF UHD Generic instance constructed
[INFO] [B200] Detected Device: B210
[INFO] [B200] Operating over USB 3.
[INFO] [B200] Detecting internal GPSDO....
[INFO] [GPS] Found an internal GPSDO: GPSTCXO , Firmware Rev 0.929a
[WARNING] [B200] The recv_frame_size must be a multiple of 8 bytes and
not a multiple of 1024 bytes.  Requested recv_frame_size of 1024
coerced to 1032.
[INFO] [B200] Initialize CODEC control...
[INFO] [B200] Initialize Radio control...
[INFO] [B200] Performing register loopback test...
[INFO] [B200] Register loopback test passed
[INFO] [B200] Performing register loopback test...
[INFO] [B200] Register loopback test passed
[INFO] [B200] Asking for clock rate 11.520000 MHz...
[INFO] [B200] Actually got clock rate 11.520000 MHz.
[INFO] [MULTI_USRP]     1) catch time transition at pps edge
[INFO] [MULTI_USRP]     2) set times next pps (synchronously)
[2022-08-31 11:18:12.400379533] Opening USRP channels=1, args:
master_clock_rate=11.52e6,recv_frame_size=1024,type=b200
[2022-08-31 11:18:12.401261562] Setting USRP time to 1661937491.000000s
[2022-08-31 11:18:12.401982356] RF device 'UHD' successfully opened
[2022-08-31 11:18:12.402970691]
[2022-08-31 11:18:12.403735479] ==== eNodeB started ===
[2022-08-31 11:18:12.404528414] Type <t> to view trace
[2022-08-31 11:18:12.405181947] Setting frequency: DL=2655.0 Mhz,
DL_SSB=2654.55 Mhz (SSB-ARFCN=530910), UL=2535.0 MHz for cc_idx=0
nof_prb=52[2022-08-31 11:18:18.733662587] RACH:  slot=5931, cc=0,
preamble=4, offset=9, temp_crnti=0x4601[2022-08-31
11:*18:36.973965842*] RACH:  slot=3691, cc=0, preamble=2, offset=1396,
temp_crnti=0x4602[2022-08-31 11:18:37.072352755] Disconnecting
rnti=0x4602.
[2022-08-31 11:18:37.133436504] RACH:  slot=3851, cc=0, preamble=6,
offset=1396, temp_crnti=0x4603
[2022-08-31 11:18:37.232712131] Disconnecting rnti=0x4603.
[2022-08-31 11:18:37.294178507] RACH:  slot=4011, cc=0, preamble=0,
offset=1396, temp_crnti=0x4604
[2022-08-31 11:18:37.393293625] Disconnecting rnti=0x4604.
[2022-08-31 11:18:37.453494272] RACH:  slot=4171, cc=0, preamble=3,
offset=1396, temp_crnti=0x4605
[2022-08-31 11:18:37.552344813] Disconnecting rnti=0x4605.
[2022-08-31 11:18:37.613804855] RACH:  slot=4331, cc=0, preamble=2,
offset=1396, temp_crnti=0x4606
[2022-08-31 11:18:37.712304317] Disconnecting rnti=0x4606.
[2022-08-31 11:18:37.773490691] RACH:  slot=4491, cc=0, preamble=3,
offset=1396, temp_crnti=0x4607
[2022-08-31 11:18:37.872352053] Disconnecting rnti=0x4607.
[2022-08-31 11:18:38.093870308] RACH:  slot=4811, cc=0, preamble=1,
offset=9, temp_crnti=0x4608
[2022-08-31 11:18:38.113321926] User 0x4608 requesting RRC
Reestablishment as 0x4601. Cause: otherFailure
[2022-08-31 11:18:38.114768882] Disconnecting rnti=0x4601.
[2022-08-31 11:18:38.253817518] RACH:  slot=4971, cc=0, preamble=7,
offset=9, temp_crnti=0x4609
[2022-08-31 11:18:38.264462015] Disconnecting rnti=0x4609.
[2022-08-31 11:18:38.573896896] RACH:  slot=5291, cc=0, preamble=3,
offset=9, temp_crnti=0x460a
[2022-08-31 11:18:38.672338152] Disconnecting rnti=0x460a.
[2022-08-31 11:18:38.733493021] RACH:  slot=5451, cc=0, preamble=4,
offset=9, temp_crnti=0x460b
[2022-08-31 11:18:38.744443571] User 0x460b requesting RRC
Reestablishment as 0x4608. Cause: reconfigurationFailure
[2022-08-31 11:18:38.745617181] Disconnecting rnti=0x4608.
[2022-08-31 11:18:38.893586462] RACH:  slot=5611, cc=0, preamble=0,
offset=9, temp_crnti=0x460c
[2022-08-31 11:18:38.992729952] Disconnecting rnti=0x460c.

The UE disconnects when the second RACH arrives, or vice versa,  Another
PRACH is created because the UE disconnects, but why does the UE disconnect?

At enb.log we can see the PRACH:

2022-08-31T09:18:36.969264 [PHY1-NR] [I] [ 3688] PUCCH: f=1 prb=51:1
symb=0:14 cs=8 occ=0 rnti=0x4601 sr=1 epre=-19.5 snr=-11.0 cfo=+694.8
delay=+10.5 val>
2022-08-31T09:*18:36.972352* [PHY-NR ] [I] [    0] PRACH: cc=0, 0/1,
preamble=2, offset=727.5 us, peak2avg=147.3, max_offset=1000.0 us
2022-08-31T09:18:36.972490 [MAC-NR ] [I] [ 3691] SCHED: rnti=0x4602, new
lcid configuration: [{lcid=0, mode=bi-dir, prio=1, lcg=0}]
2022-08-31T09:18:36.972553 [RLC-NR ] [I] Added LTE radio bearer with LCID 0
in Transparent Mode
2022-08-31T09:18:36.972557 [RRC-NR ] [I] Added new user rnti=0x4602
2022-08-31T09:18:36.972557 [MAC-NR ] [I] [ 3691] RACH:  slot=3691, cc=0,
preamble=2, offset=1396, temp_crnti=0x4602
2022-08-31T09:18:36.972565 [MAC-NR ] [I] [ 3691] rach_tprof: {mean, max,
min}={247.1, 281, 212} usec, nof_samples=2
2022-08-31T09:18:36.973223 [MAC-NR ] [I] [ 3692] SCHED: New user
rnti=0x4602, cc=0
2022-08-31T09:18:36.973224 [MAC-NR ] [I] [ 3692] SCHED: New PRACH
slot=3691, preamble=2, ra-rnti=0xf, temp_crnti=0x4602, ta_cmd=1396,
msg3_size=7
2022-08-31T09:18:36.973256 [MAC-NR ] [I] [ 3692] SCHED: RAR, cc=0,
ra-rnti=0xf, prbs=[1, 5), pdsch_slot=3696, msg3_slot=3702, nof_grants=1
2022-08-31T09:18:36.973263 [MAC-NR ] [I] [ 3692] Setting RAR Grant
tc-rnti=0x4602 dci=RAR ss=rar hop=0 f_alloc=0x68 t_alloc=0x0 mcs=0 tpc=1
csi=0
2022-08-31T09:18:36.973267 [MAC-NR ] [I] [ 3692] DL RAPID: 2, Temp C-RNTI:
0x4602, TA: 1396, UL Grant: [00 d0 00 40 ]
2022-08-31T09:18:36.973292 [PHY1-NR] [I] [ 3692] PDCCH: cc=0 ra-rnti=0x000f
dci=1_0 ss=common1 L=2 cce=0 f_alloc=0x90 t_alloc=0x0 vrb_to_prb_map=0
mcs=5 t>
2022-08-31T09:18:36.973322 [PHY1-NR] [I] [ 3692] PDSCH: cc=0 ra-rnti=0xf
prb=(1,4) symb=(1,13) CW0: mod=QPSK tbs=44 R=0.383 rv=0  tti_tx=3696
2022-08-31T09:18:36.977211 [PHY1-NR] [I] [ 3696] PDCCH: cc=0 si-rnti=0xffff
dci=1_0 ss=common0 L=2 cce=0 f_alloc=0x150 t_alloc=0x0 vrb_to_prb_map=0
mcs=5 >
2022-08-31T09:18:36.977249 [PHY1-NR] [I] [ 3696] PDSCH: cc=0 si-rnti=0xffff
prb=(1,8) symb=(2,13) CW0: mod=QPSK tbs=80 R=0.380 rv=0  tti_tx=3700
2022-08-31T09:18:36.983317 [PHY1-NR] [I] [ 3702] PUSCH: tc-rnti=0x4602
prb=(0,2) symb=(0,13) CW0: mod=QPSK tbs=11 R=0.131 rv=0 CRC=KO iter=10.0
evm=0.74 t>
2022-08-31T09:18:36.983335 [MAC-NR ] [I] [ 3702] SCHED: UL retx, cc=0,
rnti=0x4602, pid=0, cs=0, f=0_0, nrtx=1, tbs=11, bs=0, pusch_slot=3710

Before, it shows the message:

2022-08-31T09:*18:30.916264* [MAC-NR ] [I] [ 7875] SCHED: discarding
rnti=0x4601, DL TB pid=0. Cause: Maximum number of retx exceeded (4)

*Sometimes it is connected for 20 minutes and others for just a few
seconds...*

I have also tried srsRAN in *LTE* mode and I didn't have this problem,
the *connection
lasts forever.*

I attach the config files and enb.log

Also.. How can I check my antenna and make sure the UL is stable?

Thank you very much!!

BR,
Cris
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