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

Robert Falkenberg robert.falkenberg at srs.io
Thu Sep 1 11:12:24 UTC 2022 

Hi Cristina,

this is expected behavior at the moment:

Re: [srsran-users] srsran 22.04 - 5G SA on UHD B210 hardware
> Hi Bas,
>
> glad you got that working now.
>
> On 24/5/22 16:07, Vermeulen, Bas (Consultant) wrote:
>> I do occasionally see the following:
>>
>> ​PDU Session Establishment successful. IP: 10.45.0.2 │Disconnecting 
>> rnti=0x460a.
>> RRC NR reconfiguration successful.                    │RACH: 
>>  slot=3851, cc=0, preamble=0, offset=1, temp_crnti=0x460b
>> qScheduling request failed: releasing RRC connection... 
>> │Disconnecting rnti=0x460b.
>
>
> I am afraid that is expected. The UE is very basic and some of the 
> procedures in RRC connected and idle aren't implemented.
>
> What you can try is to increase the inactivity timer in the eNB so the 
> UE isn't released too soon.
>
> Thanks
> Andre 

Another option is to keep the connection busy, e.g. via "ping".

Best regards,
Robert

On 31.08.22 11:43, Cristina Posada wrote:
> 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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> srsran-users at lists.srsran.com
> https://lists.srsran.com/mailman/listinfo/srsran-users

-- 


      RobertFalkenberg

Senior Engineer

Software Radio Systems

	

	
	

	

	robert at srs.io <mailto:robert at srs.io>

	www.srs.io <//www.srs.io>

	Dortmund, Germany




	
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