SDU buffer full triggered by a COTS UE moving out of range and back in range
During our testing with a COTS UE (Crosscall Core-Z5) OTA with OAI DU from commit e15fa14c, we saw an issue when the UE moves out of range of the antenna and back in range, causing SDU buffer full errors in the DU:
2024-10-31T14:54:39.399Z [du] [MAC] UE 8fd2: request release after UL failure timer expiry
2024-10-31T14:54:40.491Z [du] [GTPU] [98] gtpv1uSend failed: while getting ue id 36818 in hashtable ue_mapping
2024-10-31T14:54:40.494Z [du] [RLC] Remove UE 36818
2024-10-31T14:54:40.494Z [du] [NR_MAC] Remove NR rnti 0x8fd2
2024-10-31T14:54:40.494Z [du] [GTPU] try to get a gtp-u not existing output
2024-10-31T14:54:40.494Z [du] [NR_MAC] Frame.Slot 768.0
2024-10-31T14:54:40.679Z [du] UE RNTI 2530 CU-UE-ID 6 out-of-sync PH 42 dB PCMAX 21 dBm, average RSRP 0 (0 meas)
2024-10-31T14:54:40.679Z [du] UE 2530: dlsch_rounds 20/0/0/0, dlsch_errors 0, pucch0_DTX 0, BLER 0.02288 MCS (0) 9
2024-10-31T14:54:40.679Z [du] UE 2530: ulsch_rounds 3842/1059/3/1, ulsch_errors 1, ulsch_DTX 177, BLER 0.16809 MCS (0) 6 (Qm 2 deltaMCS 0 dB) NPRB 5 SNR 17.5 dB
2024-10-31T14:54:40.679Z [du] UE 2530: MAC: TX 2337 RX 234059 bytes
2024-10-31T14:54:40.679Z [du] UE 2530: LCID 1: TX 31 RX 87 bytes
2024-10-31T14:54:40.679Z [du] UE RNTI 4311 CU-UE-ID 2 in-sync PH 50 dB PCMAX 21 dBm, average RSRP -103 (16 meas)
2024-10-31T14:54:40.679Z [du] UE 4311: dlsch_rounds 9248/1/0/0, dlsch_errors 0, pucch0_DTX 1, BLER 0.00000 MCS (0) 28
2024-10-31T14:54:40.679Z [du] UE 4311: ulsch_rounds 4515/332/182/62, ulsch_errors 0, ulsch_DTX 1, BLER 0.21572 MCS (1) 14 (Qm 6 deltaMCS 0 dB) NPRB 5 SNR 14.0 dB
2024-10-31T14:54:40.679Z [du] UE 4311: MAC: TX 36093287 RX 1128954 bytes
2024-10-31T14:54:40.679Z [du] UE 4311: LCID 1: TX 334 RX 1306 bytes
2024-10-31T14:54:40.679Z [du] UE 4311: LCID 2: TX 0 RX 0 bytes
2024-10-31T14:54:40.679Z [du] UE 4311: LCID 4: TX 35968352 RX 620791 bytes
2024-10-31T14:54:40.679Z [du]
2024-10-31T14:54:40.679Z [du] [RLC] 1 SDU rejected, SDU buffer full
2024-10-31T14:54:41.598Z [du] [NR_MAC] Frame.Slot 896.0
2024-10-31T14:54:41.959Z [du] UE RNTI 2530 CU-UE-ID 6 out-of-sync PH 42 dB PCMAX 21 dBm, average RSRP 0 (0 meas)
2024-10-31T14:54:41.959Z [du] UE 2530: dlsch_rounds 20/0/0/0, dlsch_errors 0, pucch0_DTX 0, BLER 0.02288 MCS (0) 9
2024-10-31T14:54:41.959Z [du] UE 2530: ulsch_rounds 3842/1059/3/1, ulsch_errors 1, ulsch_DTX 177, BLER 0.16809 MCS (0) 6 (Qm 2 deltaMCS 0 dB) NPRB 5 SNR 17.5 dB
2024-10-31T14:54:41.959Z [du] UE 2530: MAC: TX 2337 RX 234059 bytes
2024-10-31T14:54:41.959Z [du] UE 2530: LCID 1: TX 31 RX 87 bytes
2024-10-31T14:54:41.959Z [du] UE RNTI 4311 CU-UE-ID 2 in-sync PH 50 dB PCMAX 21 dBm, average RSRP -103 (16 meas)
2024-10-31T14:54:41.959Z [du] UE 4311: dlsch_rounds 10800/1/0/0, dlsch_errors 0, pucch0_DTX 1, BLER 0.00000 MCS (0) 28
2024-10-31T14:54:41.959Z [du] UE 4311: ulsch_rounds 4933/349/182/62, ulsch_errors 0, ulsch_DTX 1, BLER 0.07199 MCS (1) 8 (Qm 4 deltaMCS 0 dB) NPRB 5 SNR 14.0 dB
2024-10-31T14:54:41.959Z [du] UE 4311: MAC: TX 42985543 RX 1201484 bytes
2024-10-31T14:54:41.959Z [du] UE 4311: LCID 1: TX 337 RX 1328 bytes
2024-10-31T14:54:41.959Z [du] UE 4311: LCID 2: TX 0 RX 0 bytes
2024-10-31T14:54:41.959Z [du] UE 4311: LCID 4: TX 42841664 RX 682267 bytes
2024-10-31T14:54:41.959Z [du]
2024-10-31T14:54:41.959Z [du] [RLC] 876 SDU rejected, SDU buffer full
2024-10-31T14:54:42.605Z [du] [NR_MAC] Frame.Slot 0.0
2024-10-31T14:54:43.239Z [du] UE RNTI 2530 CU-UE-ID 6 out-of-sync PH 42 dB PCMAX 21 dBm, average RSRP 0 (0 meas)
2024-10-31T14:54:43.239Z [du] UE 2530: dlsch_rounds 20/0/0/0, dlsch_errors 0, pucch0_DTX 0, BLER 0.02288 MCS (0) 9
2024-10-31T14:54:43.239Z [du] UE 2530: ulsch_rounds 3842/1059/3/1, ulsch_errors 1, ulsch_DTX 177, BLER 0.16809 MCS (0) 6 (Qm 2 deltaMCS 0 dB) NPRB 5 SNR 17.5 dB
2024-10-31T14:54:43.239Z [du] UE 2530: MAC: TX 2337 RX 234059 bytes
2024-10-31T14:54:43.239Z [du] UE 2530: LCID 1: TX 31 RX 87 bytes
2024-10-31T14:54:43.239Z [du] UE RNTI 4311 CU-UE-ID 2 in-sync PH 38 dB PCMAX 21 dBm, average RSRP -107 (16 meas)
2024-10-31T14:54:43.239Z [du] UE 4311: dlsch_rounds 12347/6/0/0, dlsch_errors 0, pucch0_DTX 1, BLER 0.00182 MCS (0) 28
2024-10-31T14:54:43.239Z [du] UE 4311: ulsch_rounds 5331/375/182/62, ulsch_errors 0, ulsch_DTX 2, BLER 0.08246 MCS (1) 12 (Qm 6 deltaMCS 0 dB) NPRB 5 SNR 14.5 dB
2024-10-31T14:54:43.239Z [du] UE 4311: MAC: TX 49852189 RX 1266622 bytes
2024-10-31T14:54:43.239Z [du] UE 4311: LCID 1: TX 340 RX 1350 bytes
2024-10-31T14:54:43.239Z [du] UE 4311: LCID 2: TX 0 RX 0 bytes
2024-10-31T14:54:43.239Z [du] UE 4311: LCID 4: TX 49689411 RX 724191 bytes
2024-10-31T14:54:43.239Z [du]
2024-10-31T14:54:43.239Z [du] [RLC] 183 SDU rejected, SDU buffer full
2024-10-31T14:54:43.686Z [du] [NR_MAC] Frame.Slot 128.0
2024-10-31T14:54:44.520Z [du] UE RNTI 2530 CU-UE-ID 6 out-of-sync PH 42 dB PCMAX 21 dBm, average RSRP 0 (0 meas)
2024-10-31T14:54:44.520Z [du] UE 2530: dlsch_rounds 20/0/0/0, dlsch_errors 0, pucch0_DTX 0, BLER 0.02288 MCS (0) 9
2024-10-31T14:54:44.520Z [du] UE 2530: ulsch_rounds 3842/1059/3/1, ulsch_errors 1, ulsch_DTX 177, BLER 0.16809 MCS (0) 6 (Qm 2 deltaMCS 0 dB) NPRB 5 SNR 17.5 dB
2024-10-31T14:54:44.520Z [du] UE 2530: MAC: TX 2337 RX 234059 bytes
2024-10-31T14:54:44.520Z [du] UE 2530: LCID 1: TX 31 RX 87 bytes
2024-10-31T14:54:44.520Z [du] UE RNTI 4311 CU-UE-ID 2 in-sync PH 44 dB PCMAX 21 dBm, average RSRP -112 (16 meas)
2024-10-31T14:54:44.520Z [du] UE 4311: dlsch_rounds 13887/18/0/0, dlsch_errors 0, pucch0_DTX 1, BLER 0.00386 MCS (0) 28
2024-10-31T14:54:44.520Z [du] UE 4311: ulsch_rounds 5737/395/182/62, ulsch_errors 0, ulsch_DTX 2, BLER 0.05908 MCS (1) 12 (Qm 6 deltaMCS 0 dB) NPRB 5 SNR 13.5 dB
2024-10-31T14:54:44.520Z [du] UE 4311: MAC: TX 56682981 RX 1340904 bytes
2024-10-31T14:54:44.520Z [du] UE 4311: LCID 1: TX 346 RX 1394 bytes
2024-10-31T14:54:44.520Z [du] UE 4311: LCID 2: TX 0 RX 0 bytes
2024-10-31T14:54:44.520Z [du] UE 4311: LCID 4: TX 56501360 RX 765579 bytes
2024-10-31T14:54:44.520Z [du]
2024-10-31T14:54:44.520Z [du] [NR_MAC] Frame.Slot 256.0We did not find a consistent way to reproduce this issue. I do not have access anymore to an OTA environment to reproduce further.