Missing Guard Symbol in TDD Special Slot

Accelerated Computing Aerial Forum
1

Hi team,

I am trying to run Aerial DU with the OAI stack, here is my TDD config

dl_UL_TransmissionPeriodicity = 6;  // 6=ms5
nrofDownlinkSlots = 7;
nrofDownlinkSymbols = 12; 
nrofUplinkSlots = 2; 
nrofUplinkSymbols = 0;

The below image is the expected frames

image
image2372×576 32.8 KB

However, I noticed that there is no guard symbol between DL and UL.
In the special slot, DL occupies all 14 symbols, meaning that no guard symbols are present

DL C-Plane

PCAP frame number: 1
RU Port ID: 0
Direction: 1 (0=UL, 1=DL)
Frame-Subframe-Slot: 250-3-1
Start Symbol: 0
Number of Symbol: 14

image
image2822×1046 382 KB

UL C-Plane

Pcap Frame Number: 48
RU Port ID: 0
Direction: 0 (0=UL, 1=DL)
Frame-Subframe-Slot: 250-4-0
Start Symbol: 0
Number of Symbol: 14

image
image3390×1104 443 KB

Here is the pcap file nvidia-du-noguard-symbol.pcapng.zip (6.9 KB)

I checked that the cuPHY supported this feature. Did I do any wrong configuration?

image
image1516×356 46.5 KB

Any insights would be appreciated!

Thanks and best regards,
Tam

2

Hi Tam,
The reason for this is that when ru_type: 1 in the cuphycontroller yaml file, without a TDD configuration TLV in the config.request from the L2, the L1 will send all 14 symbols to the RU.

If you move this #endif up to line 1010, then then that TLV should be sent and the correct number of symbols will be sent in the S-slot.

Please also make sure that the L2 number of symbols matches the RU configuration.
In your case of nrofDownlinkSymbols = 12; with a Foxconn RU, you should have:

RRH_UL_INIT_SYM_ID = 0

While with 6:4:4 you should have:

RRH_UL_INIT_SYM_ID = 10
3

Hi,

Thank you for your response,

The modification works for me, I can see that the Downlink packets in the special slot do not use more than 12 symbols.

However, the UE now can not become “in-sync” with the gnb anymore.


[NR_MAC]   Frame.Slot 384.0

[NR_MAC]   Frame.Slot 512.0

[NR_MAC]   RACH.indication put_queue successfull
[NR_MAC]   597.19 UE RA-RNTI 010b TC-RNTI cab7: Activating RA process index 0
[NR_MAC]   UE cab7: Msg3 scheduled at 598.18 (598.7 TDA 2)
[NR_MAC]   UE cab7: 598.7 Generating RA-Msg2 DCI, RA RNTI 0x10b, state 1, CoreSetType 0, preamble_index(RAPID) 43, timing_offset = 13 (estimated distance 507.8 [m])
[NR_MAC]   598.7 Send RAR to RA-RNTI 010b
[NR_MAC]   Couldn't identify UE connected with current UL HARQ process
[NR_MAC]    59910: RA RNTI cab7 CC_id 0 Scheduling retransmission of Msg3 in (599,18)
[NR_MAC]   Couldn't identify UE connected with current UL HARQ process
[NR_MAC]    60010: RA RNTI cab7 CC_id 0 Scheduling retransmission of Msg3 in (600,18)
[NR_MAC]   Couldn't identify UE connected with current UL HARQ process
[NR_MAC]    60110: RA RNTI cab7 CC_id 0 Scheduling retransmission of Msg3 in (601,18)
[NR_MAC]   Random Access 0 failed at state WAIT_Msg3 (Reached msg3 max harq rounds)
[NR_MAC]   Couldn't identify UE connected with current UL HARQ process
[NR_MAC]   Frame.Slot 640.0

[NR_MAC]   Frame.Slot 768.0

[NR_MAC]   RACH.indication put_queue successfull
[NR_MAC]   858.19 UE RA-RNTI 010b TC-RNTI 7e96: Activating RA process index 0
[NR_MAC]   UE 7e96: Msg3 scheduled at 859.18 (859.7 TDA 2)
[NR_MAC]   UE 7e96: 859.7 Generating RA-Msg2 DCI, RA RNTI 0x10b, state 1, CoreSetType 0, preamble_index(RAPID) 2, timing_offset = 0 (estimated distance 0.0 [m])
[NR_MAC]   859.7 Send RAR to RA-RNTI 010b
[NR_MAC]   Couldn't identify UE connected with current UL HARQ process
[NR_MAC]    86010: RA RNTI 7e96 CC_id 0 Scheduling retransmission of Msg3 in (860,18)
[NR_MAC]   Couldn't identify UE connected with current UL HARQ process
[NR_MAC]    86110: RA RNTI 7e96 CC_id 0 Scheduling retransmission of Msg3 in (861,18)
[NR_MAC]   Couldn't identify UE connected with current UL HARQ process
[NR_MAC]    86210: RA RNTI 7e96 CC_id 0 Scheduling retransmission of Msg3 in (862,18)
[NR_MAC]   Random Access 0 failed at state WAIT_Msg3 (Reached msg3 max harq rounds)
[NR_MAC]   Couldn't identify UE connected with current UL HARQ process
[NR_MAC]   RACH.indication put_queue successfull
[NR_MAC]   869.19 UE RA-RNTI 010b TC-RNTI a280: Activating RA process index 0
[NR_MAC]   UE a280: Msg3 scheduled at 870.18 (870.7 TDA 2)
[NR_MAC]   UE a280: 870.7 Generating RA-Msg2 DCI, RA RNTI 0x10b, state 1, CoreSetType 0, preamble_index(RAPID) 38, timing_offset = 0 (estimated distance 0.0 [m])
[NR_MAC]   870.7 Send RAR to RA-RNTI 010b
[NR_MAC]   Couldn't identify UE connected with current UL HARQ process
[NR_MAC]    87110: RA RNTI a280 CC_id 0 Scheduling retransmission of Msg3 in (871,18)
[NR_MAC]   Couldn't identify UE connected with current UL HARQ process
[NR_MAC]    87210: RA RNTI a280 CC_id 0 Scheduling retransmission of Msg3 in (872,18)
[NR_MAC]   Couldn't identify UE connected with current UL HARQ process
[NR_MAC]    87310: RA RNTI a280 CC_id 0 Scheduling retransmission of Msg3 in (873,18)
[NR_MAC]   Random Access 0 failed at state WAIT_Msg3 (Reached msg3 max harq rounds)
[NR_MAC]   Couldn't identify UE connected with current UL HARQ process
[NR_MAC]   RACH.indication put_queue successfull
[NR_MAC]   881.19 UE RA-RNTI 010b TC-RNTI 107d: Activating RA process index 0
[NR_MAC]   UE 107d: Msg3 scheduled at 882.18 (882.7 TDA 2)
[NR_MAC]   UE 107d: 882.7 Generating RA-Msg2 DCI, RA RNTI 0x10b, state 1, CoreSetType 0, preamble_index(RAPID) 26, timing_offset = 0 (estimated distance 0.0 [m])
[NR_MAC]   882.7 Send RAR to RA-RNTI 010b
[NR_MAC]   Couldn't identify UE connected with current UL HARQ process
[NR_MAC]    88310: RA RNTI 107d CC_id 0 Scheduling retransmission of Msg3 in (883,18)
[NR_MAC]   Couldn't identify UE connected with current UL HARQ process
[NR_MAC]    88410: RA RNTI 107d CC_id 0 Scheduling retransmission of Msg3 in (884,18)
[NR_MAC]   Couldn't identify UE connected with current UL HARQ process
[NR_MAC]    88510: RA RNTI 107d CC_id 0 Scheduling retransmission of Msg3 in (885,18)
[NR_MAC]   Random Access 0 failed at state WAIT_Msg3 (Reached msg3 max harq rounds)
[NR_MAC]   Couldn't identify UE connected with current UL HARQ process
[NR_MAC]   RACH.indication put_queue successfull
[NR_MAC]   892.19 UE RA-RNTI 010b TC-RNTI 205e: Activating RA process index 0
[NR_MAC]   UE 205e: Msg3 scheduled at 893.18 (893.7 TDA 2)
[NR_MAC]   UE 205e: 893.7 Generating RA-Msg2 DCI, RA RNTI 0x10b, state 1, CoreSetType 0, preamble_index(RAPID) 56, timing_offset = 0 (estimated distance 0.0 [m])
[NR_MAC]   893.7 Send RAR to RA-RNTI 010b
[NR_MAC]   Couldn't identify UE connected with current UL HARQ process
[NR_MAC]    89410: RA RNTI 205e CC_id 0 Scheduling retransmission of Msg3 in (894,18)
[NR_MAC]   Couldn't identify UE connected with current UL HARQ process
[NR_MAC]    89510: RA RNTI 205e CC_id 0 Scheduling retransmission of Msg3 in (895,18)
[NR_MAC]   Frame.Slot 896.0

[NR_MAC]   Couldn't identify UE connected with current UL HARQ process
[NR_MAC]    89610: RA RNTI 205e CC_id 0 Scheduling retransmission of Msg3 in (896,18)
[NR_MAC]   Random Access 0 failed at state WAIT_Msg3 (Reached msg3 max harq rounds)
[NR_MAC]   Couldn't identify UE connected with current UL HARQ process
[NR_MAC]   Frame.Slot 0.0

Previously, the UE could successfully connect to the 5G system in a few cases.
Could you help with this?
Thank you

4

Hi,

I have tried the setup using the latest OAI and CUBB versions (24-3). However, the behavior remains unchanged.
Do you have any guidelines or alternative solutions to address this issue?

Thank you.

5

As discussed in the meeting, here is the pcap on O-FH when the UE is attaching, there are no packet in NGAP because the UE was not in-sync with the gnb.

nvidia-du-applied-solution-from-nhedberg.pcapng.zip (9.1 MB)

Thanks,
Tam

6

Hi, I added some debug code in cubb and found that the received config.request was wrong; as a result, the TDD pattern is not correct, as depicted in the picture below

image
image1094×768 275 KB

I did a walkaround solution by hardcoding the TDD pattern in cubb, and now everything is working. In special slot, I can find that there have guard symbols and it work perfectly with the RU. My UE can establish the connection smoothly and get around 800Mbps Downlink throughput.

Thank you!