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Generated UL Data is pure zeros in OTA and not random as in RF Simulation

The TX payload generation on UE has a bug. There is a difference between UL data transmitted in OTA vs that in RF Simulation.

  • Run OAI Soft UE in OAI RF Simulation: The generated UL payload is as expected. It is random (zeros and ones).
  • Run OAI Soft UE with Real RF (with USRP): The generated UL payload is just zeros.

I added this portion of code to print tx payload to openair1/PHY/NR_UE_TRANSPORT/nr_ulsch_coding.c :

#ifdef DEPUG_TX_SLOT_PAYLOAD printf("\ndata of %d bytes:", A); for (int ii = 0; ii < A; ii++) { printf("%d,", harq_process->payload_AB[ii]); } printf("\n"); #endif

Snapshot from the code: image

Resulting data in case of OTA (pure zeros):

image

Resulting data in case of RF Simulation (random as expected):

image

Commands: gNB CMDs:

  • # Real RF: sudo ./cmake_targets/ran_build/build/nr-softmodem -O ./targets/PROJECTS/GENERIC-NR-5GC/CONF/gnb.band78.sa.fr1.106PRB.1x1.usrpx410_3300MHz.conf --gNBs.[0].min_rxtxtime 6 --usrp-tx-thread-config 1 --parallel-config PARALLEL_SINGLE_THREAD --phy-test -T 6
  • # RF Simulation: sudo ./cmake_targets/ran_build/build/nr-softmodem -O ./targets/PROJECTS/GENERIC-NR-5GC/CONF/gnb.band78.sa.fr1.106PRB.1x1.usrpx410_3300MHz.conf --gNBs.[0].min_rxtxtime 6 --rfsim --rfsimulator.serveraddr server --parallel-config PARALLEL_SINGLE_THREAD --phy-test -T 6

UE CMDs:

  • # RF Real: sudo ./cmake_targets/ran_build/build/nr-uesoftmodem --usrp-args "type=x4xx,addr=192.168.10.2,second_addr=192.168.11.2,clock_source=external,time_source=external" --phy-test --numerology 1 -O ./targets/PROJECTS/GENERIC-NR-5GC/CONF/ue.conf --reconfig-file /home/user/workarea/rrc_files/reconfig.raw --rbconfig-file /home/user/workarea/rrc_files/rbconfig.raw --ue-rxgain 40 --ue-txgain 12
  • # RF Simulation: sudo ./cmake_targets/ran_build/build/nr-uesoftmodem --rfsim --rfsimulator.serveraddr 192.168.100.2 --phy-test --numerology 1 -O ./targets/PROJECTS/GENERIC-NR-5GC/CONF/ue.conf --reconfig-file /home/user/workarea/rrc_files/reconfig.raw --rbconfig-file /home/user/workarea/rrc_files/rbconfig.raw