vrtsim: add CIR DB playback with CLI flags

VRTSIM: CIR DB playback via CLI

This change adds an optional in-process CIR DB path to VRTSIM. When enabled with --vrtsim.cirdb and optional --vrtsim.cirdb-path, VRTSIM reads precomputed taps from cir_db.bin. Default behavior is unchanged when the flag is not set.

Files touched

• radio/vrtsim/vrtsim.c
• radio/vrtsim/cirdb_provider.c
• radio/vrtsim/cirdb_provider.h
• radio/vrtsim/CMakeLists.txt

Build

cmake ../../ -GNinja -DOAI_VRTSIM_CIRDB=ON -DOAI_VRTSIM_TAPS_CLIENT=OFF
cmake --build . --target vrtsim

How to run

gNB

sudo ./nr-softmodem \
  -O ./targets/PROJECTS/GENERIC-NR-5GC/CONF/gnb.sa.band78.fr1.106PRB.usrpb210.conf \
  --device.name vrtsim \
  --vrtsim.role server \
  --gNBs.[0].min_rxtxtime 3 \
  --vrtsim.cirdb 1 \
  --vrtsim.cirdb-path /home/merkeb/oai-cir-emitter/cir_db.bin

UE

sudo ./nr-uesoftmodem \
  -C 3619200000 -r 106 --numerology 1 --ssb 516 --band 78 \
  --device.name vrtsim

Expected logs

• VRTSIM prints that channel modelling is active and uses DB backed taps
• CIRDB ready: model=..., shape=Tx x Rx, L=..., S=..., fs=..., dt=..., speed=...

CLI behavior and fallbacks

• TAPS client and chanmod paths are unchanged
• If --vrtsim.cirdb is not set or equals 0, VRTSIM uses the existing channel model path