Introduce uplink multi-user MIMO (MU-MIMO) simulator

This commit introduces a dedicated simulation environment to validate
the uplink MU-MIMO joint processing framework. It models a scenario
where a single gNB serves multiple spatially multiplexed UEs sharing
the exact same time and frequency resources.

The simulator executes the complete physical layer baseband pipeline:
- PUSCH data generation and LDPC encoding per UE
- OFDM modulation (TX)
- Signal propagation through a multi-path channel model
- OFDM demodulation (RX) at the gNB
- Joint PUSCH decoding, equalization, and spatial demultiplexing

Performance metrics such as scrambling errors and BLER per UE is
evaluated at the end of the simulation.
Signed-off-by: Rakesh Mundlamuri <rakesh.mundlamuri@openairinterface.org>

CMakeLists.txt

@@ -2043,6 +2043,19 @@ target_link_libraries(nr_srssim PRIVATE
   m pthread ITTI dl nr_ue_phy_meas physim_common softmodem_common
   )
 
+add_executable(nr_ulsim_mu_mimo
+  ${OPENAIR1_DIR}/SIMULATION/NR_PHY/ulsim_mu_mimo.c
+  ${NFAPI_USER_DIR}/nfapi.c
+  ${NFAPI_USER_DIR}/gnb_ind_vars.c
+  ${PHY_INTERFACE_DIR}/queue_t.c
+  )
+
+target_link_libraries(nr_ulsim_mu_mimo PRIVATE
+  -Wl,--start-group UTIL SIMU PHY_NR_COMMON PHY_NR PHY_NR_UE SCHED_NR_LIB SCHED_NR_UE_LIB MAC_UE_NR MAC_NR_COMMON CONFIG_LIB L2_NR -Wl,--end-group
+  m pthread ${T_LIB} ITTI dl nr_ue_phy_meas physim_common softmodem_common NR_L2_UE
+  )
+target_link_libraries(nr_ulsim_mu_mimo PRIVATE asn1_nr_rrc_hdrs asn1_lte_rrc_hdrs)
+
 if(ENABLE_CHANNEL_SIM_CUDA)
   if (TARGET oai_cuda_lib)
       target_link_libraries(nr_dlsim PRIVATE oai_cuda_lib)
@@ -2100,7 +2113,7 @@ if (${T_TRACER})
         nr-uesoftmodem dlsim dlsim_tm4 dlsim_tm7
         ulsim pbchsim scansim mbmssim pdcchsim pucchsim prachsim
         syncsim nr_ulsim nr_dlsim nr_dlschsim nr_pbchsim nr_pucchsim
-        nr_ulschsim ldpctest polartest smallblocktest nr_srssim
+        nr_ulschsim ldpctest polartest smallblocktest nr_srssim nr_ulsim_mu_mimo
         #all "add_library" definitions
         ITTI lte_rrc nr_rrc s1ap x2ap m2ap m3ap f1ap
         params_libconfig

cmake_targets/build_oai

@@ -284,7 +284,7 @@ function main() {
             SIMUS_PHY=1
             CMAKE_CMD="$CMAKE_CMD -DENABLE_PHYSIM_TESTS=ON"
             # TODO: fix: dlsim_tm4 pucchsim prachsim pdcchsim pbchsim mbmssim
-            TARGET_LIST="$TARGET_LIST dlsim ulsim ldpctest polartest smallblocktest nr_pbchsim nr_dlschsim nr_ulschsim nr_dlsim nr_ulsim nr_pucchsim nr_prachsim nr_psbchsim nr_srssim"
+            TARGET_LIST="$TARGET_LIST dlsim ulsim ldpctest polartest smallblocktest nr_pbchsim nr_dlschsim nr_ulschsim nr_dlsim nr_ulsim nr_pucchsim nr_prachsim nr_psbchsim nr_srssim nr_ulsim_mu_mimo"
             echo_info "Will compile dlsim, ulsim, ..."
             shift;;
        -V | --vcd)

tools/packages/packages.cmake

@@ -222,7 +222,7 @@ if(PACKAGING_PHYSIM)
     --------------------------------------------------------
     Coding focused: polartest, smallblocktest, ldpctest
     Downlink PHY: nr_dlschsim, nr_psbchsim, nr_dlsim
-    Uplink PHY: nr_pucchsim nr_prachsim nr_ulschsim nr_ulsim
+    Uplink PHY: nr_pucchsim nr_prachsim nr_ulschsim nr_ulsim nr_ulsim_mu_mimo
     --------------------------------------------------------
     polartest: test polar codes which are used in 5G control channels, validates encoding, decoding and error correction performance*
     smallblocktest: generic test for small channel coding blocks, validates encoding and decoding for small transport blocks
@@ -233,7 +233,8 @@ if(PACKAGING_PHYSIM)
     nr_dlsim: simulates NR downlink, including multiple downlink channels and measurements of BLER/throughput
     nr_prachsim: simulates the Physical Random Access Channel, including UE initial access, preamble detection and timing alignment
     nr_ulschsim: simulates the Uplink Shared Channel, including LDPC encoding, modulation, transmission and decoding
-    nr_ulsim: simulates the NR uplink simulation, including PUCCH, PUSCH and PRACH")
+    nr_ulsim: simulates the NR uplink simulation, including PUCCH, PUSCH and PRACH
+    nr_ulsim_mu_mimo: simulates the NR uplink simulation with PUSCH multi user MIMO")
 
   if(PACKAGING_RPM)
     set(CPACK_RPM_PACKAGE_OAI-PHYSIM_SUMMARY "OpenAirInterface PhySim package")
@@ -254,7 +255,7 @@ if(PACKAGING_PHYSIM)
   install(FILES "${CMAKE_SOURCE_DIR}/doc/physical-simulators.md" DESTINATION share/doc/ COMPONENT oai-physim)
 
   #Add the targets to the package
-  install(TARGETS polartest smallblocktest ldpctest nr_dlschsim nr_psbchsim nr_pucchsim nr_dlsim nr_prachsim nr_ulschsim nr_ulsim
+  install(TARGETS polartest smallblocktest ldpctest nr_dlschsim nr_psbchsim nr_pucchsim nr_dlsim nr_prachsim nr_ulschsim nr_ulsim nr_ulsim_mu_mimo
         COMPONENT oai-physim
         RUNTIME DESTINATION /usr/bin
         LIBRARY DESTINATION /usr/lib