Allow >1 channel models on rfsim server

Use `rfsimu_channel_ue1`, `rfsimu_channel_ue2`, etc. if you want to
use different channel models for each client. The client connection
order determines its channel model name.

openair1/SIMULATION/TOOLS/DOC/channel_simulation.md

@@ -90,7 +90,11 @@ channelmod = {
 };
 ```
 
-where `rfsimu_channel_ue0` will be activated on server side (i.e. eNB/gNB) for uplink and `rfsimu_channel_enB0` will be activated on client side (i.e. UE) for downlink.
+where `rfsimu_channel_ue0` will be activated on server side for uplink and `rfsimu_channel_enB0` will be activated on client side for downlink.
+
+Use `rfsimu_channel_ue1`, `rfsimu_channel_ue2`, etc. if you want to use different channel models for each client. The client connection order determines its channel model.
+
+The server could be either the UE or the gNB, the channel name suffix does not depend on the application but on the rfsimulators role (server/client).
 
 ## Edit the configuration file
 

radio/rfsimulator/simulator.c

@@ -260,11 +260,17 @@ static int allocCirBuf(rfsimulator_state_t *bridge, int sock)
       tableNor(rand);
       init_done=true;
     }
-    char *modelname = (bridge->role == SIMU_ROLE_SERVER) ? "rfsimu_channel_ue0" : "rfsimu_channel_enB0";
+    char modelname[30];
+    snprintf(modelname, sizeofArray(modelname), "rfsimu_channel_%s%d", (bridge->role == SIMU_ROLE_SERVER) ? "ue" : "enB", nb_ue);
     ptr->channel_model = find_channel_desc_fromname(modelname); // path_loss in dB
     if (!ptr->channel_model) {
-      LOG_E(HW, "Channel model %s not found, check config file\n", modelname);
-      return -1;
+      // Use legacy method to find channel model - this will use the same channel model for all clients
+      char *legacy_model_name = (bridge->role == SIMU_ROLE_SERVER) ? "rfsimu_channel_ue0" : "rfsimu_channel_enB0";
+      ptr->channel_model = find_channel_desc_fromname(legacy_model_name);
+      if (!ptr->channel_model) {
+        LOG_E(HW, "Channel model %s/%s not found, check config file\n", modelname, legacy_model_name);
+        return -1;
+      }
     }
 
     set_channeldesc_owner(ptr->channel_model, RFSIMU_MODULEID);