noise power

ci-scripts/conf_files/channelmod_rfsimu.conf

@@ -6,10 +6,10 @@ channelmod = {
   modellist="modellist_rfsimu_1";
   modellist_rfsimu_1 = (
     {
-        model_name                       = "rfsimu_channel_ue0"
+        model_name                       = "rfsimu_channel_enB0"
       	type                             = "AWGN";			  
       	ploss_dB                         = 0;
-        noise_power_dB                   = 0; 
+        noise_power_dB                   = -10; 
         forgetfact                       = 0;  
         offset                           = 0;      
         ds_tdl                           = 0;      

openair1/SIMULATION/TOOLS/sim.h

@@ -269,7 +269,7 @@ typedef enum {
     {CHANNELMOD_MODEL_NAME_PNAME, "name of the model\n",               0,  strptr:NULL ,             defstrval:"",                    TYPE_STRING,    0 },\
     {CHANNELMOD_MODEL_TYPE_PNAME, "name of the model type\n",          0,  strptr:NULL ,             defstrval:"AWGN",                TYPE_STRING,    0 },\
     {CHANNELMOD_MODEL_PL_PNAME,   "channel path loss in dB\n",         0,  dblptr:NULL,              defdblval:0,                     TYPE_DOUBLE,    0 },\
-    {CHANNELMOD_MODEL_NP_PNAME,   "channel noise in dB\n",             0,  dblptr:NULL,              defdblval:0,                     TYPE_DOUBLE,    0 },\
+    {CHANNELMOD_MODEL_NP_PNAME,   "channel noise in dB\n",             0,  dblptr:NULL,              defdblval:-50,                     TYPE_DOUBLE,    0 },\
     {CHANNELMOD_MODEL_FF_PNAME,   "channel forget factor ((0 to 1)\n", 0,  dblptr:NULL,              defdblval:0,                     TYPE_DOUBLE,    0 },\
     {CHANNELMOD_MODEL_CO_PNAME,   "channel offset in samps\n",         0,  iptr:NULL,                defintval:0,                     TYPE_INT,       0 },\
     {CHANNELMOD_MODEL_DT_PNAME,    "delay spread for TDL models\n",    0,  dblptr:NULL,              defdblval:0,                     TYPE_DOUBLE,    0 }\

targets/ARCH/rfsimulator/apply_channelmod.c

@@ -65,17 +65,8 @@ void rxAddInput( struct complex16 *input_sig, struct complex16 *after_channel_si
   // Fixme: not sure when it is "volts" so dB is 20*log10(...) or "power", so dB is 10*log10(...)
   const double pathLossLinear = pow(10,channelDesc->path_loss_dB/20.0);
   // Energy in one sample to calibrate input noise
-  //Fixme: modified the N0W computation, not understand the origin value
-  const double KT=1.38e-23*290; //Boltzman*temperature
-  // sampling rate is linked to acquisition band (the input pass band filter)
-  const double noise_figure_watt = KT*channelDesc->sampling_rate;
-  // Fixme: how to convert a noise in Watt into a 12 bits value out of the RF ADC ?
-  // the parameter "-s" is declared as SNR, but the input power is not well defined
-  // −132.24 dBm is a LTE subcarrier noise, that was used in origin code (15KHz BW thermal noise)
-  const double rxGain= 132.24 - channelDesc->noise_power_dB;
-  // sqrt(4*noise_figure_watt) is the thermal noise factor (volts)
-  // fixme: the last constant is pure trial results to make decent noise
-  const double noise_per_sample = sqrt(4*noise_figure_watt) * pow(10,rxGain/20) *10;
+  // the normalized OAI value seems to be 256 as average amplitude (numerical amplification = 1)
+  const double noise_per_sample = pow(10,channelDesc->noise_power_dB/10.0) * 256;
   // Fixme: we don't fill the offset length samples at begining ?
   // anyway, in today code, channel_offset=0
   const int dd = abs(channelDesc->channel_offset);