Noise level in MIMO is not divided by number of antennas

lib/examples/pdsch_enodeb.c

@@ -84,6 +84,8 @@ int mbsfn_area_id = -1;
 char *rf_args = "";
 float rf_amp = 0.8, rf_gain = 70.0, rf_freq = 2400000000;
 
+float output_file_snr = +INFINITY;
+
 bool null_file_sink=false; 
 srslte_filesink_t fsink;
 srslte_ofdm_t ifft[SRSLTE_MAX_PORTS];
@@ -145,13 +147,14 @@ void usage(char *prog) {
   printf("\t-w Number of codewords/layers (multiplex mode only)* [Default %d]\n", multiplex_nof_layers);
   printf("\t-u listen TCP port for input data (-1 is random) [Default %d]\n", net_port);
   printf("\t-v [set srslte_verbose to debug, default none]\n");
+  printf("\t-s output file SNR [Default %f]\n", output_file_snr);
   printf("\n");
   printf("\t*: See 3GPP 36.212 Table  5.3.3.1.5-4 for more information\n");
 }
 
 void parse_args(int argc, char **argv) {
   int opt;
-  while ((opt = getopt(argc, argv, "aglfmoncpvutxbwM")) != -1) {
+  while ((opt = getopt(argc, argv, "aglfmoncpvutxbwMs")) != -1) {
 
     switch (opt) {
     case 'a':
@@ -200,6 +203,9 @@ void parse_args(int argc, char **argv) {
     case 'v':
       srslte_verbose++;
       break;
+    case 's':
+      output_file_snr = atof(argv[optind]);
+      break;
     default:
       usage(argv[0]);
       exit(-1);
@@ -989,7 +995,14 @@ int main(int argc, char **argv) {
       /* send to file or usrp */
       if (output_file_name) {
         if (!null_file_sink) {
-           srslte_filesink_write_multi(&fsink, (void**) output_buffer, sf_n_samples, cell.nof_ports);       
+          /* Apply AWGN */
+          if (output_file_snr != +INFINITY) {
+            float var = powf(10.0f, -(output_file_snr + 3.0f) / 20.0f);
+            for (int k = 0; k < cell.nof_ports; k++) {
+              srslte_ch_awgn_c(output_buffer[k], output_buffer[k], var, sf_n_samples);
+            }
+          }
+          srslte_filesink_write_multi(&fsink, (void**) output_buffer, sf_n_samples, cell.nof_ports);
         }
         usleep(1000);
       } else {

lib/src/phy/ch_estimation/chest_dl.c

@@ -291,7 +291,7 @@ static float estimate_noise_pilots(srslte_chest_dl_t *q, uint32_t port_id, srslt
       norm /= norm3;
     }
   }
-  float power = norm*q->cell.nof_ports*srslte_vec_avg_power_cf(q->tmp_noise, nref);
+  float power = norm*srslte_vec_avg_power_cf(q->tmp_noise, nref);
   return power; 
 }
 
@@ -543,7 +543,7 @@ void chest_interpolate_noise_est(srslte_chest_dl_t *q, cf_t *input, cf_t *ce, ui
 
   /* Compute RSRP for the channel estimates in this port */
   uint32_t npilots = SRSLTE_REFSIGNAL_NUM_SF(q->cell.nof_prb, port_id);
-  q->rsrp[rxant_id][port_id] = __real__ srslte_vec_dot_prod_conj_ccc(q->pilot_estimates, q->pilot_estimates, npilots) / npilots;
+  q->rsrp[rxant_id][port_id] = srslte_vec_avg_power_cf(q->pilot_estimates, npilots);
   q->rssi[rxant_id][port_id] = srslte_chest_dl_rssi(q, input, port_id);
 }
 
@@ -639,7 +639,10 @@ float srslte_chest_dl_get_noise_estimate(srslte_chest_dl_t *q) {
   for (int i=0;i<q->last_nof_antennas;i++) {
     n += srslte_vec_acc_ff(q->noise_estimate[i], q->cell.nof_ports)/q->cell.nof_ports;
   }
-  return n/q->last_nof_antennas;
+  if (q->last_nof_antennas) {
+    n /= q->last_nof_antennas;
+  }
+  return n;
 }
 
 float srslte_chest_dl_get_snr(srslte_chest_dl_t *q) {
@@ -691,20 +694,23 @@ float srslte_chest_dl_get_rsrp_ant_port(srslte_chest_dl_t *q, uint32_t ant_idx,
 }
 
 float srslte_chest_dl_get_rsrp_port(srslte_chest_dl_t *q, uint32_t port) {
-  float max = -INFINITY;
-  for (int i = 0; i < q->last_nof_antennas; i++) {
-      if (q->rsrp[i][port] > max) {
-        max = q->rsrp[i][port];
-      }
+  float sum = 0.0f;
+  for (int j = 0; j < q->cell.nof_ports; ++j) {
+    sum +=q->rsrp[port][j];
   }
-  return max;
+
+  if (q->cell.nof_ports) {
+    sum /= q->cell.nof_ports;
+  }
+
+  return sum;
 }
 
 float srslte_chest_dl_get_rsrp(srslte_chest_dl_t *q) {
-  float max = -INFINITY;
-  for (int i = 0; i < q->cell.nof_ports; ++i) {
+  float max = -0.0f;
+  for (int i = 0; i < q->last_nof_antennas; ++i) {
     float v = srslte_chest_dl_get_rsrp_port(q, i);
-    if (max < v) {
+    if (v > max) {
       max = v;
     }
   }