Added cell_measurement calibration with RSSI sensor

srslte/examples/cell_measurement.c

@@ -236,6 +236,8 @@ int main(int argc, char **argv) {
   }
   
   cuhd_start_rx_stream(uhd);
+  
+  float rx_gain_offset = 0;
 
   /* Main loop */
   while (sf_cnt < prog_args.nof_subframes || prog_args.nof_subframes == -1) {
@@ -301,16 +303,26 @@ int main(int argc, char **argv) {
           snr = SRSLTE_VEC_EMA(srslte_chest_dl_get_snr(&chest),snr,0.05);      
           
           nframes++;          
-        }        
+        } 
+        
+        
+        if ((nframes%100) == 0 || rx_gain_offset == 0) {
+          if (cuhd_has_rssi(uhd)) {
+            rx_gain_offset = 10*log10(rssi)-cuhd_get_rssi(uhd);
+          } else {
+            rx_gain_offset = cuhd_get_rx_gain(uhd);
+          }
+        }
         
         // Plot and Printf
         if ((nframes%10) == 0) {
+
           printf("CFO: %+8.4f KHz, SFO: %+8.4f Khz, RSSI: %5.1f dBm, RSSI/ref-symbol: %+5.1f dBm, "
                  "RSRP: %+5.1f dBm, RSRQ: %5.1f dB, SNR: %5.1f dB\r",
                 srslte_ue_sync_get_cfo(&ue_sync)/1000, srslte_ue_sync_get_sfo(&ue_sync)/1000, 
-                10*log10(rssi*1000) - cuhd_get_rx_gain(uhd), 
+                10*log10(rssi*1000) - rx_gain_offset,                                  
-                10*log10(rssi_utra*1000)- cuhd_get_rx_gain(uhd), 
+                10*log10(rssi_utra*1000)- rx_gain_offset, 
-                10*log10(rsrp*1000)- cuhd_get_rx_gain(uhd), 
+                10*log10(rsrp*1000) - rx_gain_offset, 
                 10*log10(rsrq), 10*log10(snr));                
           if (srslte_verbose != SRSLTE_VERBOSE_NONE) {
             printf("\n");

srslte/include/srslte/cuhd/cuhd.h

@@ -53,6 +53,10 @@ SRSLTE_API int cuhd_stop_rx_stream(void *h);
 
 SRSLTE_API void cuhd_flush_buffer(void *h);
 
+SRSLTE_API bool cuhd_has_rssi(void *h);
+
+SRSLTE_API float cuhd_get_rssi(void *h); 
+
 SRSLTE_API bool cuhd_rx_wait_lo_locked(void *h);
 
 SRSLTE_API void cuhd_set_master_clock_rate(void *h, 

srslte/lib/cuhd/src/cuhd_imp.cpp

@@ -108,6 +108,27 @@ void cuhd_flush_buffer(void *h)
   } while (n > 0);  
 }
 
+bool cuhd_has_rssi(void *h) {
+  cuhd_handler *handler = static_cast < cuhd_handler * >(h);
+  std::vector < std::string > mb_sensors = handler->usrp->get_mboard_sensor_names();
+  std::vector < std::string > rx_sensors = handler->usrp->get_rx_sensor_names(0);
+  if (std::find(rx_sensors.begin(), rx_sensors.end(), "rssi") != rx_sensors.end()) {
+    return true;
+  } else {
+    return false; 
+  }
+}
+
+float cuhd_get_rssi(void *h) {
+  cuhd_handler *handler = static_cast < cuhd_handler * >(h);
+  if (cuhd_has_rssi(h)) {
+    uhd::sensor_value_t value = handler->usrp->get_rx_sensor("rssi");
+    return value.to_real();
+  } else {
+    return 0;
+  }
+}
+
 int cuhd_start_rx_stream_nsamples(void *h, uint32_t nsamples)
 {
   cuhd_handler *handler = static_cast < cuhd_handler * >(h);