Review NR NSA CFO estimation and compensation

lib/include/srsran/interfaces/ue_nr_interfaces.h

@@ -180,6 +180,7 @@ struct phy_args_nr_t {
   bool                   store_pdsch_ko     = false;
   float                  trs_epre_ema_alpha = 0.1f; ///< EPRE measurement exponential average alpha
   float                  trs_rsrp_ema_alpha = 0.1f; ///< RSRP measurement exponential average alpha
+  float                  trs_sinr_ema_alpha = 0.1f; ///< SINR measurement exponential average alpha
   float                  trs_cfo_ema_alpha  = 0.1f; ///< RSRP measurement exponential average alpha
   bool                   enable_worker_cfo  = true; ///< Enable/Disable open loop CFO correction at the workers
 

lib/src/phy/ch_estimation/csi_rs.c

@@ -719,7 +719,7 @@ int srsran_csi_rs_nzp_measure_trs(const srsran_carrier_nr_t*     carrier,
   float cfo_max = 0.0f;
   for (uint32_t i = 1; i < count; i++) {
     float time_diff    = srsran_symbol_distance_s(measurements[i - 1].l0, measurements[i].l0, carrier->scs);
-    float phase_diff   = cargf(measurements[i - 1].corr * conjf(measurements[i].corr));
+    float phase_diff   = cargf(measurements[i].corr * conjf(measurements[i - 1].corr));
     float cfo_max_temp = 0.0f;
 
     // Avoid zero division

lib/src/phy/sync/ssb.c

@@ -697,7 +697,7 @@ ssb_measure(srsran_ssb_t* q, const cf_t ssb_grid[SRSRAN_SSB_NOF_RE], uint32_t N_
   // Compute CFO in Hz
   float distance_s = srsran_symbol_distance_s(SRSRAN_PSS_NR_SYMBOL_IDX, SRSRAN_SSS_NR_SYMBOL_IDX, q->cfg.scs);
   float cfo_hz_max = 1.0f / distance_s;
-  float cfo_hz     = cargf(corr_pss * conjf(corr_sss)) / (2.0f * M_PI) * cfo_hz_max;
+  float cfo_hz     = cargf(corr_sss * conjf(corr_pss)) / (2.0f * M_PI) * cfo_hz_max;
 
   // Compute average RSRP
   float rsrp_pss = SRSRAN_CSQABS(corr_pss);

lib/src/phy/sync/test/ssb_measure_test.c

@@ -71,7 +71,7 @@ static void run_channel()
   }
 
   // CFO
-  srsran_vec_apply_cfo(buffer, -cfo_hz / srate_hz, buffer, sf_len);
+  srsran_vec_apply_cfo(buffer, cfo_hz / srate_hz, buffer, sf_len);
 
   // AWGN
   srsran_channel_awgn_run_c(&awgn, buffer, buffer, sf_len);

lib/src/phy/ue/ue_ul_nr.c

@@ -101,7 +101,7 @@ void srsran_ue_ul_nr_set_freq_offset(srsran_ue_ul_nr_t* q, float freq_offset_hz)
     return;
   }
 
-  q->freq_offset_hz = freq_offset_hz;
+  q->freq_offset_hz = -freq_offset_hz;
 }
 
 int srsran_ue_ul_nr_encode_pusch(srsran_ue_ul_nr_t*            q,

srsue/hdr/phy/nr/state.h

@@ -482,8 +482,8 @@ public:
 
     // Compute synch metrics and report it to the PHY state
     sync_metrics_t new_sync_metrics = {};
-    new_sync_metrics.cfo            = new_meas.cfo_hz;
-    set_sync_metrics(sync_metrics);
+    new_sync_metrics.cfo            = new_meas.cfo_hz + ul_ext_cfo_hz;
+    set_sync_metrics(new_sync_metrics);
 
     // Convert to CSI channel measurement and report new NZP-CSI-RS measurement to the PHY state
     srsran_csi_channel_measurements_t measurements = {};
@@ -499,11 +499,10 @@ public:
     trs_measurements_mutex.lock();
     trs_measurements.rsrp_dB = SRSRAN_VEC_SAFE_EMA(new_meas.rsrp_dB, trs_measurements.rsrp_dB, args.trs_epre_ema_alpha);
     trs_measurements.epre_dB = SRSRAN_VEC_SAFE_EMA(new_meas.epre_dB, trs_measurements.epre_dB, args.trs_rsrp_ema_alpha);
+    trs_measurements.snr_dB  = SRSRAN_VEC_SAFE_EMA(new_meas.snr_dB, trs_measurements.snr_dB, args.trs_sinr_ema_alpha);
     // Consider CFO measurement invalid if the SNR is negative. In this case, set CFO to 0.
-    if (trs_measurements.snr_dB > 0.0f) {
+    if (new_meas.snr_dB > 0.0f) {
       trs_measurements.cfo_hz = SRSRAN_VEC_SAFE_EMA(new_meas.cfo_hz, trs_measurements.cfo_hz, args.trs_cfo_ema_alpha);
-    } else {
-      trs_measurements.cfo_hz = 0.0f;
     }
     trs_measurements.nof_re++;
     trs_measurements_mutex.unlock();

srsue/src/phy/nr/cc_worker.cc

@@ -488,9 +488,10 @@ bool cc_worker::work_dl()
   // Compensate CFO from TRS measurements
   if (std::isnormal(phy.args.enable_worker_cfo)) {
     float dl_cfo_hz   = phy.get_dl_cfo();
+    float dl_cfo_norm = -dl_cfo_hz / (1000.0f * ue_ul.ifft.sf_sz);
     for (cf_t* b : rx_buffer) {
       if (b != nullptr and ue_ul.ifft.sf_sz != 0) {
-        srsran_vec_apply_cfo(b, dl_cfo_hz / (1000.0f * ue_ul.ifft.sf_sz), b, ue_ul.ifft.sf_sz);
+        srsran_vec_apply_cfo(b, dl_cfo_norm, b, ue_ul.ifft.sf_sz);
       }
     }
   }

srsue/src/phy/nr/worker_pool.cc

@@ -79,7 +79,7 @@ sf_worker* worker_pool::wait_worker(uint32_t tti)
   if (prach_buffer->is_ready_to_send(tti, phy_state.cfg.carrier.pci)) {
     uint32_t nof_prach_sf       = 0;
     float    prach_target_power = 0.0f;
-    cf_t*    prach_ptr = prach_buffer->generate(-phy_state.get_ul_cfo() / 15000, &nof_prach_sf, &prach_target_power);
+    cf_t*    prach_ptr = prach_buffer->generate(phy_state.get_ul_cfo() / 15000, &nof_prach_sf, &prach_target_power);
     worker->set_prach(prach_ptr, prach_target_power);
   }
 

srsue/src/phy/sync.cc

@@ -543,7 +543,7 @@ void sync::run_camping_in_sync_state(lte::sf_worker*      lte_worker,
 
     // As UE sync compensates CFO externally based on LTE signal and the NR carrier may estimate the CFO from the LTE
     // signal. It is necessary setting an NR external CFO offset to compensate it.
-    nr_worker_pool->set_ul_ext_cfo(-srsran_ue_sync_get_cfo(&ue_sync));
+    nr_worker_pool->set_ul_ext_cfo(srsran_ue_sync_get_cfo(&ue_sync));
 
     // NR worker needs to be launched first, phy_common::worker_end expects first the NR worker and the LTE worker.
     worker_com->semaphore.push(nr_worker);