SRSENB: calculate TA from PUCCH messages

lib/include/srslte/phy/phch/pucch.h

@@ -94,6 +94,10 @@ typedef struct SRSLTE_API {
   float              dmrs_correlation;
   float              correlation;
   bool               detected;
+
+  // PUCCH Measurements
+  bool  ta_valid;
+  float ta_us;
 } srslte_pucch_res_t;
 
 SRSLTE_API int srslte_pucch_init_ue(srslte_pucch_t* q);

lib/include/srslte/phy/phch/pucch_cfg.h

@@ -77,6 +77,7 @@ typedef struct SRSLTE_API {
   float threshold_data_valid_format2;
   float threshold_data_valid_format3;
   float threshold_dmrs_detection;
+  bool  meas_ta_en;
 
   // PUCCH configuration generated during a call to encode/decode
   srslte_pucch_format_t format;

lib/src/phy/ch_estimation/chest_ul.c

@@ -455,6 +455,26 @@ int srslte_chest_ul_estimate_pucch(srslte_chest_ul_t*     q,
     srslte_vec_prod_conj_ccc(q->pilot_recv_signal, q->pilot_known_signal, q->pilot_estimates, nrefs_sf);
   }
 
+  if (cfg->meas_ta_en && n_rs > 0) {
+    float ta_err = 0.0;
+    for (int ns = 0; ns < SRSLTE_NOF_SLOTS_PER_SF; ns++) {
+      for (int i = 0; i < n_rs; i++) {
+        ta_err += srslte_vec_estimate_frequency(&q->pilot_estimates[(i + ns * n_rs) * SRSLTE_NRE], SRSLTE_NRE) /
+                  (float)(SRSLTE_NOF_SLOTS_PER_SF * n_rs);
+      }
+    }
+
+    // Calculate actual time alignment error in micro-seconds
+    if (isnormal(ta_err)) {
+      ta_err /= 15e3f;                             // Convert from normalized frequency to seconds
+      ta_err *= 1e6f;                              // Convert to micro-seconds
+      ta_err     = roundf(ta_err * 10.0f) / 10.0f; // Round to one tenth of micro-second
+      res->ta_us = ta_err;
+    } else {
+      res->ta_us = 0.0f;
+    }
+  }
+
   if (res->ce != NULL) {
     /* TODO: Currently averaging entire slot, performance good enough? */
     for (int ns = 0; ns < 2; ns++) {

lib/src/phy/enb/enb_ul.c

@@ -175,10 +175,9 @@ void srslte_enb_ul_fft(srslte_enb_ul_t* q)
 
 static int get_pucch(srslte_enb_ul_t* q, srslte_ul_sf_cfg_t* ul_sf, srslte_pucch_cfg_t* cfg, srslte_pucch_res_t* res)
 {
-  int                ret                               = SRSLTE_SUCCESS;
-  uint32_t           n_pucch_i[SRSLTE_PUCCH_MAX_ALLOC] = {};
-  srslte_pucch_res_t pucch_res                         = {};
-  uint32_t           uci_cfg_total_ack                 = srslte_uci_cfg_total_ack(&cfg->uci_cfg);
+  int      ret                               = SRSLTE_SUCCESS;
+  uint32_t n_pucch_i[SRSLTE_PUCCH_MAX_ALLOC] = {};
+  uint32_t uci_cfg_total_ack                 = srslte_uci_cfg_total_ack(&cfg->uci_cfg);
 
   // Drop CQI if there is collision with ACK
   if (!cfg->simul_cqi_ack && uci_cfg_total_ack > 0 && cfg->uci_cfg.cqi.data_enable) {
@@ -204,6 +203,8 @@ static int get_pucch(srslte_enb_ul_t* q, srslte_ul_sf_cfg_t* ul_sf, srslte_pucch
 
   // Iterate possible resources and select the one with higher correlation
   for (int i = 0; i < nof_resources && ret == SRSLTE_SUCCESS; i++) {
+    srslte_pucch_res_t pucch_res = {};
+
     // Configure resource
     cfg->n_pucch = n_pucch_i[i];
 
@@ -213,6 +214,12 @@ static int get_pucch(srslte_enb_ul_t* q, srslte_ul_sf_cfg_t* ul_sf, srslte_pucch
       return SRSLTE_ERROR;
     }
 
+    // Copy measurements
+    if (cfg->meas_ta_en) {
+      pucch_res.ta_valid = !(isnan(q->chest_res.ta_us) || isinf(q->chest_res.ta_us));
+      pucch_res.ta_us    = q->chest_res.ta_us;
+    }
+
     ret = srslte_pucch_decode(&q->pucch, ul_sf, cfg, &q->chest_res, q->sf_symbols, &pucch_res);
     if (ret < SRSLTE_SUCCESS) {
       ERROR("Error decoding PUCCH\n");

lib/src/phy/phch/pucch.c

@@ -1394,6 +1394,10 @@ void srslte_pucch_rx_info(srslte_pucch_cfg_t* cfg, srslte_pucch_res_t* pucch_res
 
     n = srslte_print_check(str, str_len, n, ", corr=%.3f", pucch_res->correlation);
 
-    srslte_uci_data_info(&cfg->uci_cfg, &pucch_res->uci_data, &str[n], str_len - n);
+    n += srslte_uci_data_info(&cfg->uci_cfg, &pucch_res->uci_data, &str[n], str_len - n);
+
+    if (pucch_res->ta_valid) {
+      n = srslte_print_check(str, str_len, n, ", ta=%.1f us", pucch_res->ta_us);
+    }
   }
 }

srsenb/hdr/phy/phy_interfaces.h

@@ -57,6 +57,7 @@ struct phy_args_t {
   bool        pusch_meas_epre     = true;
   bool        pusch_meas_evm      = false;
   bool        pusch_meas_ta       = true;
+  bool        pucch_meas_ta       = true;
 
   srslte::channel::args_t dl_channel_args;
   srslte::channel::args_t ul_channel_args;

srsenb/src/phy/cc_worker.cc

@@ -332,12 +332,9 @@ void cc_worker::decode_pusch_rnti(stack_interface_phy_lte::ul_sched_grant_t& ul_
     // Notify MAC UL channel quality
     phy->stack->snr_info(ul_sf.tti, rnti, cc_idx, snr_db);
 
-    if (ul_grant.dci.tb.rv == 0) {
-      // Notify MAC of Time Alignment only if it enabled and valid measurement, ignore value otherwise
-      if (ul_cfg.pusch.meas_ta_en and not std::isnan(enb_ul.chest_res.ta_us) and
-          not std::isinf(enb_ul.chest_res.ta_us)) {
-        phy->stack->ta_info(ul_sf.tti, rnti, enb_ul.chest_res.ta_us);
-      }
+    // Notify MAC of Time Alignment only if it enabled and valid measurement, ignore value otherwise
+    if (ul_cfg.pusch.meas_ta_en and not std::isnan(enb_ul.chest_res.ta_us) and not std::isinf(enb_ul.chest_res.ta_us)) {
+      phy->stack->ta_info(ul_sf.tti, rnti, enb_ul.chest_res.ta_us);
     }
   }
 
@@ -404,6 +401,10 @@ int cc_worker::decode_pucch()
         // Send UCI data to MAC
         phy->ue_db.send_uci_data(tti_rx, rnti, cc_idx, ul_cfg.pucch.uci_cfg, pucch_res.uci_data);
 
+        if (pucch_res.detected and pucch_res.ta_valid) {
+          phy->stack->ta_info(tti_rx, rnti, pucch_res.ta_us);
+        }
+
         // Logging
         if (log_h->get_level() >= srslte::LOG_LEVEL_INFO) {
           char str[512];

srsenb/src/phy/phy_ue_db.cc

@@ -103,6 +103,7 @@ inline void phy_ue_db::_set_common_config_rnti(uint16_t rnti, srslte::phy_cfg_t&
   phy_cfg.ul_cfg.pucch.threshold_data_valid_format2  = SRSLTE_PUCCH_DEFAULT_THRESHOLD_FORMAT2;
   phy_cfg.ul_cfg.pucch.threshold_data_valid_format3  = SRSLTE_PUCCH_DEFAULT_THRESHOLD_FORMAT3;
   phy_cfg.ul_cfg.pucch.threshold_dmrs_detection      = SRSLTE_PUCCH_DEFAULT_THRESHOLD_DMRS;
+  phy_cfg.ul_cfg.pucch.meas_ta_en                    = phy_args->pucch_meas_ta;
 }
 
 inline uint32_t phy_ue_db::_get_ue_cc_idx(uint16_t rnti, uint32_t enb_cc_idx) const