Handle changing N_TA_offset on the UE correctly in higher layers

Send new N_TA_offset in config_request to PHY. Remove N_TA_offset update
from ta_command.

executables/nr-ue.c

@@ -147,6 +147,24 @@ static void *nrL1_UE_stats_thread(void *param)
   return NULL;
 }
 
+static int determine_N_TA_offset(PHY_VARS_NR_UE *ue) {
+  if (ue->sl_mode == 2)
+    return 0;
+  else {
+    int N_TA_offset = ue->nrUE_config.cell_config.N_TA_offset;
+    if (N_TA_offset == -1) {
+      return set_default_nta_offset(ue->frame_parms.freq_range, ue->frame_parms.samples_per_subframe);
+    } else {
+      // Return N_TA_offet in samples, as described in 38.211 4.1 and 4.3.1
+      // T_c[s] =  1/(Δf_max x N_f) = 1 / (480 * 1000 * 4096)
+      // N_TA_offset[s] = N_TA_offset x T_c
+      // N_TA_offset[samples] = samples_per_second x N_TA_offset[s]
+      // N_TA_offset[samples] = N_TA_offset x samples_per_subframe x 1000 x T_c
+      return (N_TA_offset * ue->frame_parms.samples_per_subframe) / (4096 * 480);
+    }
+  }
+}
+
 void init_nr_ue_vars(PHY_VARS_NR_UE *ue, uint8_t UE_id)
 {
   int nb_connected_gNB = 1;
@@ -165,8 +183,8 @@ void init_nr_ue_vars(PHY_VARS_NR_UE *ue, uint8_t UE_id)
   // intialize transport
   init_nr_ue_transport(ue);
 
-  // init N_TA offset
-  init_N_TA_offset(ue);
+  ue->ta_frame = -1;
+  ue->ta_slot = -1;
 }
 
 void init_nrUE_standalone_thread(int ue_idx)
@@ -867,7 +885,7 @@ void *UE_thread(void *arg)
   initNotifiedFIFO_nothreadSafe(&freeBlocks);
 
   int timing_advance = UE->timing_advance;
-  int N_TA_offset = UE->N_TA_offset;
+  UE->N_TA_offset = determine_N_TA_offset(UE);
   NR_UE_MAC_INST_t *mac = get_mac_inst(UE->Mod_id);
 
   bool syncRunning = false;
@@ -1090,7 +1108,7 @@ void *UE_thread(void *arg)
 
     // use previous timing_advance value to compute writeTimestamp
     const openair0_timestamp writeTimestamp = rx_timestamp + fp->get_samples_slot_timestamp(slot_nr, fp, duration_rx_to_tx)
-                                              - firstSymSamp - N_TA_offset - timing_advance;
+                                              - firstSymSamp - UE->N_TA_offset - timing_advance;
 
     // but use current UE->timing_advance value to compute writeBlockSize
     int writeBlockSize = fp->get_samples_per_slot((slot_nr + duration_rx_to_tx) % nb_slot_frame, fp) - iq_shift_to_apply;
@@ -1099,10 +1117,11 @@ void *UE_thread(void *arg)
       writeBlockSize -= new_timing_advance- timing_advance;
       timing_advance = new_timing_advance;
     }
-    int new_N_TA_offset = UE->N_TA_offset;
-    if (new_N_TA_offset != N_TA_offset) {
-      writeBlockSize -= new_N_TA_offset - N_TA_offset;
-      N_TA_offset = new_N_TA_offset;
+    int new_N_TA_offset = determine_N_TA_offset(UE);
+    if (new_N_TA_offset != UE->N_TA_offset) {
+      LOG_I(PHY, "N_TA_offset changed from %d to %d\n", UE->N_TA_offset, new_N_TA_offset);
+      writeBlockSize -= new_N_TA_offset - UE->N_TA_offset;
+      UE->N_TA_offset = new_N_TA_offset;
     }
 
     if (curMsg.proc.nr_slot_tx == 0)

nfapi/open-nFAPI/nfapi/public_inc/fapi_nr_ue_interface.h

@@ -551,7 +551,6 @@ typedef struct {
  int ta_frame;
  int ta_slot;
  int ta_command;
- int ta_offset;
  bool is_rar;
 } fapi_nr_ta_command_pdu;
 
@@ -616,7 +615,7 @@ typedef struct
 {
   uint8_t phy_cell_id;//Physical Cell ID, 𝑁_{𝐼𝐷}^{𝑐𝑒𝑙𝑙} [38.211, sec 7.4.2.1] Value: 0 ->1007
   uint8_t frame_duplex_type;//Frame duplex type Value: 0 = FDD 1 = TDD
-
+  uint32_t N_TA_offset;
 } fapi_nr_cell_config_t;
 
 typedef struct 

openair1/PHY/INIT/nr_init_ue.c

@@ -492,24 +492,6 @@ void clean_UE_harq(PHY_VARS_NR_UE *UE)
   }
 }
 
-
-void init_N_TA_offset(PHY_VARS_NR_UE *ue)
-{
-  NR_DL_FRAME_PARMS *fp = &ue->frame_parms;
-
-  // No timing offset for Sidelink, refer to 3GPP 38.211 Section 8.5
-  if (ue->sl_mode == 2)
-    ue->N_TA_offset = 0;
-  else
-    ue->N_TA_offset = set_default_nta_offset(fp->freq_range, fp->samples_per_subframe);
-  ue->ta_frame = -1;
-  ue->ta_slot = -1;
-
-  LOG_I(PHY,
-        "UE %d Setting N_TA_offset to %d samples (UL Freq %lu, N_RB %d, mu %d)\n",
-        ue->Mod_id, ue->N_TA_offset, fp->ul_CarrierFreq, fp->N_RB_DL, fp->numerology_index);
-}
-
 void phy_init_nr_top(PHY_VARS_NR_UE *ue) {
   NR_DL_FRAME_PARMS *frame_parms = &ue->frame_parms;
   init_delay_table(frame_parms->ofdm_symbol_size, MAX_DELAY_COMP, NR_MAX_OFDM_SYMBOL_SIZE, frame_parms->delay_table);

openair1/PHY/INIT/nr_phy_init.h

@@ -36,7 +36,6 @@ int nr_init_frame_parms_ue_sl(NR_DL_FRAME_PARMS *fp,
 int init_nr_ue_signal(PHY_VARS_NR_UE *ue,int nb_connected_eNB);
 void term_nr_ue_signal(PHY_VARS_NR_UE *ue, int nb_connected_gNB);
 void init_nr_ue_transport(PHY_VARS_NR_UE *ue);
-void init_N_TA_offset(PHY_VARS_NR_UE *ue);
 void nr_dump_frame_parms(NR_DL_FRAME_PARMS *frame_parms);
 void phy_init_nr_gNB(PHY_VARS_gNB *gNB);
 int init_codebook_gNB(PHY_VARS_gNB *gNB);

openair1/SCHED_NR_UE/fapi_nr_ue_l1.c

@@ -419,15 +419,6 @@ static void configure_ta_command(PHY_VARS_NR_UE *ue, fapi_nr_ta_command_pdu *ta_
   LOG_D(PHY,
         "TA command received in %d.%d Starting UL time alignment procedures. TA update will be applied at frame %d slot %d\n",
         ta_command_pdu->ta_frame, ta_command_pdu->ta_slot, ue->ta_frame, ue->ta_slot);
-
-  if (ta_command_pdu->ta_offset != -1) {
-    // ta_offset_samples : ta_offset = samples_per_subframe : (Δf_max x N_f / 1000)
-    // As described in Section 4.3.1 in 38.211
-    int ta_offset_samples = (ta_command_pdu->ta_offset * samples_per_subframe) / (4096 * 480);
-    ue->N_TA_offset = ta_offset_samples;
-    LOG_D(PHY, "Received N_TA offset %d from upper layers. Corresponds to %d samples.\n",
-          ta_command_pdu->ta_offset, ta_offset_samples);
-  }
 }
 
 static void nr_ue_scheduled_response_dl(NR_UE_MAC_INST_t *mac,

openair2/LAYER2/NR_MAC_UE/config_ue.c

@@ -44,6 +44,24 @@
 #include "oai_asn1.h"
 #include "executables/position_interface.h"
 
+static int get_ta_offset(long *n_TimingAdvanceOffset)
+{
+  if (!n_TimingAdvanceOffset)
+    return -1;
+
+  switch (*n_TimingAdvanceOffset) {
+    case NR_ServingCellConfigCommonSIB__n_TimingAdvanceOffset_n0 :
+      return 0;
+    case NR_ServingCellConfigCommonSIB__n_TimingAdvanceOffset_n25600 :
+      return 25600;
+    case NR_ServingCellConfigCommonSIB__n_TimingAdvanceOffset_n39936 :
+      return 39936;
+    default :
+      AssertFatal(false, "Invalid n-TimingAdvanceOffset\n");
+  }
+  return -1;
+}
+
 static void set_tdd_config_nr_ue(fapi_nr_tdd_table_t *tdd_table, const frame_structure_t *fs)
 {
   tdd_table->tdd_period_in_slots = fs->numb_slots_period;
@@ -143,6 +161,7 @@ static void config_common_ue_sa(NR_UE_MAC_INST_t *mac, NR_ServingCellConfigCommo
   // cell config
   cfg->cell_config.phy_cell_id = mac->physCellId;
   cfg->cell_config.frame_duplex_type = frame_type;
+  cfg->cell_config.N_TA_offset = get_ta_offset(scc->n_TimingAdvanceOffset);
 
   // SSB config
   cfg->ssb_config.ss_pbch_power = scc->ss_PBCH_BlockPower;
@@ -345,6 +364,7 @@ static void config_common_ue(NR_UE_MAC_INST_t *mac, NR_ServingCellConfigCommon_t
   // cell config
   cfg->cell_config.phy_cell_id = *scc->physCellId;
   cfg->cell_config.frame_duplex_type = frame_type;
+  cfg->cell_config.N_TA_offset = get_ta_offset(scc->n_TimingAdvanceOffset);
 
   // SSB config
   cfg->ssb_config.ss_pbch_power = scc->ss_PBCH_BlockPower;
@@ -1685,24 +1705,6 @@ void nr_rrc_mac_config_req_reset(module_id_t module_id, NR_UE_MAC_reset_cause_t
   AssertFatal(!ret, "mutex failed %d\n", ret);
 }
 
-static int get_ta_offset(long *n_TimingAdvanceOffset)
-{
-  if (!n_TimingAdvanceOffset)
-    return -1;
-
-  switch (*n_TimingAdvanceOffset) {
-    case NR_ServingCellConfigCommonSIB__n_TimingAdvanceOffset_n0 :
-      return 0;
-    case NR_ServingCellConfigCommonSIB__n_TimingAdvanceOffset_n25600 :
-      return 25600;
-    case NR_ServingCellConfigCommonSIB__n_TimingAdvanceOffset_n39936 :
-      return 39936;
-    default :
-      AssertFatal(false, "Invalid n-TimingAdvanceOffset\n");
-  }
-  return -1;
-}
-
 static void configure_si_schedulingInfo(NR_UE_MAC_INST_t *mac,
                                         NR_SI_SchedulingInfo_t *si_SchedulingInfo,
                                         NR_SI_SchedulingInfo_v1700_t *si_SchedulingInfo_v1700)
@@ -1744,7 +1746,6 @@ void nr_rrc_mac_config_req_sib1(module_id_t module_id, int cc_idP, NR_SIB1_t *si
   AssertFatal(scc, "SIB1 SCC should not be NULL\n");
   UPDATE_IE(mac->tdd_UL_DL_ConfigurationCommon, scc->tdd_UL_DL_ConfigurationCommon, NR_TDD_UL_DL_ConfigCommon_t);
   configure_si_schedulingInfo(mac, si_SchedulingInfo, si_SchedulingInfo_v1700);
-  mac->n_ta_offset = get_ta_offset(scc->n_TimingAdvanceOffset);
 
   config_common_ue_sa(mac, scc, cc_idP);
   configure_common_BWP_dl(mac,
@@ -1813,7 +1814,6 @@ static void handle_reconfiguration_with_sync(NR_UE_MAC_INST_t *mac,
 
   if (reconfWithSync->spCellConfigCommon) {
     NR_ServingCellConfigCommon_t *scc = reconfWithSync->spCellConfigCommon;
-    mac->n_ta_offset = get_ta_offset(scc->n_TimingAdvanceOffset);
     if (scc->physCellId)
       mac->physCellId = *scc->physCellId;
     mac->dmrs_TypeA_Position = scc->dmrs_TypeA_Position;

openair2/LAYER2/NR_MAC_UE/mac_defs.h

@@ -633,7 +633,6 @@ typedef struct NR_UE_MAC_INST_s {
   int dmrs_TypeA_Position;
   int p_Max;
   int p_Max_alt;
-  int n_ta_offset; // -1 not present, otherwise value to be applied
 
   ntn_timing_advance_componets_t ntn_ta;
 

openair2/LAYER2/NR_MAC_UE/main_ue_nr.c

@@ -68,7 +68,6 @@ void nr_ue_init_mac(NR_UE_MAC_INST_t *mac)
   mac->uecap_maxMIMO_PUSCH_layers_nocb = 0;
   mac->p_Max = INT_MIN;
   mac->p_Max_alt = INT_MIN;
-  mac->n_ta_offset = -1;
   mac->ntn_ta.ntn_params_changed = false;
   reset_mac_inst(mac);
 

openair2/LAYER2/NR_MAC_UE/nr_ue_scheduler.c

@@ -3626,7 +3626,6 @@ static void schedule_ta_command(fapi_nr_dl_config_request_t *dl_config, NR_UE_MA
   fapi_nr_ta_command_pdu *ta = &dl_config->dl_config_list[dl_config->number_pdus].ta_command_pdu;
   ta->ta_frame = ul_time_alignment->frame;
   ta->ta_slot = ul_time_alignment->slot;
-  ta->ta_offset = mac->n_ta_offset;
   ta->is_rar = ul_time_alignment->ta_apply == rar_ta;
   ta->ta_command = ul_time_alignment->ta_command;
   dl_config->dl_config_list[dl_config->number_pdus].pdu_type = FAPI_NR_CONFIG_TA_COMMAND;