Introduce group-based processing using FAPI groups

Refactor ULSCH_id based processing of the PUSCH PDUs to group based
processing using FAPI groups. This is required to process multiple
PUSCH PDUs jointly for MU-MIMO. This is an initial commit that
supports group size = 1 and will be extended to > 1 in the following
commits.

The flow of group information from MAC to PHY using FAPI is as follows:

- In MAC, nr_fill_pusch_fapi_groups() is introduced to fill UEs in
  groups. The FAPI groups consist of UE lists filled with a PDU index.
  Based on the parameter UL_tti_req->n_group, the number of unique groups are
  identified. In each group, the parameter group->n_ue defines the
  number of UEs present in the group along with their PDU indices.

- After receiving the FAPI message in the PHY from MAC, in
  nr_save_ul_tti_req(), a group number and group size for each
  PUSCH PDU is allocated in nr_fill_ulsch(), and a PUSCH job is created.

- Further, after a job is created, in phy_procedures_gNB_uespec_RX(),
  the PUSCH PDUs of the ULSCH_ids for each group are segregated based
  on the group index. They are processed jointly using
  handle_pusch_rx_group_trigger(), and the PUSCH DTX per UE in the
  group is calculated using handle_pusch_DTX().
Signed-off-by: Rakesh Mundlamuri <rakesh.mundlamuri@openairinterface.org>

openair1/PHY/NR_TRANSPORT/nr_transport_proto.h

@@ -112,7 +112,9 @@ void reset_active_ulsch(PHY_VARS_gNB *gNB, int frame);
 void nr_fill_ulsch(PHY_VARS_gNB *gNB,
                    int frame,
                    int slot,
-                   nfapi_nr_pusch_pdu_t *ulsch_pdu);
+                   nfapi_nr_pusch_pdu_t *ulsch_pdu,
+                   int16_t mu_group_idx,
+                   uint8_t mu_group_size);
 
 void nr_schedule_rx_prach(PHY_VARS_gNB *gNB, int SFN, int Slot, nfapi_nr_prach_pdu_t *prach_pdu);
 

openair1/PHY/NR_TRANSPORT/nr_ulsch.c

@@ -89,8 +89,12 @@ static void dump_pusch_pdu(int instance, int frame, int slot, nfapi_nr_pusch_pdu
         pusch_pdu->pusch_data.num_cb);
 }
 
-
-void nr_fill_ulsch(PHY_VARS_gNB *gNB, int frame, int slot, nfapi_nr_pusch_pdu_t *ulsch_pdu)
+void nr_fill_ulsch(PHY_VARS_gNB *gNB,
+                   int frame,
+                   int slot,
+                   nfapi_nr_pusch_pdu_t *ulsch_pdu,
+                   int16_t mu_group_idx,
+                   uint8_t mu_group_size)
 {
   dump_pusch_pdu(gNB->Mod_id, frame, slot, ulsch_pdu);
   LOG_D(NR_PHY,
@@ -101,7 +105,11 @@ void nr_fill_ulsch(PHY_VARS_gNB *gNB, int frame, int slot, nfapi_nr_pusch_pdu_t
         ulsch_pdu->pusch_data.harq_process_id,
         ulsch_pdu->pusch_data.new_data_indicator);
 
-  NR_gNB_PUSCH_job_t pusch = {.frame = frame, .slot = slot, .pusch_pdu = *ulsch_pdu};
+  NR_gNB_PUSCH_job_t pusch = {.frame = frame,
+                              .slot = slot,
+                              .pusch_pdu = *ulsch_pdu,
+                              .mu_group_idx = mu_group_idx,
+                              .mu_group_size = mu_group_size};
   if (gNB->common_vars.beam_id) {
     int fapi_beam_idx = ulsch_pdu->beamforming.prgs_list[0].dig_bf_interface_list[0].beam_idx;
     int bitmap = SL_to_bitmap(ulsch_pdu->start_symbol_index, ulsch_pdu->nr_of_symbols);

openair1/PHY/defs_gNB.h

@@ -181,6 +181,11 @@ typedef struct {
   uint32_t slot;
   /// ULSCH PDU
   nfapi_nr_pusch_pdu_t pusch_pdu;
+  // Multi-User (MU) group index
+  // -1 : unallocated
+  int16_t mu_group_idx;
+  // 1 for Single-User (SU) and > 1 is MU
+  uint8_t mu_group_size;
 } NR_gNB_PUSCH_job_t;
 
 typedef struct {

openair1/SIMULATION/NR_PHY/ulsim.c

@@ -1326,6 +1326,12 @@ int main(int argc, char *argv[])
           srs_pdu->beamforming.prg_size = 1;
         }
 
+        // Fill FAPI PUSCH groups for 1 UE
+        UL_tti_req->n_group = 1;
+        nfapi_nr_ul_tti_request_number_of_groups_t *group = &UL_tti_req->groups_list[0];
+        group->n_ue = 1;
+        group->ue_list[0].pdu_idx = 0;
+
         /* load FAPI into RX of L1 */
         nr_save_ul_tti_req(gNB, &Sched_INFO->UL_tti_req);
 

openair2/LAYER2/NR_MAC_gNB/gNB_scheduler.c

@@ -115,6 +115,20 @@ static void copy_ul_tti_req(nfapi_nr_ul_tti_request_t *to, nfapi_nr_ul_tti_reque
     to->groups_list[i] = from->groups_list[i];
 }
 
+static void nr_fill_pusch_fapi_groups(nfapi_nr_ul_tti_request_t *UL_tti_req)
+{
+  // Single User MIMO
+  UL_tti_req->n_group = 0;
+  for (int i = 0; i < UL_tti_req->n_pdus; i++) {
+    if (UL_tti_req->pdus_list[i].pdu_type != NFAPI_NR_UL_CONFIG_PUSCH_PDU_TYPE)
+      continue;
+    nfapi_nr_ul_tti_request_number_of_groups_t *group = &UL_tti_req->groups_list[UL_tti_req->n_group];
+    group->n_ue = 0;
+    group->ue_list[group->n_ue++].pdu_idx = i;
+    UL_tti_req->n_group++;
+  }
+}
+
 void gNB_dlsch_ulsch_scheduler(module_id_t module_idP, frame_t frame, slot_t slot, NR_Sched_Rsp_t *sched_info)
 {
   protocol_ctxt_t ctxt = {0};
@@ -233,6 +247,8 @@ void gNB_dlsch_ulsch_scheduler(module_id_t module_idP, frame_t frame, slot_t slo
   const int current_index = ul_buffer_index(frame, slot, slots_frame, gNB->UL_tti_req_ahead_size);
   copy_ul_tti_req(&sched_info->UL_tti_req, &gNB->UL_tti_req_ahead[0][current_index]);
 
+  nr_fill_pusch_fapi_groups(&sched_info->UL_tti_req);
+
   stop_meas(&gNB->gNB_scheduler);
   NR_SCHED_UNLOCK(&gNB->sched_lock);
 }

openair2/NR_PHY_INTERFACE/NR_IF_Module.c

@@ -486,6 +486,7 @@ void reset_sched_response(NR_Sched_Rsp_t *sched_response, int frame, int slot, i
   UL_tti_req->SFN = frame;
   UL_tti_req->Slot = slot;
   UL_tti_req->n_pdus = 0;
+  UL_tti_req->n_group = 0;
 
   nfapi_nr_tx_data_request_t *TX_req = &sched_response->TX_req;
   TX_req->SFN = frame;