Merge remote-tracking branch 'origin/fhi_mux3' into integration_2026_w12 (!3986)

handle start symbol on non-zeroth downlink symbol for SIB1 for multiplexing
pattern 3 configuration.

This MR adds support for handling a non-zero start symbol for SIB1 when using
multiplexing pattern 3 with the per-slot CP format.

Previously, the implementation assumed that the first downlink symbol used by
a PDU always starts at symbol 0. However, this assumption does not hold for
SIB1 under multiplexing pattern 3, where the start symbol can be non-zero.

This issue does not apply to the per-symbol CP format.

Testing:
a. Microamp using the branch microamp_1048: UE registration ok. end-to-end ok.
b. Benetel: UE registration ok. end-to-end ok.

radio/fhi_72/oaioran.c

@@ -542,7 +542,6 @@ int xran_fh_tx_send_slot(ru_info_t *ru, int frame, int slot, uint64_t timestamp)
   // Need to use --continuous-tx so that this routine will be triggered in RX slot.
   for (uint16_t cc_id = 0; cc_id < 1 /*nSectorNum*/; cc_id++) { // OAI does not support multiple CC yet.
     for (uint8_t ant_id = 0; ant_id < ru->nb_rx; ant_id++) {
-      int first = 1; // The first UL symbol
       const struct xran_frame_config *frame_conf = &get_xran_fh_config(ant_id / nb_rx_per_ru)->frame_conf;
       // skip processing this slot is TX (no RX in this slot)
       if (!is_tdd_ul_guard_slot(frame_conf, slot)) {
@@ -580,17 +579,10 @@ int xran_fh_tx_send_slot(ru_info_t *ru, int frame, int slot, uint64_t timestamp)
                 pRbElm->nBeamIndex = 0;
             }
           } else {
-            if (first) {
-              // ant_id / no of antenna per beam gives the beam_nb
-              pRbElm->nBeamIndex =
-                  ru->beam_id[ant_id / (ru->nb_rx / ru->num_beams_period)][slot * XRAN_NUM_OF_SYMBOL_PER_SLOT + sym_idx];
-              // In phy-f-1.0/fhi_lib/lib/api/xran_pkt_cp.h, beamId:15 is of 15bit. -1 set extension bit ef:1 to 1 mistakenly.
-              if (pRbElm->nBeamIndex == -1) {
-                pRbElm->nBeamIndex = 0;
-              } else {
-                first = 0;
-              }
-            }
+            // ant_id / no of antenna per beam gives the beam_nb
+            int16_t beam_id = ru->beam_id[ant_id / (ru->nb_tx / ru->num_beams_period)][slot * XRAN_NUM_OF_SYMBOL_PER_SLOT + sym_idx];
+            if (beam_id != -1)
+              pRbElm->nBeamIndex = beam_id;
           }
         }
       }
@@ -662,13 +654,6 @@ int xran_fh_tx_send_slot(ru_info_t *ru, int frame, int slot, uint64_t timestamp)
           for (uint32_t idxElm = 0; idxElm < pPrbMap->nPrbElm; idxElm++) {
             struct xran_section_desc *p_sec_desc = NULL;
             struct xran_prb_elm *p_prbMapElm = &pPrbMap->prbMap[idxElm];
-            if (sym_idx == 0) {
-              // ant_id / no of antenna per beam gives the beam_nb
-              p_prbMapElm->nBeamIndex = ru->beam_id[ant_id / (ru->nb_tx / ru->num_beams_period)][slot * XRAN_NUM_OF_SYMBOL_PER_SLOT];
-              // In phy-f-1.0/fhi_lib/lib/api/xran_pkt_cp.h, beamId:15 is of 15bit. -1 set extension bit ef:1 to 1 mistakenly.
-              if (p_prbMapElm->nBeamIndex == -1)
-                p_prbMapElm->nBeamIndex = 0;
-            }
 
             // radio-transport fragmentation is not supported in xran F release;
             // E-bit = 1 => each ethernet frame is considered as the last fragment;
@@ -699,13 +684,10 @@ int xran_fh_tx_send_slot(ru_info_t *ru, int frame, int slot, uint64_t timestamp)
               if (p_prbMapElm->nBeamIndex == -1)
                 p_prbMapElm->nBeamIndex = 0;
             } else {
-              if (sym_idx == 0) {
-                // ant_id / no of antenna per beam gives the beam_nb
-                p_prbMapElm->nBeamIndex = ru->beam_id[ant_id / (ru->nb_tx / ru->num_beams_period)][slot * XRAN_NUM_OF_SYMBOL_PER_SLOT];
-                // In phy-f-1.0/fhi_lib/lib/api/xran_pkt_cp.h, beamId:15 is of 15bit. -1 set extension bit ef:1 to 1 mistakenly.
-                if (p_prbMapElm->nBeamIndex == -1)
-                  p_prbMapElm->nBeamIndex = 0;
-              }
+              // ant_id / no of antenna per beam gives the beam_nb
+              int16_t beam_id = ru->beam_id[ant_id / (ru->nb_tx / ru->num_beams_period)][slot * XRAN_NUM_OF_SYMBOL_PER_SLOT + sym_idx];
+              if ( beam_id != -1)
+                p_prbMapElm->nBeamIndex = beam_id;
             }
 
             dst = xran_add_hdr_offset(dst, p_prbMapElm->compMethod);