mac_sch_pdu_nr: add unpacking of TA CE in DL-SCH

also add basic test to verify correct unpacking

lib/include/srsran/mac/mac_sch_pdu_nr.h

@@ -79,6 +79,13 @@ public:
   static const uint8_t                    max_num_lcg_lbsr = 8;
   std::array<lcg_bsr_t, max_num_lcg_lbsr> get_lbsr();
 
+  // TA
+  struct ta_t {
+    uint8_t tag_id;
+    uint8_t ta_command;
+  };
+  ta_t get_ta();
+
   // setters
   void set_sdu(const uint32_t lcid_, const uint8_t* payload_, const uint32_t len_);
   void set_padding(const uint32_t len_);

lib/src/mac/mac_sch_pdu_nr.cc

@@ -218,6 +218,16 @@ uint8_t mac_sch_subpdu_nr::get_pcmax()
   return 0;
 }
 
+mac_sch_subpdu_nr::ta_t mac_sch_subpdu_nr::get_ta()
+{
+  ta_t ta = {};
+  if (lcid == TA_CMD) {
+    ta.tag_id     = (sdu[0] & 0xc0) >> 6;
+    ta.ta_command = sdu[0] & 0x3f;
+  }
+  return ta;
+}
+
 mac_sch_subpdu_nr::lcg_bsr_t mac_sch_subpdu_nr::get_sbsr()
 {
   lcg_bsr_t sbsr = {};

lib/test/mac/mac_pdu_nr_test.cc

@@ -326,6 +326,26 @@ int mac_rar_pdu_unpack_test8()
   return SRSRAN_SUCCESS;
 }
 
+int mac_dl_sch_pdu_unpack_test9()
+{
+  // MAC PDU with Timing Advance CE and padding
+  uint8_t tv[] = {0x3d, 0x1f, 0x3f, 0x00, 0x00, 0x00};
+
+  if (pcap_handle) {
+    pcap_handle->write_dl_crnti_nr(tv, sizeof(tv), PCAP_CRNTI, true, PCAP_TTI);
+  }
+
+  srsran::mac_sch_pdu_nr pdu;
+  pdu.unpack(tv, sizeof(tv));
+  TESTASSERT(pdu.get_num_subpdus() == 2);
+  mac_sch_subpdu_nr subpdu = pdu.get_subpdu(0);
+
+  TESTASSERT(subpdu.get_ta().tag_id == 0);
+  TESTASSERT(subpdu.get_ta().ta_command == 31);
+
+  return SRSRAN_SUCCESS;
+}
+
 int mac_ul_sch_pdu_unpack_test1()
 {
   // UL-SCH MAC PDU with fixed-size CE and DL-SCH subheader with 16-bit length field
@@ -657,6 +677,11 @@ int main(int argc, char** argv)
     return SRSRAN_ERROR;
   }
 
+  if (mac_dl_sch_pdu_unpack_test9()) {
+    fprintf(stderr, "mac_dl_sch_pdu_unpack_test9() failed.\n");
+    return SRSRAN_ERROR;
+  }
+
   if (mac_ul_sch_pdu_unpack_test1()) {
     fprintf(stderr, "mac_ul_sch_pdu_unpack_test1() failed.\n");
     return SRSRAN_ERROR;