LDPC processing: bugfix: clear d[] if first transmission is DTX

If first transmission (round == 0) is DTX then d[] will not be cleared
for following transmissions (those that are not DTX) in
nr_rate_matching_ldpc_rx() because new_rx will not be 1, leading
to potential wrong decoding.

openair1/PHY/NR_TRANSPORT/nr_ulsch_decoding.c

@@ -78,6 +78,7 @@ void free_gNB_ulsch(NR_gNB_ULSCH_t **ulschptr, uint16_t N_RB_UL)
       }
       free_and_zero(ulsch->harq_processes[i]->c);
       free_and_zero(ulsch->harq_processes[i]->d);
+      free_and_zero(ulsch->harq_processes[i]->crc_ok);
       free_and_zero(ulsch->harq_processes[i]);
       ulsch->harq_processes[i] = NULL;
     }
@@ -102,11 +103,13 @@ NR_gNB_ULSCH_t *new_gNB_ulsch(uint8_t max_ldpc_iterations, uint16_t N_RB_UL)
   ulsch = (NR_gNB_ULSCH_t *)malloc16_clear(sizeof(NR_gNB_ULSCH_t));
 
   ulsch->max_ldpc_iterations = max_ldpc_iterations;
+  ulsch->a_segments = a_segments;
 
   for (i=0; i<NR_MAX_ULSCH_HARQ_PROCESSES; i++) {
     ulsch->harq_processes[i] = (NR_UL_gNB_HARQ_t *)malloc16_clear(sizeof(NR_UL_gNB_HARQ_t));
     ulsch->harq_processes[i]->b = (uint8_t*)malloc16_clear(ulsch_bytes);
     ulsch->harq_processes[i]->c = (uint8_t**)malloc16_clear(a_segments*sizeof(uint8_t *));
+    ulsch->harq_processes[i]->crc_ok = malloc16_clear(a_segments*sizeof(bool));
     ulsch->harq_processes[i]->d = (int16_t**)malloc16_clear(a_segments*sizeof(int16_t *));
     for (r=0; r<a_segments; r++) {
       ulsch->harq_processes[i]->c[r] = (uint8_t*)malloc16_clear(8448*sizeof(uint8_t));
@@ -165,6 +168,11 @@ void nr_processULSegment(void* arg) {
   ldpcDecode_t *rdata = (ldpcDecode_t*) arg;
   PHY_VARS_gNB *phy_vars_gNB = rdata->gNB;
   NR_UL_gNB_HARQ_t *ulsch_harq = rdata->ulsch_harq;
+  if (ulsch_harq->crc_ok[rdata->segment_r]) {
+    LOG_D(PHY, "segment %d already decoded in a previous transmission, do nothing\n", rdata->segment_r);
+    rdata->decodeIterations = 0;
+    return;
+  }
   t_nrLDPC_dec_params *p_decoderParms = &rdata->decoderParms;
   int length_dec;
   int no_iteration_ldpc;
@@ -252,6 +260,15 @@ void nr_processULSegment(void* arg) {
     stop_meas(&phy_vars_gNB->ulsch_rate_unmatching_stats);
   }
 
+  /* don't run LDPC decoding if some other thread had a failure */
+  /* nr_rate_matching_ldpc_rx() must be called to feed d[r] in all cases
+   * so this test has to come after the call to nr_rate_matching_ldpc_rx()
+   */
+  if (__atomic_load_n(&ulsch_harq->skip_ldpc_decoding, __ATOMIC_SEQ_CST)) {
+    LOG_D(PHY, "skipping nrLDPC_decoder() for r %d because decoding of some other segment failed\n", r);
+    return;
+  }
+
   memset(ulsch_harq->c[r],0,Kr_bytes);
 
   if (ulsch_harq->C == 1) {
@@ -302,11 +319,15 @@ void nr_processULSegment(void* arg) {
 #endif
     rdata->decodeIterations = no_iteration_ldpc;
     if (rdata->decodeIterations > p_decoderParms->numMaxIter) rdata->decodeIterations--;
+    /* remember that the data is ok to not decode it again in case of retransmission */
+    ulsch_harq->crc_ok[r] = true;
   } else {
 #ifdef PRINT_CRC_CHECK
       LOG_I(PHY,"CRC NOK\n");
 #endif
     rdata->decodeIterations = max_ldpc_iterations + 1;
+    /* set skip_ldpc_decoding to 1 to indicate to remaining threads that they shall not run LDPC decoding */
+    __atomic_store_n(&ulsch_harq->skip_ldpc_decoding, 1, __ATOMIC_SEQ_CST);
   }
 
   for (int m=0; m < Kr>>3; m ++) {
@@ -623,6 +644,9 @@ uint32_t nr_ulsch_decoding(PHY_VARS_gNB *phy_vars_gNB,
   else {
     dtx_det = 0;
 
+    /* tell to the threads that LDPC decoding has to be done */
+    __atomic_store_n(&harq_process->skip_ldpc_decoding, 0, __ATOMIC_SEQ_CST);
+
     for (int r = 0; r < harq_process->C; r++) {
       int E = nr_get_E(G, harq_process->C, Qm, n_layers, r);
       union ldpcReqUnion id = {.s = {ulsch->rnti, frame, nr_tti_rx, 0, 0}};
@@ -647,6 +671,9 @@ uint32_t nr_ulsch_decoding(PHY_VARS_gNB *phy_vars_gNB,
       rdata->ulsch = ulsch;
       rdata->ulsch_id = ULSCH_id;
       rdata->tbslbrm = pusch_pdu->maintenance_parms_v3.tbSizeLbrmBytes;
+      /* in case of a new rx, tell nr_processULSegment() to process the data, so set crc_ok[r] to false */
+      if (harq_process->new_rx)
+        harq_process->crc_ok[r] = false;
       pushTpool(&phy_vars_gNB->threadPool, req);
       phy_vars_gNB->nbDecode++;
       LOG_D(PHY, "Added a block to decode, in pipe: %d\n", phy_vars_gNB->nbDecode);

openair1/PHY/defs_gNB.h

@@ -227,6 +227,8 @@ typedef struct {
   uint32_t B;
   /// Pointers to code blocks after code block segmentation and CRC attachment (38.212 V15.4.0 section 5.2.2)
   uint8_t **c;
+  /// array to indicate that a segment has a valid CRC from a previous transmission to not run LDPC decoder again in a retransmission
+  bool *crc_ok;
   /// Number of bits in each code block (38.212 V15.4.0 section 5.2.2)
   uint32_t K;
   /// Number of "Filler" bits added in the code block segmentation (38.212 V15.4.0 section 5.2.2)
@@ -244,6 +246,11 @@ typedef struct {
   /// Last index of LLR buffer that contains information.
   /// Used for computing LDPC decoder R
   int llrLen;
+  /// used to indicate to remaining threads that LDPC decoding has to be skipped
+  /// this is set to true when a crc fails to avoid unnecessary computation
+  /// all accesses must be done with __atomic operations
+  /// (we can't use bool, it does not work with __atomic operations)
+  uint8_t skip_ldpc_decoding;
   //////////////////////////////////////////////////////////////
 } NR_UL_gNB_HARQ_t;
 
@@ -261,6 +268,8 @@ typedef struct {
   uint8_t max_ldpc_iterations;
   /// number of iterations used in last LDPC decoding
   uint8_t last_iteration_cnt;  
+  /// max number of segments for LDPC decoding
+  int a_segments;
 } NR_gNB_ULSCH_t;
 
 typedef struct {

openair1/SCHED_NR/phy_procedures_nr_gNB.c

@@ -208,13 +208,15 @@ void phy_procedures_gNB_TX(processingData_L1tx_t *msgTx,
   VCD_SIGNAL_DUMPER_DUMP_FUNCTION_BY_NAME(VCD_SIGNAL_DUMPER_FUNCTIONS_PHY_PROCEDURES_gNB_TX+offset,0);
 }
 
-void nr_postDecode(PHY_VARS_gNB *gNB, notifiedFIFO_elt_t *req) {
+void nr_postDecode(PHY_VARS_gNB *gNB, notifiedFIFO_elt_t *req, int *decodeSuccessCount) {
   ldpcDecode_t *rdata = (ldpcDecode_t*) NotifiedFifoData(req);
   NR_UL_gNB_HARQ_t *ulsch_harq = rdata->ulsch_harq;
   NR_gNB_ULSCH_t *ulsch = rdata->ulsch;
   int r = rdata->segment_r;
   nfapi_nr_pusch_pdu_t *pusch_pdu = &gNB->ulsch[rdata->ulsch_id]->harq_processes[rdata->harq_pid]->ulsch_pdu;
   bool decodeSuccess = (rdata->decodeIterations <= rdata->decoderParms.numMaxIter);
+  if (decodeSuccess)
+    (*decodeSuccessCount)++;
   ulsch_harq->processedSegments++;
   LOG_D(PHY, "processing result of segment: %d, processed %d/%d\n",
 	rdata->segment_r, ulsch_harq->processedSegments, rdata->nbSegments);
@@ -224,24 +226,25 @@ void nr_postDecode(PHY_VARS_gNB *gNB, notifiedFIFO_elt_t *req) {
     memcpy(ulsch_harq->b+rdata->offset,
            ulsch_harq->c[r],
            rdata->Kr_bytes - (ulsch_harq->F>>3) -((ulsch_harq->C>1)?3:0));
-
   } else {
-    if ( rdata->nbSegments != ulsch_harq->processedSegments ) {
+    LOG_D(PHY,"uplink segment error %d/%d\n",rdata->segment_r,rdata->nbSegments);
-      int nb = abortTpoolJob(&gNB->threadPool, req->key);
+    LOG_D(PHY, "ULSCH %d in error\n",rdata->ulsch_id);
-      nb += abortNotifiedFIFOJob(&gNB->respDecode, req->key);
-      gNB->nbDecode-=nb;
-      LOG_D(PHY,"uplink segment error %d/%d, aborted %d segments\n",rdata->segment_r,rdata->nbSegments, nb);
-      LOG_D(PHY, "ULSCH %d in error\n",rdata->ulsch_id);
-      AssertFatal(ulsch_harq->processedSegments+nb == rdata->nbSegments,"processed: %d, aborted: %d, total %d\n",
-		  ulsch_harq->processedSegments, nb, rdata->nbSegments);
-      ulsch_harq->processedSegments=rdata->nbSegments;
-    }
   }
 
   //int dumpsig=0;
   // if all segments are done
   if (rdata->nbSegments == ulsch_harq->processedSegments) {
-    if (decodeSuccess && !gNB->pusch_vars[rdata->ulsch_id]->DTX) {
+    /* check global CRC */
+    if (*decodeSuccessCount == rdata->nbSegments && rdata->nbSegments > 1) {
+      int A = ulsch_harq->TBS * 8;
+      int crc_length = A > 3824 ? 3 : 2;
+      int crc_type   = A > 3824 ? CRC24_A : CRC16;
+      if (!check_crc(ulsch_harq->b, A + crc_length*8, 0 /* F - unused */, crc_type)) {
+        *decodeSuccessCount = 0;
+        LOG_E(PHY, "LDPC global CRC fails, but individual LDPC CRC succeeded\n");
+      }
+    }
+    if (*decodeSuccessCount == rdata->nbSegments && !gNB->pusch_vars[rdata->ulsch_id]->DTX) {
       LOG_D(PHY,"[gNB %d] ULSCH: Setting ACK for SFN/SF %d.%d (pid %d, ndi %d, status %d, round %d, TBS %d, Max interation (all seg) %d)\n",
             gNB->Mod_id,ulsch_harq->frame,ulsch_harq->slot,rdata->harq_pid,pusch_pdu->pusch_data.new_data_indicator,ulsch_harq->status,ulsch_harq->round,ulsch_harq->TBS,rdata->decodeIterations);
       ulsch_harq->status = SCH_IDLE;
@@ -379,11 +382,12 @@ void nr_ulsch_procedures(PHY_VARS_gNB *gNB, int frame_rx, int slot_rx, int ULSCH
                     harq_pid,
                     G);
   if (enable_ldpc_offload ==0) {
+    int decodeSuccessCount = 0;
     while (gNB->nbDecode > 0) {
       notifiedFIFO_elt_t *req = pullTpool(&gNB->respDecode, &gNB->threadPool);
       if (req == NULL)
 	break; // Tpool has been stopped
-      nr_postDecode(gNB, req);
+      nr_postDecode(gNB, req, &decodeSuccessCount);
       delNotifiedFIFO_elt(req);
     }
   } 
@@ -839,6 +843,15 @@ int phy_procedures_gNB_uespec_RX(PHY_VARS_gNB *gNB, int frame_rx, int slot_rx) {
                   Therefore, we don't yet call nr_fill_indication, it will be called later */
                nr_fill_indication(gNB,frame_rx, slot_rx, ULSCH_id, harq_pid, 1,1);
                pusch_DTX++;
+               /* if round == 0 we need to clear some data because nr_ulsch_decoding() won't do it for the retransmissions */
+               if (ulsch_harq->round == 0) {
+                 int r;
+                 LOG_D(PHY, "DTX for round 0, clear mandatory data\n");
+                 for (r = 0; r < ulsch->a_segments; r++) {
+                   ulsch_harq->crc_ok[r] = false;
+                   memset(ulsch_harq->d[r], 0, (68*384)*sizeof(int16_t));
+                 }
+               }
                continue;
              }
           } else {