Added CRC-based early stopping to Turbo decoder

lte/phy/examples/iodev.c

@@ -48,7 +48,7 @@ int cuhd_recv_wrapper(void *h, void *data, uint32_t nsamples) {
 }
 
 /* Setup USRP or input file */
-int iodev_init(iodev_t *q, iodev_cfg_t *config) {
+int iodev_init(iodev_t *q, iodev_cfg_t *config, uint32_t file_sf_len) {
   
   if (config->input_file_name) {
     if (filesource_init(&q->fsrc, config->input_file_name, COMPLEX_FLOAT_BIN)) {
@@ -61,7 +61,7 @@ int iodev_init(iodev_t *q, iodev_cfg_t *config) {
     }
 
     q->mode = FILESOURCE;
-    q->sf_len = 1920;
+    q->sf_len = file_sf_len;
     
   } else {
 #ifndef DISABLE_UHD

lte/phy/examples/iodev.h

@@ -74,7 +74,8 @@ typedef struct LIBLTE_API {
 
 
 LIBLTE_API int iodev_init(iodev_t *q, 
-                          iodev_cfg_t *config);
+                          iodev_cfg_t *config, 
+                          uint32_t file_sf_len);
 
 LIBLTE_API void iodev_free(iodev_t *q);
 

lte/phy/examples/pdsch_enodeb.c

@@ -359,7 +359,10 @@ int main(int argc, char **argv) {
         exit(-1);
       }
       
-      pdsch_encode(&pdsch, data, sf_symbols, sf_idx, &harq_process, ra_dl.rv_idx);        
+      if (pdsch_encode(&pdsch, data, sf_symbols, sf_idx, &harq_process, ra_dl.rv_idx)) {
+        fprintf(stderr, "Error encoding PDSCH\n");
+        exit(-1);
+      }
 
       /* Transform to OFDM symbols */
       lte_ifft_run_sf(&ifft, sf_buffer, output_buffer);

lte/phy/examples/pdsch_ue.c

@@ -165,11 +165,18 @@ int main(int argc, char **argv) {
   pbch_mib_t mib; 
   bool printed_sib = false; 
   int rlen; 
+  int symbol_sz; 
   
   parse_args(&prog_args, argc, argv);
   
-  if (iodev_init(&iodev, &prog_args.io_config)) {
+  symbol_sz = lte_symbol_sz(prog_args.nof_prb_file);
-    fprintf(stderr, "Error initiating input device\n");
+  if (symbol_sz > 0) {
+    if (iodev_init(&iodev, &prog_args.io_config, SF_LEN(symbol_sz, CPNORM))) {
+      fprintf(stderr, "Error initiating input device\n");
+      exit(-1);
+    }    
+  } else {
+    fprintf(stderr, "Invalid number of PRB %d\n", prog_args.nof_prb_file);
     exit(-1);
   }
   
@@ -242,9 +249,10 @@ int main(int argc, char **argv) {
           printed_sib = true; 
         }
         if (!(sf_cnt % 10)) {       
-          printf("RSSI: %+.2f dBm, CFO: %+.4f KHz, SFO: %+.4f Khz, TimeOffset: %4d, Errors: %4d/%4d, BLER: %.1e\r",
+          printf("RSSI: %+.2f dBm, CFO: %+.4f KHz, SFO: %+.4f Khz, NOI: %.2f Errors: %4d/%4d, BLER: %.1e\r",
                  20*log10f(agc_get_rssi(&iodev.sframe.agc))+30, 
-                 ue_sync_get_cfo(&iodev.sframe)/1000, ue_sync_get_sfo(&iodev.sframe)/1000, iodev.sframe.peak_idx,
+                 ue_sync_get_cfo(&iodev.sframe)/1000, ue_sync_get_sfo(&iodev.sframe)/1000, 
+                 pdsch_average_noi(&ue_dl.pdsch),
                  (int) ue_dl.pkt_errors, (int) ue_dl.pkts_total, (float) ue_dl.pkt_errors / ue_dl.pkts_total);
           
           fflush(stdout);       

lte/phy/include/liblte/phy/phch/pdsch.h

@@ -43,7 +43,7 @@
 #include "liblte/phy/phch/dci.h"
 #include "liblte/phy/phch/regs.h"
 
-#define TDEC_ITERATIONS         3
+#define TDEC_MAX_ITERATIONS         6
 
 typedef _Complex float cf_t;
 
@@ -75,6 +75,9 @@ typedef struct LIBLTE_API {
   uint32_t max_symbols;
   bool rnti_is_set; 
   uint16_t rnti; 
+  uint32_t nof_iterations; 
+  uint64_t average_nof_iterations_n; 
+  float average_nof_iterations; 
   
   /* buffers */
   // void buffers are shared for tx and rx
@@ -128,6 +131,10 @@ LIBLTE_API int pdsch_decode(pdsch_t *q,
                             pdsch_harq_t *harq_process, 
                             uint32_t rv_idx);
 
+LIBLTE_API float pdsch_average_noi(pdsch_t *q); 
+
+LIBLTE_API uint32_t pdsch_last_noi(pdsch_t *q); 
+
 LIBLTE_API int pdsch_get(pdsch_t *q, 
                          cf_t *sf_symbols, 
                          cf_t *pdsch_symbols,

lte/phy/lib/phch/src/pdsch.c

@@ -183,7 +183,7 @@ int pdsch_init(pdsch_t *q, lte_cell_t cell) {
     ret = LIBLTE_ERROR;
     
     q->cell = cell;
-    
+    q->average_nof_iterations_n = 0; 
     q->max_symbols = q->cell.nof_prb * MAX_PDSCH_RE(q->cell.cp);
 
     INFO("Init PDSCH: %d ports %d PRBs, max_symbols: %d\n", q->cell.nof_ports,
@@ -459,6 +459,15 @@ int pdsch_harq_setup(pdsch_harq_t *p, ra_mcs_t mcs, ra_prb_t *prb_alloc) {
 }
 
 
+float pdsch_average_noi(pdsch_t *q) {
+  return q->average_nof_iterations; 
+}
+
+uint32_t pdsch_last_noi(pdsch_t *q) {
+  return q->nof_iterations;
+}
+
+
 /* Decode a transport block according to 36.212 5.3.2
  *
  */
@@ -516,17 +525,42 @@ int pdsch_decode_tb(pdsch_t *q, char *data, uint32_t tbs, uint32_t nb_e,
         return LIBLTE_ERROR;
       }
 
-      /* Turbo Decoding */
+      /* Turbo Decoding with CRC-based early stopping */
-      tdec_run_all(&q->decoder, (float*) q->cb_out, q->cb_in, TDEC_ITERATIONS,
+      q->nof_iterations = 0; 
-          cb_len);
+      bool early_stop = false;
-
+      uint32_t len_crc; 
-      if (harq_process->cb_segm.C > 1) {
+      char *cb_in_ptr; 
+      crc_t *crc_ptr; 
+      tdec_reset(&q->decoder, cb_len);
+      
+      do {
+        
+        tdec_iteration(&q->decoder, (float*) q->cb_out, cb_len); 
+        q->nof_iterations++;
+        
+        if (harq_process->cb_segm.C > 1) {
+          len_crc = cb_len; 
+          cb_in_ptr = q->cb_in; 
+          crc_ptr = &q->crc_cb; 
+        } else {
+          len_crc = tbs+24; 
+          cb_in_ptr = &q->cb_in[F];
+          crc_ptr = &q->crc_tb; 
+        }
+        
         /* Check Codeblock CRC and stop early if incorrect */
-        if (crc_checksum(&q->crc_cb, q->cb_in, cb_len)) {
+        if (!crc_checksum(crc_ptr, cb_in_ptr, len_crc)) {
-          INFO("Error in CB#%d\n",i);
+          early_stop = true;           
-          return LIBLTE_ERROR;
         }
-      }
+        
+      } while (q->nof_iterations < TDEC_MAX_ITERATIONS && !early_stop);
+      
+      tdec_decision(&q->decoder, q->cb_in, cb_len);
+      
+      q->average_nof_iterations = EXPAVERAGE((float) q->nof_iterations, 
+                                             q->average_nof_iterations, 
+                                             q->average_nof_iterations_n);
+      q->average_nof_iterations_n++;
 
       /* Copy data to another buffer, removing the Codeblock CRC */
       if (i < harq_process->cb_segm.C - 1) {
@@ -534,6 +568,7 @@ int pdsch_decode_tb(pdsch_t *q, char *data, uint32_t tbs, uint32_t nb_e,
       } else {
         DEBUG("Last CB, appending parity: %d to %d from %d and 24 from %d\n",
             rlen - F - 24, wp, F, rlen - 24);
+        
         /* Append Transport Block parity bits to the last CB */
         memcpy(&data[wp], &q->cb_in[F], (rlen - F - 24) * sizeof(char));
         memcpy(parity, &q->cb_in[rlen - 24], 24 * sizeof(char));
@@ -553,6 +588,7 @@ int pdsch_decode_tb(pdsch_t *q, char *data, uint32_t tbs, uint32_t nb_e,
     par_tx = bit_unpack(&p_parity, 24);
 
     if (!par_rx) {
+      vec_fprint_hex(stdout, data, tbs);
       printf("\n\tCAUTION!! Received all-zero transport block\n\n");
     }