Merge pull request #376 from grantsavill/ras-fixes

DMR: Prevent false RAS detection on non-RAS data bursts

src/bptc.c

@@ -213,8 +213,8 @@ uint32_t BPTC_196x96_Extract_Data(uint8_t InputDeInteleavedData[196],
     }
   }
 
-  /* ========== Pass 1: row Hamming(15,11) on rows 0..8 ========== */
-  for (i = 0; i < 9; i++)
+  /* ========== Pass 1: row Hamming(15,11) on rows 0..12 ========== */
+  for (i = 0; i < 13; i++)
   {
     for (j = 0; j < 15; j++)
     {
@@ -232,8 +232,8 @@ uint32_t BPTC_196x96_Extract_Data(uint8_t InputDeInteleavedData[196],
         fprintf(stderr, "%u", LineBefore[j] & 1);
       fprintf(stderr, "\n");
 #endif
-      /* Keep original data bits on failure */
-      for (j = 0; j < 11; j++)
+      /* Keep original bits on failure */
+      for (j = 0; j < 15; j++)
         DataMatrix[i][j] = LineBefore[j];
     }
     else
@@ -253,8 +253,9 @@ uint32_t BPTC_196x96_Extract_Data(uint8_t InputDeInteleavedData[196],
 #endif
         }
       }
-      for (j = 0; j < 11; j++)
-        DataMatrix[i][j] = LineCorrected[j];
+      /* Re-inject the full line (including corrected parity bits) in the matrix */
+      for (j = 0; j < 15; j++)
+        DataMatrix[i][j] = LineUncorrected[j];
     }
   }
 #if BPTC_196x96_DEBUG
@@ -282,7 +283,7 @@ uint32_t BPTC_196x96_Extract_Data(uint8_t InputDeInteleavedData[196],
         fprintf(stderr, "%u", ColumnBefore[j] & 1);
       fprintf(stderr, "\n");
 #endif
-      for (j = 0; j < 9; j++)
+      for (j = 0; j < 13; j++)
         DataMatrix[j][i] = ColumnBefore[j];
     }
     else
@@ -301,8 +302,9 @@ uint32_t BPTC_196x96_Extract_Data(uint8_t InputDeInteleavedData[196],
 #endif
         }
       }
-      for (j = 0; j < 9; j++)
-        DataMatrix[j][i] = ColumnCorrected[j];
+      /* Re-inject the full column (including corrected parity bits) in the matrix */
+      for (j = 0; j < 13; j++)
+        DataMatrix[j][i] = ColumnUncorrected[j];
     }
   }
 #if BPTC_196x96_DEBUG
@@ -315,7 +317,7 @@ uint32_t BPTC_196x96_Extract_Data(uint8_t InputDeInteleavedData[196],
   HammingIrrecoverableErrorNb = 0;
 
   /* ========== Pass 2: rows ========== */
-  for (i = 0; i < 9; i++)
+  for (i = 0; i < 13; i++)
   {
     for (j = 0; j < 15; j++)
     {
@@ -333,7 +335,7 @@ uint32_t BPTC_196x96_Extract_Data(uint8_t InputDeInteleavedData[196],
         fprintf(stderr, "%u", LineBefore[j] & 1);
       fprintf(stderr, "\n");
 #endif
-      for (j = 0; j < 11; j++)
+      for (j = 0; j < 15; j++)
         DataMatrix[i][j] = LineBefore[j];
     }
     else
@@ -352,8 +354,9 @@ uint32_t BPTC_196x96_Extract_Data(uint8_t InputDeInteleavedData[196],
 #endif
         }
       }
-      for (j = 0; j < 11; j++)
-        DataMatrix[i][j] = LineCorrected[j];
+      /* Re-inject the full line (including corrected parity bits) in the matrix */
+      for (j = 0; j < 15; j++)
+        DataMatrix[i][j] = LineUncorrected[j];
     }
   }
 #if BPTC_196x96_DEBUG
@@ -381,7 +384,7 @@ uint32_t BPTC_196x96_Extract_Data(uint8_t InputDeInteleavedData[196],
         fprintf(stderr, "%u", ColumnBefore[j] & 1);
       fprintf(stderr, "\n");
 #endif
-      for (j = 0; j < 9; j++)
+      for (j = 0; j < 13; j++)
         DataMatrix[j][i] = ColumnBefore[j];
     }
     else
@@ -400,8 +403,58 @@ uint32_t BPTC_196x96_Extract_Data(uint8_t InputDeInteleavedData[196],
 #endif
         }
       }
-      for (j = 0; j < 9; j++)
-        DataMatrix[j][i] = ColumnCorrected[j];
+      /* Re-inject the full column (including corrected parity bits) in the matrix */
+      for (j = 0; j < 13; j++)
+        DataMatrix[j][i] = ColumnUncorrected[j];
+    }
+  }
+
+  /* Verify that all rows (0..12) and columns (0..14) have converged to zero syndrome.
+   * Hamming_15_11_decode never returns false because all 15 non-zero 4-bit syndromes
+   * map to a bit flip, so without a post-pass consistency check a noisy burst can
+   * mis-correct data bits in Pass 2 Columns while still reporting 0 errors. */
+  for (i = 0; i < 13; i++)
+  {
+    for (j = 0; j < 15; j++)
+    {
+      LineUncorrected[j] = DataMatrix[i][j];
+    }
+    if (Hamming_15_11_decode(LineUncorrected, LineCorrected, 1) == false)
+    {
+      HammingIrrecoverableErrorNb++;
+    }
+    else
+    {
+      for (j = 0; j < 15; j++)
+      {
+        if (LineUncorrected[j] != DataMatrix[i][j])
+        {
+          HammingIrrecoverableErrorNb++;
+          break;
+        }
+      }
+    }
+  }
+  for (i = 0; i < 15; i++)
+  {
+    for (j = 0; j < 13; j++)
+    {
+      ColumnUncorrected[j] = DataMatrix[j][i];
+    }
+    if (Hamming_13_9_decode(ColumnUncorrected, ColumnCorrected, 1) == false)
+    {
+      HammingIrrecoverableErrorNb++;
+    }
+    else
+    {
+      for (j = 0; j < 13; j++)
+      {
+        if (ColumnUncorrected[j] != DataMatrix[j][i])
+        {
+          HammingIrrecoverableErrorNb++;
+          break;
+        }
+      }
     }
   }
 #if BPTC_196x96_DEBUG
@@ -430,12 +483,33 @@ uint32_t BPTC_196x96_Extract_Data(uint8_t InputDeInteleavedData[196],
       DMRDataExtracted[k++] = DataMatrix[i][j];
   }
 
+  uint32_t total_corr = row_corr_p1 + col_corr_p1 + row_corr_p2 + col_corr_p2;
+  uint32_t p2_corr = row_corr_p2 + col_corr_p2;
+
+  /* In DMR BPTC(196,96), R(0) and R(1) must be 0. Also reject R(2)==1 when the
+   * received R(2) bit was 0 or the matrix required heavy multi-pass corrections,
+   * because is_ras==1 bypasses downstream CRC checks when no RAS key is loaded. */
+  if (DataMatrix[0][2] != 0 || DataMatrix[0][1] != 0)
+  {
+    HammingIrrecoverableErrorNb++;
+  }
+  else if (DataMatrix[0][0] == 1 && ((InputDeInteleavedData[1] & 1) == 0 || total_corr > 8 || p2_corr > 2))
+  {
+    HammingIrrecoverableErrorNb++;
+  }
+
   if (HammingIrrecoverableErrorNb == 0)
   {
     R[0] = DataMatrix[0][2]; /* R(0) */
     R[1] = DataMatrix[0][1]; /* R(1) */
     R[2] = DataMatrix[0][0]; /* R(2) */
   }
+  else
+  {
+    R[0] = 0;
+    R[1] = 0;
+    R[2] = 0;
+  }
 
   if (R[0] == 0 && R[1] == 0 && R[2] == 1)
     *is_ras = 1;
@@ -466,7 +540,7 @@ uint32_t BPTC_128x77_Extract_Data(uint8_t InputDataMatrix[8][16], uint8_t DMRDat
   uint32_t ParityCheckErrorNb = 0;
   uint32_t NbOfOne;
 
-  uint8_t row_bad[7];
+  uint8_t row_bad[8];
   uint8_t col_bad[16];
 
 #if BPTC_128x77_DEBUG
@@ -479,9 +553,9 @@ uint32_t BPTC_128x77_Extract_Data(uint8_t InputDataMatrix[8][16], uint8_t DMRDat
       DataMatrix[i][j] = (InputDataMatrix[i][j] & 1);
   }
 
-  /* ---------- Pass 1: Hamming (16,11,4) on rows 0..6 ---------- */
+  /* ---------- Pass 1: Hamming (16,11,4) on rows 0..7 ---------- */
   memset(row_bad, 0, sizeof(row_bad));
-  for (i = 0; i < 7; i++)
+  for (i = 0; i < 8; i++)
   {
     for (j = 0; j < 16; j++)
       LineUncorrected[j] = DataMatrix[i][j];
@@ -496,13 +570,11 @@ uint32_t BPTC_128x77_Extract_Data(uint8_t InputDataMatrix[8][16], uint8_t DMRDat
         fprintf(stderr, "%u", LineUncorrected[j] & 1);
       fprintf(stderr, "\n");
 #endif
-      for (j = 0; j < 11; j++)
-        DataMatrix[i][j] = LineUncorrected[j];
     }
     else
     {
-      for (j = 0; j < 11; j++)
-        DataMatrix[i][j] = LineCorrected[j];
+      for (j = 0; j < 16; j++)
+        DataMatrix[i][j] = LineUncorrected[j];
     }
   }
 #if BPTC_128x77_DEBUG
@@ -537,12 +609,14 @@ uint32_t BPTC_128x77_Extract_Data(uint8_t InputDataMatrix[8][16], uint8_t DMRDat
             (unsigned)ParityCheckErrorNb);
 #endif
 
-  /* ---------- Parity-guided single-bit repair ---------- */
+  /* ---------- Parity-guided bit repair ---------- */
   {
     uint32_t n_bad_rows = 0, n_bad_cols = 0;
     uint32_t br = 0, bc = 0;
 
-    for (i = 0; i < 7; i++)
+    UNUSED(bc);
+
+    for (i = 0; i < 8; i++)
       if (row_bad[i]) { n_bad_rows++; br = i; }
     for (i = 0; i < 16; i++)
       if (col_bad[i]) { n_bad_cols++; bc = i; }
@@ -558,29 +632,35 @@ uint32_t BPTC_128x77_Extract_Data(uint8_t InputDataMatrix[8][16], uint8_t DMRDat
     fprintf(stderr, "\n");
 #endif
 
-    if (n_bad_rows == 1 && n_bad_cols == 1 && bc < 11)
+    if (n_bad_rows == 1 && (n_bad_cols == 1 || n_bad_cols == 2))
     {
-      DataMatrix[br][bc] ^= 1;
-      row_bad[br] = 0;
+      for (i = 0; i < 16; i++)
+      {
+        if (col_bad[i])
+        {
+          DataMatrix[br][i] ^= 1;
 #if BPTC_128x77_DEBUG
-      fprintf(stderr,
-              " BPTC128 parity-guided FLIP at row=%u col=%u -> %u\n",
-              (unsigned)br, (unsigned)bc, (unsigned)DataMatrix[br][bc]);
+          fprintf(stderr,
+                  " BPTC128 parity-guided FLIP at row=%u col=%u -> %u\n",
+                  (unsigned)br, (unsigned)i, (unsigned)DataMatrix[br][i]);
 #endif
+        }
+      }
+      row_bad[br] = 0;
     }
 #if BPTC_128x77_DEBUG
     else if (n_bad_rows || n_bad_cols)
     {
       fprintf(stderr,
-              " BPTC128 no single-intersection flip "
-              "(need exactly 1 bad row and 1 data col)\n");
+              " BPTC128 no repair flip "
+              "(need 1 bad row and 1 or 2 bad cols)\n");
     }
 #endif
   }
 
   /* ---------- Pass 2: Hamming (16,11,4) again ---------- */
   HammingIrrecoverableErrorNb = 0;
-  for (i = 0; i < 7; i++)
+  for (i = 0; i < 8; i++)
   {
     for (j = 0; j < 16; j++)
       LineUncorrected[j] = DataMatrix[i][j];
@@ -594,13 +674,11 @@ uint32_t BPTC_128x77_Extract_Data(uint8_t InputDataMatrix[8][16], uint8_t DMRDat
         fprintf(stderr, "%u", LineUncorrected[j] & 1);
       fprintf(stderr, "\n");
 #endif
-      for (j = 0; j < 11; j++)
-        DataMatrix[i][j] = LineUncorrected[j];
     }
     else
     {
-      for (j = 0; j < 11; j++)
-        DataMatrix[i][j] = LineCorrected[j];
+      for (j = 0; j < 16; j++)
+        DataMatrix[i][j] = LineUncorrected[j];
     }
   }
 #if BPTC_128x77_DEBUG
@@ -696,22 +774,45 @@ uint32_t BPTC_16x2_Extract_Data(uint8_t InputInterleavedData[32], uint8_t DMRDat
     DMRDataExtracted[i] = DataMatrix[i] & 1;
   }
 
-  /* Prepare the line to be corrected */
+  /* Prepare the first row (bits 0..15) to be corrected */
   for(i = 0; i < 16; i++)
   {
     LineUncorrected[i] = DataMatrix[i] & 1;
   }
 
-  /* Apply Hamming (16,11,4) code correction */
+  /* Apply Hamming (16,11,4) code correction to row 0 */
   if(Hamming_16_11_4_decode(LineUncorrected, LineCorrected, 1) == false)
   {
     HammingIrrecoverableErrorNb++;
   }
-
-  /* Copy the corrected content to the output buffer */
-  for(i = 0; i < 11; i++)
+  else
   {
-    DMRDataExtracted[i] = LineCorrected[i] & 1;
+    /* Copy all 16 corrected bits (including parity bits 11..15) */
+    for(i = 0; i < 16; i++)
+    {
+      DMRDataExtracted[i] = LineUncorrected[i] & 1;
+    }
+  }
+
+  /* Prepare the second row (bits 16..31) to be corrected;
+   * 1^16 is a codeword of Hamming(16,11,4), so both even and odd parity rows are valid codewords */
+  for(i = 0; i < 16; i++)
+  {
+    LineUncorrected[i] = DataMatrix[i + 16] & 1;
+  }
+
+  /* Apply Hamming (16,11,4) code correction to row 1 */
+  if(Hamming_16_11_4_decode(LineUncorrected, LineCorrected, 1) == false)
+  {
+    HammingIrrecoverableErrorNb++;
+  }
+  else
+  {
+    /* Copy all 16 corrected bits (including parity bits 11..15) */
+    for(i = 0; i < 16; i++)
+    {
+      DMRDataExtracted[i + 16] = LineUncorrected[i] & 1;
+    }
   }
 
   /* Check Parity bits */

src/dmr_dburst.c

@@ -60,6 +60,10 @@ void dmr_data_burst_handler(dsd_opts * opts, dsd_state * state, uint8_t info[196
   uint8_t bptc_res_bits[3];
   memset (bptc_res_bits, 0, sizeof(bptc_res_bits));
   uint8_t crc_original_validity = 0;
+  static uint8_t ras_confirm_count = 0;
+  static uint8_t prev_dmr_is_ras = 0;
+  if (prev_dmr_is_ras == 1 && state->dmr_is_ras == 0)
+    ras_confirm_count = 0;
 
   uint32_t crcmask = 0;
   uint8_t  crclen = 0;
@@ -305,13 +309,26 @@ void dmr_data_burst_handler(dsd_opts * opts, dsd_state * state, uint8_t info[196
     {
       if (is_ras)
       {
-        CRCComputed = ras_mac_calculator(state, BPTCDmrDataByte, 9, 1);
-        if (CRCComputed == CRCExtracted)
+        uint8_t tmp_bytes[12];
+        uint32_t std_crc = 0;
+        memcpy (tmp_bytes, BPTCDmrDataByte, sizeof(tmp_bytes));
+        if (ComputeAndCorrectFullLinkControlCrc(tmp_bytes, &std_crc, crcmask) && std_crc == CRCExtracted)
+        {
+          memcpy (BPTCDmrDataByte, tmp_bytes, sizeof(tmp_bytes));
+          is_ras = 0;
+          CRCComputed = std_crc;
           CRCCorrect = 1;
+        }
+        else
+        {
+          CRCComputed = ras_mac_calculator(state, BPTCDmrDataByte, 9, 1);
+          if (CRCComputed == CRCExtracted)
+            CRCCorrect = 1;
 
-        #ifdef DEBUG_RAS
-        fprintf (stderr, " EXT: %06X; MAC: %06X;", CRCExtracted, CRCComputed);
-        #endif
+          #ifdef DEBUG_RAS
+          fprintf (stderr, " EXT: %06X; MAC: %06X;", CRCExtracted, CRCComputed);
+          #endif
+        }
       }
       else CRCCorrect = ComputeAndCorrectFullLinkControlCrc(BPTCDmrDataByte, &CRCComputed, crcmask);
 
@@ -354,18 +371,28 @@ void dmr_data_burst_handler(dsd_opts * opts, dsd_state * state, uint8_t info[196
     //run CCITT on other data forms
     else
     {
-      if (is_ras == 1)
+      uint32_t std_crc = ComputeCrcCCITT(BPTCDmrDataBit);
+      if (std_crc == CRCExtracted)
+      {
+        is_ras = 0;
+        CRCComputed = std_crc;
+        CRCCorrect = 1;
+      }
+      else if (is_ras == 1)
       {
         CRCComputed = ras_mac_calculator(state, BPTCDmrDataByte, 10, 0);
+        if (CRCComputed == CRCExtracted) CRCCorrect = 1;
+        else CRCCorrect = 0;
 
         #ifdef DEBUG_RAS
         fprintf (stderr, " EXT: %04X; MAC: %04X;", CRCExtracted, CRCComputed);
         #endif
       }
-      else CRCComputed = ComputeCrcCCITT(BPTCDmrDataBit);
-
-      if (CRCComputed == CRCExtracted) CRCCorrect = 1;
-      else CRCCorrect = 0;
+      else
+      {
+        CRCComputed = std_crc;
+        CRCCorrect = 0;
+      }
     }
 
     //if this is a RAS system, set the CRC to okay if irrecoverable errors are okay
@@ -473,9 +500,11 @@ void dmr_data_burst_handler(dsd_opts * opts, dsd_state * state, uint8_t info[196
     /* Compute the 5 bit CRC */
     CRCComputed = ComputeCrc5Bit(LC_DataBit);
 
-    //read ahead first two bytes, look for 1X10 or 2X10 pattern
+    //read ahead first two bytes, look for 1X10 or 2X10 pattern (with PF/R bits 0)
     uint16_t ras_test = (uint16_t)(ConvertBitIntoBytes(&LC_DataBit[0], 16) & 0x30FF);
-    if ((IrrecoverableErrors == 0) && (ras_test == 0x2010 || ras_test == 0x1010))
+    if ((IrrecoverableErrors == 0) &&
+        (LC_DataBit[0] == 0) && (LC_DataBit[1] == 0) &&
+        (ras_test == 0x2010 || ras_test == 0x1010))
     {
       is_ras = 1;
       if (state->ras_effective_key != 0)
@@ -702,9 +731,28 @@ void dmr_data_burst_handler(dsd_opts * opts, dsd_state * state, uint8_t info[196
     fprintf (stderr, "%s", KNRM);
   }
 
-  //might flicker the terminal on partially enabled systems, may need to find a better placement
-  if (IrrecoverableErrors == 0 && (is_bptc || is_emb) && databurst != 0x05 && databurst != 0x07 && databurst != 0x09)
-    state->dmr_is_ras = is_ras;
+  //require a key-verified RAS burst or 2 RAS bursts to latch [RAS]; clear on valid non-PI non-RAS BPTC burst
+  if (IrrecoverableErrors == 0 && is_ras == 1 && (is_bptc || is_emb) && databurst != 0x05 && databurst != 0x07 && databurst != 0x09)
+  {
+    if (state->ras_effective_key != 0 && CRCCorrect == 1)
+    {
+      ras_confirm_count = 2;
+      state->dmr_is_ras = 1;
+    }
+    else if ((is_bptc || is_emb) && databurst != 0x00)
+    {
+      if (ras_confirm_count < 2)
+        ras_confirm_count++;
+      if (ras_confirm_count >= 2)
+        state->dmr_is_ras = 1;
+    }
+  }
+  else if (IrrecoverableErrors == 0 && is_ras == 0 && is_bptc && CRCCorrect == 1 && databurst != 0x00 && databurst != 0x05 && databurst != 0x07 && databurst != 0x09)
+  {
+    ras_confirm_count = 0;
+    state->dmr_is_ras = 0;
+  }
+  prev_dmr_is_ras = state->dmr_is_ras;
 
   if (IrrecoverableErrors == 0 && CRCCorrect == 0 && is_ras == 0 && databurst != 0x09 && databurst != 0x05)
   {