Changed NID error detection and correction (edac) to using Berlekemp Massey 63-bit block decoder for the BCH(63,16,11) code so that we can correct up to 11 bit errors in a NID (versus previous 2).

src/bits/BitSetBuffer.java

@@ -220,6 +220,36 @@ public class BitSetBuffer extends BitSet
         
         return sb.toString();
     }
+
+    /**
+     * Returns this bitset as an array of integer ones and zeros
+     */
+    public int[] toIntegerArray()
+    {
+    	int[] values = new int[ mSize ];
+    	
+		for (int i = nextSetBit( 0 ); i >= 0 && i < mSize; i = nextSetBit( i+1 ) ) 
+		{
+			values[ i ] = 1;
+		}
+		
+		return values;
+    }
+    
+    /**
+     * Returns this bitset as a reversed bit order array of integer ones and zeros
+     */
+    public int[] toReverseIntegerArray()
+    {
+    	int[] values = new int[ mSize ];
+    	
+		for (int i = nextSetBit( 0 ); i >= 0 && i < mSize; i = nextSetBit( i+1 ) ) 
+		{
+			values[ mSize - i - 1 ] = 1;
+		}
+		
+		return values;
+    }
     
     /**
      * Returns a boolean array from startIndex to end of the bitset

src/decode/p25/message/ldu/LDUMessage.java

@@ -51,6 +51,7 @@ public class LDUMessage extends P25Message
 		sb.append( getDUID().getLabel() );
 		sb.append( " LSD:" );
 		sb.append( getLowSpeedData() );
+		sb.append( " " );
 		
 		return sb.toString();
     }

src/dsp/fsk/P25MessageFramer.java

@@ -28,6 +28,7 @@ import decode.p25.message.tdu.lc.TDULinkControlMessage;
 import decode.p25.message.tsbk.TSBKMessage;
 import decode.p25.message.tsbk.TSBKMessageFactory;
 import decode.p25.reference.DataUnitID;
+import edac.BCH_63_16_11;
 import edac.CRC;
 import edac.CRCP25;
 
@@ -60,6 +61,7 @@ public class P25MessageFramer implements Listener<Dibit>
 	private SyncPatternMatcher mMatcher;
 	private boolean mInverted = false;
 	private TrellisHalfRate mHalfRate = new TrellisHalfRate();
+	private BCH_63_16_11 mNIDDecoder = new BCH_63_16_11();
 	
 	/**
 	 * Constructs a C4FM message framer to receive a stream of C4FM symbols and
@@ -229,14 +231,14 @@ public class P25MessageFramer implements Listener<Dibit>
         	switch( mDUID )
         	{
 				case NID:
-					CRC crc = CRCP25.correctNID( mMessage );
+					CRC crc = mNIDDecoder.correctNID( mMessage );
 					
 					if( crc != CRC.FAILED_CRC )
 					{
 						int value = mMessage.getInt( P25Message.DUID );
 						
 						DataUnitID duid = DataUnitID.fromValue( value );
-
+						
 						if( duid != DataUnitID.UNKN )
 						{
 							setDUID( duid );

src/edac/BCH_63_16_11.java

@@ -0,0 +1,103 @@
+package edac;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import bits.BitSetBuffer;
+
+/*******************************************************************************
+ *     SDR Trunk 
+ *     Copyright (C) 2014 Dennis Sheirer
+ * 
+ *     This program is free software: you can redistribute it and/or modify
+ *     it under the terms of the GNU General Public License as published by
+ *     the Free Software Foundation, either version 3 of the License, or
+ *     (at your option) any later version.
+ * 
+ *     This program is distributed in the hope that it will be useful,
+ *     but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *     GNU General Public License for more details.
+ * 
+ *     You should have received a copy of the GNU General Public License
+ *     along with this program.  If not, see <http://www.gnu.org/licenses/>
+ ******************************************************************************/
+
+public class BCH_63_16_11 extends BerlekempMassey_63
+{
+	private final static Logger mLog = LoggerFactory.getLogger( BCH_63_16_11.class );
+
+	/**
+	 * BCH( 63,16,11) decoder
+	 */
+	public BCH_63_16_11()
+    {
+		/* TT = 11 = maximum correctable bit errors */
+	    super( 11 );
+    }
+	
+	/**
+	 * Performs error detection and correction on the first 63 bits of the 
+	 * message argument.  If the message is correctable, only the first 16 bits
+	 * (information bits) are corrected.
+	 * 
+	 * @return - true = success, false = failure
+	 */
+	public CRC correctNID( BitSetBuffer message )
+	{
+		CRC status = CRC.PASSED;
+		
+		int[] original = message.toReverseIntegerArray();
+		int[] corrected = new int[ 63 ];
+
+		boolean irrecoverableErrors = decode( original, corrected );
+
+		if( irrecoverableErrors )
+		{
+			return CRC.FAILED_CRC;
+		}
+		else
+		{
+			for( int x = 0; x < 16; x++ )
+			{
+				int index = 63 - x - 1;
+				
+				if( corrected[ index ] != original[ index ] )
+				{
+					status = CRC.CORRECTED;
+					
+					if( corrected[ index ] == 1 )
+					{
+						message.set( x );
+					}
+					else
+					{
+						message.clear( x );
+					}
+				}
+			}
+		}
+		
+		return status;
+	}
+	
+	public static void main( String[] args )
+	{
+		String orig  = "001001100000110010100101011111010001010101101001111111001010110";
+		String error = "010110000000110010100101011011010001011101101001101111001110110";
+//                       xxxxxx                    x          x          x       x
+		BitSetBuffer errorMessage = BitSetBuffer.load( error );
+
+		BCH_63_16_11 bch = new BCH_63_16_11();
+
+		mLog.debug( "ORIG:" + orig );
+		mLog.debug( " ERR:" + errorMessage.toString() );
+		mLog.debug( " " );
+
+		CRC status = bch.correctNID( errorMessage );
+		
+		mLog.debug( " CRC: " + status.name() );
+		mLog.debug( "CORR:" + errorMessage.toString().substring( 0, 16 ) );
+		mLog.debug( "ORIG:" + orig );
+	}
+}

src/edac/BerlekempMassey_63.java

@@ -41,9 +41,12 @@ package edac;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
-public class ReedSolomon
+/**
+ * Berlekemp Massey decoder for 63-bit primitive RS/BCH block codes
+ */
+public class BerlekempMassey_63
 {
-	public final static Logger mLog = LoggerFactory.getLogger( ReedSolomon.class );
+	public final static Logger mLog = LoggerFactory.getLogger( BerlekempMassey_63.class );
 
 	/* Golay field size GF( 2 ** MM ) */
 	private static final int MM = 6;
@@ -61,7 +64,7 @@ public class ReedSolomon
 	int[] index_of;
 	int[] gg;
 	
-	public ReedSolomon( int tt )
+	public BerlekempMassey_63( int tt )
     {
 		TT = tt;
 		KK = NN - 2 * TT;

src/edac/CRCP25.java

@@ -29,33 +29,6 @@ public class CRCP25
 {
 	private final static Logger mLog = LoggerFactory.getLogger( CRCP25.class );
 	
-	private static final int NID_MESSAGE_START = 0;
-	private static final int NID_CRC_START = 16;
-	private static final int NID_CRC_END = 48;
-
-	/**
-	 * Network ID and Data Unit ID checksums
-	 */
-	private static long[] NID_DUID_CHECKSUMS = new long[] 
-	{
-		0xCD930BDD3B2Al, 0xAB5A8E33A6BEl, 0x983E4CC4E874l, 0x4C1F2662743Al,
-		0xEB9C98EC0136l, 0xB85D47AB3BB0l, 0x5C2EA3D59DD8l, 0x2E1751EACEECl,
-		0x170BA8F56776l, 0xC616DFA78890l, 0x630B6FD3C448l, 0x3185B7E9E224l,
-		0x18C2DBF4F112l, 0xC1F2662743A2l, 0xAD6A38CE9AFBl, 0x9B2617BA7657l, 
-		0x800000000000l, 0x400000000000l, 0x200000000000l, 0x100000000000l,
-		0x080000000000l, 0x040000000000l, 0x020000000000l, 0x010000000000l,
-		0x008000000000l, 0x004000000000l, 0x002000000000l, 0x001000000000l,
-		0x000800000000l, 0x000400000000l, 0x000200000000l, 0x000100000000l,
-		0x000080000000l, 0x000040000000l, 0x000020000000l, 0x000010000000l,
-		0x000008000000l, 0x000004000000l, 0x000002000000l, 0x000001000000l,
-		0x000000800000l, 0x000000400000l, 0x000000200000l, 0x000000100000l,
-		0x000000080000l, 0x000000040000l, 0x000000020000l, 0x000000010000l,
-		0x000000008000l, 0x000000004000l, 0x000000002000l, 0x000000001000l,
-		0x000000000800l, 0x000000000400l, 0x000000000200l, 0x000000000100l,
-		0x000000000080l, 0x000000000040l, 0x000000000020l, 0x000000000010l,
-		0x000000000008l, 0x000000000004l, 0x000000000002l, 0x000000000001l
-	};
-
 	/**
 	 * CRC-CCITT 16-bit checksums for a message length of 80 bits plus 16
 	 * additional checksums representing CRC checksum bit errors
@@ -222,47 +195,6 @@ public class CRCP25
 	    0x20000000l, 0x40000000l, 0x80000000l 
 	};
 	
-	
-
-	/**
-	 * Performs CRC check and corrects single-bit errors against the message.
-	 * @param message - bitsetbuffer containing a message of at least 64 bits.
-	 * @return - results of CRC check and/or correction attempt
-	 */
-	public static CRC correctNID( BitSetBuffer message )
-	{
-		long calculated = 0; //Starting value
-
-		/* Iterate the set bits and XOR running checksum with lookup value */
-		for (int i = message.nextSetBit( NID_MESSAGE_START ); 
-				 i >= NID_MESSAGE_START && i < NID_CRC_START; 
-				 i = message.nextSetBit( i+1 ) ) 
-		{
-			calculated ^= NID_DUID_CHECKSUMS[ i - NID_MESSAGE_START ];
-		}
-		
-		long checksum = getLongChecksum( message, NID_CRC_START, NID_CRC_END );
-
-		if( calculated == checksum )
-		{
-			return CRC.PASSED;
-		}
-		else
-		{
-			int errorLocation = getBitError( calculated ^ checksum, 
-											 NID_DUID_CHECKSUMS );
-			
-			if( errorLocation >= 0 )
-			{
-				message.flip( errorLocation + NID_MESSAGE_START );
-				
-				return CRC.CORRECTED;
-			}
-		}
-
-		return CRC.FAILED_CRC;
-	}
-
 	/**
 	 * Performs error detection and single-bit error correction against the
 	 * data blocks of a PDU1 message.

src/edac/ReedSolomon_24_12_13.java

@@ -18,7 +18,7 @@ package edac;
  *     along with this program.  If not, see <http://www.gnu.org/licenses/>
  ******************************************************************************/
 
-public class ReedSolomon_24_12_13 extends ReedSolomon
+public class ReedSolomon_24_12_13 extends BerlekempMassey_63
 {
 	/**
 	 * Reed-Solomon RS(24,12,13) decoder