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).

2026-11-13 09:07:27 -05:00 · 2015-01-04 15:29:34 +00:00
parent bb27d5cb42
commit 84261a4be9
7 changed files with 145 additions and 74 deletions
--- a/src/edac/BCH_63_16_11.java
+++ b/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 );
+	}
+}