GitHub/sdrtrunk
1
0
Fork 0
mirror of https://github.com/DSheirer/sdrtrunk.git synced 2026-11-12 16:47:31 -05:00
Code Issues Packages Projects Releases 2 Wiki Activity

P25 - enhancement for LSM demod phase lock errors - adds new sync pattern detectors to detect Costas Loop phase lock errors and apply immediate correction to enable accurate symbol slicing.

Browse Source
This commit is contained in:
dennis.sheirer
2015-04-26 16:58:25 +00:00
parent c12123a81b
commit 2c4b3ab1b5
11 changed files with 376 additions and 72 deletions
Download Patch File Download Diff File Expand all files Collapse all files

159
src/decode/p25/P25MessageFramer.java
View File

@@ -11,7 +11,10 @@ import sample.Listener;
import alias.AliasList;
import bits.BinaryMessage;
import bits.BitSetFullException;
import bits.SyncPatternMatcher;
import bits.ISyncDetectListener;
import bits.MultiSyncPatternMatcher;
import bits.SoftSyncDetector;
import bits.SyncDetector;
import decode.p25.message.P25Message;
import decode.p25.message.hdu.HDUMessage;
import decode.p25.message.ldu.LDU1Message;
@@ -27,20 +30,32 @@ 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 dsp.psk.CQPSKDemodulator;
import dsp.symbol.Dibit;
import dsp.symbol.FrameSync;
import edac.BCH_63_16_11;
import edac.CRC;
import edac.CRCP25;
public class P25MessageFramer implements Listener<Dibit>
{
private static final int SYNC_PATTERN_MISMATCH_THRESHOLD = 2;
private final static Logger mLog =
LoggerFactory.getLogger( P25MessageFramer.class );
LoggerFactory.getLogger( P25MessageFramer.class );
/* Determines the threshold for sync pattern soft matching */
private static final int SYNC_PATTERN_SOFT_MATCH_THRESHOLD = 4;
/* Costas Loop phase lock error correction values. A phase lock error of
* 90 degrees requires a correction of 1/4 of the symbol rate (1200Hz). An
* error of 180 degrees requires a correction of 1/2 of the symbol rate
* (2400Hz) */
public static final double SYMBOL_FREQUENCY = 2.0d * Math.PI * 4800.0d / 48000.0d;
public static final double PHASE_CORRECTION_90_DEGREES = SYMBOL_FREQUENCY / 4.0d;
public static final double PHASE_CORRECTION_180_DEGREES = SYMBOL_FREQUENCY / 2.0d;
private MultiSyncPatternMatcher mMatcher = new MultiSyncPatternMatcher( 48 );
private ArrayList<P25MessageAssembler> mAssemblers =
new ArrayList<P25MessageAssembler>();
new ArrayList<P25MessageAssembler>();
public static final int TSBK_BEGIN = 64;
public static final int TSBK_CRC_START = 144;
@@ -60,31 +75,41 @@ public class P25MessageFramer implements Listener<Dibit>
private Listener<Message> mListener;
private AliasList mAliasList;
private SyncPatternMatcher mMatcher;
private boolean mInverted = false;
private Trellis_1_2_Rate mHalfRate = new Trellis_1_2_Rate();
private Trellis_3_4_Rate mThreeQuarterRate = new Trellis_3_4_Rate();
private BCH_63_16_11 mNIDDecoder = new BCH_63_16_11();
/**
* Constructs a C4FM message framer to receive a stream of C4FM symbols and
* Constructs a P25 message framer to receive a stream of symbols and
* detect the sync pattern then capture the following stream of symbols up
* to the message length, and then broadcast that bit buffer to the registered
* listener.
*
* @param sync - sync pattern (maximum of 63 bits)
* @param messageLength - in bits
* @param inverted - optional flag to indicate the symbol stream should be
* uninverted prior to processing
*/
public P25MessageFramer( long sync,
int messageLength,
boolean inverted,
AliasList aliasList )
public P25MessageFramer( AliasList aliasList )
{
mMatcher = new SyncPatternMatcher( sync, SYNC_PATTERN_MISMATCH_THRESHOLD );
mInverted = inverted;
mAliasList = aliasList;
SoftSyncDetector primarySyncDetector = new SoftSyncDetector(
FrameSync.P25_PHASE1_NORMAL.getSync(), SYNC_PATTERN_SOFT_MATCH_THRESHOLD );
primarySyncDetector.setListener( new ISyncDetectListener()
{
@Override
public void syncDetected()
{
for( P25MessageAssembler assembler: mAssemblers )
{
if( !assembler.isActive() )
{
assembler.setActive( true );
break;
}
}
}
} );
mMatcher.add( primarySyncDetector );
/**
* We use two message assemblers to catch any sync detections, so that
@@ -98,6 +123,22 @@ public class P25MessageFramer implements Listener<Dibit>
mAssemblers.add( new P25MessageAssembler() );
}
public P25MessageFramer( AliasList aliasList, CQPSKDemodulator demodulator )
{
this( aliasList );
/* For CQPSK, we include 3 additional sync detectors to watch for and
* correction +/-90 and 180 degree costas loop phase lock errors */
mMatcher.add( new CostasPhaseErrorDetector( FrameSync.P25_PHASE1_ERROR_90_CCW,
demodulator, PHASE_CORRECTION_90_DEGREES ) );
mMatcher.add( new CostasPhaseErrorDetector( FrameSync.P25_PHASE1_ERROR_90_CW,
demodulator, -PHASE_CORRECTION_90_DEGREES ) );
mMatcher.add( new CostasPhaseErrorDetector( FrameSync.P25_PHASE1_ERROR_180,
demodulator, PHASE_CORRECTION_180_DEGREES ) );
}
private void dispatch( Message message )
{
if( mListener != null )
@@ -109,9 +150,6 @@ public class P25MessageFramer implements Listener<Dibit>
@Override
public void receive( Dibit symbol )
{
mMatcher.receive( symbol.getBit1() );
mMatcher.receive( symbol.getBit2() );
for( P25MessageAssembler assembler: mAssemblers )
{
if( assembler.isActive() )
@@ -125,27 +163,7 @@ public class P25MessageFramer implements Listener<Dibit>
}
}
/* Check for sync match and activate a message assembler, if we can
* find an inactive assembler. Otherwise, ignore and log the issue */
if( mMatcher.matches() )
{
boolean found = false;
for( P25MessageAssembler assembler: mAssemblers )
{
if( !assembler.isActive() )
{
assembler.setActive( true );
found = true;
break;
}
}
if( !found )
{
mLog.debug( "no inactive P25 message assemblers available" );
}
}
mMatcher.receive( symbol.getBit1(), symbol.getBit2() );
}
public void setListener( Listener<Message> listener )
@@ -258,12 +276,10 @@ public class P25MessageFramer implements Listener<Dibit>
break;
case HDU:
mComplete = true;
mMatcher.setSoftMode( true );
dispatch( new HDUMessage( mMessage.copy(), mDUID, mAliasList ) );
break;
case LDU1:
mComplete = true;
mMatcher.setSoftMode( true );
LDU1Message ldu1 = new LDU1Message( mMessage.copy(),
mDUID, mAliasList );
@@ -273,11 +289,9 @@ public class P25MessageFramer implements Listener<Dibit>
break;
case LDU2:
mComplete = true;
mMatcher.setSoftMode( true );
dispatch( new LDU2Message( mMessage.copy(), mDUID, mAliasList ) );
break;
case PDU0:
mMatcher.setSoftMode( false );
/* Remove interleaving */
P25Interleave.deinterleaveData( mMessage, PDU0_BEGIN, PDU0_END );
@@ -397,8 +411,6 @@ public class P25MessageFramer implements Listener<Dibit>
mComplete = true;
break;
case PDUC:
mMatcher.setSoftMode( true );
/* De-interleave the latest block*/
P25Interleave.deinterleaveData( mMessage,
mMessage.size() - 196, mMessage.size() );
@@ -447,12 +459,10 @@ public class P25MessageFramer implements Listener<Dibit>
}
break;
case TDU:
mMatcher.setSoftMode( true );
dispatch( new TDUMessage( mMessage.copy(), mDUID, mAliasList ) );
mComplete = true;
break;
case TDULC:
mMatcher.setSoftMode( true );
TDULinkControlMessage tdulc = new TDULinkControlMessage(
mMessage.copy(), mDUID, mAliasList );
@@ -463,7 +473,6 @@ public class P25MessageFramer implements Listener<Dibit>
mComplete = true;
break;
case TSBK1:
mMatcher.setSoftMode( true );
/* Remove interleaving */
P25Interleave.deinterleaveData( mMessage, TSBK_BEGIN, TSBK_END );
@@ -602,4 +611,50 @@ public class P25MessageFramer implements Listener<Dibit>
return mActive;
}
}
/**
* Sync pattern detector to listen for costas loop phase lock errors and
* apply a phase correction to the costas loop so that we don't miss any
* messages.
*
* When the costas loop locks with a +/- 90 degree or 180 degree phase
* error, the slicer will incorrectly apply the symbol pattern rotated left
* or right by the phase error. However, we can detect these rotated sync
* patterns and apply immediate phase correction so that message processing
* can continue.
*/
public class CostasPhaseErrorDetector extends SyncDetector
{
private CQPSKDemodulator mDemodulator;
private double mCorrection;
public CostasPhaseErrorDetector( FrameSync frameSync,
CQPSKDemodulator demodulator, double correction )
{
super( frameSync.getSync() );
mDemodulator = demodulator;
mCorrection = correction;
setListener( new ISyncDetectListener()
{
@Override
public void syncDetected()
{
mDemodulator.correctPhaseError( mCorrection );
/* Since we detected a sync pattern, start a message assembler */
for( P25MessageAssembler assembler: mAssemblers )
{
if( !assembler.isActive() )
{
assembler.setActive( true );
break;
}
}
}
} );
}
}
}