ptolemy.actor.lib.comm
Class ConvolutionalCoder

java.lang.Object
  ptolemy.kernel.util.NamedObj
      ptolemy.kernel.InstantiableNamedObj
          ptolemy.kernel.Entity
              ptolemy.kernel.ComponentEntity
                  ptolemy.actor.AtomicActor
                      ptolemy.actor.TypedAtomicActor
                          ptolemy.actor.lib.Transformer
                              ptolemy.actor.lib.comm.ConvolutionalCoder

All Implemented Interfaces:

java.io.Serializable, java.lang.Cloneable, Actor, Executable, FiringsRecordable, Initializable, TypedActor, Changeable, Debuggable, DebugListener, Derivable, Instantiable, ModelErrorHandler, MoMLExportable, Moveable, Nameable

public class ConvolutionalCoder
extends Transformer

Encode an input sequence with a convolutional code. The inputs and outputs are booleans. The input sequence enters a shift register, and the contents of the shift register are combined using boolean functions given by the polynomialArray parameter. The initial state of the shift register is given by the initialState parameter, which should be a non-negative integer. The uncodedRate parameter, often denoted by k in the coding literature, is the number of bits per firing that are shifted into the shift register. The polynomialArray parameter is an array of positive integers. Each integer indicates one polynomial used for computing output bits. To get a k/n convolutional code, set uncodedRate to k and provide n integers in polynomialArray.

The integers in polynomialArray are usually most conveniently given as octal numbers. A leading zero indicates an octal number. The i-th bit of the integer indicates whether the i-th tap of the delay line should be used. All bits that are used are exclusive-ored, thus yielding the parity of the selected bits. See more details in Scrambler actor on using an integer to define a polynomial. The n parity results are produced on the output in a sequence.

A good convolutional code should have large Hamming distance between any two of its codewords. This is not easily checked, but there are some simple rules that all "good" codes should satisfy:

1. k should be strictly smaller than n, otherwise the code is not uniquely decodable. Thus, uncodedRate should be less than the length of polynomialArray.
2. k should not be higher than the highest order of all polynomials, otherwise, some input bits never get involved in computing parities.

If these rules are violated, the actor will throw an exception. However, these rules do not guarantee the codeword can be decoded successfully, and it is not always true that larger polynomials yield better codes. Users should check tables for convolutional codes from professional references. For convenience, we list here some convolutional codes that have large distance property.

 Rate = 1/2
 polynomialArray
 {05, 07}
 {013, 017}
 {031, 027}
 {065, 057}
 {0155, 0117}
 

 Rate = 1/3
 polynomialArray
 {05, 07, 07}
 {015, 013, 017}
 {025, 033, 037}
 {071, 065, 057}
 {0155, 0123, 0137}
 

 Rate = 1/4
 polynomialArray
 {05, 07, 07, 07}
 {015, 013, 013, 017}
 {025, 035, 033, 037}
 {065, 073, 047, 057}
 {0135, 0135, 0163, 0147}
 

 Rate = 1/5
 polynomialArray
 {07, 07, 07, 05, 05}
 {017, 017, 015, 013, 013}
 {037, 035, 033, 025, 027}
 {057, 047, 067, 053, 075}
 

 Rate = 1/6
 polynomialArray
 {07, 07, 07, 07, 05, 05}
 {017, 017, 015, 015, 013, 013}
 {037, 027, 035, 033, 025, 027}
 {067, 057, 055, 053, 071, 075}
 

 Rate = 2/3
 polynomialArray
 {017, 06, 013}
 {072, 057, 027}
 {0171, 0166, 0273}
 

 Rate = k/5
 k     polynomialArray
 2     {017, 016, 011, 05, 02}
 2     {072, 047, 025, 053, 075}
 3     {056, 062, 057, 043, 071}
 

 Rate = k/7
 k     polynomialArray
 2     {012, 06, 05, 013, 013, 015, 017}
 2     {066, 055, 027, 071, 052, 056, 057}
 3     {051, 042, 036, 023, 075, 061, 047}
 

 Rate  polynomialArray
 3/4   {064, 052, 043, 071}
 3/8   {054, 021, 062, 043, 045, 036, 057, 071}
 

Note that this implementation is limited to a shift register length of 32 because of the specification of the polynomials and initial shift register state as 32-bit integers.

For more information on convolutional codes, see Proakis, Digital Communications, Fourth Edition, McGraw-Hill, 2001, pp. 471-477, or Barry, Lee and Messerschmitt, Digital Communication, Third Edition, Kluwer, 2004.

Since:

Ptolemy II 3.0

Version:

$Id: ConvolutionalCoder.java 57040 2010-01-27 20:52:32Z cxh $

Author:

Ye Zhou, contributor: Edward A. Lee

See Also:

Scrambler, ViterbiDecoder, Serialized Form

Accepted Rating:

Red (cxh)

Proposed Rating:

Yellow (eal)

Nested Class Summary

Nested classes/interfaces inherited from class ptolemy.kernel.Entity

Entity.ContainedObjectsIterator

Field Summary

private int	_inputNumber
private boolean	_inputNumberInvalid
private Parameter	_inputRate
private int	_latestShiftReg
private int[]	_mask
private int	_maskNumber
private int	_maxPolyValue
private Parameter	_outputRate
private int	_shiftReg
Parameter	initialState Integer defining the initial state of the shift register.
Parameter	polynomialArray An array of integers defining an array of polynomials with binary coefficients.
Parameter	uncodedRate Integer defining the number of bits that the shift register takes in each firing.

Fields inherited from class ptolemy.actor.lib.Transformer

input, output

Fields inherited from class ptolemy.actor.AtomicActor

_actorFiringListeners, _initializables, _notifyingActorFiring, _stopRequested

Fields inherited from class ptolemy.kernel.util.NamedObj

_changeListeners, _changeLock, _changeRequests, _debugging, _debugListeners, _elementName, _isPersistent, _verbose, _workspace, ATTRIBUTES, CLASSNAME, COMPLETE, CONTENTS, DEEP, FULLNAME, LINKS

Fields inherited from interface ptolemy.actor.Executable

COMPLETED, NOT_READY, STOP_ITERATING

Constructor Summary

ConvolutionalCoder(CompositeEntity container, java.lang.String name)
Construct an actor with the given container and name.

Method Summary

private int[]	_calculateParity(int[] mask, int maskNumber, int reg) Calculate the parities given by the polynomial array and the state of shift register.
void	attributeChanged(Attribute attribute) If the attribute being changed is uncodedRate, then verify that it is a positive integer; if it is polynomialArray, then verify that each of its elements is a positive integer and find the maximum value among them, which is used to compute the highest order among all polynomials.
java.lang.Object	clone(Workspace workspace) Clone the actor into the specified workspace.
void	fire() Read uncodedRate bits from the input port and shift them into the shift register.
void	initialize() Initialize the actor by resetting the shift register state equal to the value of initialState.
boolean	postfire() Record the most recent shift register state as the new state for the next iteration.

Methods inherited from class ptolemy.actor.TypedAtomicActor

_addPort, _fireAt, _fireAt, attributeTypeChanged, clone, newPort, typeConstraintList, typeConstraints

Methods inherited from class ptolemy.actor.AtomicActor

_actorFiring, _actorFiring, addActorFiringListener, addInitializable, connectionsChanged, createReceivers, declareDelayDependency, getCausalityInterface, getDirector, getExecutiveDirector, getManager, inputPortList, isFireFunctional, isStrict, iterate, newReceiver, outputPortList, prefire, preinitialize, pruneDependencies, recordFiring, removeActorFiringListener, removeDependency, removeInitializable, setContainer, stop, stopFire, terminate, wrapup

Methods inherited from class ptolemy.kernel.ComponentEntity

_adjustDeferrals, _checkContainer, _getContainedObject, _propagateExistence, getContainer, instantiate, isAtomic, isOpaque, moveDown, moveToFirst, moveToIndex, moveToLast, moveUp, propagateExistence, setName

Methods inherited from class ptolemy.kernel.Entity

_description, _exportMoMLContents, _removePort, _validateSettables, connectedPortList, connectedPorts, containedObjectsIterator, getAttribute, getPort, getPorts, linkedRelationList, linkedRelations, portList, removeAllPorts, setClassDefinition, uniqueName

Methods inherited from class ptolemy.kernel.InstantiableNamedObj

_setParent, exportMoML, getChildren, getElementName, getParent, getPrototypeList, isClassDefinition, isWithinClassDefinition

Methods inherited from class ptolemy.kernel.util.NamedObj

_addAttribute, _adjustOverride, _attachText, _cloneFixAttributeFields, _debug, _debug, _debug, _debug, _debug, _getIndentPrefix, _isMoMLSuppressed, _markContentsDerived, _propagateValue, _recordDecoratedAttributes, _removeAttribute, _splitName, _stripNumericSuffix, addChangeListener, addDebugListener, attributeList, attributeList, deepContains, depthInHierarchy, description, description, event, executeChangeRequests, exportMoML, exportMoML, exportMoML, exportMoML, exportMoMLPlain, getAttribute, getAttributes, getChangeListeners, getClassName, getDecoratorAttribute, getDecoratorAttributes, getDerivedLevel, getDerivedList, getDisplayName, getFullName, getModelErrorHandler, getName, getName, getSource, handleModelError, isDeferringChangeRequests, isOverridden, isPersistent, lazyContainedObjectsIterator, message, propagateValue, propagateValues, removeChangeListener, removeDebugListener, requestChange, setClassName, setDeferringChangeRequests, setDerivedLevel, setDisplayName, setModelErrorHandler, setPersistent, setSource, sortContainedObjects, toplevel, toString, validateSettables, workspace

Methods inherited from class java.lang.Object

equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Methods inherited from interface ptolemy.actor.Actor

createReceivers, getCausalityInterface, getDirector, getExecutiveDirector, getManager, inputPortList, newReceiver, outputPortList

Methods inherited from interface ptolemy.actor.Executable

isFireFunctional, isStrict, iterate, prefire, stop, stopFire, terminate

Methods inherited from interface ptolemy.actor.Initializable

addInitializable, preinitialize, removeInitializable, wrapup

Methods inherited from interface ptolemy.kernel.util.Nameable

description, getContainer, getDisplayName, getFullName, getName, getName, setName

Methods inherited from interface ptolemy.kernel.util.Derivable

getDerivedLevel, getDerivedList, propagateValue

Field Detail

polynomialArray

public Parameter polynomialArray

An array of integers defining an array of polynomials with binary coefficients. The coefficients indicate the presence (1) or absence (0) of a tap in the shift register. Each element of this array parameter should be a positive integer. The default value is {05, 07}.

initialState

public Parameter initialState

Integer defining the initial state of the shift register. The i-th bit of the integer indicates the value of the i-th register. This parameter should be a non-negative integer. Its default value is the integer 0.

uncodedRate

public Parameter uncodedRate

Integer defining the number of bits that the shift register takes in each firing. It should be a positive integer. Its default value is the integer 1.

_inputRate

private Parameter _inputRate

_outputRate

private Parameter _outputRate

_shiftReg

private int _shiftReg

_latestShiftReg

private int _latestShiftReg

_inputNumber

private int _inputNumber

_mask

private int[] _mask

_maskNumber

private int _maskNumber

_maxPolyValue

private int _maxPolyValue

_inputNumberInvalid

private transient boolean _inputNumberInvalid

Constructor Detail

ConvolutionalCoder

public ConvolutionalCoder(CompositeEntity container,
                          java.lang.String name)
                   throws NameDuplicationException,
                          IllegalActionException

Construct an actor with the given container and name. The output and trigger ports are also constructed.

Parameters:

container - The container.

name - The name of this actor.

Throws:

IllegalActionException - If the entity cannot be contained by the proposed container.

NameDuplicationException - If the container already has an actor with this name.

Method Detail

attributeChanged

public void attributeChanged(Attribute attribute)
                      throws IllegalActionException

If the attribute being changed is uncodedRate, then verify that it is a positive integer; if it is polynomialArray, then verify that each of its elements is a positive integer and find the maximum value among them, which is used to compute the highest order among all polynomials.

Overrides:

attributeChanged in class NamedObj

Parameters:

attribute - The attribute that changed.

Throws:

IllegalActionException - If uncodedRate is non-positive or any element of polynomialArray is non-positive.

clone

public java.lang.Object clone(Workspace workspace)
                       throws java.lang.CloneNotSupportedException

Clone the actor into the specified workspace.

Overrides:

clone in class AtomicActor

Parameters:

workspace - The workspace for the new object.

Returns:

A new actor.

Throws:

java.lang.CloneNotSupportedException - If a derived class contains an attribute that cannot be cloned.

See Also:

NamedObj.exportMoML(Writer, int, String), NamedObj.setDeferringChangeRequests(boolean)

fire

public void fire()
          throws IllegalActionException

Read uncodedRate bits from the input port and shift them into the shift register. Compute the parity for each polynomial specified in polynomialArray. Send the results in sequence to the output. The i-th bit in the output corresponds to the parity computed using the i-th polynomial.

Specified by:

fire in interface Executable

Overrides:

fire in class AtomicActor

Throws:

IllegalActionException - Not thrown in this base class.

initialize

public void initialize()
                throws IllegalActionException

Initialize the actor by resetting the shift register state equal to the value of initialState.

Specified by:

initialize in interface Initializable

Overrides:

initialize in class AtomicActor

Throws:

IllegalActionException - If the parent class throws it.

postfire

public boolean postfire()
                 throws IllegalActionException

Record the most recent shift register state as the new state for the next iteration.

Specified by:

postfire in interface Executable

Overrides:

postfire in class AtomicActor

Returns:

True if execution can continue into the next iteration.

Throws:

IllegalActionException - If the base class throws it

_calculateParity

private int[] _calculateParity(int[] mask,
                               int maskNumber,
                               int reg)

Calculate the parities given by the polynomial array and the state of shift register.

Parameters:

mask - The polynomial array.

reg - State of shift register.

Returns:

Parities stored in an array.