public class CollisionDetector extends TypedAtomicActor
The inputs are:
The outputs are:
This actor is typically used with a channel that delivers a properties record token that contains power and duration fields. These fields can be extracted by using a GetProperties actor followed by a RecordDisassembler. The PowerLossChannel, for example, can be used. However, in order for the type constraints to be satisfied, the PowerLossChannel's defaultProperties parameter must be augmented with a default value for the duration. Each transmitter can override that default with its own message duration and transmit power.
Any message whose power (as specified at the power input) is less than the value of the powerThreshold parameter is ignored. It will not cause collisions and is not produced at the collided output. The powerThreshold parameter thus specifies the power level at which the receiver simply fails to detect the signal. It is given in a linear scale (vs. DB) with the same units as the power input. The default value is zero, i.e. by default it won't ignore any received signal.
Any message whose power exceeds powerThreshold has the potential of being successfully received, of failing to be received due to a collision, and of causing a collision. A message is successfully received if throughout its duration, its power exceeds the sum of all other message powers by at least SNRThresholdInDB (which as the name suggests, is given in decibels, rather than in a linear scale, as is customary for power ratios). Formally, let the message power for the i-th message be pi(t) at time t. Before the message is received and after its duration expires, this power is zero. The i-th message is successfully received if
pi(t) ≥ P Σ(j != i) pj(t)for all t where pi(t) > 0, where
P = 10^(SNRThresholdInDB/10)which is the signal to interference ratio in a linear scale.
The way this actor works is that each input that has sufficient power is recorded in a hash table indexed by the time at which its duration expires. In addition, the director is requested to fire this actor at that time. Any time a message arrives, the actor checks for collisions, and marks any message subjected to a collision by this arrival. When the duration expires, the message is produced on one of the two outputs depending on whether it is marked as having encountered a collision, and it is removed from the hash table.
NOTE: This actor assumes that the duration of messages is short relative to the rate at which the actors move. That is, the received power (and whether a receiver is in range) is determined once, at the time the message starts, and remains constant throughout the transmission. It also requires that all three inputs have tokens when fired.
PowerLossChannel,
GetProperties,
RecordDisassemblerEntity.ContainedObjectsIterator| Modifier and Type | Field and Description |
|---|---|
TypedIOPort |
collided
The output port that produces messages that cannot be
received because of a collision.
|
TypedIOPort |
duration
The input port for the time that a message transmission takes.
|
TypedIOPort |
message
The input port for the message.
|
TypedIOPort |
power
The input port for power.
|
Parameter |
powerThreshold
The power threshold above which the signal can be
detected at the receiver.
|
TypedIOPort |
received
The output port that produces messages that are successfully
received.
|
Parameter |
SNRThresholdInDB
The threshold for the signal to be recognized from interference.
|
_typesValid_actorFiringListeners, _initializables, _notifyingActorFiring, _stopRequested_changeListeners, _changeLock, _changeRequests, _debugging, _debugListeners, _deferChangeRequests, _elementName, _isPersistent, _verbose, _workspace, ATTRIBUTES, CLASSNAME, COMPLETE, CONTENTS, DEEP, FULLNAME, LINKSCOMPLETED, NOT_READY, STOP_ITERATING| Constructor and Description |
|---|
CollisionDetector(CompositeEntity container,
java.lang.String name)
Construct an actor with the specified name and container.
|
| Modifier and Type | Method and Description |
|---|---|
void |
attributeChanged(Attribute attribute)
If the specified attribute is SNRThresholdInDB,
or powerThreshold then
check that a non-negative number is given.
|
java.lang.Object |
clone(Workspace workspace)
Clone the object into the specified workspace.
|
void |
fire()
If a new message is available at the inputs, record it in the
list indexed with the time that the message shall be completed,
and loop through the list to check whether there is collision.
|
void |
initialize()
Initialize the private variables.
|
_containedTypeConstraints, _customTypeConstraints, _defaultTypeConstraints, _fireAt, _fireAt, attributeTypeChanged, clone, isBackwardTypeInferenceEnabled, newPort, typeConstraintList, typeConstraints_actorFiring, _actorFiring, _declareDelayDependency, addActorFiringListener, addInitializable, connectionsChanged, createReceivers, declareDelayDependency, getCausalityInterface, getDirector, getExecutiveDirector, getManager, inputPortList, isFireFunctional, isStrict, iterate, newReceiver, outputPortList, postfire, prefire, preinitialize, pruneDependencies, recordFiring, removeActorFiringListener, removeDependency, removeInitializable, setContainer, stop, stopFire, terminate, wrapup_adjustDeferrals, _checkContainer, _getContainedObject, _propagateExistence, getContainer, instantiate, isAtomic, isOpaque, moveDown, moveToFirst, moveToIndex, moveToLast, moveUp, propagateExistence, setName_addPort, _description, _exportMoMLContents, _removePort, _validateSettables, connectedPortList, connectedPorts, containedObjectsIterator, getAttribute, getPort, getPorts, linkedRelationList, linkedRelations, portList, removeAllPorts, setClassDefinition, uniqueName_setParent, exportMoML, getChildren, getElementName, getParent, getPrototypeList, isClassDefinition, isWithinClassDefinition_addAttribute, _adjustOverride, _attachText, _cloneFixAttributeFields, _containedDecorators, _copyChangeRequestList, _debug, _debug, _debug, _debug, _debug, _executeChangeRequests, _getIndentPrefix, _isMoMLSuppressed, _markContentsDerived, _notifyHierarchyListenersAfterChange, _notifyHierarchyListenersBeforeChange, _propagateValue, _removeAttribute, _splitName, _stripNumericSuffix, addChangeListener, addDebugListener, addHierarchyListener, attributeDeleted, attributeList, attributeList, decorators, 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, notifyOfNameChange, propagateValue, propagateValues, removeAttribute, removeChangeListener, removeDebugListener, removeHierarchyListener, requestChange, setClassName, setDeferringChangeRequests, setDerivedLevel, setDisplayName, setModelErrorHandler, setPersistent, setSource, sortContainedObjects, toplevel, toString, validateSettables, workspaceequals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, waitcreateReceivers, getCausalityInterface, getDirector, getExecutiveDirector, getManager, inputPortList, newReceiver, outputPortListisFireFunctional, isStrict, iterate, postfire, prefire, stop, stopFire, terminateaddInitializable, preinitialize, removeInitializable, wrapupdescription, getContainer, getDisplayName, getFullName, getName, getName, setNamegetDerivedLevel, getDerivedList, propagateValuepublic TypedIOPort message
public TypedIOPort power
public TypedIOPort duration
public TypedIOPort received
public TypedIOPort collided
public Parameter SNRThresholdInDB
public Parameter powerThreshold
public CollisionDetector(CompositeEntity container, java.lang.String name) throws IllegalActionException, NameDuplicationException
container - The container.name - The name of the actor.IllegalActionException - If the container is incompatible
with this actor.NameDuplicationException - If the name coincides with
an actor already in the container.public void attributeChanged(Attribute attribute) throws IllegalActionException
attributeChanged in class NamedObjattribute - The attribute that changed.IllegalActionException - If the change is not acceptable
to this container.public java.lang.Object clone(Workspace workspace) throws java.lang.CloneNotSupportedException
clone in class TypedAtomicActorworkspace - The workspace for the cloned object.java.lang.CloneNotSupportedException - Not thrown in this base classNamedObj.exportMoML(Writer, int, String),
NamedObj.setDeferringChangeRequests(boolean)public void fire()
throws IllegalActionException
fire in interface Executablefire in class AtomicActor<TypedIOPort>IllegalActionException - If an error occurs reading
or writing inputs or outputs.public void initialize()
throws IllegalActionException
initialize in interface Initializableinitialize in class AtomicActor<TypedIOPort>IllegalActionException - If thrown by the base class.