Mac80211 Class Reference

#include <Mac80211.h>

Inheritance diagram for Mac80211:

List of all members.

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Detailed Description

An implementation of the 802.11b MAC.

For more info, see the NED file.

Author:

David Raguin

Public Member Functions
	Mac80211 ()
virtual	~Mac80211 ()
Protected Member Functions
virtual int	numInitStages () const
	Initialization of the module and some variables.
virtual void	initialize (int)
	Initialization of the module and some variables.
void	registerInterface ()
	Register the interface in InterfaceTable.
virtual void	receiveChangeNotification (int category, cPolymorphic *details)
	Called by the NotificationBoard whenever a change occurs we're interested in.
virtual void	handleSelfMsg (cMessage *)
	Handle self messages such as timer...
virtual void	handleUpperMsg (cMessage *)
	Handle messages from upper layer.
virtual void	handleLowerMsg (cMessage *)
	Handle messages from lower layer.
virtual void	handleEndContentionTimer ()
	handle end of contention
void	handleMsgNotForMe (Mac80211Pkt *)
	handle a message that is not for me or errornous
void	handleMsgForMe (Mac80211Pkt *)
	handle a message that was meant for me
void	handleBroadcastMsg (Mac80211Pkt *)
void	handleEndTransmissionTimer ()
	handle the end of a transmission...
void	handleEndSifsTimer ()
	handle end of SIFS
void	handleTimeoutTimer ()
	handle time out
void	handleNavTimer ()
	NAV timer expired, the exchange of messages of other stations is done.
void	handleRTSframe (Mac80211Pkt *)
void	handleDATAframe (Mac80211Pkt *)
void	handleACKframe (Mac80211Pkt *)
void	handleCTSframe (Mac80211Pkt *)
virtual void	sendDATAframe ()
	send data frame
void	sendACKframe (Mac80211Pkt *)
	send Acknoledgement
void	sendCTSframe (Mac80211Pkt *)
	send CTS frame
virtual void	sendRTSframe ()
	send RTS frame
void	sendBROADCASTframe ()
	send broadcast frame
Mac80211Pkt *	encapsMsg (cMessage *netw)
	encapsulate packet
void	decapsulateAndSendUp (Mac80211Pkt *frame)
	decapsulate packet and send to higher layer
virtual Mac80211Pkt *	buildDATAframe ()
	build a data frame
Mac80211Pkt *	buildACKframe (Mac80211Pkt *)
	build an ACK
Mac80211Pkt *	buildCTSframe (Mac80211Pkt *)
	build a CTS frame
virtual Mac80211Pkt *	buildRTSframe ()
	build an RTS frame
Mac80211Pkt *	buildBROADCASTframe ()
	build a broadcast frame
virtual void	beginNewCycle ()
	start a new contention period
double	backoff ()
	Compute a backoff value.
int	contentionWindow ()
	Compute a new contention window.
void	testMaxAttempts ()
	Test if maximum number of retries to transmit is exceeded.
double	timeOut (_802_11frameType type, double last_frame_duration)
	return a timeOut value for a certain type of frame
double	packetDuration (int bits)
	computes the duration of a transmission over the physical channel
const char *	stateName (State state)
	Produce a readable name of the given state.
void	setState (State state)
	Sets the state, and produces a log message in between.
Protected Attributes
MACAddress	myMacAddr
	mac address
cMessage *	timeout
	Timer used for time-outs after the transmission of a RTS, a CTS, or a DATA packet.
cMessage *	nav
	Timer used for the defer time of a node. Also called NAV : networks allocation vector.
cMessage *	contention
	Timer used for contention periods.
cMessage *	endTransmission
	Timer used to indicate the end of the transmission of an ACK or a BROADCAST packet.
cMessage *	endSifs
	Timer used to indicate the end of a SIFS.
double	EIFS
	extended interframe space
double	BW
	Variable to store the current backoff value.
State	state
	Current state of the MAC.
RadioState::States	radioState
	Current state of the radio (kept updated by receiveChangeNotification()).
int	maxQueueSize
	Maximal number of packets in the queue; should be set in the omnetpp.ini.
bool	nextIsBroadcast
	Boolean used to know if the next packet is a broadcast packet.
MacPktList	fromUpperLayer
	Buffering of messages from upper layer.
int	retryCounter
	Number of frame transmission attempt.
bool	tryWithoutBackoff
	If there's a new packet to send and the channel is free, no backoff is needed.
bool	rtsCts
	true if Rts/Cts is used, false if not; can be set in omnetpp.ini
double	delta
	Very small value used in timer scheduling in order to avoid multiple changements of state in the same simulation time.
double	bitrate
	The bitrate should be set in omnetpp.ini; be sure to use a valid 802.11 bitrate.
int	broadcastBackoff
	Should be set in the omnetpp.ini.
Private Types
typedef std::list< Mac80211Pkt * >	MacPktList
enum	timerType {   TIMEOUT, NAV, CONTENTION, END_TRANSMISSION,   END_SIFS }
enum	State {   WFDATA = 0, QUIET = 1, IDLE = 2, CONTEND = 3,   WFCTS = 4, WFACK = 5, BUSY = 6 }

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Member Typedef Documentation

typedef std::list<Mac80211Pkt*> Mac80211::MacPktList [private]

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Member Enumeration Documentation

enum Mac80211::State [private]

Definition of the states Enumeration values: WFDATA  QUIET  IDLE  CONTEND  WFCTS  WFACK  BUSY  { WFDATA = 0, // waiting for data packet QUIET = 1, // waiting for the communication between two other nodes to end IDLE = 2, // no packet to send, no packet receiving CONTEND = 3,// contention state (battle for the channel) WFCTS = 4, // RTS sent, waiting for CTS WFACK = 5, // DATA packet sent, waiting for ACK BUSY = 6 // during transmission of an ACK or a BROADCAST packet };

enum Mac80211::timerType [private]

Definition of the timer types Enumeration values: TIMEOUT  NAV  CONTENTION  END_TRANSMISSION  END_SIFS  { TIMEOUT, NAV, CONTENTION, END_TRANSMISSION, END_SIFS };

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Constructor & Destructor Documentation

Mac80211::Mac80211 (   )

{ timeout = nav = contention = endTransmission = endSifs = NULL; }

Mac80211::~Mac80211 (   )  [virtual]

{ cancelAndDelete(timeout); cancelAndDelete(nav); cancelAndDelete(contention); cancelAndDelete(endTransmission); cancelAndDelete(endSifs); }

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Member Function Documentation

double Mac80211::backoff (   )  [protected]

Compute a backoff value. Compute the backoff value. { // the MAC has won the previous contention. We have to compute a new // backoff window if (BW == 0) BW = ((double) intrand(contentionWindow() + 1)) * ST; // CW is the contention window (see the function). ST is the // slot time. else we take the old value of BW, in order to give a // bigger priority to a node which has lost a previous contention // period. EV << "backing off for: " << BW + DIFS << endl; return BW; }

void Mac80211::beginNewCycle (   )  [protected, virtual]

start a new contention period Start a new contention period if the channel is free and if there's a packet to send. Called at the end of a deferring period, a busy period, or after a failure. Called by the HandleMsgForMe(), HandleTimer() HandleUpperMsg(), and, without RTS/CTS, by handleMsgNotForMe(). { // before trying to send one more time a packet, test if the // maximum retry limit is reached. If it is the case, then // delete the packet and send the next packet. testMaxAttempts(); if (!fromUpperLayer.empty()) { // look if the next packet is unicast or broadcast nextIsBroadcast = (((Mac80211Pkt *) fromUpperLayer.front())->getDestAddr().isBroadcast()); // print("next is broadcast = "<<nextIsBroadcast); // if the channel is free then wait a random time and transmit if (radioState == RadioState::IDLE) { // if channel is idle AND I was not the last one that transmitted // data: no backoff if (tryWithoutBackoff) { EV << "trying to send without backoff...\n"; scheduleAt(simTime() + DIFS, contention); } else { // backoff! scheduleAt(simTime() + backoff() + DIFS, contention); } } tryWithoutBackoff = false; // else wait until the channel gets free; the state is now contend setState(CONTEND); } else { tryWithoutBackoff = false; setState(IDLE); } }

Mac80211Pkt * Mac80211::buildACKframe (  Mac80211Pkt *  af  )  [protected]

build an ACK Build an ACK frame. Called by sendACKframe() { Mac80211Pkt *frame = new Mac80211Pkt("wlan-ack"); frame->setKind(ACK); frame->setLength(LENGTH_ACK); // the dest address must be the src adress of the RTS or the DATA // packet received. The src adress is the adress of the node frame->setSrcAddr(myMacAddr); frame->setDestAddr(af->getSrcAddr()); frame->setDuration(0); return frame; }

Mac80211Pkt * Mac80211::buildBROADCASTframe (   )  [protected]

build a broadcast frame Build a BROADCAST frame. Called sendBROADCASTframe() { // send a copy of the frame in front of the queue Mac80211Pkt *frame = (Mac80211Pkt *) (fromUpperLayer.front())->dup(); frame->setKind(BROADCAST); return frame; }

Mac80211Pkt * Mac80211::buildCTSframe (  Mac80211Pkt *  af  )  [protected]

build a CTS frame Build a CTS frame. Called by sendCTSframe() { Mac80211Pkt *frame = new Mac80211Pkt("wlan-cts"); frame->setKind(CTS); frame->setLength(LENGTH_CTS); // the dest adress must be the src adress of the RTS received. The // src adress is the adress of the node frame->setSrcAddr(myMacAddr); frame->setDestAddr(af->getSrcAddr()); frame->setDuration(af->getDuration() - SIFS - packetDuration(LENGTH_CTS)); return frame; }

Mac80211Pkt * Mac80211::buildDATAframe (   )  [protected, virtual]

build a data frame Build a DATA frame. Called by sendDATAframe() { // build a copy of the frame in front of the queue Mac80211Pkt *frame = (Mac80211Pkt *) (fromUpperLayer.front())->dup(); frame->setSrcAddr(myMacAddr); frame->setKind(DATA); if (rtsCts) frame->setDuration(SIFS + packetDuration(LENGTH_ACK)); else frame->setDuration(0); return frame; }

Mac80211Pkt * Mac80211::buildRTSframe (   )  [protected, virtual]

build an RTS frame Build a RTS frame. Called by sendRTSframe() { Mac80211Pkt *frame = new Mac80211Pkt("wlan-rts"); frame->setKind(RTS); frame->setLength(LENGTH_RTS); // the src adress and dest address are copied in the frame in the queue (frame to be sent) frame->setSrcAddr(((Mac80211Pkt *) fromUpperLayer.front())->getSrcAddr()); frame->setDestAddr(((Mac80211Pkt *) fromUpperLayer.front())->getDestAddr()); frame->setDuration(3 * SIFS + packetDuration(LENGTH_CTS) + packetDuration(fromUpperLayer.front()->length()) + packetDuration(LENGTH_ACK)); return frame; }

int Mac80211::contentionWindow (   )  [protected]

Compute a new contention window. Compute the contention window with the binary backoff algorithm. Use the variable counter (attempts to transmit packet), the constant values CWmax (contention window maximum) and m (parameter for the initial backoff window, usally m=7). Called by backoff() { // the next packet is an unicast packet if (!nextIsBroadcast) { int cw; cw = (CW_MIN + 1) * (unsigned int) pow(2.0, (int) retryCounter - 1) - 1; // return the calculated value or CWmax if the maximal value is reached if (cw <= CW_MAX) return cw; else return CW_MAX; } // the next packet is broadcast : the contention window must be maximal else return broadcastBackoff; }

void Mac80211::decapsulateAndSendUp (  Mac80211Pkt *  frame  )  [protected]

decapsulate packet and send to higher layer { cMessage *msg = frame->decapsulate(); // FIXME TBD set control info delete frame; sendUp(msg); }

Mac80211Pkt * Mac80211::encapsMsg (  cMessage *  netw  )  [protected]

encapsulate packet Encapsulates the received network-layer packet into a MacPkt and set all needed header fields. { Mac80211Pkt *pkt = new Mac80211Pkt(netw->name()); pkt->setLength(272); // headerLength, including final CRC-field // copy dest address from the control info Ieee802Ctrl *ctrl = check_and_cast<Ieee802Ctrl *>(netw->removeControlInfo()); pkt->setDestAddr(ctrl->getDest()); delete ctrl; // set the src address to own mac address (nic module id()) pkt->setSrcAddr(myMacAddr); // encapsulate the network packet pkt->encapsulate(netw); return pkt; }

void Mac80211::handleACKframe (  Mac80211Pkt *  af  )  [protected]

Handle a frame which is expected to be an ACK.Called by HandleMsgForMe(MAcawFrame* af) { // cancel time-out event cancelEvent(timeout); // the the transmission is acknowledged : initialize long_retry_counter retryCounter = 1; // removes the acknowledged packet from the queue Mac80211Pkt *temp = fromUpperLayer.front(); fromUpperLayer.pop_front(); delete temp; // if thre's a packet to send and if the channel is free then start a new contention period beginNewCycle(); }

void Mac80211::handleBroadcastMsg (  Mac80211Pkt *  af  )  [protected]

Handle a broadcast packet. This packet is simply passed to the upper layer. No acknowledgement is needed. Called by handleLowerMsg(Mac80211Pkt *af) { EV << "handle broadcast\n"; if (state == BUSY) error("logic error: node is currently transmitting, can not receive " "(does the physical layer do its job correctly?)"); decapsulateAndSendUp(af); if (state == CONTEND) beginNewCycle(); }

void Mac80211::handleCTSframe (  Mac80211Pkt *  af  )  [protected]

Handle a CTS frame. Called by HandleMsgForMe(Mac80211Pkt* af) { // cancel time-out event cancelEvent(timeout); // wait a short interframe space endSifs->setContextPointer(af); scheduleAt(simTime() + SIFS, endSifs); }

void Mac80211::handleDATAframe (  Mac80211Pkt *  af  )  [protected]

Handle a frame which expected to be a DATA frame. Called by HandleMsgForMe() { if (rtsCts) cancelEvent(timeout); // cancel time-out event // make a copy Mac80211Pkt *copy = (Mac80211Pkt *) af->dup(); // pass the packet to the upper layer decapsulateAndSendUp(af); // wait a short interframe space endSifs->setContextPointer(copy); scheduleAt(simTime() + SIFS, endSifs); }

void Mac80211::handleEndContentionTimer (   )  [protected, virtual]

handle end of contention The node has won the contention, and is now allowed to send an RTS/DATA or Broadcast packet. The backoff value is deleted and will be newly computed in the next contention period { if (state != CONTEND) error("logic error: expiration of the contention timer outside of CONTEND state, should not happen"); // the node has won the channel, the backoff window is deleted and // will be new calculated in the next contention period BW = 0; // unicast packet if (!nextIsBroadcast) { if (rtsCts) { // send a RTS sendRTSframe(); setState(WFCTS); } else { sendDATAframe(); setState(WFACK); } // broadcast packet } else { sendBROADCASTframe(); // removes the packet from the queue without waiting for an acknowledgement Mac80211Pkt *temp = fromUpperLayer.front(); fromUpperLayer.pop_front(); delete(temp); } }

void Mac80211::handleEndSifsTimer (   )  [protected]

handle end of SIFS Handle the end sifs timer. Then sends a CTS, a DATA, or an ACK frame { Mac80211Pkt *frame = (Mac80211Pkt *) endSifs->contextPointer(); switch (frame->kind()) { case RTS: sendCTSframe(frame); break; case CTS: sendDATAframe(); break; case DATA: sendACKframe(frame); break; default: error("logic error: end sifs timer when previously received packet is not RTS/CTS/DATA"); } // don't need previous frame any more delete frame; }

void Mac80211::handleEndTransmissionTimer (   )  [protected]

handle the end of a transmission... Handle the end of transmission timer (end of the transmission of an ACK or a broadcast packet). Called by HandleTimer(cMessage* msg) { EV << "transmission of ACK/BROADCAST is over\n"; if (state != BUSY) error("logic error: expiration of the end transmission timer outside the BUSY state, should not happen"); // if there's a packet to send and if the channel is free, then start a new contention period beginNewCycle(); }

void Mac80211::handleLowerMsg (  cMessage *  msg  )  [protected, virtual]

Handle messages from lower layer. Handle all messages from lower layer. Checks the destination MAC adress of the packet. Then calls one of the three functions : handleMsgNotForMe(), handleBroadcastMsg(), or handleMsgForMe(). Called by handleMessage(). Implements WirelessMacBase. { Mac80211Pkt *af = check_and_cast<Mac80211Pkt *>(msg); // end of the reception EV << "frame " << af << " received\n"; switch (af->kind()) { case COLLISION: // packet lost or bit error delete af; if (state == CONTEND) beginNewCycle(); break; case BITERROR: handleMsgNotForMe(af); break; case BROADCAST: // broadcast packet handleBroadcastMsg(af); break; default: // other packet if (af->getDestAddr() == myMacAddr) // FIXME verify broadcast dest addr works! handleMsgForMe(af); else handleMsgNotForMe(af); } }

void Mac80211::handleMsgForMe (  Mac80211Pkt *  af  )  [protected]

handle a message that was meant for me Handle a packet for the node. The result of this reception is a function of the type of the received message (RTS,CTS,DATA, or ACK), and of the current state of the MAC (WFDATA, CONTEND, IDLE, WFCTS, or WFACK). Called by handleLowerMsg() { EV << "handle msg for me\n"; switch (state) { case IDLE: // waiting for the end of the contention period case CONTEND: // or waiting for RTS // RTS or DATA accepted if (af->kind() == RTS) handleRTSframe(af); else if (af->kind() == DATA) handleDATAframe(af); else EV << "in handleMsgForMe() IDLE/CONTEND, strange message, darf das?\n"; break; case WFDATA: // waiting for DATA if (af->kind() == DATA) handleDATAframe(af); else EV << "in handleMsgForMe() WFDATA, strange message, darf das?\n"; break; case WFACK: // waiting for ACK if (af->kind() == ACK) handleACKframe(af); else EV << "in handleMsgForMe() WFACK, strange message, darf das?\n"; delete af; break; case WFCTS: // The MAC is waiting for CTS if (af->kind() == CTS) handleCTSframe(af); else EV << "in handleMsgForMe() WFCTS, strange message, darf das?\n"; break; case QUIET: // the node is currently deferring. // cannot handle any packet with its MAC adress delete af; break; case BUSY: // currently transmitting an ACK or a BROADCAST packet error("logic error: node is currently transmitting, can not receive " "(does the physical layer do its job correctly?)"); break; default: error("unknown state %d", state); } }

void Mac80211::handleMsgNotForMe (  Mac80211Pkt *  af  )  [protected]

handle a message that is not for me or errornous Handle all ACKs,RTS, CTS, or DATA not for the node. If RTS/CTS is used the node must stay quiet until the current handshake between the two communicating nodes is over. This is done by scheduling the timer message nav (Network Allocation Vector). Without RTS/CTS a new contention is started. If an error occured the node must defer for EIFS. Called by handleLowerMsg() { EV << "handle msg not for me\n"; // if this packet can not be correctly read if (af->kind() == BITERROR) af->setDuration(EIFS); // if the duration of the packet is null, then do nothing (to avoid // the unuseful scheduling of a self message) if (af->getDuration() != 0) { // the node is already deferring if (state == QUIET) { // the current value of the NAV is not sufficient if (nav->arrivalTime() < simTime() + af->getDuration()) { cancelEvent(nav); scheduleAt(simTime() + af->getDuration(), nav); EV << "NAV timer started for: " << af->getDuration() << " State QUIET\n"; } } // other states else { // if the MAC wait for another frame, it can delete its time out // (exchange is aborted) if (timeout->isScheduled()) cancelEvent(timeout); // is state == WFCTS or WFACK, the data transfer has failed ... // the node must defer for the time of the transmission scheduleAt(simTime() + af->getDuration(), nav); EV << "NAV timer started, not QUIET: " << af->getDuration() << endl; setState(QUIET); } } if (!rtsCts) { // todo: Nachgucken: was passiert bei Error ohne rtsCts! if (state == CONTEND) { if (af->kind() == BITERROR) { if (contention->isScheduled()) cancelEvent(contention); scheduleAt(simTime() + backoff() + EIFS, contention); } else beginNewCycle(); } } delete af; }

void Mac80211::handleNavTimer (   )  [protected]

NAV timer expired, the exchange of messages of other stations is done. Handle the NAV timer (end of a defering period). Called by HandleTimer(cMessage* msg) { if (state != QUIET) error("logic error: expiration of the NAV timer outside of the state QUIET, should not happen"); // if there's a packet to send and if the channel is free, then start a new contention period beginNewCycle(); }

void Mac80211::handleRTSframe (  Mac80211Pkt *  af  )  [protected]

Handle aframe wich is expected to be an RTS. Called by HandleMsgForMe() { // wait a short interframe space endSifs->setContextPointer(af); scheduleAt(simTime() + SIFS, endSifs); }

void Mac80211::handleSelfMsg (  cMessage *  msg  )  [protected, virtual]

Handle self messages such as timer... handle timers Implements WirelessMacBase. { switch (msg->kind()) { case END_SIFS: handleEndSifsTimer(); // noch zu betrachten break; case END_TRANSMISSION: handleEndTransmissionTimer(); // noch zu betrachten break; case CONTENTION: handleEndContentionTimer(); break; // the MAC was waiting for a CTS, a DATA, or an ACK packet but the timer has expired. case TIMEOUT: handleTimeoutTimer(); // noch zu betrachten.. break; // the MAC was waiting because an other communication had won the channel. This communication is now over case NAV: handleNavTimer(); // noch zu betrachten... break; default: error("unknown timer type"); } }

void Mac80211::handleTimeoutTimer (   )  [protected]

handle time out Handle the time out timer. Called by handleTimer(cMessage* msg) { // if (state == WFCTS || state == WFACK)testMaxAttempts(); // if there's a packet to send and if the channel is free then // start a new contention period if (state != QUIET) beginNewCycle(); }

void Mac80211::handleUpperMsg (  cMessage *  msg  )  [protected, virtual]

Handle messages from upper layer. This implementation does not support fragmentation, so it is tested if the maximum length of the MPDU is exceeded. Implements WirelessMacBase. { if (msg->byteLength() > 2312) error("packet from higher layer (%s)%s is too long for 802.11b, %d bytes (fragmentation is not supported yet)", msg->className(), msg->name(), msg->byteLength()); if (maxQueueSize && fromUpperLayer.size() == maxQueueSize) { EV << "packet " << msg << " received from higher layer but MAC queue is full, deleting\n"; delete msg; return; } Mac80211Pkt *mac = encapsMsg(msg); EV << "packet " << msg << " received from higher layer, dest=" << mac->getDestAddr() << ", encapsulated\n"; fromUpperLayer.push_back(mac); // If the MAC is in the IDLE state, then start a new contention period if (state == IDLE && !endSifs->isScheduled()) { tryWithoutBackoff = true; beginNewCycle(); } else { EV << "enqueued, will be transmitted later\n"; } }

void Mac80211::initialize (  int   )  [protected, virtual]

Initialization of the module and some variables. Reimplemented from WirelessMacBase. { WirelessMacBase::initialize(stage); if (stage == 0) { EV << "Initializing stage 0\n"; maxQueueSize = par("maxQueueSize"); // subscribe for the information of the carrier sense nb->subscribe(this, NF_RADIOSTATE_CHANGED); // timers timeout = new cMessage("timeout", TIMEOUT); nav = new cMessage("NAV", NAV); contention = new cMessage("contention", CONTENTION); endTransmission = new cMessage("transmission", END_TRANSMISSION); endSifs = new cMessage("end SIFS", END_SIFS); BW = 0; state = IDLE; retryCounter = 1; broadcastBackoff = par("broadcastBackoff"); rtsCts = par("rtsCts"); bitrate = par("bitrate"); delta = 1E-9; radioState = RadioState::IDLE; // until 1st receiveChangeNotification() EIFS = SIFS + DIFS + packetDuration(LENGTH_ACK); EV << "SIFS: " << SIFS << " DIFS: " << DIFS << " EIFS: " << EIFS << endl; // get registered in InterfaceTable registerInterface(); } }

virtual int Mac80211::numInitStages (   )  const [inline, protected, virtual]

Initialization of the module and some variables. {return 2;}

double Mac80211::packetDuration (  int  bits  )  [protected]

computes the duration of a transmission over the physical channel Computes the duration of the transmission of a frame over the physical channel. 'bits' should be the total length of the MAC packet in bits. { return bits / bitrate + PHY_HEADER_LENGTH / BITRATE_HEADER; }

void Mac80211::receiveChangeNotification (  int  category, cPolymorphic *  details )  [protected, virtual]

Called by the NotificationBoard whenever a change occurs we're interested in. Handle change nofitications. In this layer it is usually information about the radio channel, i.e. if it is IDLE etc. Implements INotifiable. { Enter_Method("receiveChangeNotification(%s, %s)", notificationCategoryName(category), details?details->info().c_str() : "n/a"); if (category == NF_RADIOSTATE_CHANGED) { // update the local copy of the radio state radioState = check_and_cast<RadioState *>(details)->getState(); // NOTE: we may be invoked during INIT STAGE 1 too, when SnrEval notifies us // about the initial radio state. This function has to work correctly // even when called during initialization phase! EV << "** Radio state update in " << className() << ": " << details->info() << " (at T=" << simtimeToStr(simTime()) << ")\n"; // beginning of a reception if (radioState == RadioState::RECV) { // if there's a contention period if (contention->isScheduled()) { // update the backoff window in order to give higher priority in // the next battle if (simTime() - contention->sendingTime() >= DIFS) { BW = contention->arrivalTime() - simTime(); EV << "Backoff window made smaller, new BW: " << BW << endl; } cancelEvent(contention); } // if there's a SIFS period if (endSifs->isScheduled()) { // delete the previously received frame delete (Mac80211Pkt *)endSifs->contextPointer(); // cancel the next transmission cancelEvent(endSifs); // state in now IDLE or CONTEND if (fromUpperLayer.empty()) setState(IDLE); else setState(CONTEND); } } } }

void Mac80211::registerInterface (   )  [protected]

Register the interface in InterfaceTable. { InterfaceEntry *e = new InterfaceEntry(); // interface name: NetworkInterface module's name without special characters ([]) char *interfaceName = new char[strlen(parentModule()->fullName()) + 1]; char *d = interfaceName; for (const char *s = parentModule()->fullName(); *s; s++) if (isalnum(*s)) *d++ = *s; *d = '\0'; e->setName(interfaceName); delete [] interfaceName; const char *addrstr = par("address"); if (!strcmp(addrstr, "auto")) { // assign automatic address myMacAddr = MACAddress::generateAutoAddress(); // change module parameter from "auto" to concrete address par("address").setStringValue(myMacAddr.str().c_str()); } else { myMacAddr.setAddress(addrstr); } e->setMACAddress(myMacAddr); // generate interface identifier for IPv6 e->setInterfaceToken(myMacAddr.formInterfaceIdentifier()); // MTU on 802.11 = ? e->setMtu(1500); // FIXME // capabilities e->setBroadcast(true); e->setMulticast(true); e->setPointToPoint(false); // add InterfaceTable *ift = InterfaceTableAccess().get(); ift->addInterface(e, this); }

void Mac80211::sendACKframe (  Mac80211Pkt *  af  )  [protected]

send Acknoledgement Send an ACK frame.Called by HandleEndSifsTimer() { // the MAC must wait the end of the transmission before beginning an // other contention period scheduleAt(simTime() + packetDuration(LENGTH_ACK) + delta, endTransmission); // send ACK frame sendDown(buildACKframe(af)); EV << "sent ACK frame!\n"; // update state and display setState(BUSY); }

void Mac80211::sendBROADCASTframe (   )  [protected]

send broadcast frame Send a BROADCAST frame.Called by handleContentionTimer() { // the MAC must wait the end of the transmission before beginning any // other contention period scheduleAt(simTime() + packetDuration(fromUpperLayer.front()->length()), endTransmission); // send ACK frame sendDown(buildBROADCASTframe()); // update state and display setState(BUSY); }

void Mac80211::sendCTSframe (  Mac80211Pkt *  af  )  [protected]

send CTS frame Send a CTS frame.Called by HandleEndSifsTimer() { // schedule time-out scheduleAt(simTime() + timeOut(CTS, af->getDuration()), timeout); // send CTS frame sendDown(buildCTSframe(af)); // update state and display setState(WFDATA); }

void Mac80211::sendDATAframe (   )  [protected, virtual]

send data frame Send a DATA frame. Called by HandleEndSifsTimer() or handleEndContentionTimer() { // schedule time out scheduleAt(simTime() + timeOut(DATA, 0), timeout); if (!rtsCts) // retryCounter incremented retryCounter++; // send DATA frame sendDown(buildDATAframe()); // update state and display setState(WFACK); }

void Mac80211::sendRTSframe (   )  [protected, virtual]

send RTS frame Send a RTS frame.Called by handleContentionTimer() { // schedule time-out scheduleAt(simTime() + timeOut(RTS, 0), timeout); // long_retry_counter incremented retryCounter++; // send RTS frame sendDown(buildRTSframe()); // update state and display setState(WFCTS); }

void Mac80211::setState (  State  state  )  [protected]

Sets the state, and produces a log message in between. { if (state==newState) EV << "staying in state " << stateName(state) << "\n"; else EV << "state " << stateName(state) << " --> " << stateName(newState) << "\n"; state = newState; }

const char * Mac80211::stateName (  State  state  )  [protected]

Produce a readable name of the given state. { #define CASE(x) case x: s=#x; break const char *s = "???"; switch (state) { CASE(WFDATA); CASE(QUIET); CASE(IDLE); CASE(CONTEND); CASE(WFCTS); CASE(WFACK); CASE(BUSY); } return s; #undef CASE }

void Mac80211::testMaxAttempts (   )  [protected]

Test if maximum number of retries to transmit is exceeded. Test if the maximal retry limit is reached, and delete the frame to send in this case. { if (retryCounter > RETRY_LIMIT) { // initialize counter retryCounter = 1; // reportLost(fromUpperLayer.front()); // delete the frame to transmit Mac80211Pkt *temp = fromUpperLayer.front(); fromUpperLayer.pop_front(); delete(temp); } }

double Mac80211::timeOut (  _802_11frameType  type, double  last_frame_duration )  [protected]

return a timeOut value for a certain type of frame Return a time-out value for a type of frame. Called by SendRTSframe, sendCTSframe, etc. { double time_out = 0; switch (type) { case RTS: time_out = SIFS + packetDuration(LENGTH_RTS) + packetDuration(LENGTH_CTS) + delta; break; case CTS: time_out = last_frame_duration - packetDuration(LENGTH_ACK) - 2 * SIFS + delta; break; case DATA: time_out = SIFS + packetDuration(fromUpperLayer.front()->length()) + packetDuration(LENGTH_ACK) + delta; break; default: EV << "Unused frame type was given when calling timeOut(), this should not happen!\n"; } return time_out; }

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Member Data Documentation

double Mac80211::bitrate [protected]

The bitrate should be set in omnetpp.ini; be sure to use a valid 802.11 bitrate.

int Mac80211::broadcastBackoff [protected]

Should be set in the omnetpp.ini.

double Mac80211::BW [protected]

Variable to store the current backoff value.

cMessage* Mac80211::contention [protected]

Timer used for contention periods.

double Mac80211::delta [protected]

Very small value used in timer scheduling in order to avoid multiple changements of state in the same simulation time.

double Mac80211::EIFS [protected]

extended interframe space

cMessage* Mac80211::endSifs [protected]

Timer used to indicate the end of a SIFS.

cMessage* Mac80211::endTransmission [protected]

Timer used to indicate the end of the transmission of an ACK or a BROADCAST packet.

MacPktList Mac80211::fromUpperLayer [protected]

Buffering of messages from upper layer.

int Mac80211::maxQueueSize [protected]

Maximal number of packets in the queue; should be set in the omnetpp.ini.

MACAddress Mac80211::myMacAddr [protected]

mac address

cMessage* Mac80211::nav [protected]

Timer used for the defer time of a node. Also called NAV : networks allocation vector.

bool Mac80211::nextIsBroadcast [protected]

Boolean used to know if the next packet is a broadcast packet.

RadioState::States Mac80211::radioState [protected]

Current state of the radio (kept updated by receiveChangeNotification()).

int Mac80211::retryCounter [protected]

Number of frame transmission attempt.

bool Mac80211::rtsCts [protected]

true if Rts/Cts is used, false if not; can be set in omnetpp.ini

State Mac80211::state [protected]

Current state of the MAC.

cMessage* Mac80211::timeout [protected]

Timer used for time-outs after the transmission of a RTS, a CTS, or a DATA packet.

bool Mac80211::tryWithoutBackoff [protected]

If there's a new packet to send and the channel is free, no backoff is needed.

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The documentation for this class was generated from the following files:

• Mac80211.h
• Mac80211.cc

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