Make sure that when multiple broadcast packets are queued on the same device in a short succession, that: 1) no backoff occurs if the frame arrives and the idle time >= DIFS or AIFSn (this is 'DCF immediate access', Figure 9-3 of IEEE 802.11-2012) 2) a backoff occurs for the second frame that arrives (this is clearly stated in Sec. More...

Inheritance diagram for DcfImmediateAccessBroadcastTestCase:

Collaboration diagram for DcfImmediateAccessBroadcastTestCase:

Public Member Functions
	DcfImmediateAccessBroadcastTestCase ()

void	DoRun () override
	Implementation to actually run this TestCase.

Public Member Functions inherited from ns3::TestCase
	TestCase (const TestCase &)=delete

virtual	~TestCase ()
	Destructor.

std::string	GetName () const

TestCase &	operator= (const TestCase &)=delete

Private Member Functions
void	NotifyPhyTxBegin (Ptr< const Packet > p, double txPowerW)
	Notify Phy transmit begin.

void	SendOnePacket (Ptr< WifiNetDevice > dev)
	Send one packet function.

Private Attributes
Time	m_firstTransmissionTime
	first transmission time

ObjectFactory	m_mac
	MAC.

ObjectFactory	m_manager
	manager

unsigned int	m_numSentPackets
	number of sent packets

ObjectFactory	m_propDelay
	propagation delay

Time	m_secondTransmissionTime
	second transmission time

Additional Inherited Members
Public Types inherited from ns3::TestCase
enum class	Duration { QUICK = 1 , EXTENSIVE = 2 , TAKES_FOREVER = 3 }
	How long the test takes to execute. More...

using	instead = Duration

Static Public Attributes inherited from ns3::TestCase
static constexpr auto	EXTENSIVE = Duration::EXTENSIVE

static constexpr auto	QUICK = Duration::QUICK

static constexpr auto	TAKES_FOREVER

Protected Member Functions inherited from ns3::TestCase
	TestCase (std::string name)
	Constructor.

void	AddTestCase (TestCase *testCase, Duration duration=Duration::QUICK)
	Add an individual child TestCase to this test suite.

TestCase *	GetParent () const
	Get the parent of this TestCase.

bool	IsStatusFailure () const
	Check if any tests failed.

bool	IsStatusSuccess () const
	Check if all tests passed.

void	SetDataDir (std::string directory)
	Set the data directory where reference trace files can be found.

void	ReportTestFailure (std::string cond, std::string actual, std::string limit, std::string message, std::string file, int32_t line)
	Log the failure of this TestCase.

bool	MustAssertOnFailure () const
	Check if this run should assert on failure.

bool	MustContinueOnFailure () const
	Check if this run should continue on failure.

std::string	CreateDataDirFilename (std::string filename)
	Construct the full path to a file in the data directory.

std::string	CreateTempDirFilename (std::string filename)
	Construct the full path to a file in a temporary directory.

Detailed Description

Make sure that when multiple broadcast packets are queued on the same device in a short succession, that: 1) no backoff occurs if the frame arrives and the idle time >= DIFS or AIFSn (this is 'DCF immediate access', Figure 9-3 of IEEE 802.11-2012) 2) a backoff occurs for the second frame that arrives (this is clearly stated in Sec.

9.3.4.2 of IEEE 802.11-2012, (basic access, which applies to group-addressed frames) where it states "If, under these conditions, the medium is determined by the CS mechanism to be busy when a STA desires to initiate the initial frame of a frame exchange sequence (described in Annex G), exclusive of the CF period, the random backoff procedure described in 9.3.4.3 shall be followed." and from 9.3.4.3 "The result of this procedure is that transmitted frames from a STA are always separated by at least one backoff interval."

The observed behavior is that the first frame will be sent immediately, and the frames are spaced by (backoff + DIFS) time intervals (where backoff is a random number of slot sizes up to maximum CW)

The following test case should not generate virtual collision for the second frame. The seed and run numbers were pick such that the second frame gets backoff = 1 slot.

                 frame 1, frame 2
                 arrive                DIFS = 2 x slot + SIFS
                 |                          = 2 x 9us + 16us for 11a
                 |                    <----------->
                 V                                 <-backoff->

time |-----------—|----------------—|----------—|--------—> 0 1s 1.001408s 1.001442s |1.001451s ^ ^ ^ start TX finish TX start TX frame 1 frame 1 frame 2 ^ frame 2 backoff = 1 slot

The buggy behavior observed in prior versions was shown by picking RngSeedManager::SetRun (17); which generated a 0 slot backoff for frame 2. Then, frame 2 experiences a virtual collision and re-selects the backoff again. As a result, the actual backoff experience by frame 2 is less likely to be 0 since that would require two successions of 0 backoff (one that generates the virtual collision and one after the virtual collision).

See Bug 555 for past behavior.

Definition at line 475 of file wifi-test.cc.

Constructor & Destructor Documentation

◆ DcfImmediateAccessBroadcastTestCase()

DcfImmediateAccessBroadcastTestCase::DcfImmediateAccessBroadcastTestCase ( )

Definition at line 505 of file wifi-test.cc.

Member Function Documentation

◆ DoRun()

void DcfImmediateAccessBroadcastTestCase::DoRun ( )

overridevirtual

Implementation to actually run this TestCase.

Subclasses should override this method to conduct their tests.

Implements ns3::TestCase.

Definition at line 532 of file wifi-test.cc.

References ns3::Mac48Address::Allocate(), AssignWifiRandomStreams(), ns3::ObjectFactory::Create(), ns3::Simulator::Destroy(), m_firstTransmissionTime, m_mac, m_manager, m_numSentPackets, m_propDelay, m_secondTransmissionTime, ns3::MakeCallback(), ns3::MicroSeconds(), NotifyPhyTxBegin(), NS_TEST_ASSERT_MSG_EQ, ns3::Simulator::Run(), ns3::Simulator::Schedule(), ns3::Seconds(), SendOnePacket(), ns3::WifiMac::SetDevice(), ns3::RngSeedManager::SetRun(), ns3::RngSeedManager::SetSeed(), ns3::ObjectFactory::SetTypeId(), ns3::Simulator::Stop(), and ns3::WIFI_STANDARD_80211a.

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◆ NotifyPhyTxBegin()

void DcfImmediateAccessBroadcastTestCase::NotifyPhyTxBegin	(	Ptr< const Packet >	p,
		double	txPowerW
	)

private

Notify Phy transmit begin.

Parameters

p	the packet
txPowerW	the tx power

Definition at line 511 of file wifi-test.cc.

References m_firstTransmissionTime, m_numSentPackets, m_secondTransmissionTime, and ns3::Simulator::Now().

Referenced by DoRun().

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◆ SendOnePacket()

void DcfImmediateAccessBroadcastTestCase::SendOnePacket ( Ptr< WifiNetDevice > dev )

private

Send one packet function.

Parameters

dev	the device

Definition at line 525 of file wifi-test.cc.

Referenced by DoRun().

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Member Data Documentation

◆ m_firstTransmissionTime

Time DcfImmediateAccessBroadcastTestCase::m_firstTransmissionTime

private

first transmission time

Definition at line 493 of file wifi-test.cc.

Referenced by DoRun(), and NotifyPhyTxBegin().

◆ m_mac

ObjectFactory DcfImmediateAccessBroadcastTestCase::m_mac

private

MAC.

Definition at line 490 of file wifi-test.cc.

Referenced by DoRun().

◆ m_manager

ObjectFactory DcfImmediateAccessBroadcastTestCase::m_manager

private

manager

Definition at line 489 of file wifi-test.cc.

Referenced by DoRun().

◆ m_numSentPackets

unsigned int DcfImmediateAccessBroadcastTestCase::m_numSentPackets

private

number of sent packets

Definition at line 495 of file wifi-test.cc.

Referenced by DoRun(), and NotifyPhyTxBegin().

◆ m_propDelay

ObjectFactory DcfImmediateAccessBroadcastTestCase::m_propDelay

private

propagation delay

Definition at line 491 of file wifi-test.cc.

Referenced by DoRun().

◆ m_secondTransmissionTime

Time DcfImmediateAccessBroadcastTestCase::m_secondTransmissionTime

private

second transmission time

Definition at line 494 of file wifi-test.cc.

Referenced by DoRun(), and NotifyPhyTxBegin().

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

src/wifi/test/wifi-test.cc

Public Member Functions

Private Member Functions

Private Attributes

Additional Inherited Members

Detailed Description

Constructor & Destructor Documentation

◆ DcfImmediateAccessBroadcastTestCase()

Member Function Documentation

◆ DoRun()

◆ NotifyPhyTxBegin()

◆ SendOnePacket()

Member Data Documentation

◆ m_firstTransmissionTime

◆ m_mac

◆ m_manager

◆ m_numSentPackets

◆ m_propDelay

◆ m_secondTransmissionTime