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A Discrete-Event Network Simulator
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API |
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A Discrete-Event Network Simulator
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API |
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:Public Member Functions | |
| DcfImmediateAccessBroadcastTestCase () | |
| virtual void | DoRun (void) |
| Implementation to actually run this TestCase. More... | |
| Public Member Functions inherited from ns3::TestCase | |
| virtual | ~TestCase () |
| Destructor. More... | |
| std::string | GetName (void) const |
Private Member Functions | |
| void | NotifyPhyTxBegin (Ptr< const Packet > p) |
| Notify Phy transmit begin. More... | |
| void | SendOnePacket (Ptr< WifiNetDevice > dev) |
| Send one packet function. More... | |
Private Attributes | |
| Time | m_firstTransmissionTime |
| first transmission time More... | |
| ObjectFactory | m_mac |
| MAC. More... | |
| ObjectFactory | m_manager |
| manager More... | |
| unsigned int | m_numSentPackets |
| number of sent packets More... | |
| ObjectFactory | m_propDelay |
| propagation delay More... | |
| Time | m_secondTransmissionTime |
| second transmission time More... | |
Additional Inherited Members | |
| Public Types inherited from ns3::TestCase | |
| enum | TestDuration { QUICK = 1, EXTENSIVE = 2, TAKES_FOREVER = 3 } |
| How long the test takes to execute. More... | |
| Protected Member Functions inherited from ns3::TestCase | |
| TestCase (std::string name) | |
| Constructor. More... | |
| void | AddTestCase (TestCase *testCase, TestDuration duration=QUICK) |
| Add an individual child TestCase to this test suite. More... | |
| TestCase * | GetParent () const |
| Get the parent of this TestCsse. More... | |
| bool | IsStatusFailure (void) const |
| Check if any tests failed. More... | |
| bool | IsStatusSuccess (void) const |
| Check if all tests passed. More... | |
| void | SetDataDir (std::string directory) |
| Set the data directory where reference trace files can be found. More... | |
| 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. More... | |
| bool | MustAssertOnFailure (void) const |
| Check if this run should assert on failure. More... | |
| bool | MustContinueOnFailure (void) const |
| Check if this run should continue on failure. More... | |
| std::string | CreateDataDirFilename (std::string filename) |
| Construct the full path to a file in the data directory. More... | |
| std::string | CreateTempDirFilename (std::string filename) |
| Construct the full path to a file in a temporary directory. More... | |
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 417 of file wifi-test.cc.
| DcfImmediateAccessBroadcastTestCase::DcfImmediateAccessBroadcastTestCase | ( | ) |
Definition at line 447 of file wifi-test.cc.
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virtual |
Implementation to actually run this TestCase.
Subclasses should override this method to conduct their tests.
Implements ns3::TestCase.
Definition at line 475 of file wifi-test.cc.
References ns3::Node::AddDevice(), ns3::Object::AggregateObject(), AssignWifiRandomStreams(), third::channel, ns3::WifiMac::ConfigureStandard(), ns3::ObjectFactory::Create(), m_firstTransmissionTime, m_mac, m_manager, m_numSentPackets, m_propDelay, m_secondTransmissionTime, ns3::MakeCallback(), ns3::MicroSeconds(), ns3::MilliSeconds(), NotifyPhyTxBegin(), NS_TEST_ASSERT_MSG_EQ, ns3::Seconds(), SendOnePacket(), ns3::MobilityModel::SetPosition(), ns3::ObjectFactory::SetTypeId(), and ns3::WIFI_PHY_STANDARD_80211a.
Notify Phy transmit begin.
| p | the packet |
Definition at line 453 of file wifi-test.cc.
References m_firstTransmissionTime, m_numSentPackets, m_secondTransmissionTime, ns3::Now(), NS_ASSERT_MSG(), and ns3::Seconds().
Referenced by DoRun().
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Send one packet function.
| dev | the device |
Definition at line 468 of file wifi-test.cc.
References ns3::WifiNetDevice::GetBroadcast(), and ns3::WifiNetDevice::Send().
Referenced by DoRun().
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first transmission time
Definition at line 436 of file wifi-test.cc.
Referenced by DoRun(), and NotifyPhyTxBegin().
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number of sent packets
Definition at line 438 of file wifi-test.cc.
Referenced by DoRun(), and NotifyPhyTxBegin().
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second transmission time
Definition at line 437 of file wifi-test.cc.
Referenced by DoRun(), and NotifyPhyTxBegin().
1.8.14