wifi: (fixes #2926) Align SSRC and SLRC mechanism to the standard

RELEASE_NOTES

@@ -43,6 +43,7 @@ Bugs fixed
 - Bug 2920 - wifi: Default MaxSlrc and fragmentation threshold values differ from standard
 - Bug 2924 - documentation about Peek/Dequeue usage
 - Bug 2925 - wifi: MinstrelHt provides strange results at low SNR with A-MPDU enabled
+- Bug 2926 - wifi: SSRC and SLRC mechanism not fully aligned to the standard
 - Bug 2931 - Queue Disc drops the CE marked packets
 
 Known issues

examples/wireless/examples-to-run.py

@@ -47,8 +47,8 @@ cpp_examples = [
     ("he-wifi-network --simulationTime=0.3 --frequency=5 --useRts=1 --minExpectedThroughput=6 --maxExpectedThroughput=639", "True", "True"),
     ("he-wifi-network --simulationTime=0.25 --frequency=2.4 --useRts=0 --minExpectedThroughput=6 --maxExpectedThroughput=238", "True", "True"),
     ("he-wifi-network --simulationTime=0.3 --frequency=2.4 --useRts=1 --minExpectedThroughput=6 --maxExpectedThroughput=224", "True", "True"),
-    ("simple-ht-hidden-stations --simulationTime=1 --enableRts=0 --minExpectedThroughput=16.5 --maxExpectedThroughput=17", "True", "True"),
-    ("simple-ht-hidden-stations --simulationTime=1 --enableRts=1 --minExpectedThroughput=20 --maxExpectedThroughput=20.5", "True", "True"),
+    ("simple-ht-hidden-stations --simulationTime=1 --enableRts=0 --nMpdus=32 --minExpectedThroughput=55 --maxExpectedThroughput=56", "True", "True"),
+    ("simple-ht-hidden-stations --simulationTime=1 --enableRts=1 --nMpdus=32 --minExpectedThroughput=57 --maxExpectedThroughput=58", "True", "True"),
     ("mixed-network --simulationTime=1", "True", "True"),
     ("wifi-aggregation --simulationTime=1 --verifyResults=1", "True", "True"),
     ("80211e-txop --simulationTime=1 --verifyResults=1", "True", "True"),

src/wifi/model/minstrel-ht-wifi-manager.cc

@@ -958,7 +958,7 @@ MinstrelHtWifiManager::DoGetRtsTxVector (WifiRemoteStation *st)
 }
 
 bool
-MinstrelHtWifiManager::DoNeedDataRetransmission (WifiRemoteStation *st, Ptr<const Packet> packet, bool normally)
+MinstrelHtWifiManager::DoNeedRetransmission (WifiRemoteStation *st, Ptr<const Packet> packet, bool normally)
 {
   NS_LOG_FUNCTION (this << st << packet << normally);
 

src/wifi/model/minstrel-ht-wifi-manager.h

@@ -241,7 +241,7 @@ private:
                               uint8_t nSuccessfulMpdus, uint8_t nFailedMpdus,
                               double rxSnr, double dataSnr);
   bool IsLowLatency (void) const;
-  bool DoNeedDataRetransmission (WifiRemoteStation *st, Ptr<const Packet> packet, bool normally);
+  bool DoNeedRetransmission (WifiRemoteStation *st, Ptr<const Packet> packet, bool normally);
 
   /**
    * Check the validity of a combination of number of streams, chWidth and mode.

src/wifi/model/minstrel-wifi-manager.cc

@@ -855,7 +855,7 @@ MinstrelWifiManager::DoGetRtsTxVector (WifiRemoteStation *st)
 }
 
 bool
-MinstrelWifiManager::DoNeedDataRetransmission (WifiRemoteStation *st, Ptr<const Packet> packet, bool normally)
+MinstrelWifiManager::DoNeedRetransmission (WifiRemoteStation *st, Ptr<const Packet> packet, bool normally)
 {
   NS_LOG_FUNCTION (this << st << packet << normally);
   MinstrelWifiRemoteStation *station = (MinstrelWifiRemoteStation *)st;

src/wifi/model/minstrel-wifi-manager.h

@@ -273,7 +273,7 @@ private:
   WifiTxVector DoGetDataTxVector (WifiRemoteStation *station);
   WifiTxVector DoGetRtsTxVector (WifiRemoteStation *station);
 
-  bool DoNeedDataRetransmission (WifiRemoteStation *st,
+  bool DoNeedRetransmission (WifiRemoteStation *st,
                                  Ptr<const Packet> packet, bool normally);
 
   bool IsLowLatency (void) const;

src/wifi/model/txop.cc

@@ -353,14 +353,14 @@ bool
 Txop::NeedRtsRetransmission (Ptr<const Packet> packet, const WifiMacHeader &hdr)
 {
   NS_LOG_FUNCTION (this);
-  return m_stationManager->NeedRtsRetransmission (hdr.GetAddr1 (), &hdr, packet);
+  return m_stationManager->NeedRetransmission (hdr.GetAddr1 (), &hdr, packet);
 }
 
 bool
 Txop::NeedDataRetransmission (Ptr<const Packet> packet, const WifiMacHeader &hdr)
 {
   NS_LOG_FUNCTION (this);
-  return m_stationManager->NeedDataRetransmission (hdr.GetAddr1 (), &hdr, packet);
+  return m_stationManager->NeedRetransmission (hdr.GetAddr1 (), &hdr, packet);
 }
 
 bool

src/wifi/model/wifi-remote-station-manager.cc

@@ -334,13 +334,13 @@ WifiRemoteStationManager::GetTypeId (void)
                    MakeBooleanAccessor (&WifiRemoteStationManager::IsLowLatency),
                    MakeBooleanChecker ())
     .AddAttribute ("MaxSsrc",
-                   "The maximum number of retransmission attempts for an RTS. "
-                   " This value will not have any effect on some rate control algorithms.",
+                   "The maximum number of retransmission attempts for any packet with size <= RtsCtsThreshold. "
+                   "This value will not have any effect on some rate control algorithms.",
                    UintegerValue (7),
                    MakeUintegerAccessor (&WifiRemoteStationManager::SetMaxSsrc),
                    MakeUintegerChecker<uint32_t> ())
     .AddAttribute ("MaxSlrc",
-                   "The maximum number of retransmission attempts for a DATA packet. "
+                   "The maximum number of retransmission attempts for any packet with size > RtsCtsThreshold. "
                    "This value will not have any effect on some rate control algorithms.",
                    UintegerValue (4),
                    MakeUintegerAccessor (&WifiRemoteStationManager::SetMaxSlrc),
@@ -1144,27 +1144,27 @@ WifiRemoteStationManager::GetUseGreenfieldProtection (void) const
 }
 
 bool
-WifiRemoteStationManager::NeedRtsRetransmission (Mac48Address address, const WifiMacHeader *header,
+WifiRemoteStationManager::NeedRetransmission (Mac48Address address, const WifiMacHeader *header,
                                                  Ptr<const Packet> packet)
 {
   NS_LOG_FUNCTION (this << address << packet << *header);
   NS_ASSERT (!address.IsGroup ());
   WifiRemoteStation *station = Lookup (address, header);
-  bool normally = station->m_ssrc < m_maxSsrc;
-  NS_LOG_DEBUG ("WifiRemoteStationManager::NeedDataRetransmission count: " << station->m_ssrc << " result: " << std::boolalpha << normally);
-  return DoNeedRtsRetransmission (station, packet, normally);
-}
-
-bool
-WifiRemoteStationManager::NeedDataRetransmission (Mac48Address address, const WifiMacHeader *header,
-                                                  Ptr<const Packet> packet)
-{
-  NS_LOG_FUNCTION (this << address << packet << *header);
-  NS_ASSERT (!address.IsGroup ());
-  WifiRemoteStation *station = Lookup (address, header);
-  bool normally = station->m_slrc < m_maxSlrc;
-  NS_LOG_DEBUG ("WifiRemoteStationManager::NeedDataRetransmission count: " << station->m_slrc << " result: " << std::boolalpha << normally);
-  return DoNeedDataRetransmission (station, packet, normally);
+  bool longMpdu = (packet->GetSize () + header->GetSize () + WIFI_MAC_FCS_LENGTH) > m_rtsCtsThreshold;
+  uint32_t retryCount, maxRetryCount;
+  if (longMpdu)
+    {
+      retryCount = station->m_slrc;
+      maxRetryCount = m_maxSlrc;
+    }
+  else
+    {
+      retryCount = station->m_ssrc;
+      maxRetryCount = m_maxSsrc;
+    }
+  bool normally = retryCount < maxRetryCount;
+  NS_LOG_DEBUG ("WifiRemoteStationManager::NeedRetransmission count: " << retryCount << " result: " << std::boolalpha << normally);
+  return DoNeedRetransmission (station, packet, normally);
 }
 
 bool
@@ -1979,15 +1979,8 @@ WifiRemoteStationManager::DoNeedRts (WifiRemoteStation *station,
 }
 
 bool
-WifiRemoteStationManager::DoNeedRtsRetransmission (WifiRemoteStation *station,
-                                                   Ptr<const Packet> packet, bool normally)
-{
-  return normally;
-}
-
-bool
-WifiRemoteStationManager::DoNeedDataRetransmission (WifiRemoteStation *station,
-                                                    Ptr<const Packet> packet, bool normally)
+WifiRemoteStationManager::DoNeedRetransmission (WifiRemoteStation *station,
+                                                Ptr<const Packet> packet, bool normally)
 {
   return normally;
 }

src/wifi/model/wifi-remote-station-manager.h

@@ -688,7 +688,7 @@ public:
                      double ackSnr, WifiMode ackMode, double dataSnr);
   /**
    * Should be invoked after calling ReportRtsFailed if
-   * NeedRtsRetransmission returns false
+   * NeedRetransmission returns false
    *
    * \param address the address of the receiver
    * \param header MAC header of the DATA packet
@@ -696,7 +696,7 @@ public:
   void ReportFinalRtsFailed (Mac48Address address, const WifiMacHeader *header);
   /**
    * Should be invoked after calling ReportDataFailed if
-   * NeedDataRetransmission returns false
+   * NeedRetransmission returns false
    *
    * \param address the address of the receiver
    * \param header MAC header of the DATA packet
@@ -748,16 +748,6 @@ public:
    */
   bool NeedCtsToSelf (WifiTxVector txVector);
 
-  /**
-   * \param address remote address
-   * \param header MAC header
-   * \param packet the packet to send
-   *
-   * \return true if we want to restart a failed RTS/CTS handshake,
-   *         false otherwise.
-   */
-  bool NeedRtsRetransmission (Mac48Address address, const WifiMacHeader *header,
-                              Ptr<const Packet> packet);
   /**
    * \param address remote address
    * \param header MAC header
@@ -766,8 +756,8 @@ public:
    * \return true if we want to resend a packet after a failed transmission attempt,
    *         false otherwise.
    */
-  bool NeedDataRetransmission (Mac48Address address, const WifiMacHeader *header,
-                               Ptr<const Packet> packet);
+  bool NeedRetransmission (Mac48Address address, const WifiMacHeader *header,
+                           Ptr<const Packet> packet);
   /**
    * \param address remote address
    * \param header MAC header
@@ -1080,20 +1070,6 @@ private:
    */
   virtual bool DoNeedRts (WifiRemoteStation *station,
                           Ptr<const Packet> packet, bool normally);
-  /**
-   * \param station the station that we need to communicate
-   * \param packet the packet to send
-   * \param normally indicates whether the normal 802.11 rts enable mechanism would
-   *        request that the rts is retransmitted or not.
-   *
-   * \return true if we want to restart a failed RTS/CTS handshake,
-   *         false otherwise.
-   *
-   * Note: This method is called after an rts/cts handshake has been attempted
-   *       and has failed.
-   */
-  virtual bool DoNeedRtsRetransmission (WifiRemoteStation *station,
-                                        Ptr<const Packet> packet, bool normally);
   /**
    * \param station the station that we need to communicate
    * \param packet the packet to send
@@ -1102,10 +1078,10 @@ private:
    * \return true if we want to resend a packet after a failed transmission attempt,
    *         false otherwise.
    *
-   * Note: This method is called after a unicast packet transmission has been attempted
-   *       and has failed.
+   * Note: This method is called after any unicast packet transmission (control, management,
+   *       or data) has been attempted and has failed.
    */
-  virtual bool DoNeedDataRetransmission (WifiRemoteStation *station,
+  virtual bool DoNeedRetransmission (WifiRemoteStation *station,
                                          Ptr<const Packet> packet, bool normally);
   /**
    * \param station the station that we need to communicate

src/wifi/test/wifi-aggregation-test.cc

@@ -231,7 +231,7 @@ AmpduAggregationTest::DoRun (void)
   NS_TEST_EXPECT_MSG_EQ (isAmpdu, false, "no MPDU aggregation should be performed if there is no agreement");
   NS_TEST_EXPECT_MSG_EQ (m_low->m_aggregateQueue[0]->GetNPackets (), 0, "aggregation queue is not flushed");
 
-  m_manager->SetMaxSlrc (0); //set to 0 in order to fake that the maximum number of retries has been reached
+  m_manager->SetMaxSsrc (0); //set to 0 in order to fake that the maximum number of retries has been reached
   m_txop->MissedAck ();
 
   NS_TEST_EXPECT_MSG_EQ (m_txop->m_currentPacket, 0, "packet should be discarded");