From e55628fc387755f7162ebaa9363472c65973e150 Mon Sep 17 00:00:00 2001
From: Stefano Avallone <stavallo@unina.it>
Date: Wed, 22 Jun 2022 11:08:08 +0200
Subject: [PATCH] wifi: Limit the delay among TB PPDUs to the duration of
 training fields

---
 src/wifi/model/he/he-configuration.cc | 13 +++++++------
 src/wifi/model/he/he-phy.cc           | 15 ++++++++++++---
 2 files changed, 19 insertions(+), 9 deletions(-)

diff --git a/src/wifi/model/he/he-configuration.cc b/src/wifi/model/he/he-configuration.cc
index 685b84cd3..9229a1836 100644
--- a/src/wifi/model/he/he-configuration.cc
+++ b/src/wifi/model/he/he-configuration.cc
@@ -53,15 +53,16 @@ HeConfiguration::GetTypeId (void)
                                          &HeConfiguration::SetBssColor),
                    MakeUintegerChecker<uint8_t> ())
     .AddAttribute ("MaxTbPpduDelay",
-                   "Specify the maximum delay with which a TB PPDU can be received "
-                   "after the reception of the first TB PPDU. If the delay is higher "
-                   "than this value, the TB PPDU is dropped and considered interference. "
-                   "A zero value indicates no delay limit. This attribute is only "
-                   "valid for APs.",
+                   "If positive, the value of this attribute specifies the maximum "
+                   "delay with which a TB PPDU can be received after the reception of "
+                   "the first TB PPDU. If the delay is higher than this value, the "
+                   "TB PPDU is dropped and considered interference. The maximum delay "
+                   "is anyway capped at the duration of the training fields in the PPDU. "
+                   "This attribute is only valid for APs.",
                    TimeValue (Seconds (0)),
                    MakeTimeAccessor (&HeConfiguration::GetMaxTbPpduDelay,
                                      &HeConfiguration::SetMaxTbPpduDelay),
-                   MakeTimeChecker ())
+                   MakeTimeChecker (Seconds (0)))
     .AddAttribute ("MpduBufferSize",
                    "The MPDU buffer size for receiving A-MPDUs",
                    UintegerValue (64),
diff --git a/src/wifi/model/he/he-phy.cc b/src/wifi/model/he/he-phy.cc
index 953c6fa73..040bf4d3c 100644
--- a/src/wifi/model/he/he-phy.cc
+++ b/src/wifi/model/he/he-phy.cc
@@ -452,10 +452,19 @@ HePhy::DoGetEvent (Ptr<const WifiPpdu> ppdu, RxPowerWattPerChannelBand& rxPowers
 
           auto heConfiguration = m_wifiPhy->GetDevice ()->GetHeConfiguration ();
           NS_ASSERT (heConfiguration);
-          Time maxDelay = heConfiguration->GetMaxTbPpduDelay ();
+          // DoStartReceivePayload(), which is called when we start receiving the Data field,
+          // computes the max offset among TB PPDUs based on the begin OFDMA payload RX events,
+          // which are scheduled by StartReceivePreamble() when starting the reception of the
+          // OFDMA portion. Therefore, the maximum delay cannot exceed the duration of the
+          // training fields that are between the start of the OFDMA portion and the start
+          // of the Data field.
+          Time maxDelay = GetDuration (WIFI_PPDU_FIELD_TRAINING, txVector);
+          if (heConfiguration->GetMaxTbPpduDelay ().IsStrictlyPositive ())
+            {
+              maxDelay = Min (maxDelay, heConfiguration->GetMaxTbPpduDelay ());
+            }
 
-          if (maxDelay.IsStrictlyPositive ()
-              && Simulator::Now () - event->GetStartTime () > maxDelay)
+          if (Simulator::Now () - event->GetStartTime () > maxDelay)
             {
               // This HE TB PPDU arrived too late to be decoded properly. The HE TB PPDU
               // is dropped and added as interference