Ieee80211: add support for HT primary and secondary channels (HT40- and HT40+)

.gitignore

@@ -1,3 +1,5 @@
+#local files
+implementation_plan*
 # local and generated files not to be committed
 doc/src/showcases
 doc/src/tutorials

examples/wireless/channelwidths/ChannelWidthsNetwork.ned

@@ -0,0 +1,37 @@
+//
+// Copyright (C) 2026 OpenSim Ltd.
+//
+// SPDX-License-Identifier: LGPL-3.0-or-later
+//
+
+package inet.examples.wireless.channelwidths;
+
+import inet.networks.base.WirelessNetworkBase;
+import inet.node.inet.WirelessHost;
+import inet.node.wireless.AccessPoint;
+
+network ChannelWidthsNetwork extends WirelessNetworkBase
+{
+    parameters:
+        @display("bgb=650,450");
+    submodules:
+        ap: AccessPoint {
+            @display("p=250,200;r=,,#707070");
+            wlan[*].mgmt.typename = "Ieee80211MgmtApSimplified";
+        }
+        sta1: WirelessHost {
+            @display("p=400,150;r=,,#707070");
+            wlan[*].mgmt.typename = "Ieee80211MgmtStaSimplified";
+            wlan[*].agent.typename = "";
+        }
+        sta2: WirelessHost {
+            @display("p=400,250;r=,,#707070");
+            wlan[*].mgmt.typename = "Ieee80211MgmtStaSimplified";
+            wlan[*].agent.typename = "";
+        }
+        interferer: WirelessHost {
+            @display("p=400,350;r=,,#707070");
+            wlan[*].mgmt.typename = "Ieee80211MgmtStaSimplified";
+            wlan[*].agent.typename = "";
+        }
+}

examples/wireless/channelwidths/omnetpp.ini

@@ -0,0 +1,72 @@
+[General]
+network = ChannelWidthsNetwork
+sim-time-limit = 2s
+
+# AP and STA configuration
+**.ap.wlan[*].address = "10:00:00:00:00:01"
+**.sta1.wlan[*].mgmt.accessPointAddress = "10:00:00:00:00:01"
+**.sta2.wlan[*].mgmt.accessPointAddress = "10:00:00:00:00:01"
+**.interferer.wlan[*].mgmt.accessPointAddress = "10:00:00:00:00:01"
+
+# Radio medium parameters
+**.radioMedium.backgroundNoise.power = -110dBm
+**.radioMedium.analogModel.ignorePartialInterference = true
+**.radioMedium.sameTransmissionStartTimeCheck = "ignore"
+
+# Wi-Fi physical parameters
+**.wlan[*].opMode = "n(mixed-2.4Ghz)"
+**.wlan[*].radio.transmitter.power = 20mW
+**.wlan[*].radio.receiver.sensitivity = -85dBm
+**.wlan[*].radio.receiver.energyDetection = -85dBm
+**.wlan[*].radio.receiver.snirThreshold = 4dB
+
+# Application: UDP traffic between STA1 and STA2
+*.sta1.numApps = 1
+*.sta1.app[0].typename = "UdpBasicApp"
+*.sta1.app[0].destAddresses = "sta2"
+*.sta1.app[0].destPort = 5000
+*.sta1.app[0].messageLength = 1000B
+*.sta1.app[0].sendInterval = 1ms
+*.sta1.app[0].startTime = 0.1s
+*.sta1.app[0].stopTime = 1.9s
+
+*.sta2.numApps = 1
+*.sta2.app[0].typename = "UdpSink"
+*.sta2.app[0].localPort = 5000
+
+# Base HT20 config
+[Config Ht20MHz]
+description = "IEEE 802.11n 20 MHz operation on 2.4 GHz channel 0"
+**.wlan[*].radio.bandwidth = 20MHz
+**.wlan[*].radio.channelNumber = 0
+**.wlan[*].htSecondaryChannelOffset = "none"
+
+# HT40+ (secondary above)
+[Config Ht40MHzSecondaryAbove]
+description = "IEEE 802.11n 40 MHz operation with secondary channel above (+20 MHz)"
+**.wlan[*].radio.bandwidth = 40MHz
+**.wlan[*].radio.channelNumber = 0
+**.wlan[*].htSecondaryChannelOffset = "above"
+
+# HT40- (secondary below)
+[Config Ht40MHzSecondaryBelow]
+description = "IEEE 802.11n 40 MHz operation with secondary channel below (-20 MHz)"
+**.wlan[*].radio.bandwidth = 40MHz
+**.wlan[*].radio.channelNumber = 4
+**.wlan[*].htSecondaryChannelOffset = "below"
+
+# HT40+ with interferer on secondary channel
+[Config Ht40MHzSecondaryAboveWithInterferer]
+description = "HT40+ with secondary channel interferer causing EDCA backoff restart"
+extends = Ht40MHzSecondaryAbove
+*.interferer.numApps = 1
+*.interferer.app[0].typename = "UdpBasicApp"
+*.interferer.app[0].destAddresses = "sta2"
+*.interferer.app[0].destPort = 6000
+*.interferer.app[0].messageLength = 500B
+*.interferer.app[0].sendInterval = 2ms
+*.interferer.app[0].startTime = 0.2s
+*.interferer.app[0].stopTime = 1.8s
+*.interferer.wlan[*].radio.bandwidth = 20MHz
+*.interferer.wlan[*].radio.channelNumber = 4
+*.interferer.wlan[*].htSecondaryChannelOffset = "none"

src/inet/linklayer/ieee80211/Ieee80211Interface.ned

@@ -64,13 +64,16 @@ module Ieee80211Interface extends NetworkInterface like IWirelessInterface
         string interfaceTableModule;
         string energySourceModule = default("");
         string opMode @enum("a","b","g(erp)","g(mixed)","n(mixed-2.4Ghz)","p","ac") = default("g(mixed)");
+        string htSecondaryChannelOffset @enum("none", "above", "below") = default("none");
         string address @mutable = default("auto"); // MAC address as hex string (12 hex digits), or
                                                    // "auto". "auto" values will be replaced by
                                                    // a generated MAC address in init stage 0.
         string protocol = default("");
         double bitrate @unit(bps) = default(-1bps);
         **.opMode = this.opMode;
         **.bitrate = this.bitrate;
+        radio.htSecondaryChannelOffset = default(this.htSecondaryChannelOffset);
+        mib.htSecondaryChannelOffset = default(this.htSecondaryChannelOffset);
         mac.modeSet = default(this.opMode);
         mac.*.rateSelection.dataFrameBitrate = default(this.bitrate);
         *.macModule = default(absPath(".mac"));

src/inet/linklayer/ieee80211/mac/Ieee80211Mac.cc

@@ -25,6 +25,7 @@
 #include "inet/linklayer/ieee80211/mac/contract/IRx.h"
 #include "inet/linklayer/ieee80211/mac/contract/ITx.h"
 #include "inet/networklayer/contract/IInterfaceTable.h"
+#include "inet/physicallayer/wireless/ieee80211/contract/IIeee80211CcaProvider.h"
 #include "inet/physicallayer/wireless/ieee80211/packetlevel/Ieee80211ControlInfo_m.h"
 #include "inet/physicallayer/wireless/ieee80211/packetlevel/Ieee80211Tag_m.h"
 
@@ -66,11 +67,14 @@ void Ieee80211Mac::initialize(int stage)
         ds = check_and_cast<IDs *>(getSubmodule("ds"));
         rx = check_and_cast<IRx *>(getSubmodule("rx"));
         tx = check_and_cast<ITx *>(getSubmodule("tx"));
+        auto ccaProvider = dynamic_cast<IIeee80211CcaProvider *>(radio.get());
+        if (ccaProvider != nullptr) {
+            radioModule->subscribe(IIeee80211CcaProvider::ccaStateChangedSignal, this);
+            rx->ccaStateChanged(ccaProvider->getCcaSnapshot());
+        }
         emit(modesetChangedSignal, modeSet);
         if (isUp())
             initializeRadioMode();
-        rx = check_and_cast<IRx *>(getSubmodule("rx"));
-        tx = check_and_cast<ITx *>(getSubmodule("tx"));
         dcf = check_and_cast<Dcf *>(getSubmodule("dcf"));
         hcf = check_and_cast_nullable<Hcf *>(getSubmodule("hcf"));
         if (mib->qos && !hcf)
@@ -327,6 +331,13 @@ void Ieee80211Mac::receiveSignal(cComponent *source, simsignal_t signalID, intva
     }
 }
 
+void Ieee80211Mac::receiveSignal(cComponent *source, simsignal_t signalID, cObject *value, cObject *details)
+{
+    Enter_Method("%s", cComponent::getSignalName(signalID));
+    if (signalID == IIeee80211CcaProvider::ccaStateChangedSignal)
+        rx->ccaStateChanged(*check_and_cast<Ieee80211CcaSnapshot *>(value));
+}
+
 void Ieee80211Mac::configureRadioMode(IRadio::RadioMode radioMode)
 {
     if (radio->getRadioMode() != radioMode) {

src/inet/linklayer/ieee80211/mac/Ieee80211Mac.h

@@ -64,6 +64,7 @@ class INET_API Ieee80211Mac : public MacProtocolBase
     virtual void initializeRadioMode();
 
     virtual void receiveSignal(cComponent *source, simsignal_t signalID, intval_t value, cObject *details) override;
+    virtual void receiveSignal(cComponent *source, simsignal_t signalID, cObject *value, cObject *details) override;
     using MacProtocolBase::receiveSignal;
     virtual void configureRadioMode(physicallayer::IRadio::RadioMode radioMode);
     virtual void configureNetworkInterface() override;

src/inet/linklayer/ieee80211/mac/Rx.cc

@@ -159,13 +159,36 @@ void Rx::recomputeMediumFree()
 {
     bool oldMediumFree = mediumFree;
     // note: the duration of mode switching (rx-to-tx or tx-to-rx) should also count as busy
-    mediumFree = receptionState == IRadio::RECEPTION_STATE_IDLE && transmissionState == IRadio::TRANSMISSION_STATE_UNDEFINED && !endNavTimer->isScheduled();
+    bool primaryPhysicallyIdle = (receptionState != IRadio::RECEPTION_STATE_RECEIVING) &&
+            (!ht40Cca ? (receptionState == IRadio::RECEPTION_STATE_IDLE) : !primaryCcaBusy);
+    mediumFree = primaryPhysicallyIdle && transmissionState == IRadio::TRANSMISSION_STATE_UNDEFINED && !endNavTimer->isScheduled();
     if (mediumFree != oldMediumFree) {
         for (auto contention : contentions)
             contention->mediumStateChanged(mediumFree);
     }
 }
 
+bool Rx::isSecondaryChannelIdleFor(simtime_t interval) const
+{
+    return !ht40Cca || (!secondaryCcaBusy && secondaryCcaIdleSince >= SIMTIME_ZERO &&
+            simTime() - secondaryCcaIdleSince >= interval);
+}
+
+void Rx::ccaStateChanged(const Ieee80211CcaSnapshot& snapshot)
+{
+    Enter_Method("ccaStateChanged");
+    bool wasHt40Cca = ht40Cca;
+    bool wasSecondaryBusy = secondaryCcaBusy;
+    ht40Cca = snapshot.isHt40();
+    primaryCcaBusy = snapshot.isPrimaryBusy();
+    secondaryCcaBusy = snapshot.isSecondaryBusy();
+    if (!ht40Cca || secondaryCcaBusy)
+        secondaryCcaIdleSince = -1;
+    else if (!wasHt40Cca || wasSecondaryBusy)
+        secondaryCcaIdleSince = simTime();
+    recomputeMediumFree();
+}
+
 void Rx::receptionStateChanged(IRadio::ReceptionState state)
 {
     Enter_Method("receptionStateChanged");

src/inet/linklayer/ieee80211/mac/Rx.h

@@ -37,6 +37,10 @@ class INET_API Rx : public SimpleModule, public IRx
     physicallayer::IRadio::TransmissionState transmissionState = physicallayer::IRadio::TRANSMISSION_STATE_UNDEFINED;
     physicallayer::IRadioSignal::SignalPart receivedPart = physicallayer::IRadioSignal::SIGNAL_PART_NONE;
     bool mediumFree = true; // cached state
+    bool ht40Cca = false;
+    bool primaryCcaBusy = false;
+    bool secondaryCcaBusy = false;
+    simtime_t secondaryCcaIdleSince = -1;
 
   protected:
     virtual int numInitStages() const override { return NUM_INIT_STAGES; }
@@ -53,7 +57,9 @@ class INET_API Rx : public SimpleModule, public IRx
 
     virtual bool isReceptionInProgress() const override;
     virtual bool isMediumFree() const override { return mediumFree; }
+    virtual bool isSecondaryChannelIdleFor(simtime_t interval) const override;
     virtual void receptionStateChanged(physicallayer::IRadio::ReceptionState newReceptionState) override;
+    virtual void ccaStateChanged(const physicallayer::Ieee80211CcaSnapshot& snapshot) override;
     virtual void transmissionStateChanged(physicallayer::IRadio::TransmissionState transmissionState) override;
     virtual void receivedSignalPartChanged(physicallayer::IRadioSignal::SignalPart part) override;
     virtual bool lowerFrameReceived(Packet *packet) override;

src/inet/linklayer/ieee80211/mac/channelaccess/Dcaf.cc

@@ -105,6 +105,17 @@ void Dcaf::releaseChannel(IChannelAccess::ICallback *callback)
     EV_INFO << "Channel released.\n";
 }
 
+void Dcaf::restartChannelAccess(IChannelAccess::ICallback *callback)
+{
+    Enter_Method("restartChannelAccess");
+    ASSERT(owning && (callback == nullptr || this->callback == callback));
+    owning = false;
+    emit(channelOwnershipChangedSignal, owning);
+    // IEEE Std 802.11-2024, 11.15.9 item b): retain the current CW and draw a
+    // fresh random backoff without updating any retry counter.
+    contention->startContention(cw, ifs, eifs, slotTime, this);
+}
+
 void Dcaf::requestChannel(IChannelAccess::ICallback *callback)
 {
     Enter_Method("requestChannel");

src/inet/linklayer/ieee80211/mac/channelaccess/Dcaf.h

@@ -52,6 +52,7 @@ class INET_API Dcaf : public IChannelAccess, public IContention::ICallback, publ
     // IChannelAccess::ICallback
     virtual void requestChannel(IChannelAccess::ICallback *callback) override;
     virtual void releaseChannel(IChannelAccess::ICallback *callback) override;
+    virtual void restartChannelAccess(IChannelAccess::ICallback *callback);
 
     // IContention::ICallback
     virtual void channelAccessGranted() override;

src/inet/linklayer/ieee80211/mac/channelaccess/Edcaf.cc

@@ -143,6 +143,17 @@ void Edcaf::releaseChannel(IChannelAccess::ICallback *callback)
     EV_INFO << "Channel released.\n";
 }
 
+void Edcaf::restartChannelAccess(IChannelAccess::ICallback *callback)
+{
+    Enter_Method("restartChannelAccess");
+    ASSERT(owning && (callback == nullptr || this->callback == callback));
+    owning = false;
+    emit(channelOwnershipChangedSignal, owning);
+    // IEEE Std 802.11-2024, 11.15.9 item b): retain CW[AC], select a new
+    // random backoff, and leave retry counters and queued frames unchanged.
+    contention->startContention(cw, ifs, eifs, slotTime, this);
+}
+
 void Edcaf::requestChannel(IChannelAccess::ICallback *callback)
 {
     Enter_Method("requestChannel");

src/inet/linklayer/ieee80211/mac/channelaccess/Edcaf.h

@@ -86,6 +86,7 @@ class INET_API Edcaf : public IChannelAccess, public IContention::ICallback, pub
     // IChannelAccess
     virtual void requestChannel(IChannelAccess::ICallback *callback) override;
     virtual void releaseChannel(IChannelAccess::ICallback *callback) override;
+    virtual void restartChannelAccess(IChannelAccess::ICallback *callback);
 
     // IContention::ICallback
     virtual void channelAccessGranted() override;

src/inet/linklayer/ieee80211/mac/contention/Contention.cc

@@ -171,8 +171,9 @@ void Contention::handleMessage(cMessage *msg)
     else if (msg == channelGrantedEvent) {
         EV_INFO << "Channel granted: startTime = " << startTime << std::endl;
         emit(channelAccessGrantedSignal, this);
-        callback->channelAccessGranted();
+        auto cb = callback;
         callback = nullptr;
+        cb->channelAccessGranted();
     }
     else
         throw cRuntimeError("Unknown msg");

src/inet/linklayer/ieee80211/mac/contract/IRx.h

@@ -12,6 +12,7 @@
 #include "inet/linklayer/ieee80211/mac/Ieee80211Frame_m.h"
 #include "inet/linklayer/ieee80211/mac/contract/IContention.h"
 #include "inet/physicallayer/wireless/common/contract/packetlevel/IRadio.h"
+#include "inet/physicallayer/wireless/ieee80211/contract/IIeee80211CcaProvider.h"
 
 namespace inet {
 namespace ieee80211 {
@@ -35,13 +36,15 @@ class INET_API IRx
 
     // from Contention
     virtual bool isMediumFree() const = 0;
+    virtual bool isSecondaryChannelIdleFor(simtime_t interval) const = 0;
     virtual void frameTransmitted(simtime_t durationField) = 0;
 
     // from Coordination functions
     virtual void registerContention(IContention *contention) = 0;
 
     // events
     virtual void receptionStateChanged(physicallayer::IRadio::ReceptionState state) = 0;
+    virtual void ccaStateChanged(const physicallayer::Ieee80211CcaSnapshot& snapshot) = 0;
     virtual void transmissionStateChanged(physicallayer::IRadio::TransmissionState state) = 0;
     virtual void receivedSignalPartChanged(physicallayer::IRadioSignal::SignalPart part) = 0;
     virtual bool lowerFrameReceived(Packet *packet) = 0;

src/inet/linklayer/ieee80211/mac/coordinationfunction/Dcf.cc

@@ -12,6 +12,7 @@
 #include "inet/linklayer/ieee80211/mac/framesequence/DcfFs.h"
 #include "inet/linklayer/ieee80211/mac/rateselection/RateSelection.h"
 #include "inet/linklayer/ieee80211/mac/recipient/RecipientAckProcedure.h"
+#include "inet/physicallayer/wireless/ieee80211/packetlevel/Ieee80211Tag_m.h"
 
 namespace inet {
 namespace ieee80211 {
@@ -164,7 +165,8 @@ void Dcf::transmitFrame(Packet *packet, simtime_t ifs)
 {
     Enter_Method("transmitFrame");
     const auto& header = packet->peekAtFront<Ieee80211MacHeader>();
-    auto mode = rateSelection->computeMode(packet, header);
+    auto modeReq = packet->findTag<Ieee80211ModeReq>();
+    auto mode = modeReq != nullptr ? modeReq->getMode() : rateSelection->computeMode(packet, header);
     RateSelection::setFrameMode(packet, header, mode);
     emit(IRateSelection::datarateSelectedSignal, mode->getDataMode()->getNetBitrate().get<bps>(), packet);
     EV_DEBUG << "Datarate for " << packet->getName() << " is set to " << mode->getDataMode()->getNetBitrate() << ".\n";

src/inet/linklayer/ieee80211/mac/coordinationfunction/Hcf.cc

@@ -14,6 +14,7 @@
 #include "inet/linklayer/ieee80211/mac/blockack/RecipientBlockAckAgreementHandler.h"
 #include "inet/linklayer/ieee80211/mac/framesequence/HcfFs.h"
 #include "inet/linklayer/ieee80211/mac/recipient/RecipientAckProcedure.h"
+#include "inet/physicallayer/wireless/ieee80211/mode/Ieee80211HtMode.h"
 #include "inet/physicallayer/wireless/ieee80211/packetlevel/Ieee80211Tag_m.h"
 
 namespace inet {
@@ -193,20 +194,45 @@ void Hcf::processLowerFrame(Packet *packet, const Ptr<const Ieee80211MacHeader>&
     }
 }
 
+bool Hcf::shouldRestartHt40ChannelAccess(Edcaf *edcaf)
+{
+    Packet *frame = edcaf->getInProgressFrames()->getFrameToTransmit();
+    if (frame == nullptr)
+        return false;
+    const auto& header = frame->peekAtFront<Ieee80211MacHeader>();
+    auto modeReq = frame->findTag<Ieee80211ModeReq>();
+    auto mode = modeReq != nullptr ? modeReq->getMode() : rateSelection->computeMode(frame, header, edcaf->getTxopProcedure());
+    if (mode == nullptr || dynamic_cast<const Ieee80211HtMode *>(mode) == nullptr ||
+            mode->getDataMode()->getBandwidth() != MHz(40))
+        return false;
+    // IEEE Std 802.11-2024, 11.15.9 item b):
+    // Secondary channel must be idle during an interval of DIFS for the 2.4 GHz band
+    // and PIFS for the 5 GHz band immediately preceding the expiration of the backoff counter.
+    // If the secondary channel was busy during this interval, invoke the backoff procedure with the current CW[AC].
+    bool is24GHz = modeSet != nullptr && strstr(modeSet->getName(), "2.4Ghz") != nullptr;
+    simtime_t requiredIdle = modeSet->getSifsTime() + (is24GHz ? 2 : 1) * modeSet->getSlotTime();
+    return !rx->isSecondaryChannelIdleFor(requiredIdle);
+}
+
 void Hcf::channelGranted(IChannelAccess *channelAccess)
 {
     Enter_Method("channelGranted");
     auto edcaf = check_and_cast<Edcaf *>(channelAccess);
     if (edcaf) {
         AccessCategory ac = edcaf->getAccessCategory();
         EV_DETAIL << "Channel access granted to the " << printAccessCategory(ac) << " queue" << std::endl;
-        edcaf->getTxopProcedure()->startTxop(ac);
         auto internallyCollidedEdcafs = edca->getInternallyCollidedEdcafs();
         if (internallyCollidedEdcafs.size() > 0) {
             EV_INFO << "Internal collision happened with the following queues:" << std::endl;
             handleInternalCollision(internallyCollidedEdcafs);
             emit(edcaCollisionDetectedSignal, (unsigned long)internallyCollidedEdcafs.size());
         }
+        if (shouldRestartHt40ChannelAccess(edcaf)) {
+            EV_INFO << "Secondary channel was busy during required interval before channel access for HT40 transmission, restarting backoff.\n";
+            edcaf->restartChannelAccess(this);
+            return;
+        }
+        edcaf->getTxopProcedure()->startTxop(ac);
         startFrameSequence(ac);
     }
     else