wifi: (fixes #2673) Update WiFi spectrum model when channel is switched at run-time

RELEASE_NOTES

@@ -101,6 +101,7 @@ Bugs fixed
 - Bug 2660 - TrafficControlHelper::Default should not configure internal queue sizes
 - Bug 2665 - Ipv4RawSocket can not send packets to broadcast or multicast
 - Bug 2671 - ArpCache::Entry::SetMacAddress is misspelled
+- Bug 2673 - run-time channel switch does not update WiFi spectrum model
 - Bug 2717 - Fix mask generation for Ipv4RoutingTableEntry::CreateDefaultRoute
 - Bug 2722 - 802.11g sends DSSS spectrum signals using CreateOfdmTxPowerSpectralDensity
 - Bug 2741 - IPv4 fragmentation fails when last fragment have to be re-fragmented.

src/wifi/model/spectrum-wifi-phy.cc

@@ -125,6 +125,62 @@ SpectrumWifiPhy::SetChannel (const Ptr<SpectrumChannel> channel)
   m_channel = channel;
 }
 
+void
+SpectrumWifiPhy::ResetSpectrumModel (void)
+{
+  NS_LOG_FUNCTION (this);
+  NS_ASSERT_MSG (IsInitialized (), "Executing method before run-time");
+  NS_LOG_DEBUG ("Run-time change of spectrum model from frequency/width pair of (" << GetFrequency () << ", " << (uint16_t)GetChannelWidth () << ")");
+  // Replace existing spectrum model with new one, and must call AddRx ()
+  // on the SpectrumChannel to provide this new spectrum model to it
+  m_rxSpectrumModel = WifiSpectrumValueHelper::GetSpectrumModel (GetFrequency (), GetChannelWidth (), GetBandBandwidth (), GetGuardBandwidth ());
+  m_channel->AddRx (m_wifiSpectrumPhyInterface);
+}
+
+void
+SpectrumWifiPhy::SetChannelNumber (uint8_t nch)
+{
+  NS_LOG_FUNCTION (this << (uint16_t) nch);
+  WifiPhy::SetChannelNumber (nch);
+  if (IsInitialized ())
+    {
+      ResetSpectrumModel ();
+    }
+}
+
+void
+SpectrumWifiPhy::SetFrequency (uint16_t freq)
+{
+  NS_LOG_FUNCTION (this << freq);
+  WifiPhy::SetFrequency (freq);
+  if (IsInitialized ())
+    {
+      ResetSpectrumModel ();
+    }
+}
+
+void
+SpectrumWifiPhy::SetChannelWidth (uint8_t channelwidth)
+{
+  NS_LOG_FUNCTION (this << (uint16_t) channelwidth);
+  WifiPhy::SetChannelWidth (channelwidth);
+  if (IsInitialized ())
+    {
+      ResetSpectrumModel ();
+    }
+}
+
+void 
+SpectrumWifiPhy::ConfigureStandard (WifiPhyStandard standard)
+{
+  NS_LOG_FUNCTION (this << standard);
+  WifiPhy::ConfigureStandard (standard);
+  if (IsInitialized ())
+    {
+      ResetSpectrumModel ();
+    }
+}
+
 void
 SpectrumWifiPhy::AddOperationalChannel (uint8_t channelNumber)
 {

src/wifi/model/spectrum-wifi-phy.h

@@ -160,6 +160,16 @@ public:
 
   Ptr<Channel> GetChannel (void) const;
 
+  // The following four methods call to the base WifiPhy class method
+  // but also generate a new SpectrumModel if called during runtime
+
+  virtual void SetChannelNumber (uint8_t id);
+
+  virtual void SetFrequency (uint16_t freq);
+
+  virtual void SetChannelWidth (uint8_t channelwidth);
+
+  virtual void ConfigureStandard (WifiPhyStandard standard);
 
 protected:
   // Inherited
@@ -180,6 +190,11 @@ private:
    */
   Ptr<SpectrumValue> GetTxPowerSpectralDensity (uint16_t centerFrequency, uint8_t channelWidth, double txPowerW, WifiModulationClass modulationClass) const;
 
+  /**
+   * Perform run-time spectrum model change
+   */
+  void ResetSpectrumModel (void);
+
   Ptr<SpectrumChannel> m_channel;        //!< SpectrumChannel that this SpectrumWifiPhy is connected to
   std::vector<uint8_t> m_operationalChannelList; //!< List of possible channels
 

src/wifi/model/wifi-phy.h

@@ -588,14 +588,14 @@ public:
    *
    * Channel center frequency = Channel starting frequency + 5 MHz * (nch - 1)
    *
-   * where Starting channel frequency is standard-dependent, see SetStandard()
+   * where Starting channel frequency is standard-dependent,
    * as defined in (Section 18.3.8.4.2 "Channel numbering"; IEEE Std 802.11-2012).
    * This method may fail to take action if the Phy model determines that
    * the channel number cannot be switched for some reason (e.g. sleep state)
    *
    * \param id the channel number
    */
-  void SetChannelNumber (uint8_t id);
+  virtual void SetChannelNumber (uint8_t id);
   /**
    * Return current channel number.
    *
@@ -612,7 +612,7 @@ public:
    *
    * \param standard the Wi-Fi standard
    */
-  void ConfigureStandard (WifiPhyStandard standard);
+  virtual void ConfigureStandard (WifiPhyStandard standard);
 
   /**
    * Get the configured Wi-Fi standard
@@ -1488,7 +1488,7 @@ public:
   /**
    * \param freq the operating center frequency (MHz) on this node.
    */
-  void SetFrequency (uint16_t freq);
+  virtual void SetFrequency (uint16_t freq);
   /**
    * \return the operating center frequency (MHz)
    */
@@ -1628,7 +1628,7 @@ public:
   /**
    * \param channelwidth channel width
    */
-  void SetChannelWidth (uint8_t channelwidth);
+  virtual void SetChannelWidth (uint8_t channelwidth);
   /**
    * \param channelwidth channel width (in MHz) to support
    */
@@ -1695,7 +1695,6 @@ protected:
   EventId m_endRxEvent;                //!< the end reeive event
   EventId m_endPlcpRxEvent;            //!< the end PLCP receive event
 
-
 private:
   /**
    * \brief post-construction setting of frequency and/or channel number