diff --git a/src/wifi/model/he/he-ru.cc b/src/wifi/model/he/he-ru.cc
index e1e95e038..740468c19 100644
--- a/src/wifi/model/he/he-ru.cc
+++ b/src/wifi/model/he/he-ru.cc
@@ -157,7 +157,8 @@ HeRu::RuSpec::RuSpec ()
 HeRu::RuSpec::RuSpec (RuType ruType, std::size_t index, bool primary80MHz)
   : m_ruType (ruType),
     m_index (index),
-    m_primary80MHz (primary80MHz)
+    m_primary80MHz (primary80MHz),
+    m_phyIndex (0)
 {
   NS_ABORT_MSG_IF (index == 0, "Index cannot be zero");
 }
@@ -183,6 +184,37 @@ HeRu::RuSpec::GetPrimary80MHz (void) const
   return m_primary80MHz;
 }
 
+void
+HeRu::RuSpec::SetPhyIndex (uint16_t bw, uint8_t p20Index)
+{
+  bool primary80IsLower80 = (p20Index < bw / 40);
+
+  if (bw < 160
+      || m_ruType == HeRu::RU_2x996_TONE
+      || (primary80IsLower80 && m_primary80MHz)
+      || (!primary80IsLower80 && !m_primary80MHz))
+    {
+      m_phyIndex = m_index;
+    }
+  else
+    {
+      m_phyIndex = m_index + GetNRus (bw, m_ruType) / 2;
+    }
+}
+
+bool
+HeRu::RuSpec::IsPhyIndexSet (void) const
+{
+  return (m_phyIndex != 0);
+}
+
+std::size_t
+HeRu::RuSpec::GetPhyIndex (void) const
+{
+  NS_ABORT_MSG_IF (m_phyIndex == 0, "RU PHY index not set");
+  return m_phyIndex;
+}
+
 std::size_t
 HeRu::GetNRus (uint16_t bw, RuType ruType)
 {
@@ -431,7 +463,12 @@ std::ostream& operator<< (std::ostream& os, const HeRu::RuType &ruType)
 
 std::ostream& operator<< (std::ostream& os, const HeRu::RuSpec &ru)
 {
-  os << "RU{" << ru.GetRuType () << "/" << ru.GetIndex () << "/" << (ru.GetPrimary80MHz () ? "primary80MHz" : "secondary80MHz") << "}";
+  os << "RU{" << ru.GetRuType () << "/" << ru.GetIndex () << "/" << (ru.GetPrimary80MHz () ? "primary80MHz" : "secondary80MHz");
+  if (ru.IsPhyIndexSet ())
+    {
+      os << "[" << ru.GetPhyIndex () << "]";
+    }
+  os << "}";
   return os;
 }
 
diff --git a/src/wifi/model/he/he-ru.h b/src/wifi/model/he/he-ru.h
index e83ea63dd..d853ae2b9 100644
--- a/src/wifi/model/he/he-ru.h
+++ b/src/wifi/model/he/he-ru.h
@@ -57,9 +57,12 @@ public:
 
 
   /**
-   * RU Specification. Stores the information carried by the RU Allocation
-   * subfield of the User Info field of Trigger frames. Note that primary80MHz
-   * must be true if ruType is RU_2x996_TONE.
+   * RU Specification. Stores the information carried by the RU Allocation subfield
+   * of the User Info field of Trigger frames (see 9.3.1.22.1 of 802.11ax D8.0).
+   * Note that primary80MHz must be true if ruType is RU_2x996_TONE.
+   * Internally, this class also stores the RU PHY index (ranging from 1 to the number
+   * of RUs of the given type in a channel of the considered width), so that this class
+   * contains all the information needed to locate the RU in a 160 MHz channel.
    */
   class RuSpec
   {
@@ -95,11 +98,35 @@ public:
      * \return true if the RU is in the primary 80 MHz channel and false otherwise
      */
     bool GetPrimary80MHz (void) const;
+    /**
+     * Set the RU PHY index
+     *
+     * \param bw the width of the channel of which the RU is part (in MHz)
+     * \param p20Index the index of the primary20 channel
+     */
+    void SetPhyIndex (uint16_t bw, uint8_t p20Index);
+    /**
+     * Return true if the RU PHY index has been set, false otherwise
+     *
+     * \return true if the RU PHY index has been set, false otherwise
+     */
+    bool IsPhyIndexSet (void) const;
+    /**
+     * Get the RU PHY index
+     *
+     * \return the RU PHY index
+     */
+    std::size_t GetPhyIndex (void) const;
 
   private:
     RuType m_ruType;         //!< RU type
-    std::size_t m_index;     //!< index (starting at 1)
+    std::size_t m_index;     /**< RU index (starting at 1) as defined by Tables 27-7
+                                  to 27-9 of 802.11ax D8.0 */
     bool m_primary80MHz;     //!< true if the RU is allocated in the primary 80MHz channel
+    std::size_t m_phyIndex;  /**< the RU PHY index, which is used to indicate whether an
+                                  RU is located in the lower half or the higher half of
+                                  a 160MHz channel. For channel widths less than 160MHz,
+                                  the RU PHY index equals the RU index */
   };