diff -r 89b7f8fbf3d0 src/devices/wifi/wifi-mac.cc
--- a/src/devices/wifi/wifi-mac.cc	Thu Oct 01 14:08:52 2009 +0200
+++ b/src/devices/wifi/wifi-mac.cc	Thu Oct 01 16:40:15 2009 +0400
@@ -230,7 +230,7 @@
 void
 WifiMac::Configure80211a (void)
 {
-  SetSifs(MicroSeconds(16));
+  SetSifs(MicroSeconds(16 + 2*GetDefaultMaxPropagationDelay().GetMicroSeconds ()));
   SetSlot(MicroSeconds(9)); 
   SetEifsNoDifs(MicroSeconds(16+44));
   SetPifs(MicroSeconds(16+9));
@@ -241,7 +241,7 @@
 void
 WifiMac::Configure80211b (void)
 {
-  SetSifs(MicroSeconds(10));
+  SetSifs(MicroSeconds(10 + 2*GetDefaultMaxPropagationDelay().GetMicroSeconds ()));
   SetSlot(MicroSeconds(20));
   SetEifsNoDifs(MicroSeconds(10+304));
   SetPifs(MicroSeconds(10+20));
@@ -252,7 +252,7 @@
 void
 WifiMac::Configure80211_10Mhz (void)
 {
-  SetSifs(MicroSeconds(32));
+  SetSifs(MicroSeconds(32 + 2*GetDefaultMaxPropagationDelay().GetMicroSeconds ()));
   SetSlot(MicroSeconds(13)); 
   SetEifsNoDifs(MicroSeconds(32+88));
   SetPifs(MicroSeconds(32+13));
@@ -263,7 +263,7 @@
 void
 WifiMac::Configure80211_5Mhz (void)
 {
-  SetSifs(MicroSeconds(64));
+  SetSifs(MicroSeconds(64 + 2*GetDefaultMaxPropagationDelay().GetMicroSeconds ()));
   SetSlot(MicroSeconds(21));
   SetEifsNoDifs(MicroSeconds(64+176));
   SetPifs(MicroSeconds(64+21));