--- a/src/devices/wifi/wifi-mac.cc	Thu Oct 01 14:08:52 2009 +0200
+++ a/src/devices/wifi/wifi-mac.cc	Thu Oct 01 16:49:45 2009 +0400
@@ -231,7 +231,7 @@ 
 WifiMac::Configure80211a (void)
 {
   SetSifs(MicroSeconds(16));
-  SetSlot(MicroSeconds(9)); 
+  SetSlot(MicroSeconds(9 + 2*GetDefaultMaxPropagationDelay().GetMicroSeconds ())); 
   SetEifsNoDifs(MicroSeconds(16+44));
   SetPifs(MicroSeconds(16+9));
   SetCtsTimeout(MicroSeconds(16+44+9+GetDefaultMaxPropagationDelay().GetMicroSeconds ()*2));
@@ -242,7 +242,7 @@ 
 WifiMac::Configure80211b (void)
 {
   SetSifs(MicroSeconds(10));
-  SetSlot(MicroSeconds(20));
+  SetSlot(MicroSeconds(20 + 2*GetDefaultMaxPropagationDelay().GetMicroSeconds ()));
   SetEifsNoDifs(MicroSeconds(10+304));
   SetPifs(MicroSeconds(10+20));
   SetCtsTimeout(MicroSeconds(10+304+20+GetDefaultMaxPropagationDelay().GetMicroSeconds ()*2));
@@ -253,7 +253,7 @@ 
 WifiMac::Configure80211_10Mhz (void)
 {
   SetSifs(MicroSeconds(32));
-  SetSlot(MicroSeconds(13)); 
+  SetSlot(MicroSeconds(13 + 2*GetDefaultMaxPropagationDelay().GetMicroSeconds ())); 
   SetEifsNoDifs(MicroSeconds(32+88));
   SetPifs(MicroSeconds(32+13));
   SetCtsTimeout(MicroSeconds(32+88+13+GetDefaultMaxPropagationDelay().GetMicroSeconds ()*2));
@@ -264,7 +264,7 @@ 
 WifiMac::Configure80211_5Mhz (void)
 {
   SetSifs(MicroSeconds(64));
-  SetSlot(MicroSeconds(21));
+  SetSlot(MicroSeconds(21 + 2*GetDefaultMaxPropagationDelay().GetMicroSeconds ()));
   SetEifsNoDifs(MicroSeconds(64+176));
   SetPifs(MicroSeconds(64+21));
   SetCtsTimeout(MicroSeconds(64+176+21+GetDefaultMaxPropagationDelay().GetMicroSeconds ()*2));