slow connection with SoftAP !

i'am using alfa rt8187L for airbase-ng et zydas connection to my wireless connection.
i setup a fake AP in bt5r3 manually or with easy-creds,same results...
the client has a slow internet speed,it's take a century to start a youtube video or downloading something.
i don't know why is that slower than a RealAp.
In wireshark,i can see that for every get request there's 4 or 5 tcp retransmission of the same request...
i tried to change the mtu value in at0,wlan1,wlan2 intefaces ,but it's just make the client lose connection.

if you have any idea how to fix this,help will be appreciated ;)

Have you svn'd up aircrack? There are bugs with the distro version of airbase-ng. If you svn up to the latest release, some of those issues may go away.