Wireless no internet access problem

Hello,

I have a problem about wireless connection. I can connet with ethernet cable.
Actually I previously could connet with wireless but suddenyl can not connet.
(I dont remember any changes about wireless )

My roommate can connect and I compare the ip adresses and default gateway & dns proeprties , all are same
I can get ip adress automaticly
but when I try ipconfig/all
"wireless disconnected " is written

please help me