Dell Vostro 1500 Wifi connection issues

My son's Dell Vostro 1500 has been having issues staying connected to our AT&T Uverse wifi connection.  Upon booting up, the computer connects with a very strong signal and after a few minutes, disconnect from network.  A few seconds it will connect again.  Does anyone know what can be causing this issue?  After a while, the computer will stay connected for longer intervals, but eventually will dis-connect.  Thanks in advance for any and all help.