this is for our thesis project. we proposed to study the Wi-Fi security in most related to the users.
closed as not a real question by Rory Alsop♦ Apr 2 '12 at 12:25
It's difficult to tell what is being asked here. This question is ambiguous, vague, incomplete, overly broad, or rhetorical and cannot be reasonably answered in its current form. For help clarifying this question so that it can be reopened, see the FAQ.
The usual method is called "Captive Portal".
When the client first connects, all web page requests are intercepted and sent to the the login page instead. (Any non-web traffic sent at this point is dropped.)
One the user authenticates, the access point notes that it's authenticated, and subsequently allows traffic from that connection through to the Internet.