Client computers when they aren't signed in can still try and grab HTTP requests from the internet, these are intercepted and served by the Hotspot, usually by redirecting them to the login page (thus generating the traffic you are seeing an a higher than normal CPU load). That is how a client gets to the login page in the first place. This means that a client computer can continually request HTTP content over and over and over again, what you are seeing is that. Possibly because of a virus on the client computer, or some other program that wants to get content and just keeps asking for it until it gets it.
You can set up a firewall filter rule that will restrict the number of connections the router will service on the input chain to lessen the impact of this, but this won't prevent a client from doing it.
Thanks , but is that mean that there is no solution for it and from where i can get that filter rule ??