Facing problem useing v.92 modem with As5300 access server

Dear all
we are using a As5350 access router.Everything is running well with old modem like v.90 or v.34 but with v.92 modem it is not working well.When we using v.92 modem its connect speed is verry slow and the connection disconnect every 5 min.If any one who have idea pls advice me how i will solve the problem.

Thanks in advance

Md. Kamal Hossain
System Administrator