A method of transmitting an overhead message via a control channel which has at least one slot is disclosed. More specifically, a base station (BS) transmits an overhead slot cycle index for providing the overhead message to a mobile station (MS) and thereafter, receives the overhead slot cycle index and determining an overhead slot cycle. Furthermore, the BS transmits the overhead message on a first slot of each overhead slot cycle according to a variable duration of the slot, and then receives the overhead message from the first slot of each overhead slot cycle according to the variable duration of the slot.