Patent ID: 7672696

Claim:
A method of determining when to terminate a sleep mode between a base station and a mobile station in a wireless access system, comprising: receiving a traffic indication message during a listening interval from the base station; receiving a ranging response message from the base station in response to a ranging request message transmitted to the base station through uplink resources allocated by the base station, wherein the ranging response message comprises a next periodic ranging time; checking whether or not the traffic indication message indicates that a downlink traffic exists; checking whether or not the ranging response message indicates that the downlink traffic exists; maintaining a sleep mode if the traffic indication message indicates that the downlink traffic does not exist; terminating the sleep mode and receiving data if the traffic indication message indicates that the downlink traffic exists; when the next periodic ranging time has been reached, transmitting another ranging request message to the base station through the uplink resources allocated by the base station if the ranging response message indicates that the downlink traffic does not exist; and terminating the sleep mode and receiving data if the ranging response message indicates that the downlink traffic exists.