Patent ID: 7558605

Claim:
A method of checking status of a mobile station in sleep mode, the method comprising: receiving, by a base station, a sleep request message (SLP-REQ) from the mobile station; transmitting, from the base station, a sleep response message (SLP-RSP) in response to the sleep request message, the sleep response message comprising a first periodic ranging frame offset indicating when the mobile station transmits a ranging request message; receiving, by the base station, the ranging request message which the mobile station transmits at a first time indicated by the first periodic ranging frame offset; transmitting, from the base station, a ranging response message in response to the ranging request message, the ranging response message comprising information required for performing a ranging process and a second periodic ranging frame offset; and receiving, by the base station, an additional ranging request message which the mobile station transmits at a second time indicated by the second periodic ranging frame offset.