Patent ID: 8379554

Claim:
A base station (BS) for checking status of a mobile station (MS) in a sleep mode, the BS comprising: a processor configured to: receive a sleep request (SLP-REQ) message from the MS; transmit a sleep response (SLP-RSP) message to the MS in response to the SLP-REQ message, the SLP-RSP message comprising a first periodic ranging frame offset; allocate a first uplink bandwidth (UL-BW) when a first time indicated by the first periodic ranging frame offset is reached, the first UL-BW allocated for a ranging request (RNG-REQ) message to be transmitted by the MS; receive the RNG-REQ message which is transmitted through the first UL-BW from the MS; transmit a ranging response (RNG-RSP) message to the MS in response to the RNG-REQ message, the RNG-RSP message comprising information required for performing a ranging process and a second periodic ranging frame offset; allocate a second uplink bandwidth (UL-BW) when a second time indicated by the second periodic ranging frame offset is reached, the second UL-BW allocated for an additional RNG-REQ message to be transmitted by the MS; and receive the additional RNG-REQ message which is transmitted through the second UL-BW from the MS.