Wimax standards and Security The Wimax

MOB_SLP-REQ

MOB_SLP-RSP
BS

MS

UL packet arrival


FIGURE 6.3
Operation of PSC II.

PSC II differs from PSC I in the following respects. During the listening interval, the BS does not transmit the traffic indication message (MOB_TRF- IND). Instead, the MS and BS exchange their real-time packets with each other directly. Hence, sleep mode is maintained uninterrupted, which is more effi- cient for real-time traffic because the signaling overhead required to restart sleep mode can be eliminated. In PSC II, sleep mode is terminated by the spec- ified management message (i.e., MOB_SLP-REQ or MOB_SLP-RSP) issued by either the MS or BS.

3. Power-Saving Class of Type III

PSC III is recommended for multicast connections, as well as for management operations, such as periodic ranging, dynamic service operations, and adver- tisement message broadcasting. Two parameters, final-sleep window and start frame number, are required for PSC III. An MS using PSC III initiates sleep mode operation at the start frame number, and powers off during a sleep interval specified as the size of the final-sleep window. After the expiration of one sleep interval, the MS powers on and PSC III operation finishes automati- cally. PSC III allows just one sleep cycle at a time and terminates automatically unless another sleep request is made at the time that the final-sleep window is finished.
Figure 6.4 shows a basic PSC III operation used for the periodic ranging. PSC III can be activated efficiently by a next periodic ranging type/length/value (TLV) encoding included in an RNG-RSP message. If a next periodic ranging TLV encoding in a certain RNG-RSP message is set to a positive value during the periodic ranging process, it activates a special PSC III associated with the ranging process. If the MS confirms that the RNG-RSP message contains TLV encoding, it starts PSC III operation at the next frame immediately and con- tinues to sleep during the frames that the next periodic ranging TLV indicates. When the MS’s sleep period ends, the MS and BS perform a periodic ranging each other. After completing periodic ranging successfully, the BS instructs

DL packet arrival