Wimax standards and Security The Wimax

FIGURE 6.1
Example of sleep mode operation with two power-saving classes.

interval is a time interval that does not overlap with any unavailability inter- val. During the availability interval, the MS is expected to receive all downlink transmissions in the same way as in the wake mode.

For sleep mode operation, the IEEE 802.16e standard defines management messages as follows:

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  MOB_SLP-REQ is transmitted from an MS to the BS and used to request the activation of PSC types I, II, and III. It contains the definition of the new PSC that is requested.
  
• 
  MOB_SLP-RSP is sent from the BS to the MS in response to the MOB_SLP-REQ message or is sent unsolicited by the BS to activate sleep mode operation. It contains the definition of a new PSC.
  
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  MOB_TRF-IND is sent from the BS to the MS by using broadcast or multicast. This message indicates whether there has been any traffic addressed to each MS that is in sleep mode. Whenever an MS enters the listening state, it wakes up, decodes this message, and confirms an indication addressed to itself.
  

1. Power-Saving Class of Type I

PSC of type I (PSC I) is recommended for BE and NRT-VR connections, which are used for such activities as web browsing, email, and FTP. Figure 6.2 illustrates the basic sleep mode operation of PSC I in IEEE 802.16e. To start PSC I operation, an MS sends an MOB_SLP-REQ message and a BS responds with an MOB_SLP-RSP message. While these request and response messages are exchanged, the sleep mode parameters, such as initial-sleep window (T_min), final-sleep window (T_max), listening window, and start frame num- ber, are negotiated. These parameters are used to decide the sleep interval and listening interval in each sleep cycle during PSC I operation.
Both MS and BS initiate the sleep mode operation at the promised start frame. The size of the first sleep window is set to the initial-sleep window T_min.

DL packet arrival