Wimax standards and Security The Wimax

FIGURE 6.9
MDHO procedure.

The MS can reject the diversity set recommended by the anchor BS by setting the type field in MOB_HO-IND to diversity set update reject. In this case, the BS reconfigures the diversity set list and retransmits the MOB_BSHO-RSP message to the MS. In addition, the MS can cancel a diversity set update at any time during a diversity set update process. The cancellation is made by transmitting an MOB_HO-IND with the type field set to diversity set update cancel.

2. Fast BS Switching

The MS and the BS involved in FBSS manage a diversity set by using the same threshold mechanism and an anchor BS is defined in the diversity set. When operating in FBSS, the MS only communicates with the anchor BS for UL and DL data. The transition from one anchor BS to another BS is performed without invoking the normal HO procedure. The FBSS procedure is shown in Figure 6.10. Anchor BS updating begins when the MS sends an MOB_MSHO- REQ or the anchor BS sends an MOB_BSHO-REQ. The preferred anchor BS is a member of the MS’s current diversity set. The MS selects the preferred anchor BS through a prior measurement of signal strength and reports it to the serving BS by using the MOB_MSHO-REQ message. ABS decides the target anchor BS





FIGURE 6.10
FBSS procedure.

on the basis of the MS report and then informs the MS of the anchor BS update by sending an MOB_BSHO-RSP containing the estimated switching time. Figure 6.10 illustrates a case in which the anchor BS is updated from BS1 to BS2. The MS updates its anchor BS on the basis of the information received in the MOB_BSHO-RSP message. The MS indicates its acceptance of the new anchor BS by sending an MOB_HO-IND message with the type field set to confirm anchor BS update. At this time, the MS can receive data from a new anchor BS (BS2). The MS can also reject or cancel the anchor BS update instruction by sending an MOB_HO-IND message with the type field set to reject or cancel.

4.