Wimax standards and Security The Wimax

FIGURE 7.4
The sequence diagram of predicted handover scheme.

16. 
    , and we simplify the complex definition. The details of centralized control handover processes of PHS are given in the following nine steps, as shown in Figure 7.4:
    
    • 
      Step a: The IEEE 802.16e standard [16] recommends that the BS has to broadcast a report request (REP-REQ) message to all MSSs for channel measurements within 10 s to check whether the MSS is still in the service set. Therefore, the BS can get the SNR value by the replied REP-RSP message from each MSS to estimate the distance periodically. According to Equation 7.17, for location pre- diction and channel migration, the SBS measures the radio quality of MSSs and then using their SNR, determines the distance of
      

∆d_i1(∆t₁) of MSS_i.

= ,, + − ,
According to the geographic channel alignment (GCA) frame- work [7], we can calculate h by


h ^{NC − 3} 2 1 (7.18)
3|C₀₀|



| |
where N_C is the number of channels for usage in a macrocell and the number of channels in C₀₀ is represented as C₀₀ . The macrocell’s boundary is denoted as d_cell and can be obtained by


d_cell = d₀ × 10 exp P_t + G_t + G_r

— 20 log

c
4πd₀ F_H − (3(h − 1)²|C₀₀|+ 1)B

— X_σ − C_f − C_H − L − SNR_r,min − N₀ ,10ρ

(7.19)

•