Wimax standards and Security The Wimax

MOB_NBR-ADV
	(N_NEIGHBORS = 2) MOB_SCN-REQ (Scan duration = N frames, nterleaving interval = P frames, Scan iteration = T times) MOB_SCN-RSP (Start frame = M frames, Scan duration = N frames)

Iteration #T
FIGURE 6.5
Operation of network topology advertisement and scanning.

or after completing the scanning operation. These scanning and interleaving intervals are repeated alternately for the number of scan iterations specified.

3. Association

Association is an optional initial ranging procedure performed with one of the neighboring BSs during the scanning interval. Association enables the

MS to acquire and record information about ranging parameters and service availability, for the purpose of properly selecting the HO target and expedit- ing a potential future HO to a target BS. The recorded ranging parameters of an associated BS can be further used to set the initial ranging values in future ranging events during an actual HO. According to the use of BS coordination and network assistance, there are three levels of association:

• 
  Association level 0: Scan/association without coordination
  
• 
  Association level 1: Association with coordination
  
• 
  Association level 2: Network-assisted association reporting
  

At association level 0, the MS performs the basic initial ranging process with each target BS during the scanning interval. Figure 6.6 shows the scanning operation at association level 0. The exchange of the MOB_SCN-REQ and MOB_SCN-RSP messages requires the process of association level 0 together with the scanning process. During the scanning interval, the MS not only scans but also performs the initial ranging process with the target BSs referred in

BS #1
^MS (serving)
BS #2
(target)

MOB_SCN-REQ
(Scan type = Association level 0)

M frames
MOB_SCN-RSP
(Scan type = Association level 0, Start frame = M frames,
Scan duration = N frames)

Synchronize with BS #2 and measure PHY channel quality

Scanning interval

(N frames)