Wimax standards and Security The Wimax

UL-MAP



...
Ranging code


RNG-RSP (success)


RNG-REQ
(Serving BSID, MS MAC address)
Association process (level 0)

FIGURE 6.6
Operation of scanning with association of level 0.

the MOB_NBR-ADV message. Since the target BS has no knowledge of the MS and provides only contention-based ranging allocations, the MS chooses randomly a ranging code from the initial ranging domain of the target BS and transmits it in the contention-based ranging region. After the target BS has received the ranging code and sends an RNG-RSP message with the ranging status “success,’’ it will provide an uplink allocation of adequate size for the MS to transmit an RNG-REQ message. Then, the MS transmits the RNG-REQ message with the serving BSID and its MAC address related to the associ- ation ranging. Association level 0 uses only a basic initial ranging process for the association with the target BS and does not require any coordination of its serving BS. However, this simplicity may cause collisions of ranging codes during the association process; hence, time required to complete the association process is increased.

At association level 1, the serving BS provides the MS with the association
parameters and coordinates the association between the MS and neighboring BSs, to reduce the time required for association. Figure 6.7 shows the scan- ning operation at association level 1. At association level 1, each neighboring

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

M frames Rendezvous
time
MOB_SCN-REQ
(Scan type = Association level 1)
MOB_SCN-RSP
(Scan type = Association level 1, Rendezvous time, Dedicated code, Dedicated TX. OP.)

Assign association ranging info.

(Dedicated code, Dedicated TX. OP.)

(# of frame)
Synchronize with BS #2 and measure PHY channel quality

Scanning interval

(N frames)