Building a MAC Frame
Each MAC frame is started with a sequence of BCHs. The number of BCHs is equal to the number of sectors used by the AP. BCHs are transmitted according to the ascending sector identifier number. A single BCH is used per sector and they are transmitted periodically every two ms, except in cases where the AP is performing its own measurements related to the dynamic frequency selection (DFS) procedure [4]. In that case, some BCHs may be left out to allow the AP to perform measurements related to channel selection. BCHs are always transmitted using BPSK and coding rate 1/2.
The FCH follows directly after the BCH in the case of one sector. In the case of more than one sector, a pointer is used in the BCCH to identify the starting ...
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