Start Frame Delimiter
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From: ashu on 29 Jul 2010 10:34 Hi All, I would like to understand the real importance of "start frame delimitor" in a wireless protocol. Especially why do we need a fixed pattern like SFD when we already do some pattern matching to detect the beginning of frame in wireless? Why do some protocols have a SFD and some dont ? Is it jsut purely a matter of choice ? regs ashu
From: Mark Borgerson on 29 Jul 2010 10:57
In article <b8844b9d-0d78-43b3-9bc8-d4e349946fc9 @f33g2000yqe.googlegroups.com>, ashutosh.ghildiyal(a)gmail.com says... > Hi All, > > I would like to understand the real importance of "start frame > delimitor" in a wireless protocol. Especially why do we need a fixed > pattern like SFD when we already do some pattern matching to detect > the beginning of frame in wireless? > Why do some protocols have a SFD and some dont ? Is it jsut purely a > matter of choice ? > Start frame delimiters are most useful when a receiver can start up in the middle of a continuous data stream. Pattern matching for small start-frame delimiter is easier (and costs fewer CPU cycles) than trying to pattern match a larger data frame. In addition to the frame delimiter, you generally need a checksum to exclude the possibility of the frame delimiter pattern occuring in the middle of a data frame. Mark Borgerson |