Start Frame Delimiter

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

In article <b8844b9d-0d78-43b3-9bc8-d4e349946fc9
@f33g2000yqe.googlegroups.com>, ashutosh.ghildiyal@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