Re: [Discuss-gnuradio] choosing start of frame bits, studies?

[Dan Halperin]

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George Nychis wrote:
> Was the access code picked randomly, or was there some basic rule of
> thumb for generating it?  What about the threshold of 12?  What about
> choosing a 64bit access as opposed to 32bit?

Standards for access codes are interesting. The Barker spreading code
use in 802.11 1 and 2Mbps rates, for instance, is one of a set of
optimal codes where B (dot) B = |B| while
B (dot) (B rotated by any nonzero number of bits) = 1. This means that
if you're sliding a correlator along a set of Barker-modulated bits, you
get strong peaks at the correct offset and (basically) nothing at any
other offset.

Usually access codes have a property somewhat like that. I think the
nuances of this choice are strongly tied in, however, with what
modulation scheme you're using.

- -Dan
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