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

[Johnathan Corgan]

Dan Halperin wrote:

> 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.

In addition to the auto-correlation properties described above, there
may be a requirement for a set of multiple access codes to have
negligible cross-correlation with other members of the set.  Some
protocols use multiple access codes (also known as sync codes) to signal
the type of frame that follows (e.g., the FLEX pager protocol, see
pageri_flex_codes.cc in the tree).

-- 
Johnathan Corgan
Corgan Enterprises LLC
http://corganenterprises.com