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From: Matt Frazier (mfrazier, cryptofreak dot org) Date: 2001.03.08 - 19.41 MST
X-Mailer: Microsoft Outlook Express 5.60.2296.0000 It's hard to determine that this is just phase-shift or -modulation (or both) as we're talking about, since in PSK you have basically four waveforms, none of which could ever create as the initial signal the sequence (from the notation used in the previous email) 1212. They could feasibly create a sequence 34121234, but that would be two full phase-windows (that is, two two-bit data chunks). Nothing in either the diagrams at your site on modulation http://wheelie.tees.ac.uk/users/a.clements/Async/async.htm or this one I found about PSK http://www.physics.udel.edu/wwwusers/watson/student_projects/scen167/thosguys/psk.html have those artifacts. Suppose our period is 4 units (enough that a regular cosine would be represented as 1234). We never see 11 or 22, it's always at least 12 or 34, so we'll call those (back to the idea you just emailed) bit-0 and bit-1. However, I need to recheck my visual scan because I'm not positive on my freakin' columns. Um... I tried this earlier and had to do 'real' work, but anyone wanna parse that ps file for the characters used, so we're sure-fer-sure we have a) the right data and b) the right period. As I look at it more, the only thing that drives me nuts on it being simply PSK is those damn 1212 sequences -- there's no room for it that I can find in a PSK standard (cos(0..0.5) reflected in all directions). That can never result in an initial sequence of 1212 (although it's possible for that to show up as the leading and trailing halves of two phase-shifts. Shit. You will pay for this, Jay. Matt -- This is the mod-chal mailing list. To unsubscribe, email majordomo, cryptofreak dot org with message body 'unsubscribe mod-chal'. Or, for more information, visit http://www.cryptofreak.org/.
This archive was generated by hypermail 2b30 : 2001.09.26 - 14.03 MDT |
