On Tue, Feb 27, 2007 at 05:07:31PM -0500, Tom Rondeau wrote: > > -----Original Message----- > > From: [EMAIL PROTECTED] [mailto:discuss- > > [EMAIL PROTECTED] On Behalf Of Trond Danielsen > > Sent: Tuesday, February 27, 2007 10:46 AM > > To: gnuradio mailing list > > Subject: [Discuss-gnuradio] No BPSK modulator? > > > > Hi, > > > > Is there a reason why there is no "ordinary" n-PSK modulator and > > demodulator available, only the differential one? If not, I'll modify > > the existing one and submit a patch. > > It's not so much that there isn't a non-differential BPSK modulator, it's > that there is no demod for it. Basically, we have to be able to determine > the phase orientation of the incoming signal in some way to know what our > phase is. In BPSK, this is simple, and this was the original reason why > gr_correlate_access_code_bb had a d_flip variable in it, so that when the > phase inversion was detected, it would decode it properly. > > However, this was never a good solution and ended up hurting us because > sometimes we'd trigger this flip with random data, which would screw up the > packets. This was the reason the SSH sessions would crash and why Johnathan > made the original fix in the whitener. > > The solution to this is to use the correlator to detect the phase, but let > the next guy down the line understand what to do with it. We probably want > to send a control signal out to set the phase derotation and trigger the > access code found state at the same time, specifically, in the simple framer > state machine.
You could use bit 2 of the output stream of gr_correlate_access_code_bb to encode the "I've seen the inverted pattern". Then anybody who cared could look at it and take action if they wanted to, but it wouldn't interfere with any existing code. Eric _______________________________________________ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
