Thanks I will take a look. Jeff
-----Original Message----- From: Bob McGwier [mailto:[EMAIL PROTECTED] Sent: Friday, April 11, 2008 2:09 PM To: Long, Jeffrey P. Cc: George Nychis; gnuradio mailing list Subject: Re: [Discuss-gnuradio] M&M impl, its parameters, and why does itwork for GMSK? Long, Jeffrey P. wrote: > While we are on the topic of clock recovery and someone more > knowledgeable than me is reading :) I would like to pose a question to > Bob. How might one do clock recovery on a M-ary CPM signal? It sounds > like a ML sequence technique might be an option but is there a simpler > ad-hoc technique that works as well? My "superiors" tell me to just do > clock recovery on a 2-ary modulated preamble and then hold it for the > rest of the packet when it switches to your M-ary mode. I suppose this > would work but I think it might be a little too much work in GNU right > now until the meta data extra channel thing is ready, right? For > simplicity I would prefer a technique that could run on streaming data > like the M&M. > > thanks > Jeff > > Jeff: The answer is between the two. ;-) Use the 2-ary modulated symbols for timing acquisition and also for initial carrier recovery. Then since you will be close switch to a tracking mode: Mengali's joint timing and recovery algorithm for CPM signals Search for "Joint Timing and Phase Recovery for CPM signals" by Umberto Mengali, et. al. The joint estimator helps significantly as you can read. Bob -- AMSAT Director and VP Engineering. Member: ARRL, AMSAT-DL, TAPR, Packrats, NJQRP, QRP ARCI, QCWA, FRC. ARRL SDR WG Chair "Debugging is twice as hard as writing the code in the first place. Therefore, if you write the code as cleverly as possible, you are, by definition, not smart enough to debug it." - Brian W. Kernighan _______________________________________________ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
