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Re: [Discuss-gnuradio] M&M impl, its parameters, and why does it work fo
From: |
Bob McGwier |
Subject: |
Re: [Discuss-gnuradio] M&M impl, its parameters, and why does it work for GMSK? |
Date: |
Fri, 11 Apr 2008 13:45:24 -0400 |
User-agent: |
Thunderbird 2.0.0.12 (Windows/20080213) |
George Nychis wrote:
Thanks for the response.
You're correct, it can work with complex or real input. GMSK and the
MSK implementation are both using the real input, passed on from
gr_quadrature_demod_cf. Here is the MSK impl:
https://moo.cmcl.cs.cmu.edu/trac/cmu_sdrg/browser/phys/802.15.4/trunk/src/python/ieee802_15_4.py#L84
I'm not sure if I and Q are meant to be de-staggered before hand or not.
- George
George, Jeffrey:
You are discovering by inference in the M&M research work what most
communications professionals know because someone told them (usually
Matlab) ;-).
Staggered QAM and MSK minimize envelope variation and as such, the
nonlinearity in M&M generates a much weaker clock tone. At the risk of
bringing up sore topics, Matlab uses M&M where it is appropriate. For
MSK and GMSK, they use a fourth order nonlinearity to generate the clock
tone.
I use them and their large R&D shop as "proof by intimidation" rather
than going through all of the arguments why this should be so but they
start from the small envelope variation I mentioned.
google search Matlab MSK-type signal timing recovery. They have my
favorite timing author ever (Umberto Mengali) referenced.
Long before M&M wrote, Umberto Mengali wrote a paper on the asymptotic
maximum likelihood clock recovery method. After you approximate the
hyperbolic tangent with the simplest first order approximation and use
two tap differentiator, VOILA, M&M pops out.
--
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] M&M impl, its parameters, and why does it work for GMSK?, George Nychis, 2008/04/11
- RE: [Discuss-gnuradio] M&M impl, its parameters, and why does it work for GMSK?, Long, Jeffrey P., 2008/04/11
- Re: [Discuss-gnuradio] M&M impl, its parameters, and why does it work for GMSK?, George Nychis, 2008/04/11
- RE: [Discuss-gnuradio] M&M impl, its parameters, and why does it work for GMSK?, Long, Jeffrey P., 2008/04/11
- Re: [Discuss-gnuradio] M&M impl, its parameters, and why does it work for GMSK?,
Bob McGwier <=
- RE: [Discuss-gnuradio] M&M impl, its parameters, and why does itwork for GMSK?, Long, Jeffrey P., 2008/04/11
- Re: [Discuss-gnuradio] M&M impl, its parameters, and why does itwork for GMSK?, Bob McGwier, 2008/04/11
- RE: [Discuss-gnuradio] M&M impl, its parameters, and why does itwork for GMSK?, Long, Jeffrey P., 2008/04/11
- Re: [Discuss-gnuradio] M&M impl, its parameters, and why does itwork for GMSK?, Bob McGwier, 2008/04/11