Re: [Discuss-gnuradio] rules for clock recovery parameters

[Tom Rondeau]

Eric Blossom wrote:
> On Thu, Mar 20, 2008 at 11:19:38AM -0400, George Nychis wrote:
>   
> > Hi all,
> >
> > I was wondering if anyone knows the rules for selecting clock recovery 
> > parameters for the gr_clock_recovery_mm_* block.  In specific, I'm 
> > wondering about the following parameters:
> >   mu, gain mu, omega, omega gain, and omega limit
> >
> > I would like to verify the clock recovery parameters chosen by UCLA's 
> > 802.15.4 implementation:
> > https://moo.cmcl.cs.cmu.edu/trac/cmu_sdrg/browser/802.15.4/trunk/src/python/ieee802_15_4.py#L100
> >
> > The reason is that we experience no loss when using file source/sinks but 
> > experience loss using coax, which might be due to timing errors introduced 
> > by the hardware.
> >
> > I'd greatly appreciate any help.
> >     
>
> mu specifies the point between two samples that you want the
> interpolated value of.  It's in [0.0, 1.0].  It's the input to the
> gri_mmse_fir_interpolator.  The rest of the parameters are for the
> control loop.
>   

And omega is the nominal samples per symbol.

Look at benchmark_rx.py in the digital examples file for a clue to the 
other parameters. The digital examples now use the mpsk_receiver, but 
the "mm_" parameters act on the M&M portion of the recovery loop inside.

Tom