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.
> Thanks! > George Have you taken a look at the books and papers referenced in the header files? /*! * \brief Mueller and Müller (M&M) based clock recovery block with float input, float output. * \ingroup clock * * This implements the Mueller and Müller (M&M) discrete-time error-tracking synchronizer. * * See "Digital Communication Receivers: Synchronization, Channel * Estimation and Signal Processing" by Heinrich Meyr, Marc Moeneclaey, & Stefan Fechtel. * ISBN 0-471-50275-8. */ /*! * \brief Mueller and Müller (M&M) based clock recovery block with complex input, complex output. * \ingroup clock * * This implements the Mueller and Müller (M&M) discrete-time error-tracking synchronizer. * The complex version here is based on: * Modified Mueller and Muller clock recovery circuit * Based: * G. R. Danesfahani, T.G. Jeans, "Optimisation of modified Mueller and Muller * algorithm," Electronics Letters, Vol. 31, no. 13, 22 June 1995, pp. 1032 - 1033. */ 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. /*! * \brief Compute intermediate samples between signal samples x(k*Ts) * \ingroup filter * * This implements a Mininum Mean Squared Error interpolator with 8 taps. * It is suitable for signals where the bandwidth of interest B = 1/(4*Ts) * Where Ts is the time between samples. * * Although mu, the fractional delay, is specified as a float, it is actually * quantized. 0.0 <= mu <= 1.0. That is, mu is quantized in the interpolate * method to 32nd's of a sample. */ class gri_mmse_fir_interpolator_cc _______________________________________________ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio