[Discuss-gnuradio] Reference documents for the interpolation filter in the digital clock recovery block

[Anh Duc Nguyen]

Hi all,

I am a new one to GnuRadio. Now I am studying some implemented techniques in GnuRadio, one of them is the digital clock recovery. I would like to ask you a question that what are the reference documents or papers you used for the interpolation filter in that task (digital clock recovery). When I traced back the source files - digital_clock_recovery_mm_ff and then gri_mmse_fir_interpolator, I found only a little information:

 * 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.

I find it tough to understand the algorithm you selected, so could you please help me on this problem. I make a guess with the key words " Mininum Mean Squared Error", the implementation may have some link to those below papers:

[1]. G. Watkins, “Optimal Farrow coefficients for symbol timing recovery,” IEEE Communications Letters, vol. 5, no. 9, pp. 381–383, Sep. 2001.

[2] Daeyoung Kim, M. J. Narasimba, and D. C. Coc, “Design of optimal interpolation filter for symbol timing recovery,” IEEE Transactions on Communications, vol. 45, no. 7, pp. 877–884, Jul. 1997.

I would like to thank you very much in advance,

With best regards,

Nguyen Anh Duc