Hi Perper, I took a look at your code, and I found this
//set_frequency(d_freq_offset); It seems you have turned off the the frequency offset correction as you said. Do you know the reason of the introduced instability by this part? Best, Zhenhua 2014-03-04 1:42 GMT+08:00 Perper <per...@o2.pl>: > W dniu 28.02.2014 15:31, zhenhua han pisze: > > Hi, > > > > As I have known, GSM uses GMSK modulation which BT = 0.3 and it > > uses Viterbi algorithm for demodulation. And I took a look at the code > > of GMSK demod code in GNU Radio, it use quadrature_demod but not > > Viterbi as demodulation method. So which one is better in doing > > demodulating GMSK? > > > > Moreover, GSM uses Viterbi algorithm to decode the convolution > > encoding. Would it be possible to use quadrature_demod to demodulate > > GSM signal instead of Viterbi? What about the convolution decoding > > part (maybe by some other method)? > > > > Cheers, > > Zhenhua > > > > > > _______________________________________________ > > Discuss-gnuradio mailing list > > Discuss-gnuradio@gnu.org > > https://lists.gnu.org/mailman/listinfo/discuss-gnuradio > Hello all, > > Regarding usage of viterbi algorithm for maximum likelihood sequence > estimation in GSM - you may look at and try gsm-receiver that I once > submitted to airprobe. I've prepared version where I thrown out all of > decoding stuff and left only synchronization, channel estimation and > detection of bits with viterbi algorithm. It's available for download in > here: > https://github.com/Jakotako/gr-gsm > > It compiles with newest gnu-radio and it has gnuradio companion xml file > as well. It can be easily connected to different sources in gnuradio > (file, rtl-sdr, usrp) and it has a message sink where burst bits and > gsmtap headers are sent. I've corrected some issues with synchronization > and turned off frequency offset correction that introduced instability > of the receiver. After compiling and installing you can start with > examples. > > -- > Best Regards, > Piotr Krysik > > _______________________________________________ > Discuss-gnuradio mailing list > Discuss-gnuradio@gnu.org > https://lists.gnu.org/mailman/listinfo/discuss-gnuradio >
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