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
