What confused me is the Viterbi algorithm. I saw it can be used to demodulate GMSK in more than one place (such as here: http://www.mathworks.cn/cn/help/comm/ref/comm.gmskdemodulatorclass.html )
I think it's better for me to read some materials of Viterbi and find out what really it is. Cheers Zhenhua 2014-2-28 下午10:40于 "Aditya Dhananjay" <adi...@cs.nyu.edu>写道： > >> 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)? >> >> > I think you are mixing up the modulation and coding components. > > At the transmitter, you first code (convolutional code), and then you > modulate (GMSK). > > At the receiver, you first demodulate (quadrature demodulate) and then you > decode (Viterbi). > > Coding takes a stream of bits and converts it to another stream of bits. > Modulation refers to the process of converting the post-coded bits into > "symbols" that you will then send over-the-air. > > best, > aditya > >
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