I'm about to tackle implementing a Viterbi equalizer fo a GSM system in gnuradio. I went through the internet and ieeexplore and I think that this document explains it best:
My question concerns the Matched Filter in the block diagram. Normal Burst in GSM has 8 possible midambles. First of all, the Matched Filter block should determine which midable has been transmited. Midambles have highly-peaked auto-correlation function, so the first thing to do is to compute the modulated version of the 8 midambles and then convolve each of them with the received midamble and the one with the most peak-like is the most likely to have been sent. Once I have that done, it's easy to compute the channel response estimate.
I don't have much background in DSP and I was hoping someone could let me know if I understand it correctly.