Viterbi equalizer in a GSM system 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:


  Application of Viterbi Equalizer in GSM
  System


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.
Thanks for the answer. You are correct - the training sequence is known by the time you establish any communication.

In case if somebody stumbles upon this in the future, here's how to get this done:

The synchronization burst contains an extended training sequence. It's longer than the regular one and there is only one sequence. You are supposed to use that to equalize, demodulate and decode the SCH burst. Among other useful information, it contains the color code of the BTS, which identifies the training sequence used by that BTS. 

The procedure is nicely explained in this book:

Sajal Kumar Das: "Mobile Handset Design"