Re: [Discuss-gnuradio] Posted: Enhanced GMSK demodulator

[Eric Blossom]

On Thu, Jun 05, 2008 at 03:25:29PM -0400, Steven Clark wrote:
> I've added a link to
> http://gnuradio.org/trac/wiki/Enhanced_GMSK_Demodulator  from
> http://gnuradio.org/trac/wiki/OurUsers
> 
> Summary:
> [...] offers an enhanced GMSK demodulator that I believe to be
> superior to the GNURadio standard gmsk demodulator. It should be a
> drop-in replacement for the existing demodulator in designs, except
> that the transmitted data needs to be differentially encoded (you will
> NOT, however, need a differential decoder on the receive side). The
> enhanced demodulator should offer better bit error rate (BER)
> performance, especially for lower bandwidth-bittime (BT) products,
> such as the GSM standard BT=0.3, and in lower SNR conditions.
> 
> Please check it out and comment...
> 

Steven,

If you were to generate a patch that had your demodulator show up as a
new demod called, say, gsm_demod_alt2 that hooked it into the existing
framework with this new name, we could add it to the tree and it would
get more testing without having to overwrite the known implemenation
in the tree.  As currently written, yours looks like an all-or-none
proposition that requires a change in the modulator too.  Adding a
version of modulator that did the differential encoding would be
good too.


In gmsk_alt2.py:

  class gmsk_mod_alt2(gr.hier_block2):
    # I'm guessing this does the diff enc, then connects to the existing 
gmsk_mod...
    ...


  class gmsk_demod_alt2(gr.hier_block2):
    ...


  modulation_utils.add_type_1_mod('gmsk_alt2', gmsk_mod_alt2)
  modulation_utils.add_type_1_demod('gmsk_alt2', gmsk_demod_alt2)


Thanks,
Eric