[Discuss-gnuradio] Trellis in generic_mod_demod

[Manu T S]

I want to use convolution code to transmit packet over USRP. So I ended up modifying the generic_mod_demod in digital.

The original flow graph was

Tx

packed_to_unpacked(bits_per_symbol) ---> gray_encoder ---> differential_encoder ---> chunks_to_symbol(constellation)

---> rrc_filter ---> USRP

Rx

USRP ---> fll_band_edge ---> pfb_clock_sync ---> (constellation_receiver, 0) ---> demod_pkts

Now I have modified it to the following.

Tx

packed_to_unpacked(bits_per_trellis_input) ---> trellis_encoder(fsm) ---> chunnks_to_symbol(constellatin) ---> rrc_filter ---> USRP

Rx

USRP ---> fll_band_edge ---> pfb_clock_sync ---> (constelllation_receiver, 4)(symbol) ---> viterbi_combined ---> demod_pkts

I find this structure ends up in more errors than before. ( almost all errors )

1. Does the packet size at the output of pkt.py has anything to do with the block_length in viterbi_combined?

2. Will it make any difference if I specify the starting and ending states??

--
Manu T S