gr-Trellis FSM

GNU Radio
1

I’ve implemented a Manchester Decoder via an FSM using the combined
Viterbi
algorithm in gr-trellis, and its working great decoding my signal.
However,
I’ve noticed that after ~1000 times running (see code), I get an
error…

what(): fsm::fsm(const char *name): file open error

I’d expect this to happen in case of a buffer overrun or RAM limitation,
but
even if I reduce the time between packets, I get the same error.

Thanks for your help.

Manchester_FSM_test.py

#!/usr/bin/env python

from gnuradio import gr
from gnuradio import trellis
from gnuradio import eng_notation
import math
import sys
#import fsm_utils
from gnuradio.eng_option import eng_option
from optparse import OptionParser

def main():
for i in range(2005):

x=manchester([1,0,0,1,1,0,1,0,1,0,0,1,1,0,1,0,1,0,0,1,1,0,1,0,1,0,0,1,1,0,1,0,1,0,0,1,1,0,1,0,1,0,0,1,1,0,1,0,1,0,0,1,1,0,1,0,1,0,0,1,1,0,1,0,1,0,0,1,1,0,1,0,1,0,0,1,1,0,1,0,1,0,0,1,1,0,1,0,1,0,0,1,1,0,1,0,1,0,0,1,1,0,1,0,1,0,0,1,1,0,1,0,1,0,0,1,1,0,1,0,1,0,0,1,1,0,1,0])
print i

def run_test
(f,Kb,bitspersymbol,K,dimensionality,constellation,data_in):
tb = gr.top_block ()

src = gr.vector_source_s(data_in)

#src_head = gr.head (gr.sizeof_short,Kb/16) # packet size in shorts
#s2fsmi = gr.packed_to_unpacked_ss(bitspersymbol,gr.GR_MSB_FIRST) #

unpack shorts to symbols compatible with the FSM input cardinality
#enc = trellis.encoder_bb(f,0) # initial state = 0
#mod = gr.chunks_to_symbols_sf(constellation,dimensionality)
va =
trellis.viterbi_combined_sb(f,K,0,-1,dimensionality,constellation,trellis.TRELLIS_EUCLIDEAN)

Put -1 if the Initial/Final states are not set.

dst = gr.vector_sink_b();
tb.connect (src,va,dst)

tb.run()

return dst.data()

def manchester(data_in):

fname="fsm_files/manchester_encoder.fsm"


# system parameters
f=trellis.fsm(fname) # get the FSM specification from a file (will

hopefully be automated in the future…)

Kb=64
bitspersymbol = int(round(math.log(f.I())/math.log(2))) # bits per

FSM
input symbol
K=Kb/bitspersymbol # packet size in trellis steps

dimensionality = 2
constellation = [0, 0,0,1,1,0,1,1]
if len(constellation)/dimensionality != f.O():
    sys.stderr.write ('Incompatible FSM output cardinality and

modulation size.\n’)
#sys.exit (1)

(data)=run_test(f,Kb,bitspersymbol,K,dimensionality,constellation,data_in)

run experiment with different seed to get different noise realizations
return data

if name == ‘main’:
main()

Manchester_encoder.fsm

2 2 4

0 1
0 1

1 2
1 2

Manchester Encoder

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