<?xml version="1.0" encoding="ISO-8859-1"?>
<programlisting>
  1  #!/usr/bin/env python
  2  
  3  from __future__ import print_function
  4  from __future__ import division
  5  from __future__ import unicode_literals
  6  from gnuradio import gr
  7  from gnuradio import audio
  8  from gnuradio import trellis, digital, filter, blocks
  9  from gnuradio import eng_notation
 10  import math
 11  import sys
 12  import random
 13  import fsm_utils
 14  
 15  try:
 16      from gnuradio import analog
 17  except ImportError:
 18      sys.stderr.write(&quot;Error: Program requires gr-analog.\n&quot;)
 19      sys.exit(1)
 20  
 21  def run_test (f,Kb,bitspersymbol,K,channel,modulation,dimensionality,tot_constellation,N0,seed):
 22      tb = gr.top_block ()
 23      L = len(channel)
 24  
 25      # TX
 26      # this for loop is TOO slow in python!!!
 27      packet = [0]*(K+2*L)
 28      random.seed(seed)
 29      for i in range(len(packet)):
 30          packet[i] = random.randint(0, 2**bitspersymbol - 1) # random symbols
 31      for i in range(L): # first/last L symbols set to 0
 32          packet[i] = 0
 33          packet[len(packet)-i-1] = 0
 34      src = blocks.vector_source_s(packet,False)
 35      mod = digital.chunks_to_symbols_sf(modulation[1],modulation[0])
 36  
 37      # CHANNEL
 38      isi = filter.fir_filter_fff(1,channel)
 39      add = blocks.add_ff()
 40      noise = analog.noise_source_f(analog.GR_GAUSSIAN,math.sqrt(N0 / 2),seed)
 41  
 42      # RX
 43      skip = blocks.skiphead(gr.sizeof_float, L) # skip the first L samples since you know they are coming from the L zero symbols
 44      #metrics = trellis.metrics_f(f.O(),dimensionality,tot_constellation,digital.TRELLIS_EUCLIDEAN) # data preprocessing to generate metrics for Viterbi
 45      #va = trellis.viterbi_s(f,K+L,0,0) # Put -1 if the Initial/Final states are not set.
 46      va = trellis.viterbi_combined_s(f,K+L,0,0,dimensionality,tot_constellation,digital.TRELLIS_EUCLIDEAN) # using viterbi_combined_s instead of metrics_f/viterbi_s allows larger packet lengths because metrics_f is complaining for not being able to allocate large buffers. This is due to the large f.O() in this application...
 47      dst = blocks.vector_sink_s()
 48  
 49      tb.connect (src,mod)
 50      tb.connect (mod,isi,(add,0))
 51      tb.connect (noise,(add,1))
 52      #tb.connect (add,metrics)
 53      #tb.connect (metrics,va,dst)
 54      tb.connect (add,skip,va,dst)
 55  
 56      tb.run()
 57  
 58      data = dst.data()
 59      ntotal = len(data) - L
 60      nright=0
 61      for i in range(ntotal):
 62          if packet[i+L]==data[i]:
 63              nright=nright+1
 64          #else:
 65              #print &quot;Error in &quot;, i
 66  
 67      return (ntotal,ntotal-nright)
 68  
 69  
 70  def main(args):
 71      nargs = len (args)
 72      if nargs == 2:
 73          esn0_db=float(args[0])
 74          rep=int(args[1])
 75      else:
 76          sys.stderr.write (&apos;usage: test_viterbi_equalization1.py Es/No_db  repetitions\n&apos;)
 77          sys.exit (1)
 78  
 79      # system parameters
 80      Kb=2048  # packet size in bits
 81      modulation = fsm_utils.pam4 # see fsm_utlis.py for available predefined modulations
 82      channel = fsm_utils.c_channel # see fsm_utlis.py for available predefined test channels
 83      f=trellis.fsm(len(modulation[1]),len(channel)) # generate the FSM automatically
 84      bitspersymbol = int(round(math.log(f.I()) / math.log(2))) # bits per FSM input symbol
 85      K=Kb / bitspersymbol # packet size in trellis steps
 86  
 87      tot_channel = fsm_utils.make_isi_lookup(modulation,channel,True) # generate the lookup table (normalize energy to 1)
 88      dimensionality = tot_channel[0]
 89      tot_constellation = tot_channel[1]
 90      N0=pow(10.0,-esn0_db / 10.0); # noise variance
 91      if len(tot_constellation) / dimensionality != f.O():
 92          sys.stderr.write (&apos;Incompatible FSM output cardinality and lookup table size.\n&apos;)
 93          sys.exit (1)
 94  
 95      tot_s=0 # total number of transmitted shorts
 96      terr_s=0 # total number of shorts in error
 97      terr_p=0 # total number of packets in error
 98  
 99      for i in range(rep):
100          (s,e)=run_test(f,Kb,bitspersymbol,K,channel,modulation,dimensionality,tot_constellation,N0,-int(666+i)) # run experiment with different seed to get different data and noise realizations
101          tot_s=tot_s+s
102          terr_s=terr_s+e
103          terr_p=terr_p+(terr_s!=0)
104          if ((i+1)%100==0) : # display progress
105              print(i+1,terr_p, &apos;%.2e&apos; % ((1.0*terr_p) / (i+1)),tot_s,terr_s, &apos;%.2e&apos; % ((1.0*terr_s) / tot_s))
106      # estimate of the (short or symbol) error rate
107      print(rep,terr_p, &apos;%.2e&apos; % ((1.0*terr_p) / (i+1)),tot_s,terr_s, &apos;%.2e&apos; % ((1.0*terr_s) / tot_s))
108  
109  
110  if __name__ == &apos;__main__&apos;:
111      main (sys.argv[1:])
</programlisting>
