<?xml version="1.0" encoding="ISO-8859-1"?>
<programlisting>
  1  #!/usr/bin/env python
  2  
  3  from gnuradio import gr
  4  from gnuradio import audio
  5  from gnuradio import trellis, digital, filter, blocks
  6  from gnuradio import eng_notation
  7  import math
  8  import sys
  9  import random
 10  import fsm_utils
 11  
 12  try:
 13      from gnuradio import analog
 14  except ImportError:
 15      sys.stderr.write(&quot;Error: Program requires gr-analog.\n&quot;)
 16      sys.exit(1)
 17  
 18  
 19  def run_test(f, Kb, bitspersymbol, K, channel, modulation, dimensionality, tot_constellation, N0, seed):
 20      tb = gr.top_block()
 21      L = len(channel)
 22  
 23      # TX
 24      # this for loop is TOO slow in python!!!
 25      packet = [0] * (K + 2 * L)
 26      random.seed(seed)
 27      for i in range(len(packet)):
 28          packet[i] = random.randint(0, 2**bitspersymbol - 1)  # random symbols
 29      for i in range(L):  # first/last L symbols set to 0
 30          packet[i] = 0
 31          packet[len(packet) - i - 1] = 0
 32      src = blocks.vector_source_s(packet, False)
 33      mod = digital.chunks_to_symbols_sf(modulation[1], modulation[0])
 34  
 35      # CHANNEL
 36      isi = filter.fir_filter_fff(1, channel)
 37      add = blocks.add_ff()
 38      noise = analog.noise_source_f(analog.GR_GAUSSIAN, math.sqrt(N0 / 2), seed)
 39  
 40      # RX
 41      # skip the first L samples since you know they are coming from the L zero symbols
 42      skip = blocks.skiphead(gr.sizeof_float, L)
 43      # metrics = trellis.metrics_f(f.O(),dimensionality,tot_constellation,digital.TRELLIS_EUCLIDEAN) # data preprocessing to generate metrics for Viterbi
 44      # va = trellis.viterbi_s(f,K+L,0,0) # Put -1 if the Initial/Final states are not set.
 45      # 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...
 46      va = trellis.viterbi_combined_s(
 47          f, K + L, 0, 0, dimensionality, tot_constellation, digital.TRELLIS_EUCLIDEAN)
 48      dst = blocks.vector_sink_s()
 49  
 50      tb.connect(src, mod)
 51      tb.connect(mod, isi, (add, 0))
 52      tb.connect(noise, (add, 1))
 53      #tb.connect (add,metrics)
 54      #tb.connect (metrics,va,dst)
 55      tb.connect(add, skip, va, dst)
 56  
 57      tb.run()
 58  
 59      data = dst.data()
 60      ntotal = len(data) - L
 61      nright = 0
 62      for i in range(ntotal):
 63          if packet[i + L] == data[i]:
 64              nright = nright + 1
 65          # else:
 66              # print &quot;Error in &quot;, i
 67  
 68      return (ntotal, ntotal - nright)
 69  
 70  
 71  def main(args):
 72      nargs = len(args)
 73      if nargs == 2:
 74          esn0_db = float(args[0])
 75          rep = int(args[1])
 76      else:
 77          sys.stderr.write(
 78              &apos;usage: test_viterbi_equalization1.py Es/No_db  repetitions\n&apos;)
 79          sys.exit(1)
 80  
 81      # system parameters
 82      Kb = 2048  # packet size in bits
 83      modulation = fsm_utils.pam4  # see fsm_utlis.py for available predefined modulations
 84      # see fsm_utlis.py for available predefined test channels
 85      channel = fsm_utils.c_channel
 86      # generate the FSM automatically
 87      f = trellis.fsm(len(modulation[1]), len(channel))
 88      # bits per FSM input symbol
 89      bitspersymbol = int(round(math.log(f.I()) / math.log(2)))
 90      K = Kb / bitspersymbol  # packet size in trellis steps
 91  
 92      # generate the lookup table (normalize energy to 1)
 93      tot_channel = fsm_utils.make_isi_lookup(modulation, channel, True)
 94      dimensionality = tot_channel[0]
 95      tot_constellation = tot_channel[1]
 96      N0 = pow(10.0, -esn0_db / 10.0)  # noise variance
 97      if len(tot_constellation) / dimensionality != f.O():
 98          sys.stderr.write(
 99              &apos;Incompatible FSM output cardinality and lookup table size.\n&apos;)
100          sys.exit(1)
101  
102      tot_s = 0  # total number of transmitted shorts
103      terr_s = 0  # total number of shorts in error
104      terr_p = 0  # total number of packets in error
105  
106      for i in range(rep):
107          (s, e) = run_test(f, Kb, bitspersymbol, K, channel, modulation, dimensionality, tot_constellation,
108                            N0, -int(666 + i))  # run experiment with different seed to get different data and noise realizations
109          tot_s = tot_s + s
110          terr_s = terr_s + e
111          terr_p = terr_p + (terr_s != 0)
112          if ((i + 1) % 100 == 0):  # display progress
113              print(i + 1, terr_p, &apos;%.2e&apos; % ((1.0 * terr_p) / (i + 1)),
114                    tot_s, terr_s, &apos;%.2e&apos; % ((1.0 * terr_s) / tot_s))
115      # estimate of the (short or symbol) error rate
116      print(rep, terr_p, &apos;%.2e&apos; % ((1.0 * terr_p) / (i + 1)),
117            tot_s, terr_s, &apos;%.2e&apos; % ((1.0 * terr_s) / tot_s))
118  
119  
120  if __name__ == &apos;__main__&apos;:
121      main(sys.argv[1:])
</programlisting>
