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