      1  #!/usr/bin/env python
      2
      3  from gnuradio import gr
      4  from gnuradio import audio
      5  from gnuradio import trellis, digital, 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("Error: Program requires gr-analog.\n")
     16      sys.exit(1)
     17
     18
     19  def run_test(f, Kb, bitspersymbol, K, dimensionality, constellation, N0, seed):
     20      tb = gr.top_block()
     21
     22      # TX
     23      src = blocks.lfsr_32k_source_s()
     24      src_head = blocks.head(gr.sizeof_short, Kb / 16)  # packet size in shorts
     25      # unpack shorts to symbols compatible with the FSM input cardinality
     26      s2fsmi = blocks.packed_to_unpacked_ss(bitspersymbol, gr.GR_MSB_FIRST)
     27      enc = trellis.encoder_ss(f, 0)  # initial state = 0
     28      mod = digital.chunks_to_symbols_sf(constellation, dimensionality)
     29
     30      # CHANNEL
     31      add = blocks.add_ff()
     32      noise = analog.noise_source_f(analog.GR_GAUSSIAN, math.sqrt(N0 / 2), seed)
     33
     34      # RX
     35      # data preprocessing to generate metrics for Viterbi
     36      metrics = trellis.metrics_f(
     37          f.O(), dimensionality, constellation, digital.TRELLIS_EUCLIDEAN)
     38      # Put -1 if the Initial/Final states are not set.
     39      va = trellis.viterbi_s(f, K, 0, -1)
     40      fsmi2s = blocks.unpacked_to_packed_ss(
     41          bitspersymbol, gr.GR_MSB_FIRST)  # pack FSM input symbols to shorts
     42      dst = blocks.check_lfsr_32k_s()
     43
     44      tb.connect(src, src_head, s2fsmi, enc, mod)
     45      tb.connect(mod, (add, 0))
     46      tb.connect(noise, (add, 1))
     47      tb.connect(add, metrics)
     48      tb.connect(metrics, va, fsmi2s, dst)
     49
     50      tb.run()
     51
     52      # A bit of cheating: run the program once and print the
     53      # final encoder state.
     54      # Then put it as the last argument in the viterbi block
     55      # print "final state = " , enc.ST()
     56
     57      ntotal = dst.ntotal()
     58      nright = dst.nright()
     59      runlength = dst.runlength()
     60      return (ntotal, ntotal - nright)
     61
     62
     63  def main(args):
     64      nargs = len(args)
     65      if nargs == 3:
     66          fname = args[0]
     67          esn0_db = float(args[1])  # Es/No in dB
     68          # number of times the experiment is run to collect enough errors
     69          rep = int(args[2])
     70      else:
     71          sys.stderr.write(
     72              'usage: test_tcm.py fsm_fname Es/No_db  repetitions\n')
     73          sys.exit(1)
     74
     75      # system parameters
     76      f = trellis.fsm(fname)  # get the FSM specification from a file
     77      # packet size in bits (make it multiple of 16 so it can be packed in a short)
     78      Kb = 1024 * 16
     79      # bits per FSM input symbol
     80      bitspersymbol = int(round(math.log(f.I()) / math.log(2)))
     81      K = Kb / bitspersymbol  # packet size in trellis steps
     82      modulation = fsm_utils.psk4  # see fsm_utlis.py for available predefined modulations
     83      dimensionality = modulation[0]
     84      constellation = modulation[1]
     85      if len(constellation) / dimensionality != f.O():
     86          sys.stderr.write(
     87              'Incompatible FSM output cardinality and modulation size.\n')
     88          sys.exit(1)
     89      # calculate average symbol energy
     90      Es = 0
     91      for i in range(len(constellation)):
     92          Es = Es + constellation[i]**2
     93      Es = Es / (len(constellation) // dimensionality)
     94      N0 = Es / pow(10.0, esn0_db / 10.0)  # noise variance
     95
     96      tot_s = 0
     97      terr_s = 0
     98      for i in range(rep):
     99          # run experiment with different seed to get different noise realizations
    100          (s, e) = run_test(f, Kb, bitspersymbol, K,
    101                            dimensionality, constellation, N0, -int(666 + i))
    102          tot_s = tot_s + s
    103          terr_s = terr_s + e
    104          if (i % 100 == 0):
    105              print(i, s, e, tot_s, terr_s, '%e' % ((1.0 * terr_s) / tot_s))
    106      # estimate of the (short) error rate
    107      print(tot_s, terr_s, '%e' % ((1.0 * terr_s) / tot_s))
    108
    109
    110  if __name__ == '__main__':
    111      main(sys.argv[1:])