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