      1  #!/usr/bin/env python
      2
      3  from gnuradio import gr
      4  from gnuradio import audio
      5  from gnuradio import trellis, digital
      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,dimensionality,constellation,N0,seed):
     13      tb = gr.top_block ()
     14
     15      # TX
     16      src = gr.lfsr_32k_source_s()
     17      src_head = gr.head (gr.sizeof_short,Kb/16) # packet size in shorts
     18      s2fsmi = gr.packed_to_unpacked_ss(bitspersymbol,gr.GR_MSB_FIRST) # unpack shorts to symbols compatible with the FSM input cardinality
     19      enc = trellis.encoder_ss(f,0) # initial state = 0
     20      mod = gr.chunks_to_symbols_sf(constellation,dimensionality)
     21
     22      # CHANNEL
     23      add = gr.add_ff()
     24      noise = gr.noise_source_f(gr.GR_GAUSSIAN,math.sqrt(N0/2),seed)
     25
     26      # RX
     27      metrics = trellis.metrics_f(f.O(),dimensionality,constellation,digital.TRELLIS_EUCLIDEAN) # data preprocessing to generate metrics for Viterbi
     28      va = trellis.viterbi_s(f,K,0,-1) # Put -1 if the Initial/Final states are not set.
     29      fsmi2s = gr.unpacked_to_packed_ss(bitspersymbol,gr.GR_MSB_FIRST) # pack FSM input symbols to shorts
     30      dst = gr.check_lfsr_32k_s();
     31
     32      tb.connect (src,src_head,s2fsmi,enc,mod)
     33      tb.connect (mod,(add,0))
     34      tb.connect (noise,(add,1))
     35      tb.connect (add,metrics)
     36      tb.connect (metrics,va,fsmi2s,dst)
     37
     38      tb.run()
     39
     40      # A bit of cheating: run the program once and print the
     41      # final encoder state.
     42      # Then put it as the last argument in the viterbi block
     43      #print "final state = " , enc.ST()
     44
     45      ntotal = dst.ntotal ()
     46      nright = dst.nright ()
     47      runlength = dst.runlength ()
     48      return (ntotal,ntotal-nright)
     49
     50
     51  def main(args):
     52      nargs = len (args)
     53      if nargs == 3:
     54          fname=args[0]
     55          esn0_db=float(args[1]) # Es/No in dB
     56          rep=int(args[2]) # number of times the experiment is run to collect enough errors
     57      else:
     58          sys.stderr.write ('usage: test_tcm.py fsm_fname Es/No_db  repetitions\n')
     59          sys.exit (1)
     60
     61      # system parameters
     62      f=trellis.fsm(fname) # get the FSM specification from a file
     63      Kb=1024*16  # packet size in bits (make it multiple of 16 so it can be packed in a short)
     64      bitspersymbol = int(round(math.log(f.I())/math.log(2))) # bits per FSM input symbol
     65      K=Kb/bitspersymbol # packet size in trellis steps
     66      modulation = fsm_utils.psk4 # see fsm_utlis.py for available predefined modulations
     67      dimensionality = modulation[0]
     68      constellation = modulation[1]
     69      if len(constellation)/dimensionality != f.O():
     70          sys.stderr.write ('Incompatible FSM output cardinality and modulation size.\n')
     71          sys.exit (1)
     72      # calculate average symbol energy
     73      Es = 0
     74      for i in range(len(constellation)):
     75          Es = Es + constellation[i]**2
     76      Es = Es / (len(constellation)/dimensionality)
     77      N0=Es/pow(10.0,esn0_db/10.0); # noise variance
     78
     79      tot_s=0
     80      terr_s=0
     81      for i in range(rep):
     82          (s,e)=run_test(f,Kb,bitspersymbol,K,dimensionality,constellation,N0,-long(666+i)) # run experiment with different seed to get different noise realizations
     83          tot_s=tot_s+s
     84          terr_s=terr_s+e
     85          if (i%100==0):
     86              print i,s,e,tot_s,terr_s, '%e' % ((1.0*terr_s)/tot_s)
     87      # estimate of the (short) error rate
     88      print tot_s,terr_s, '%e' % ((1.0*terr_s)/tot_s)
     89
     90
     91  if __name__ == '__main__':
     92      main (sys.argv[1:])