      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,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 = gr.vector_source_s(packet,False)
     26      mod = gr.chunks_to_symbols_sf(modulation[1],modulation[0])
     27
     28      # CHANNEL
     29      isi = gr.fir_filter_fff(1,channel)
     30      add = gr.add_ff()
     31      noise = gr.noise_source_f(gr.GR_GAUSSIAN,math.sqrt(N0/2),seed)
     32
     33      # RX
     34      skip = gr.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,digital.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,digital.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 = gr.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 "Error in ", 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 ('usage: test_viterbi_equalization1.py Es/No_db  repetitions\n')
     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 ('Incompatible FSM output cardinality and lookup table size.\n')
     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, '%.2e' % ((1.0*terr_p)/(i+1)),tot_s,terr_s, '%.2e' % ((1.0*terr_s)/tot_s)
     97      # estimate of the (short or symbol) error rate
     98      print rep,terr_p, '%.2e' % ((1.0*terr_p)/(i+1)),tot_s,terr_s, '%.2e' % ((1.0*terr_s)/tot_s)
     99
    100
    101  if __name__ == '__main__':
    102      main (sys.argv[1:])