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<?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
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 fg = gr.flow_graph ()
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,trellis.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 fg.connect (src,src_head,s2fsmi,enc,mod)
33 fg.connect (mod,(add,0))
34 fg.connect (noise,(add,1))
35 fg.connect (add,metrics)
36 fg.connect (metrics,va,fsmi2s,dst)
37
38 fg.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 (will hopefully be automated in the future...)
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:])
</programlisting>
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