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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,channel,modulation,dimensionality,tot_constellation,N0,seed):
13 fg = gr.flow_graph ()
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,trellis.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,trellis.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 fg.connect (src,mod)
41 fg.connect (mod,isi,(add,0))
42 fg.connect (noise,(add,1))
43 #fg.connect (add,metrics)
44 #fg.connect (metrics,va,dst)
45 fg.connect (add,skip,va,dst)
46
47 fg.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:])
</programlisting>
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