1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
|
#!/usr/bin/env python
# _*_ coding: utf8 _*_
# Andreas Müller, 2008
# andrmuel@ee.ethz.ch
#
# this code may be freely used under GNU GPL conditions
"""
Simulate channel with frequency offset
"""
import math, random, pylab
import dab_tb, ber
NUM_BYTES = 1000000
MODES=[1,2,3,4]
FREQ_OFFSET_RANGE = range(-300000,300000,10000)
FREQ_OFFSET_RANGE = range(0,1000,100)
PLOT_FORMAT=['-','-x','--x','-.x',':x']
# initialise test flowgraph
tb = dab_tb.dab_ofdm_testbench(ber_sink=True)
tb.gen_random_bytes(NUM_BYTES)
# prepeare plot
#pylab.title("BER in channel with frequency shift") # add caption in LaTeX -> looks better
pylab.xlabel("Frequency shift [Hz]")
pylab.ylabel("BER")
# open logfile
logfile = open("freq_shift_ber_log.txt",'w')
logfile.write("number of bytes: " + str(NUM_BYTES) + "\nFrequency shift range: " + str(FREQ_OFFSET_RANGE) + "\n\n")
for mode in MODES:
print "Mode: "+str(mode)+"\n-------\n"
tb.setup_flowgraph(mode)
ber_values = []
bytes_received = []
# estimate signal energy for this mode (disturbed by FFT ...)
tb.set_signal_energy(1)
tb.set_noise_energy(0)
tb.run()
tb.set_power_correction(tb.probe_signal.level())
print "estimated energy: " + str(tb.probe_signal.level()) + "\n"
for offset in FREQ_OFFSET_RANGE:
print "Mode: "+str(mode)+" Offset: "+str(offset)
# reset and run the test
tb.rewind_sources()
tb.clear_sinks()
tb.clear_state()
tb.set_carrier_frequency_offset(offset)
tb.run()
print "signal power: " + str(tb.probe_signal.level())
print "total power: " + str(tb.probe_total.level())
# get the result
bytes_received.append(tb.sink.bytecount())
print "bytes sent: " + str(NUM_BYTES)
print "bytes received: " + str(tb.sink.bytecount())
ber_values.append(tb.sink.ber())
print "BER: " + str(ber_values[-1])
print
# write log
logfile.write("Mode: " + str(mode)+"\n" +
"=======\n\n" +
"Frequency shift: BER (number of bytes received)\n" +
"-----------------------------------\n")
for i in range(0,len(FREQ_OFFSET_RANGE)):
logfile.write(str(FREQ_OFFSET_RANGE[i])+": "+str(ber_values[i])+" (" + str(bytes_received[i]) + ")\n")
logfile.write("\n\n")
# plot it:
if sum([abs(x) for x in ber_values])==0:
print "all BER values are 0 - not plotting"
else:
pylab.semilogy(FREQ_OFFSET_RANGE, ber_values, PLOT_FORMAT[mode], label="Mode "+str(mode))
# pylab.plot(FREQ_OFFSET_RANGE, ber_values, PLOT_FORMAT[mode], label="Mode "+str(mode))
logfile.close()
# pylab.axis([FREQ_OFFSET_RANGE[0],FREQ_OFFSET_RANGE[-1],0,0.52])
pylab.legend()
pylab.show()
|
