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
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
|
% fsk_lib_demo.m
% Uncoded FSK modem demo
fsk_lib;
% set up waveform
function [states M bits_per_frame] = modem_init(Rs,Fs,df)
M = 4;
states = fsk_init(Fs,Rs,M,P=8,nsym=100);
bits_per_frame = 512;
states.tx_real = 0; % complex signal
states.tx_tone_separation = 250;
states.ftx = -2.5*states.tx_tone_separation + states.tx_tone_separation*(1:M);
states.fest_fmin = -Fs/2;
states.fest_fmax = +Fs/2;
states.fest_min_spacing = Rs/2;
states.df = df;
states.ber_valid_thresh = 0.1;
states.ber_invalid_thresh = 0.2;
end
% Run a complete modem (freq and timing estimators running) at a
% single Eb/No point. At low Eb/No the estimators occasionally fall
% over so we get complete junk, we consider that case a packet error
% and exclude it from the BER estimation.
function [states ber per] = modem_run_test(EbNodB = 10, num_frames=10, Fs=8000, Rs=100, df=0, plots=0)
randn('state',1); rand('state',1);
[states M bits_per_frame] = modem_init(Rs, Fs, df);
N = states.N;
if plots; states.verbose = 0x4; end
EbNo = 10^(EbNodB/10);
variance = states.Fs/(states.Rs*EbNo*states.bitspersymbol);
nbits = bits_per_frame*num_frames;
test_frame = round(rand(1,bits_per_frame)); tx_bits = [];
for f=1:num_frames
tx_bits = [tx_bits test_frame];
end
tx = fsk_mod(states, tx_bits);
noise = sqrt(variance/2)*randn(length(tx),1) + j*sqrt(variance/2)*randn(length(tx),1);
rx = tx + noise;
run_frames = floor(length(rx)/N)-1;
st = 1; f_log = []; f_log2 = []; rx_bits = []; rx_bits2 = [];
for f=1:run_frames
% extract nin samples from input stream
nin = states.nin;
en = st + states.nin - 1;
% due to nin variations it's possible to overrun buffer
if en < length(rx)
sf = rx(st:en);
states = est_freq(states, sf, states.M); states.f = states.f2;
[arx_bits states] = fsk_demod(states, sf);
rx_bits = [rx_bits arx_bits];
f_log = [f_log; states.f];
st += nin;
end
end
num_frames=floor(length(rx_bits)/bits_per_frame);
log_nerrs = []; num_frames_rx = 0;
for f=1:num_frames-1
st = (f-1)*bits_per_frame + 1; en = (f+1)*bits_per_frame;
states = ber_counter(states, test_frame, rx_bits(st:en));
log_nerrs = [log_nerrs states.nerr];
if states.ber_state; num_frames_rx++; end
end
if states.Terrs
printf("Fs: %d Rs: %d df % 3.2f EbNo: %4.2f ftx: %3d frx: %3d nbits: %4d nerrs: %3d ber: %4.3f\n",
Fs, Rs, df, EbNodB, num_frames, num_frames_rx, states.Tbits, states.Terrs, states.Terrs/states.Tbits);
ber = states.Terrs/states.Tbits;
else
ber = 0.5;
end
if plots
figure(1); clf;
ideal=ones(length(f_log),1)*states.ftx;
plot((1:length(f_log)),ideal(:,1),'bk;ideal;')
hold on; plot((1:length(f_log)),ideal(:,2:states.M),'bk'); hold off;
hold on;
plot(f_log(:,1), 'linewidth', 2, 'b;peak;');
plot(f_log(:,2:states.M), 'linewidth', 2, 'b');
hold off;
xlabel('Time (frames)'); ylabel('Frequency (Hz)');
figure(2); clf; plot(log_nerrs); title('Errors per frame');
end
per = 1 - num_frames_rx/num_frames;
end
[states ber per] = modem_run_test(EbNodB=6);
BER_theory=0.01579; % for Eb/No = 6dB
if ber < 1.5*BER_theory
printf("PASS\n");
end
|
