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
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
|
% ofdm_rx.m
% David Rowe May 2018
%
% OFDM file based , uncoded rx to unit test core OFDM modem. See also
% ofdm_ldpc_rx which includes LDPC and interleaving, and ofdm_demod.c
function ofdm_rx(filename, mode="700D", error_pattern_filename)
ofdm_lib;
more off;
% init modem
[bps Rs Tcp Ns Nc] = ofdm_init_mode(mode);
states = ofdm_init(bps, Rs, Tcp, Ns, Nc);
print_config(states);
ofdm_load_const;
states.verbose = 0;
% load real samples from file
Ascale = states.amp_scale/2; % as input is a real valued signal
frx=fopen(filename,"rb"); rx = fread(frx, Inf, "short")/Ascale; fclose(frx);
Nsam = length(rx); Nframes = floor(Nsam/Nsamperframe);
prx = 1;
% OK re-generate tx frame for BER calcs
tx_bits = create_ldpc_test_frame(states, coded_frame=0);
% init logs and BER stats
rx_bits = []; rx_np_log = []; timing_est_log = []; delta_t_log = []; foff_est_hz_log = [];
phase_est_pilot_log = []; sig_var_log = []; noise_var_log = []; channel_est_log = [];
Terrs = Tbits = Terrs_coded = Tbits_coded = Tpackets = Tpacketerrs = frame_count = 0;
Nbitspervocframe = 28;
Nerrs_coded_log = Nerrs_log = [];
error_positions = [];
% 'prime' rx buf to get correct coarse timing (for now)
prx = 1;
nin = Nsamperframe+2*(M+Ncp);
%states.rxbuf(Nrxbuf-nin+1:Nrxbuf) = rx(prx:nin);
%prx += nin;
states.verbose = 1;
Nerrs = 0; rx_uw = zeros(1,states.Nuwbits);
% main loop ----------------------------------------------------------------
for f=1:Nframes
% insert samples at end of buffer, set to zero if no samples
% available to disable phase estimation on future pilots on last
% frame of simulation
lnew = min(Nsam-prx,states.nin);
rxbuf_in = zeros(1,states.nin);
if lnew
rxbuf_in(1:lnew) = rx(prx:prx+lnew-1);
end
prx += states.nin;
if strcmp(states.sync_state,'search')
[timing_valid states] = ofdm_sync_search(states, rxbuf_in);
end
if strcmp(states.sync_state,'synced') || strcmp(states.sync_state,'trial')
[rx_bits states aphase_est_pilot_log arx_np arx_amp] = ofdm_demod(states, rxbuf_in);
[rx_uw payload_syms payload_amps txt_bits] = disassemble_modem_frame(states, arx_np, arx_amp);
errors = xor(tx_bits, rx_bits);
Nerrs = sum(errors);
aber = Nerrs/Nbitsperframe;
% we are in sync so log states
rx_np_log = [rx_np_log arx_np];
timing_est_log = [timing_est_log states.timing_est];
delta_t_log = [delta_t_log states.delta_t];
foff_est_hz_log = [foff_est_hz_log states.foff_est_hz];
phase_est_pilot_log = [phase_est_pilot_log; aphase_est_pilot_log];
sig_var_log = [sig_var_log states.sig_var];
noise_var_log = [noise_var_log states.noise_var];
channel_est_log = [channel_est_log; states.achannel_est_rect];
% measure uncoded bit errors on modem frame
Nerrs_log = [Nerrs_log Nerrs];
Terrs += Nerrs;
Tbits += Nbitsperframe;
frame_count++;
end
states = sync_state_machine(states, rx_uw);
if states.verbose
printf("f: %2d nin: %4d state: %-10s uw_errors: %2d %1d pbw: %-4s Nerrs: %3d foff: %5.1f clkOff: %5.0f\n",
f, states.nin, states.last_sync_state, states.uw_errors, states.sync_counter, states.phase_est_bandwidth, Nerrs,
states.foff_est_hz, states.clock_offset_est*1E6);
end
% act on any events returned by state machine
if states.sync_start
Nerrs_log = [];
Terrs = Tbits = frame_count = 0;
rx_np_log = [];
sig_var_log = []; noise_var_log = [];
end
end
printf("\nBER..: %5.4f Tbits: %5d Terrs: %5d\n", Terrs/(Tbits+1E-12), Tbits, Terrs);
% If we have enough frames, calc BER discarding first few frames where freq
% offset is adjusting
Ndiscard = 20;
if frame_count > Ndiscard
Terrs -= sum(Nerrs_log(1:Ndiscard)); Tbits -= Ndiscard*Nbitsperframe;
printf("BER2.: %5.4f Tbits: %5d Terrs: %5d\n", Terrs/Tbits, Tbits, Terrs);
end
%EsNo_est = mean(sig_var_log(floor(end/2):end))/mean(noise_var_log(floor(end/2):end));
EsNo_est = mean(sig_var_log)/mean(noise_var_log);
EsNo_estdB = 10*log10(EsNo_est);
SNR_estdB = EsNo_estdB + 10*log10(Nc*Rs/3000);
printf("Es/No est dB: % -4.1f SNR3k: %3.2f %f %f\n", EsNo_estdB, SNR_estdB, mean(sig_var_log), mean(noise_var_log));
figure(1); clf;
plot(rx_np_log,'+');
plot(rx_np_log(floor(end/2):end),'+');
mx = 2*max(abs(rx_np_log));
axis([-mx mx -mx mx]);
title('Scatter');
figure(2); clf;
plot(phase_est_pilot_log(:,2:Nc),'g+', 'markersize', 5);
title('Phase est');
axis([1 length(phase_est_pilot_log) -pi pi]);
figure(3); clf;
subplot(211)
stem(delta_t_log)
title('delta t');
subplot(212)
plot(timing_est_log);
title('timing est');
figure(4); clf;
plot(foff_est_hz_log)
mx = max(abs(foff_est_hz_log))+1;
axis([1 max(Nframes,2) -mx mx]);
title('Fine Freq');
ylabel('Hz')
figure(5); clf;
stem(Nerrs_log);
title('Errors/modem frame')
axis([1 length(Nerrs_log) 0 Nbitsperframe*rate/2]);
figure(6); clf;
plot(10*log10(sig_var_log),'b;Es;');
hold on;
plot(10*log10(noise_var_log),'r;No;');
snr_estdB = 10*log10(sig_var_log) - 10*log10(noise_var_log) + 10*log10(Nc*Rs/3000);
snr_smoothed_estdB = filter(0.1,[1 -0.9],snr_estdB);
plot(snr_smoothed_estdB,'g;SNR3k;');
hold off;
title('Signal and Noise Power estimates');
if nargin == 3
fep = fopen(error_pattern_filename, "wb");
fwrite(fep, error_positions, "short");
fclose(fep);
end
endfunction
|
