states.Ndft = 8192;
Fs = states.Fs = 8000;
N = states.N = Fs; % processing buffer size, nice big window for f1,f2 estimation
- Rs = states.Rs = 50;
+ Rs = states.Rs = 100;
Ts = states.Ts = Fs/Rs;
states.nsym = N/Ts;
Nmem = states.Nmem = N+2*Ts; % two symbol memory in down converted signals to allow for timing adj
% filter out big jumps due to nin changes
- if abs(d_norm_rx_timing) < 0.1
+ if abs(d_norm_rx_timing) < 0.2
appm = 1E6*d_norm_rx_timing/nsym;
states.ppm = 0.9*states.ppm + 0.1*appm;
end
endfunction
-% Demo modem with simulated tx signal, add noise, channel impairments ----------------------
+% Extract ASCII string from a Horus frame of bits
+
+function str = extract_ascii(states, rx_bits_buf, uw_loc1, uw_loc2)
+ nfield = states.nfield;
+ npad = states.npad;
+
+ str = [];
+ st = uw_loc1 + length(states.uw); % first bit of first char
+ for i=st:nfield+npad:uw_loc2
+ field = rx_bits_buf(i:i+nfield-1);
+ ch_dec = field * (2.^(0:nfield-1))';
+
+ % filter out unlikely characters that bit errors may introduce, and ignore \n
+ if (ch_dec > 31) && (ch_dec < 91)
+ str = [str char(ch_dec)];
+ else
+ str = [str char(32)]; % space is "not sure"
+ end
+ end
+endfunction
+
+
+% Extract as many ASCII packets as we can from a great big buffer of bits
+
+function extract_and_print_packets(states, rx_bits_log)
+
+ % use UWs to delimit start and end of data packets
+
+ bit = 1;
+ nbits = length(rx_bits_log);
+ uw_loc = find_uw(states, bit, rx_bits_log);
+ nfield = states.nfield;
+ npad = states.npad;
+
+ while (uw_loc != -1)
+
+ st = uw_loc;
+ bit = uw_loc + length(states.uw);
+ uw_loc = find_uw(states, bit, rx_bits_log);
+
+ if uw_loc != -1
+ % Now start picking out 7 bit ascii chars from frame. It has some
+ % structure so we can guess where fields are. I hope We don't get
+ % RS232 idle bits stuck into it anywhere, ie "bit fields" don't
+ % change dynamically.
+
+ % dump msg bits so we can use them as a test signal
+ %msg = rx_bits_log(st:uw_loc-1);
+ %save -ascii horus_msg.txt msg
+
+ str = extract_ascii(states, rx_bits_log, st, uw_loc);
+ printf("%s\n", str);
+ end
+
+ endwhile
+endfunction
+
+
+% simulation of tx and rx side, add noise, channel impairments ----------------------
function run_sim
frames = 100;
- EbNodB = 10;
+ EbNodB = 20;
timing_offset = 0.0; % see resample() for clock offset below
test_frame_mode = 4;
- fading = 0; % modulates tx power at 5Hz with 20dB fade depth,
+ fading = 1; % modulates tx power at 2Hz with 10dB fade depth,
% to simulate balloon rotating at end of mission
- df = 0; % tx tone freq drift in Hz/s
+ df = 1; % tx tone freq drift in Hz/s
more off
rand('state',1);
if fading
ltx = length(tx);
- tx = tx .* (1.1 + cos(2*pi*5*(0:ltx-1)/Fs))'; % min amplitude 0.1, -20dB fade, max 3dB
+ tx = tx .* (1.316 + cos(2*pi*2*(0:ltx-1)/Fs))'; % min amplitude 0.1, -10dB fade, max 3dB
end
noise = sqrt(variance)*randn(length(tx),1);
rx = tx + noise;
-
+
% dump simulated rx file
- ftx=fopen("fsk_horus_rx.raw","wb"); rxg = rx*5000; fwrite(ftx, rxg, "short"); fclose(ftx);
+ ftx=fopen("fsk_horus_rx.raw","wb"); rxg = rx*1000; fwrite(ftx, rxg, "short"); fclose(ftx);
timing_offset_samples = round(timing_offset*states.Ts);
st = 1 + timing_offset_samples;
f2_int_resample_log = [];
f1_log = f2_log = [];
EbNodB_log = [];
+ rx_bits_log = [];
for f=1:frames
[rx_bits states] = fsk_horus_demod(states, sf);
rx_bits_buf(1:nsym) = rx_bits_buf(nsym+1:2*nsym);
rx_bits_buf(nsym+1:2*nsym) = rx_bits;
+ rx_bits_log = [rx_bits_log rx_bits];
+
norm_rx_timing_log = [norm_rx_timing_log states.norm_rx_timing];
x_log = [x_log states.x];
f1_int_resample_log = [f1_int_resample_log abs(states.f1_int_resample)];
end
if test_frame_mode == 1
- printf("frames: %d Tbits: %d Terrs: %d BER %3.2f\n", frames, Tbits, Terrs, Terrs/Tbits);
+ printf("frames: %d Tbits: %d Terrs: %d BER %4.3f\n", frames, Tbits, Terrs, Terrs/Tbits);
+ end
+
+ if test_frame_mode == 4
+ extract_and_print_packets(states, rx_bits_log)
end
figure(1);
clf
plot(EbNodB_log);
title('Eb/No estimate')
- mean(EbNodB_log)
endfunction
printf("frame sync and data extraction...\n");
- % Now perform frame sync and extract ASCII text -------------------------------------------
-
- % use UWs to delimit start and end of data packets
-
- bit = 1;
- nbits = length(rx_bits_log);
- uw_loc = find_uw(states, bit, rx_bits_log);
- nfield = states.nfield;
- npad = states.npad;
-
- while (uw_loc != -1)
-
- st = uw_loc;
- bit = uw_loc + length(states.uw);
- uw_loc = find_uw(states, bit, rx_bits_log);
-
- if uw_loc != -1
- % Now start picking out 7 bit ascii chars from frame. It has some
- % structure so we can guess where fields are. I hope We don't get
- % RS232 idle bits stuck into it anywhere, ie "bit fields" don't
- % change dynamically.
-
- % dump msg bits so we can use them as a test signal
- %msg = rx_bits_log(st:uw_loc-1);
- %save -ascii horus_msg.txt msg
+ extract_and_print_packets(states, rx_bits_log)
- str = [];
- st += length(states.uw); % first bit of first char
- for i=st:nfield+npad:uw_loc
- field = rx_bits_log(i:i+nfield-1);
- ch_dec = field * (2.^(0:nfield-1))';
- % filter out unlikely characters that bit errors may introduce, and ignore \n
- if (ch_dec > 31) && (ch_dec < 91)
- str = [str char(ch_dec)];
- else
- str = [str char(32)]; % space is "non sure"
- end
- %printf("i: %d ch_dec: %d ch: %c\n", i, ch_dec, ch_dec);
- end
- printf("%s\n", str);
- end
-
- endwhile
-
endfunction
%run_sim
%rx_bits = demod_file("~/Desktop/vk5arg-3-1.wav");
-rx_bits = demod_file("~/Desktop/fsk_horus_10dB_1000ppm.wav");
+%rx_bits = demod_file("~/Desktop/fsk_horus_10dB_1000ppm.wav");
%rx_bits = demod_file("~/Desktop/fsk_horus_6dB_0ppm.wav");
-%rx_bits = demod_file("fsk_horus_rx.raw");
+rx_bits = demod_file("fsk_horus_rx.raw");
%rx_bits = demod_file("~/Desktop/fsk_horus_20dB_0ppm_20dBfade.wav");
projects / freetel-svn-tracking.git / commitdiff