% David Rowe
% 10 April 2014
%
-% Experiments in fuzzy gray codes. Idea is that with one bit error
-% in the codeword only changes the encoded value by at most 1.
+% Various experiments in fuzzy gray codes and quantising and
+% transmitting scalars. Idea is that with one bit error in the
+% codeword only changes the encoded value by at most 1.
1;
end
endfunction
-function sim_out = test_baseline_uncoded(Ebvec, Nbits, Ntrials)
+function sim_out = test_baseline_uncoded(Ebvec, Nbits, Ntrials, enable_error_log)
Nlevels = 2.^ Nbits; powersOfTwo = 2 .^ fliplr(0:(Nbits-1));
Nsymb = Nbits;
sim_out.qnoise_log = zeros(length(Ebvec),Ntrials);
+ sim_out.error_log = [];
for ne = 1:length(Ebvec)
EbNodB = Ebvec(ne);
Nerrs = sum(error_positions);
Terrs += Nerrs;
Tbits += length(tx_bits);
+ if enable_error_log
+ sim_out.error_log = [sim_out.error_log error_positions];
+ end
+
+ rx_index = (powersOfTwo * rx_bits');
+ rx_value = unquantise_value(rx_index, 0, 1, Nlevels);
+
+ qsignal += tx_value*tx_value;
+ qnoise += (tx_value - rx_value) .^ 2;
+ sim_out.qnoise_log(ne,nn) = tx_value - rx_value;
+ end
+
+ sim_out.TERvec(ne) = Terrs;
+ sim_out.BERvec(ne) = Terrs/Tbits;
+ sim_out.QSNRvec(ne) = 10*log10(qsignal/qnoise);
+ printf("EbNo (dB): %3.2f Terrs: %6d BER %1.4f QSNR (dB): %3.2f\n",
+ EbNodB, Terrs, Terrs/Tbits, 10*log10(qsignal/qnoise));
+ end
+
+endfunction
+
+function sim_out = test_varpower(Ebvec, Nbits, Ntrials, amps, enable_error_log)
+ Nlevels = 2.^ Nbits; powersOfTwo = 2 .^ fliplr(0:(Nbits-1));
+ Nsymb = Nbits;
+
+ sim_out.qnoise_log = zeros(length(Ebvec), Ntrials);
+ sim_out.error_log = [];
+
+ for ne = 1:length(Ebvec)
+ EbNodB = Ebvec(ne);
+ EbNo = 10^(EbNodB/10);
+
+ variance = 1/EbNo;
+
+ Terrs = 0; Tbits = 0;
+ qsignal = qnoise = 0;
+
+ for nn = 1:Ntrials
+
+ tx_value = rand(1,1);
+ tx_index = quantise_value(tx_value, 0, 1, Nlevels);
+ tx_bits = dec2bin(tx_index, Nbits) - '0';
+ tx_symbols = (-1 + 2*tx_bits) .* amps;
+
+ % AWGN noise and phase/freq offset channel simulation
+ % 0.5 factor ensures var(noise) == variance , i.e. splits power between Re & Im
+
+ noise = sqrt(variance*0.5)*(randn(1,Nsymb) + j*randn(1,Nsymb));
+ rx_symbols = tx_symbols + noise;
+
+ rx_bits = rx_symbols > 0;
+
+ error_positions = xor(rx_bits, tx_bits);
+ if enable_error_log
+ sim_out.error_log = [sim_out.error_log error_positions];
+ end
+ Nerrs = sum(error_positions);
+ Terrs += Nerrs;
+ Tbits += length(tx_bits);
rx_index = (powersOfTwo * rx_bits');
rx_value = unquantise_value(rx_index, 0, 1, Nlevels);
bad_distance = 0;
for i=1:Nvalid
for k=i+1:Nvalid
- distance = sum(bitxor(valid_codewords(i,:), valid_codewords(k,:)));
+ distance = sum(bitxor(valid_codewords(i,:), valid_codewords(k,:)))
if distance < 2
bad_distance++;
end
end
endfunction
-function valid_codewords = fuzzy_code_create(ndata, nparity)
+function set_codewords = fuzzy_code_create(ndata, nparity)
Nbits = ndata + nparity;
Nvalid = 2 .^ ndata;
- codewords = binary_to_gray(0:(2 .^ Nbits)-1);
- valid_codewords = dec2bin(codewords(1:2:(2 .^ Nbits)), Nbits) - '0';
+ M = 2 .^ Nbits;
- % check all valid codewords have a hamming distance of at least 2^nparity
+ codewords = dec2bin(0:(M-1), Nbits) - '0';
- bad_distance = 0;
- for i=1:Nvalid
- for k=i+1:Nvalid
- distance = sum(bitxor(valid_codewords(i,:), valid_codewords(k,:)));
- if distance < 2
- bad_distance++;
+ set_codewords(1,:) = codewords(1,:);
+
+ for i=1:Nvalid-1
+
+ % measure distance from current set to all codewords
+
+ for m=1:i
+ printf("%d: ", m);
+ for k=1:length(codewords);
+ d(m,k) = sum(bitxor(set_codewords(m,:), codewords(k,:)));
+ printf("%d ", d(m,k));
end
+ printf("\n");
end
- end
- if bad_distance != 0
- printf("Error: Nvalid: %d bad_distance: %d\n", Nvalid, bad_distance);
- return;
- end
+ % choose new codeword for set that has maximum distance from current set
+
+ dmax = 0; best_cw = 1;
+ for k=1:length(codewords);
+ dmin = min(d(:,k));
+ if dmin > dmax
+ dmax = dmin;
+ best_cw = k;
+ end
+ end
+
+ printf("[%d %d]\n", dmax, best_cw);
+ set_codewords(i+1,:) = codewords(best_cw,:)
+ end
+
endfunction
-function sim_out = test_fuzzy_code(Ebvec, Ndata, Ntrials)
- Nparity = 1;
+function sim_out = test_fuzzy_code(Ebvec, Ndata, Nparity, Ntrials)
Nbits = Ndata + Nparity;
Nlevels = 2 .^ Ndata;
Nsymb = Nbits;
end
endfunction
-Ebvec = 0:7;
-Ntrials = 1000;
-Nbits = 5;
-
-baseline = test_baseline_uncoded(Ebvec, Nbits, Ntrials);
-fuzzy = test_fuzzy_code(Ebvec, Nbits, Ntrials);
-
-figure(1);
-clf;
-semilogy(Ebvec, baseline.BERvec)
-xlabel('Eb/N0')
-ylabel('BER')
-grid("minor")
-
-figure(2);
-clf;
-plot(Ebvec, baseline.QSNRvec,'b;baseline;')
-hold on;
-plot(Ebvec, fuzzy.QSNRvec,'r;fuzzy;')
-hold off;
-xlabel('Eb/N0')
-ylabel('SNR')
-grid("minor")
-
-figure(3);
-subplot(211)
-hist(baseline.qnoise_log(4,:),50);
-subplot(212)
-hist(fuzzy.qnoise_log(4,:),50);
-
-figure(4)
-plot(baseline.qnoise_log(4,1:250),'b;baseline;')
-hold on;
-plot(fuzzy.qnoise_log(4,1:250),'r;fuzzy;')
-hold off;
+function compare_baseline_fuzzy
+ Ebvec = 0:7;
+ Ntrials = 1000;
+ Nbits = 3; Nparity = 1;
+
+ baseline = test_baseline_uncoded(Ebvec, Nbits, Ntrials);
+ fuzzy = test_fuzzy_code(Ebvec, Nbits, Nparity, Ntrials);
+
+ figure(1);
+ clf;
+ semilogy(Ebvec, baseline.BERvec)
+ xlabel('Eb/N0')
+ ylabel('BER')
+ grid("minor")
+
+ figure(2);
+ clf;
+ plot(Ebvec, baseline.QSNRvec,'b;baseline;')
+ hold on;
+ plot(Ebvec, fuzzy.QSNRvec,'r;fuzzy;')
+ hold off;
+ xlabel('Eb/N0')
+ ylabel('SNR')
+ grid("minor")
+
+ figure(3);
+ subplot(211)
+ hist(baseline.qnoise_log(4,:),50);
+ subplot(212)
+ hist(fuzzy.qnoise_log(4,:),50);
+
+ figure(4)
+ plot(baseline.qnoise_log(1,1:250),'b;baseline;')
+ hold on;
+ plot(fuzzy.qnoise_log(1,1:250),'r;fuzzy;')
+ hold off;
+endfunction
+
+function compare_baseline_varpower_plot
+ Ebvec = -2:5;
+ Ntrials = 5000;
+ Nbits = 5;
+
+ baseline = test_baseline_uncoded(Ebvec, Nbits, Ntrials, 0);
+ amps = [2 1.5 1.0 0.5 0.5];
+ av_pwr = (amps*amps')/length(amps);
+ amps_norm = amps/sqrt(av_pwr)
+ varpower = test_varpower(Ebvec, Nbits, Ntrials, amps_norm, 0);
+
+ figure(1);
+ clf;
+ semilogy(Ebvec, baseline.BERvec)
+ xlabel('Eb/No (dB)')
+ ylabel('BER')
+ grid("minor")
+ title('BER versus Eb/No')
+
+ figure(2);
+ clf;
+ plot(Ebvec, baseline.QSNRvec,'b;baseline;')
+ hold on;
+ plot(Ebvec, varpower.QSNRvec,'r;varpower;')
+ hold off;
+ xlabel('Eb/No (dB)')
+ ylabel('SNR (dB)')
+ grid("minor")
+ title('Quantiser SNR versus Eb/No')
+
+ figure(3);
+ subplot(211)
+ hist(baseline.qnoise_log(1,:),50);
+ title('Baseline and Variable Power Error Histograms')
+ subplot(212)
+ hist(varpower.qnoise_log(1,:),50);
+
+ figure(4)
+ subplot(211)
+ plot(baseline.qnoise_log(1,1:250),'b;baseline;')
+ title('Baseline and Variable Power Error plots for Eb/No = -2dB')
+ subplot(212)
+ plot(varpower.qnoise_log(1,1:250),'r;varpower;')
+endfunction
+
+function compare_baseline_varpower_error_files
+ Ebvec = -2;
+ Fs = 25; % number of samples per second
+ Nsec = 15; % seconds to simulate
+ Ntrials = Fs*Nsec;
+ Nbits = 5;
+ bits_per_frame = 52;
+ bits_per_frame_rounded = ceil(bits_per_frame/8)*8; % c2enc uses integer number of bytes/frame
+ start_bit = 12; % first energy bit (after 4 voicing, 7 Wo bits)
+
+ baseline = test_baseline_uncoded(Ebvec, Nbits, Ntrials, 1);
+ amps = [2 1.5 1.0 0.5 0.5];
+ av_pwr = (amps*amps')/length(amps);
+ amps_norm = amps/sqrt(av_pwr);
+ varpower = test_varpower(Ebvec, Nbits, Ntrials, amps_norm, 1);
+
+ % construct error patterns to apply to c2enc bit stream
+
+ baseline_errors = [];
+ for i=1:Ntrials
+ error_positions = baseline.error_log(Nbits*(i-1)+1:Nbits*i);
+ baseline_errors = [baseline_errors zeros(1,start_bit-1) error_positions ...
+ zeros(1, bits_per_frame_rounded - Nbits - (start_bit-1))];
+ end
+
+ varpower_errors = [];
+ for i=1:Ntrials
+ error_positions = varpower.error_log(Nbits*(i-1)+1:Nbits*i);
+ varpower_errors = [varpower_errors zeros(1,start_bit-1) error_positions ...
+ zeros(1, bits_per_frame_rounded - Nbits - (start_bit-1))];
+ end
+
+ % save error patterns
+
+ fep=fopen("energy_errors_baseline.bin","wb"); fwrite(fep, baseline_errors, "short"); fclose(fep);
+ fep=fopen("energy_errors_varpower.bin","wb"); fwrite(fep, varpower_errors, "short"); fclose(fep);
+endfunction
+
+%compare_baseline_varpower_plot
+%compare_baseline_varpower_error_files
+
+%compare_baseline_fuzzy
+%fuzzy_code_create(3,1)
projects / freetel-svn-tracking.git / commitdiff