From: drowe67 Date: Tue, 7 Oct 2014 09:50:04 +0000 (+0000) Subject: maximum likelihood dqpsk, works well for AWGN, not so good for HF X-Git-Url: http://git.whiteaudio.com/gitweb/?a=commitdiff_plain;h=315306d66629f452e45e7171c42e19ea8a6db1ac;p=freetel-svn-tracking.git maximum likelihood dqpsk, works well for AWGN, not so good for HF git-svn-id: https://svn.code.sf.net/p/freetel/code@1879 01035d8c-6547-0410-b346-abe4f91aad63 --- diff --git a/codec2-dev/octave/fdmdv.m b/codec2-dev/octave/fdmdv.m index c6aaf866..415a6d7d 100644 --- a/codec2-dev/octave/fdmdv.m +++ b/codec2-dev/octave/fdmdv.m @@ -1147,7 +1147,7 @@ for c=1:Nc/2 freq_pol(c) = 2*pi*carrier_freq/Fs; freq(c) = exp(j*freq_pol(c)); end -for c=Nc/2+1:Nc +for c=floor(Nc/2)+1:Nc %carrier_freq = (-Nc/2 + c)*Fsep + Fcentre; carrier_freq = (-Nc/2 + c)*Fsep; freq_pol(c) = 2*pi*carrier_freq/Fs; diff --git a/codec2-dev/octave/ldpcut.m b/codec2-dev/octave/ldpcut.m index 80142ba6..9dfdc94e 100644 --- a/codec2-dev/octave/ldpcut.m +++ b/codec2-dev/octave/ldpcut.m @@ -53,7 +53,7 @@ end for nn = 1: Ntrials st = (nn-1)*code_param.symbols_per_frame + 1; en = (nn)*code_param.symbols_per_frame; - detected_data = ldpc_dec(code_param, max_iterations, demod_type, decoder_type, r(st:en), EsNo); + detected_data = ldpc_dec(code_param, max_iterations, demod_type, decoder_type, r(st:en), EsNo, ones(1,code_param.symbols_per_frame)); st = (nn-1)*code_param.data_bits_per_frame + 1; en = (nn)*code_param.data_bits_per_frame; error_positions = xor( detected_data(1:code_param.data_bits_per_frame), data(st:en) ); diff --git a/codec2-dev/octave/test_ml.m b/codec2-dev/octave/test_ml.m new file mode 100644 index 00000000..51dd8cb6 --- /dev/null +++ b/codec2-dev/octave/test_ml.m @@ -0,0 +1,347 @@ +% test_ml.m +% David Rowe Oct 2014 +% + +% Simulation to test FDM QPSK with maximum likelihood decoding on +% fading channels. + +1; + +% main test function + +function sim_out = ber_test(sim_in, modulation) + Fs = 8000; + + verbose = sim_in.verbose; + Ntrials = sim_in.Ntrials; + Esvec = sim_in.Esvec; + plot_scatter = sim_in.plot_scatter; + Rs = sim_in.Rs; + hf_sim = sim_in.hf_sim; + nhfdelay = sim_in.hf_delay_ms*Rs/1000; + hf_mag_only = sim_in.hf_mag_only; + framesize = sim_in.framesize; + ml = sim_in.ml; + + bps = 2; + Nc = Nsymb = framesize/bps; % total number of symbols + + prev_sym_tx = qpsk_mod([0 0])*ones(1,Nc); + prev_sym_rx = qpsk_mod([0 0])*ones(1,Nc); + r = qpsk_mod([0 0])*ones(Nc,4); + + % Init HF channel model from stored sample files of spreading signal ---------------------------------- + + % convert "spreading" samples from 1kHz carrier at Fs to complex + % baseband, generated by passing a 1kHz sine wave through PathSim + % with the ccir-poor model, enabling one path at a time. + + Fc = 1000; M = Fs/Rs; + fspread = fopen("../raw/sine1k_2Hz_spread.raw","rb"); + spread1k = fread(fspread, "int16")/10000; + fclose(fspread); + fspread = fopen("../raw/sine1k_2ms_delay_2Hz_spread.raw","rb"); + spread1k_2ms = fread(fspread, "int16")/10000; + fclose(fspread); + + % down convert to complex baseband + spreadbb = spread1k.*exp(-j*(2*pi*Fc/Fs)*(1:length(spread1k))'); + spreadbb_2ms = spread1k_2ms.*exp(-j*(2*pi*Fc/Fs)*(1:length(spread1k_2ms))'); + + % remove -2000 Hz image + b = fir1(50, 5/Fs); + spread = filter(b,1,spreadbb); + spread_2ms = filter(b,1,spreadbb_2ms); + + % discard first 1000 samples as these were near 0, probably as + % PathSim states were ramping up + + spread = spread(1000:length(spread)); + spread_2ms = spread_2ms(1000:length(spread_2ms)); + + % decimate down to Rs + + spread = spread(1:M:length(spread)); + spread_2ms = spread_2ms(1:M:length(spread_2ms)); + + % Determine "gain" of HF channel model, so we can normalise + % carrier power during HF channel sim to calibrate SNR. I imagine + % different implementations of ccir-poor would do this in + % different ways, leading to different BER results. Oh Well! + + hf_gain = 1.0/sqrt(var(spread)+var(spread_2ms)); + + % Start Simulation ---------------------------------------------------------------- + + for ne = 1:length(Esvec) + EsNodB = Esvec(ne); + EsNo = 10^(EsNodB/10); + + variance = 1/EsNo; + if verbose > 1 + printf("EsNo (dB): %f EsNo: %f variance: %f\n", EsNodB, EsNo, variance); + end + + Terrs = 0; Tbits = 0; + + tx_symb_log = []; + rx_symb_log = []; + errors_log = []; + Nerrs_log = []; + + % init HF channel + + hf_n = 1; + + % simulation starts here----------------------------------- + + for nn = 1: Ntrials + + tx_bits = round(rand(1,framesize)); + + % modulate -------------------------------------------- + + for c=1:Nc + tx_symb(c) = qpsk_mod(tx_bits((2*(c-1)+1):(2*c))); + if strcmp(modulation,'dqpsk') + tx_symb(c) *= prev_sym_tx(c); + prev_sym_tx(c) = tx_symb(c); + end + end + s_ch = tx_symb; + + % HF channel simulation ------------------------------------ + + if hf_sim + + % separation between carriers. Note this effectively + % under samples at Rs, I dont think this matters. + % Equivalent to doing freq shift at Fs, then + % decimating to Rs. + + wsep = 2*pi*(1+0.5); % e.g. 75Hz spacing at Rs=50Hz, alpha=0.5 filters + + for c=1:Nc + ahf_model = hf_gain*(spread(hf_n) + exp(-j*c*wsep*nhfdelay)*spread_2ms(hf_n)); + if hf_mag_only + s_ch(c) *= abs(ahf_model); + else + s_ch(c) *= ahf_model; + end + hf_model(hf_n, c) = ahf_model; + end + hf_n++; + end + + tx_symb_log = [tx_symb_log s_ch]; + + % 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,Nc) + j*randn(1,Nc)); + + s_ch = s_ch + noise; + + % de-modulate + + rx_bits = zeros(1, framesize); + for c=1:Nc + + r(c,1:3) = r(c, 2:4); + r(c,4) = s_ch(c); + + rx_symb(c) = s_ch(c); + if strcmp(modulation,'dqpsk') + tmp = rx_symb(c); + rx_symb(c) *= conj(prev_sym_rx(c)/abs(prev_sym_rx(c))); + prev_sym_rx(c) = tmp; + end + + % r(c,:) + + if ml == 0 + rx_bits((2*(c-1)+1):(2*c)) = qpsk_demod(rx_symb(c)); + else + tx = [1 j -j -1]; + max_eta = 0; max_symb = tx(1); + for k=1:4 + for k_1=1:4 + for k_2=1:4 + %eta = abs(r(c,1) + r(c,3)*tx(k)'*tx(k_1)' + r(c,2)*tx(k_1)')^2; + eta = abs(r(c,1) + r(c,4)*tx(k)'*tx(k_1)'*tx(k_2)' + r(c,3)*tx(k_1)'*tx(k_2)' + r(c,2)*tx(k_2)')^2; + %printf(" %d %d %f \n", k_1, k, eta); + if eta > max_eta + max_eta = eta; + max_symb = tx(k); + end + end + end + end + rx_bits((2*(c-1)+1):(2*c)) = qpsk_demod(max_symb); + end + + rx_symb_log = [rx_symb_log rx_symb(c)]; + end + + % Measure BER + + error_positions = xor(rx_bits, tx_bits); + Nerrs = sum(error_positions); + Terrs += Nerrs; + Tbits += length(tx_bits); + errors_log = [errors_log error_positions]; + Nerrs_log = [Nerrs_log Nerrs]; + end + + TERvec(ne) = Terrs; + BERvec(ne) = Terrs/Tbits; + + if verbose + av_tx_pwr = (tx_symb_log * tx_symb_log')/length(tx_symb_log) + + printf("EsNo (dB): %3.1f Terrs: %d BER %4.3f QPSK BER theory %4.3f av_tx_pwr: %3.2f", EsNodB, Terrs, + Terrs/Tbits, 0.5*erfc(sqrt(EsNo/2)), av_tx_pwr); + printf("\n"); + end + end + + Ebvec = Esvec - 10*log10(bps); + sim_out.BERvec = BERvec; + sim_out.Ebvec = Ebvec; + sim_out.TERvec = TERvec; + sim_out.errors_log = errors_log; + + if plot_scatter + figure(2); + clf; + scat = rx_symb_log .* exp(j*pi/4); + plot(real(scat), imag(scat),'+'); + title('Scatter plot'); + + if hf_sim + figure(3); + clf; + + y = 1:(hf_n-1); + x = 1:Nc; + EsNodBSurface = 20*log10(abs(hf_model(y,:))) - 10*log10(variance); + EsNodBSurface(find(EsNodBSurface < -5)) = -5; + mesh(x,y,EsNodBSurface); + grid + axis([1 Nc 1 Rs*5 -5 15]) + title('HF Channel Es/No'); + + if verbose + av_hf_pwr = sum(abs(hf_model(y)).^2)/(hf_n-1); + printf("average HF power: %3.2f over %d symbols\n", av_hf_pwr, hf_n-1); + end + end + + figure(4) + clf + stem(Nerrs_log) + end + +endfunction + +% Gray coded QPSK modulation function + +function symbol = qpsk_mod(two_bits) + two_bits_decimal = sum(two_bits .* [2 1]); + switch(two_bits_decimal) + case (0) symbol = 1; + case (1) symbol = j; + case (2) symbol = -j; + case (3) symbol = -1; + endswitch +endfunction + +% Gray coded QPSK demodulation function + +function two_bits = qpsk_demod(symbol) + if isscalar(symbol) == 0 + printf("only works with scalars\n"); + return; + end + bit0 = real(symbol*exp(j*pi/4)) < 0; + bit1 = imag(symbol*exp(j*pi/4)) < 0; + two_bits = [bit1 bit0]; +endfunction + + +function sim_in = standard_init + sim_in.verbose = 1; + sim_in.plot_scatter = 0; + + sim_in.Esvec = 5; + sim_in.Ntrials = 30; + sim_in.Rs = 50; + sim_in.framesize = 8; + sim_in.ml = 0; + + sim_in.hf_delay_ms = 2; + sim_in.hf_sim = 0; + sim_in.hf_mag_only = 0; +endfunction + + +function test_curves + + sim_in = standard_init(); + + sim_in.Ntrials = 1000; + + sim_in.hf_sim = 0; + sim_in.plot_scatter = 0; + sim_in.Esvec = 5:15; + Ebvec = sim_in.Esvec - 10*log10(2); + BER_theory = 0.5*erfc(sqrt(10.^(Ebvec/10))); + sim_in.ml = 0; + sim_dqpsk = ber_test(sim_in, 'dqpsk'); + sim_in.ml = 1; + sim_dqpsk_ml = ber_test(sim_in, 'dqpsk'); + sim_in.hf_sim = 1; + sim_in.ml = 0; + sim_dqpsk_hf = ber_test(sim_in, 'dqpsk'); + sim_in.ml = 1; + sim_dqpsk_ml_hf = ber_test(sim_in, 'dqpsk'); + + figure(1); + clf; + semilogy(Ebvec, BER_theory,'r;QPSK theory;') + hold on; + semilogy(sim_dqpsk.Ebvec, sim_dqpsk.BERvec,'c;DQPSK AWGN;') + semilogy(sim_dqpsk_ml.Ebvec, sim_dqpsk_ml.BERvec,'k;DQPSK ML AWGN;') + semilogy(sim_dqpsk_hf.Ebvec, sim_dqpsk_hf.BERvec,'c;DQPSK HF;') + semilogy(sim_dqpsk_ml_hf.Ebvec, sim_dqpsk_ml_hf.BERvec,'k;DQPSK ML HF;') + hold off; + + xlabel('Eb/N0') + ylabel('BER') + grid("minor") + axis([min(Ebvec) max(Ebvec) 1E-3 1]) +endfunction + + +function test_single + sim_in = standard_init(); + + sim_in.verbose = 1; + sim_in.plot_scatter = 1; + sim_in.Ntrials = 500; + + sim_in.hf_mag_only = 0; + sim_in.hf_sim = 1; + sim_in.ml = 0; + sim_in.Esvec = 10; + + sim_qpsk_hf = ber_test(sim_in, 'dqpsk'); +endfunction + + +% Start simulations --------------------------------------- + +more off; + +test_curves(); +%test_single(); diff --git a/codec2-dev/octave/test_qpsk2.m b/codec2-dev/octave/test_qpsk2.m index a17e1ee4..bf7bd8e9 100644 --- a/codec2-dev/octave/test_qpsk2.m +++ b/codec2-dev/octave/test_qpsk2.m @@ -515,7 +515,7 @@ function ideal sim_in.hf_sim = 0; sim_in.plot_scatter = 0; - sim_in.Esvec = 2:15; + sim_in.Esvec = 2:10; sim_in.ldpc_code = 0; Ebvec = sim_in.Esvec - 10*log10(2); BER_theory = 0.5*erfc(sqrt(10.^(Ebvec/10))); @@ -523,16 +523,13 @@ function ideal sim_dqpsk = ber_test(sim_in, 'dqpsk'); sim_in.hf_sim = 1; - sim_in.Esvec = 2:15; sim_qpsk_hf = ber_test(sim_in, 'qpsk'); sim_dqpsk_hf = ber_test(sim_in, 'dqpsk'); - sim_in.ldpc_code = 1; - sim_qpsk_hf_ldpc1 = ber_test(sim_in, 'qpsk'); sim_in.ldpc_code_rate = 1/2; - sim_qpsk_hf_ldpc2 = ber_test(sim_in, 'qpsk'); - sim_in.ldpc_code_rate = 3/4; - sim_in.hf_sim = 0; - sim_qpsk_awgn_ldpc = ber_test(sim_in, 'qpsk'); + sim_in.ldpc_code = 1; + sim_qpsk_hf_ldpc = ber_test(sim_in, 'qpsk'); + sim_in.hf_mag_only = 0; + sim_dqpsk_hf_ldpc = ber_test(sim_in, 'dqpsk'); figure(1); clf; @@ -540,11 +537,10 @@ function ideal hold on; semilogy(sim_qpsk.Ebvec, sim_qpsk.BERvec,'g;QPSK AWGN;') semilogy(sim_qpsk_hf.Ebvec, sim_qpsk_hf.BERvec,'r;QPSK HF;') - semilogy(sim_dqpsk.Ebvec, sim_dqpsk.BERvec,'c;DQPSK AWGN;') - semilogy(sim_dqpsk_hf.Ebvec, sim_dqpsk_hf.BERvec,'m;DQPSK HF;') - semilogy(sim_qpsk_hf_ldpc1.Ebvec, sim_qpsk_hf_ldpc1.BERldpcvec,'k;QPSK HF LDPC 3/4;') - semilogy(sim_qpsk_hf_ldpc2.Ebvec, sim_qpsk_hf_ldpc2.BERldpcvec,'b;QPSK HF LDPC 1/2;') - semilogy(sim_qpsk_awgn_ldpc.Ebvec, sim_qpsk_awgn_ldpc.BERldpcvec,'k;QPSK AWGN LDPC 3/4;') + semilogy(sim_dqpsk.Ebvec, sim_dqpsk.BERvec,'g;DQPSK AWGN;') + semilogy(sim_dqpsk_hf.Ebvec, sim_dqpsk_hf.BERvec,'r;DQPSK HF;') + semilogy(sim_qpsk_hf_ldpc.Ebvec, sim_qpsk_hf_ldpc.BERldpcvec,'b;QPSK HF LDPC 1/2;') + semilogy(sim_dqpsk_hf_ldpc.Ebvec, sim_dqpsk_hf_ldpc.BERldpcvec,'b;DQPSK HF LDPC 1/2;') hold off; xlabel('Eb/N0') @@ -636,4 +632,4 @@ endfunction more off; -test_phase_est(); +ideal(); diff --git a/codec2-dev/octave/test_ucinter.m b/codec2-dev/octave/test_ucinter.m deleted file mode 100644 index 365bca48..00000000 --- a/codec2-dev/octave/test_ucinter.m +++ /dev/null @@ -1,353 +0,0 @@ -% test_ucinter.m -% David Rowe August 2014 -% - -% FDM QPSK modem simulation to test uncododed interleaving ideas on HF -% channels without building a full blown modem. - -% [X] baseline QPSK simulation AWGN -% [ ] Spreading function -% [ ] visualise different carriers with and without spreading -% [ ] prove perf same as AWGN when one carrier is knocked out -% + AWGN and "faded channel" with same average SNR -% + use contrived example -% + then try less contrived but still well behaived maths channel - -% Ideas: -% + decode quickly but then slow down while playing, using full interleave -% + exp type window so we can decode using current symbols alone in gd SNR, or extend window over greater time -% + like root nyq filtering, combining multiple symbols, weighted -% + spreading could make it worse, e.g. short term average might be very low -% + SSB spreads out over a long way. We could so this too! Like spread spectrum. Don't have to be related to -% carrier width. Minimise amount of stuff that gets nailed. But didn't we try this with "1600 wide"? OK, so - key issue was BER. That, is what we need to impove, using "high areas". - -1; - -% main test function - -function sim_out = ber_test(sim_in, modulation) - Fs = 8000; - - verbose = sim_in.verbose; - framesize = sim_in.framesize; - Ntrials = sim_in.Ntrials; - Esvec = sim_in.Esvec; - phase_offset = sim_in.phase_offset; - w_offset = sim_in.w_offset; - plot_scatter = sim_in.plot_scatter; - Rs = sim_in.Rs; - hf_sim = sim_in.hf_sim; - nhfdelay = sim_in.hf_delay_ms*Rs/1000; - hf_phase_only = sim_in.hf_phase_only; - hf_mag_only = sim_in.hf_mag_only; - Nc = sim_in.Nc; - - bps = 2; - Nsymb = framesize/bps; - prev_sym_tx = qpsk_mod([0 0]); - prev_sym_rx = qpsk_mod([0 0]); - - tx_bits_buf = zeros(1,2*framesize); - rx_bits_buf = zeros(1,2*framesize); - rx_symb_buf = zeros(1,2*Nsymb); - - % Init HF channel model from stored sample files of spreading signal ---------------------------------- - - % convert "spreading" samples from 1kHz carrier at Fs to complex - % baseband, generated by passing a 1kHz sine wave through PathSim - % with the ccir-poor model, enabling one path at a time. - - Fc = 1000; M = Fs/Rs; - fspread = fopen("../raw/sine1k_2Hz_spread.raw","rb"); - spread1k = fread(fspread, "int16")/10000; - fclose(fspread); - fspread = fopen("../raw/sine1k_2ms_delay_2Hz_spread.raw","rb"); - spread1k_2ms = fread(fspread, "int16")/10000; - fclose(fspread); - - % down convert to complex baseband - spreadbb = spread1k.*exp(-j*(2*pi*Fc/Fs)*(1:length(spread1k))'); - spreadbb_2ms = spread1k_2ms.*exp(-j*(2*pi*Fc/Fs)*(1:length(spread1k_2ms))'); - - % remove -2000 Hz image - b = fir1(50, 5/Fs); - spread = filter(b,1,spreadbb); - spread_2ms = filter(b,1,spreadbb_2ms); - - % discard first 1000 samples as these were near 0, probably as - % PathSim states were ramping up - - spread = spread(1000:length(spread)); - spread_2ms = spread_2ms(1000:length(spread_2ms)); - - % decimate down to Rs - - spread = spread(1:M:length(spread)); - spread_2ms = spread_2ms(1:M:length(spread_2ms)); - - % Determine "gain" of HF channel model, so we can normalise - % carrier power during HF channel sim to calibrate SNR. I imagine - % different implementations of ccir-poor would do this in - % different ways, leading to different BER results. Oh Well! - - hf_gain = 1.0/sqrt(var(spread)+var(spread_2ms)); - - % Start Simulation ---------------------------------------------------------------- - - for ne = 1:length(Esvec) - EsNodB = Esvec(ne); - EsNo = 10^(EsNodB/10); - - variance = 1/EsNo; - if verbose > 1 - printf("EsNo (dB): %f EsNo: %f variance: %f\n", EsNodB, EsNo, variance); - end - - Terrs = 0; Tbits = 0; - - tx_symb_log = []; - rx_symb_log = []; - noise_log = []; - - % init HF channel - - hf_n = 1; - hf_angle_log = []; - hf_fading = ones(1,Nsymb); % default input for ldpc dec - hf_model = ones(Ntrials*Nsymb/Nc, Nc); % defaults for plotting surface - - for nn = 1: Ntrials - - tx_bits = round( rand( 1, framesize) ); - - % modulate -------------------------------------------- - - s = zeros(1, Nsymb); - for i=1:Nsymb - tx_symb = qpsk_mod(tx_bits(2*(i-1)+1:2*i)); - if strcmp(modulation,'dqpsk') - tx_symb *= prev_sym_tx; - prev_sym_tx = tx_symb; - end - s(i) = tx_symb; - end - s_ch = s; - - % HF channel simulation ------------------------------------ - - if hf_sim - - % separation between carriers. Note this is - % effectively under samples at Rs, I dont think this - % matters. Equivalent to doing freq shift at Fs, then - % decimating to Rs. - - wsep = 2*pi*(1+0.5); % e.g. 75Hz spacing at Rs=50Hz, alpha=0.5 filters - - if Nsymb/Nc != floor(Nsymb/Nc) - printf("Error: Nsymb/Nc must be an integrer\n") - return; - end - - % arrange symbols in Nsymb/Nc by Nc matrix - - for i=1:Nc:Nsymb - - % Determine HF channel at each carrier for this symbol - - for k=1:Nc - hf_model(hf_n, k) = hf_gain*(spread(hf_n) + exp(-j*k*wsep*nhfdelay)*spread_2ms(hf_n)); - hf_fading(i+k-1) = abs(hf_model(hf_n, k)); - if hf_mag_only - s_ch(i+k-1) *= abs(hf_model(hf_n, k)); - else - s_ch(i+k-1) *= hf_model(hf_n, k); - end - end - hf_n++; - end - end - - tx_symb_log = [tx_symb_log s_ch]; - - % 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)); - noise_log = [noise_log noise]; - - % organise into carriers to apply frequency and phase offset - - for i=1:Nc:Nsymb - for k=1:Nc - s_ch(i+k-1) = s_ch(i+k-1)*exp(j*phase_offset) + noise(i+k-1); - end - phase_offset += w_offset; - end - - % de-modulate - - rx_bits = zeros(1, framesize); - for i=1:Nsymb - rx_symb = s_ch(i); - if strcmp(modulation,'dqpsk') - tmp = rx_symb; - rx_symb *= conj(prev_sym_rx/abs(prev_sym_rx)); - prev_sym_rx = tmp; - end - rx_bits((2*(i-1)+1):(2*i)) = qpsk_demod(rx_symb); - rx_symb_log = [rx_symb_log rx_symb]; - end - - % Measure BER - - error_positions = xor(rx_bits, tx_bits); - Nerrs = sum(error_positions); - Terrs += Nerrs; - Tbits += length(tx_bits); - end - - TERvec(ne) = Terrs; - BERvec(ne) = Terrs/Tbits; - - if verbose - printf("EsNo (dB): %f Terrs: %d BER %f BER theory %f", EsNodB, Terrs, - Terrs/Tbits, 0.5*erfc(sqrt(EsNo/2))); - printf("\n"); - end - if verbose > 1 - printf("Terrs: %d BER %f BER theory %f C %f N %f Es %f No %f Es/No %f\n\n", Terrs, - Terrs/Tbits, 0.5*erfc(sqrt(EsNo/2)), var(tx_symb_log), var(noise_log), - var(tx_symb_log), var(noise_log), var(tx_symb_log)/var(noise_log)); - end - end - - Ebvec = Esvec - 10*log10(bps); - sim_out.BERvec = BERvec; - sim_out.Ebvec = Ebvec; - sim_out.TERvec = TERvec; - - if plot_scatter - figure(2); - clf; - scat = rx_symb_log .* exp(j*pi/4); - plot(real(scat), imag(scat),'+'); - title('Scatter plot'); - - figure(3); - clf; - - y = 1:Rs*2; - x = 1:Nc; - EsNodBSurface = 20*log10(abs(hf_model(y,:))) - 10*log10(variance); - mesh(x,y,EsNodBSurface); - grid - axis([1 Nc 1 Rs*2 -5 15]) - title('HF Channel Es/No'); - - figure(4); - clf; - %mesh(x,y,unwrap(angle(hf_model(y,:)))); - subplot(211) - plot(y,abs(hf_model(y,1))) - title('HF Channel Carrier 1 Mag'); - subplot(212) - plot(y,angle(hf_model(y,1))) - title('HF Channel Carrier 1 Phase'); - - figure(6) - tmp = []; - for i = 1:hf_n-1 - tmp = [tmp abs(hf_model(i,:))]; - end - hist(tmp); - end - -endfunction - -% Gray coded QPSK modulation function - -function symbol = qpsk_mod(two_bits) - two_bits_decimal = sum(two_bits .* [2 1]); - switch(two_bits_decimal) - case (0) symbol = 1; - case (1) symbol = j; - case (2) symbol = -j; - case (3) symbol = -1; - endswitch -endfunction - -% Gray coded QPSK demodulation function - -function two_bits = qpsk_demod(symbol) - if isscalar(symbol) == 0 - printf("only works with scalars\n"); - return; - end - bit0 = real(symbol*exp(j*pi/4)) < 0; - bit1 = imag(symbol*exp(j*pi/4)) < 0; - two_bits = [bit1 bit0]; -endfunction - -function sim_in = standard_init - sim_in.verbose = 1; - sim_in.plot_scatter = 0; - - sim_in.Esvec = 5; - sim_in.Ntrials = 30; - sim_in.framesize = 576; - sim_in.Rs = 100; - sim_in.Nc = 8; - - sim_in.phase_offset = 0; - sim_in.w_offset = 0; - sim_in.phase_noise_amp = 0; - - sim_in.hf_delay_ms = 2; - sim_in.hf_sim = 0; - sim_in.hf_phase_only = 0; - sim_in.hf_mag_only = 1; -endfunction - -function test_ideal - - sim_in = standard_init(); - - sim_in.verbose = 1; - sim_in.plot_scatter = 1; - - sim_in.Esvec = 5; - sim_in.hf_sim = 1; - sim_in.Ntrials = 30; - - sim_qpsk_hf = ber_test(sim_in, 'qpsk'); - - sim_in.hf_sim = 0; - sim_in.plot_scatter = 0; - sim_in.Esvec = 2:5; - Ebvec = sim_in.Esvec - 10*log10(2); - BER_theory = 0.5*erfc(sqrt(10.^(Ebvec/10))); - sim_qpsk = ber_test(sim_in, 'qpsk'); - sim_dqpsk = ber_test(sim_in, 'dqpsk'); - - figure(1); - clf; - semilogy(Ebvec, BER_theory,'r;QPSK theory;') - hold on; - semilogy(sim_qpsk.Ebvec, sim_qpsk.BERvec,'g;QPSK AWGN;') - semilogy(sim_dqpsk.Ebvec, sim_dqpsk.BERvec,'c;DQPSK AWGN;') - hold off; - - xlabel('Eb/N0') - ylabel('BER') - grid("minor") - axis([min(Ebvec) max(Ebvec) 1E-3 1]) -endfunction - - -% Start simulations --------------------------------------- - -more off; - -test_ideal();