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Diffstat (limited to 'octave/mfsk.m')
| -rw-r--r-- | octave/mfsk.m | 199 |
1 files changed, 0 insertions, 199 deletions
diff --git a/octave/mfsk.m b/octave/mfsk.m deleted file mode 100644 index 0414b5e..0000000 --- a/octave/mfsk.m +++ /dev/null @@ -1,199 +0,0 @@ -% mfsk.m -% David Rowe Nov 2015 - -% Simulation to test m=2 and m=4 FSK demod - - -1; - -function sim_out = fsk_ber_test(sim_in) - Fs = 96000; - M = sim_in.M; - Rs = sim_in.Rs; - Ts = Fs/Rs; - verbose = sim_in.verbose; - - nbits = sim_in.nbits; - nsym = sim_in.nbits*2/M; - nsam = nsym*Ts; - EsNodB = sim_in.EbNodB + 10*log10(M/2); - - % printf("M: %d nbits: %d nsym: %d\n", M, nbits, nsym); - - if M == 2 - f(1) = -Rs/2; - f(2) = Rs/2; - end - if M == 4 - f(1) = -3*Rs/2; - f(2) = -Rs/2; - f(3) = Rs/2; - f(4) = 3*Rs/2; - end - - % simulate over a range of Eb/No values - - for ne = 1:length(EsNodB) - Nerrs = Terrs = Tbits = 0; - - aEsNodB = EsNodB(ne); - EsNo = 10^(aEsNodB/10); - variance = Fs/(Rs*EsNo); - - % Modulator ------------------------------- - - tx_bits = round(rand(1, nbits)); - tx = zeros(1,nsam); - tx_phase = 0; - - for i=1:nsym - if M == 2 - tone = tx_bits(i) + 1; - else - tone = (tx_bits(2*(i-1)+1:2*i) * [2 1]') + 1; - end - - tx_phase_vec = tx_phase + (1:Ts)*2*pi*f(tone)/Fs; - tx((i-1)*Ts+1:i*Ts) = exp(j*tx_phase_vec); - tx_phase = tx_phase_vec(Ts) - floor(tx_phase_vec(Ts)/(2*pi))*2*pi; - end - - % Channel --------------------------------- - - % We use complex (single sided) channel simulation, as it's convenient - % for the FM simulation. - - noise = sqrt(variance/2)*(randn(1,nsam) + j*randn(1,nsam)); - rx = tx + noise; - if verbose > 1 - printf("EbNo: %f Eb: %f var No: %f EbNo (meas): %f\n", - EbNo, var(tx)*Ts/Fs, var(noise)/Fs, (var(tx)*Ts/Fs)/(var(noise)/Fs)); - end - - % Demodulator ----------------------------- - - % non-coherent FSK demod - - rx_bb = rx; - dc = zeros(M,nsam); - for m=1:M - dc(m,:) = rx_bb .* exp(-j*(0:nsam-1)*2*pi*f(m)/Fs); - end - - rx_bits = zeros(1, nsym); - for i=1:nsym - st = (i-1)*Ts+1; - en = st+Ts-1; - for m=1:M - int(m,i) = abs(sum(dc(m,st:en))); - end - if m == 2 - rx_bits(i) = int(1,i) < int(2,i); - else - [max_amp tone] = max([int(1,i) int(2,i) int(3,i) int(4,i)]); - if tone == 1 - rx_bits(2*(i-1)+1:2*i) = [0 0]; - end - if tone == 2 - rx_bits(2*(i-1)+1:2*i) = [0 1]; - end - if tone == 3 - rx_bits(2*(i-1)+1:2*i) = [1 0]; - end - if tone == 4 - rx_bits(2*(i-1)+1:2*i) = [1 1]; - end - end - end - - error_positions = xor(rx_bits, tx_bits); - Nerrs = sum(error_positions); - Terrs += Nerrs; - Tbits += length(error_positions); - - TERvec(ne) = Terrs; - BERvec(ne) = Terrs/Tbits; - - if verbose > 1 - figure(2) - clf - Rx = 10*log10(abs(fft(rx))); - plot(Rx(1:Fs/2)); - axis([1 Fs/2 0 50]); - - figure(3) - clf; - subplot(211) - plot(real(rx_bb(1:Ts*20))) - subplot(212) - Rx_bb = 10*log10(abs(fft(rx_bb))); - plot(Rx_bb(1:3000)); - axis([1 3000 0 50]); - - figure(4); - subplot(211) - stem(abs(mark_int(1:100))); - subplot(212) - stem(abs(space_int(1:100))); - end - - if verbose - printf("EbNo (db): %3.2f Terrs: %d BER: %4.3f \n", aEsNodB - 10*log10(M/2), Terrs, Terrs/Tbits); - end - end - - sim_out.TERvec = TERvec; - sim_out.BERvec = BERvec; -endfunction - - -function run_fsk_curves - sim_in.M = 2; - sim_in.Rs = 1200; - sim_in.nbits = 12000; - sim_in.EbNodB = 0:2:20; - sim_in.verbose = 1; - - EbNo = 10 .^ (sim_in.EbNodB/10); - fsk_theory.BERvec = 0.5*exp(-EbNo/2); % non-coherent BFSK demod - fsk2_sim = fsk_ber_test(sim_in); - - sim_in.M = 4; - fsk4_sim = fsk_ber_test(sim_in); - - % BER v Eb/No curves - - figure(1); - clf; - semilogy(sim_in.EbNodB, fsk_theory.BERvec,'r;2FSK theory;') - hold on; - semilogy(sim_in.EbNodB, fsk2_sim.BERvec,'g;2FSK sim;') - semilogy(sim_in.EbNodB, fsk4_sim.BERvec,'b;4FSK sim;') - hold off; - grid("minor"); - axis([min(sim_in.EbNodB) max(sim_in.EbNodB) 1E-4 1]) - legend("boxoff"); - xlabel("Eb/No (dB)"); - ylabel("Bit Error Rate (BER)") - -end - - -function run_fsk_single - sim_in.M = 4; - sim_in.Rs = 1200; - sim_in.nbits = 5000; - sim_in.EbNodB = 8; - sim_in.verbose = 1; - - fsk_sim = fsk_ber_test(sim_in); -endfunction - - -rand('state',1); -randn('state',1); -graphics_toolkit ("gnuplot"); - -run_fsk_curves -%run_fsk_single - |