1 files changed, 101 insertions, 0 deletions
diff --git a/octave/fsk_lib_demo.m b/octave/fsk_lib_demo.m
new file mode 100644
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+++ b/octave/fsk_lib_demo.m
@@ -0,0 +1,101 @@
+% fsk_lib_demo.m
+% Uncoded FSK modem demo
+
+fsk_lib;
+
+% set up waveform
+function [states M bits_per_frame] = modem_init(Rs,Fs,df)
+  M  = 4;
+  states = fsk_init(Fs,Rs,M,P=8,nsym=100);
+  bits_per_frame = 512;
+  states.tx_real = 0; % complex signal
+  states.tx_tone_separation = 250;
+  states.ftx = -2.5*states.tx_tone_separation + states.tx_tone_separation*(1:M);
+  states.fest_fmin = -Fs/2;
+  states.fest_fmax = +Fs/2;
+  states.fest_min_spacing = Rs/2;
+  states.df = df;
+
+  states.ber_valid_thresh = 0.1;
+  states.ber_invalid_thresh = 0.2; 
+end
+
+% Run a complete modem (freq and timing estimators running) at a
+% single Eb/No point.  At low Eb/No the estimators occasionally fall
+% over so we get complete junk, we consider that case a packet error
+% and exclude it from the BER estimation.
+
+function [states ber per] = modem_run_test(EbNodB = 10, num_frames=10, Fs=8000, Rs=100, df=0, plots=0)
+  randn('state',1); rand('state',1);
+  [states M bits_per_frame] = modem_init(Rs, Fs, df);
+  N = states.N;
+  if plots; states.verbose = 0x4; end
+  EbNo = 10^(EbNodB/10);
+  variance = states.Fs/(states.Rs*EbNo*states.bitspersymbol);
+
+  nbits = bits_per_frame*num_frames;
+  test_frame = round(rand(1,bits_per_frame)); tx_bits = [];
+  for f=1:num_frames
+    tx_bits = [tx_bits test_frame];
+  end
+
+  tx = fsk_mod(states, tx_bits);
+  noise = sqrt(variance/2)*randn(length(tx),1) + j*sqrt(variance/2)*randn(length(tx),1);
+  rx = tx + noise;
+
+  run_frames = floor(length(rx)/N)-1;
+  st = 1; f_log = []; f_log2 = []; rx_bits = []; rx_bits2 = [];
+  for f=1:run_frames
+
+    % extract nin samples from input stream
+    nin = states.nin;
+    en = st + states.nin - 1;
+
+    % due to nin variations it's possible to overrun buffer
+    if en < length(rx)
+      sf = rx(st:en);
+      states = est_freq(states, sf, states.M);  states.f = states.f2;
+      [arx_bits states] = fsk_demod(states, sf);
+      rx_bits = [rx_bits arx_bits];
+      f_log = [f_log; states.f];
+      st += nin;
+    end
+  end
+
+  num_frames=floor(length(rx_bits)/bits_per_frame);
+  log_nerrs = []; num_frames_rx = 0;
+  for f=1:num_frames-1
+    st = (f-1)*bits_per_frame + 1; en = (f+1)*bits_per_frame;
+    states = ber_counter(states, test_frame, rx_bits(st:en));
+    log_nerrs = [log_nerrs states.nerr];
+    if states.ber_state; num_frames_rx++; end
+  end
+  if states.Terrs
+    printf("Fs: %d Rs: %d df % 3.2f EbNo: %4.2f ftx: %3d frx: %3d nbits: %4d nerrs: %3d ber: %4.3f\n",
+            Fs, Rs, df, EbNodB, num_frames, num_frames_rx, states.Tbits, states.Terrs, states.Terrs/states.Tbits);
+    ber = states.Terrs/states.Tbits;
+  else
+    ber = 0.5;
+  end
+
+  if plots
+    figure(1); clf;
+    ideal=ones(length(f_log),1)*states.ftx;
+    plot((1:length(f_log)),ideal(:,1),'bk;ideal;')
+    hold on; plot((1:length(f_log)),ideal(:,2:states.M),'bk'); hold off;
+    hold on;
+    plot(f_log(:,1), 'linewidth', 2, 'b;peak;');
+    plot(f_log(:,2:states.M), 'linewidth', 2, 'b');
+    hold off;
+    xlabel('Time (frames)'); ylabel('Frequency (Hz)');
+    figure(2); clf; plot(log_nerrs); title('Errors per frame');
+  end
+
+  per = 1 - num_frames_rx/num_frames;
+end
+
+[states ber per] = modem_run_test(EbNodB=6);
+BER_theory=0.01579; % for Eb/No = 6dB
+if ber < 1.5*BER_theory
+  printf("PASS\n");
+end