1 files changed, 134 insertions, 0 deletions
diff --git a/octave/fdmdv_demod_c.m b/octave/fdmdv_demod_c.m
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+++ b/octave/fdmdv_demod_c.m
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+% fdmdv_demod_c.m
+%
+% Plots Octave dump file information from C FDMDV demodulator program,
+% to give a similar set of plots to fdmdv_demod.m.  Useful for off
+% line analysis of demod performance.
+%
+% Copyright David Rowe 2012
+% This program is distributed under the terms of the GNU General Public License 
+% Version 2
+%
+
+function fdmdv_demod_c(dumpfilename, bits)
+  pkg load signal; 
+  fdmdv; % include modem code
+  f = fdmdv_init;
+  Nc = f.Nc; Nb = f.Nb; Rs = f.Rs; M = f.M; Fs = f.Fs;
+  
+  frames = bits/(Nc*Nb);
+
+  load(dumpfilename);
+
+  % BER stats
+
+  total_bit_errors = 0;
+  total_bits = 0;
+  bit_errors_log = [];
+  sync_log = [];
+  test_frame_sync_log = [];
+  test_frame_sync_state = 0;
+
+  % Run thru received bits to look for test pattern
+
+  bits_per_frame = Nc*Nb;
+
+  for fr=1:frames
+
+    rx_bits = rx_bits_log_c((fr-1)*bits_per_frame+1:fr*bits_per_frame);
+
+    % count bit errors if we find a test frame
+
+    [test_frame_sync bit_errors error_pattern f] = put_test_bits(f, rx_bits);
+    if (test_frame_sync == 1)
+      total_bit_errors = total_bit_errors + bit_errors;
+      total_bits = total_bits + f.Ntest_bits;
+      bit_errors_log = [bit_errors_log bit_errors/f.Ntest_bits];
+    else
+      bit_errors_log = [bit_errors_log 0];
+    end
+
+    % test frame sync state machine, just for more informative plots
+    
+    next_test_frame_sync_state = test_frame_sync_state;
+    if (test_frame_sync_state == 0)
+      if (test_frame_sync == 1)      
+        next_test_frame_sync_state = 1;
+	test_frame_count = 0;
+      end
+    end
+
+    if (test_frame_sync_state == 1)
+      % we only expect another test_frame_sync pulse every 4 symbols
+      test_frame_count++;
+      if (test_frame_count == 4)
+        test_frame_count = 0;
+        if ((test_frame_sync == 0))      
+          next_test_frame_sync_state = 0;
+        end
+      end
+    end
+    test_frame_sync_state = next_test_frame_sync_state;
+    test_frame_sync_log = [test_frame_sync_log test_frame_sync_state];
+  end
+
+  ber = total_bit_errors / total_bits;
+  printf("%d bits  %d errors  BER: %1.4f\n",total_bits, total_bit_errors, ber);
+
+  % ---------------------------------------------------------------------
+  % Plots
+  % ---------------------------------------------------------------------
+
+  xt = (1:frames)/Rs;
+  secs = frames/Rs;
+
+  figure(1)
+  clf;
+  plot(real(rx_symbols_log_c(1:Nc+1,15:frames)),imag(rx_symbols_log_c(1:Nc+1,15:frames)),'+')
+  %plot(real(rx_symbols_log_c(Nc+1,15:frames)),imag(rx_symbols_log_c(Nc+1,15:frames)),'+')
+  axis([-2 2 -2 2]);
+  title('Scatter Diagram');
+
+  figure(2)
+  clf;
+  subplot(211)
+  plot(xt, rx_timing_log_c(1:frames))
+  title('timing offset (samples)');
+  subplot(212)
+  plot(xt, foff_log_c(1:frames), '-;freq offset;')
+  hold on;
+  plot(xt, sync_log_c(1:frames)*75, 'r;course-fine;');
+  hold off;
+  title('Freq offset (Hz)');
+  grid
+
+  figure(3)
+  clf;
+  subplot(211)
+  b = M*frames;
+  xt1 = (1:b)/Fs;
+  plot(xt1, rx_fdm_log_c(1:b));
+  title('Rx FDM Signal');
+  subplot(212);
+  plot_specgram(rx_fdm_log_c(1:b), 8000);
+  title('FDM Rx Spectrogram');
+
+  figure(4)
+  clf;
+  subplot(311)
+  stem(xt, sync_bit_log_c(1:frames))
+  axis([0 secs 0 1.5]);
+  title('BPSK Sync')
+  subplot(312)
+  stem(xt, bit_errors_log);
+  title('Bit Errors for test frames')
+  subplot(313)
+  plot(xt, test_frame_sync_log);
+  axis([0 secs 0 1.5]);
+  title('Test Frame Sync')
+
+  figure(5)
+  clf;
+  plot(xt, snr_est_log_c(1:frames));
+  title('SNR Estimates')
+
+endfunction