shallow zip-file copy from codec2 e9d726bf20

1 files changed, 44 insertions, 0 deletions

diff --git a/octave/fsk_lib_ldpc_tx.m b/octave/fsk_lib_ldpc_tx.m
new file mode 100644
index 0000000..408ba79
--- /dev/null
+++ b/octave/fsk_lib_ldpc_tx.m
@@ -0,0 +1,44 @@
+% fsk_lib_ldpc_tx.m
+%
+% LDPC coded 4FSK modem tx, generates a 8 kHz 16 bit short real valued sample file
+
+function fsk_lib_ldpc_tx(filename, num_frames=10, Rs=100, coderate=0.5, EbNodB=100)
+  fsk_lib_ldpc;
+  
+  % set up LDPC code
+  init_cml();
+  if coderate == 0.5
+    load H_256_512_4.mat;
+  elseif coderate == 0.75
+    load HRAa_1536_512.mat; H=HRA;
+  else
+    disp("unknown code rate");
+  end  
+  [states code_param] = fsk_lib_ldpc_init (H, Rs, Fs=8000);
+  n = code_param.coded_bits_per_frame; k = code_param.data_bits_per_frame;
+  
+  rand('seed',1);
+  data_bits = round(rand(1,code_param.data_bits_per_frame)); tx_bits = [];
+  for f=1:num_frames
+    codeword_bits = LdpcEncode(data_bits, code_param.H_rows, code_param.P_matrix);
+    tx_bits = [tx_bits codeword_bits];
+  end
+
+  tx = fsk_mod(states, tx_bits);
+
+  % set up (optional) AWGN noise
+  EcNodB = EbNodB + 10*log10(states.rate);
+  EcNo = 10^(EcNodB/10);
+  variance = states.Fs/(states.Rs*EcNo*states.bitspersymbol);
+
+  % note real noise
+  noise = sqrt(variance/2)*randn(length(tx),1);
+  rx = tx + noise;
+
+  frx=fopen(filename,"wb"); fwrite(frx, states.amp_scale*rx, "short"); fclose(frx);
+  printf("Fs: %d Rs: %d rate %4.2f (%d,%d) EbNodB: %3.1f  EcNodB: %3.1f frames transmitted: %3d\n",
+  Fs, Rs, coderate, n, k, EbNodB, EcNodB, num_frames);
+end
+
+
+