From ac661c8f66216ce539f84299647699048f73a9ba Mon Sep 17 00:00:00 2001
From: drowe67 <drowe67@01035d8c-6547-0410-b346-abe4f91aad63>
Date: Mon, 30 Dec 2013 05:17:10 +0000
Subject: [PATCH] ldpc decode and sync working with no errors

git-svn-id: https://svn.code.sf.net/p/freetel/code@1349 01035d8c-6547-0410-b346-abe4f91aad63
---
 codec2-dev/octave/ldpc.m    | 31 ++++++++++++++++++++++++++-----
 codec2-dev/octave/ldpcenc.m | 29 +++++++++++++++++++++++++----
 2 files changed, 51 insertions(+), 9 deletions(-)

diff --git a/codec2-dev/octave/ldpc.m b/codec2-dev/octave/ldpc.m
index dfed5d45..917b7efa 100644
--- a/codec2-dev/octave/ldpc.m
+++ b/codec2-dev/octave/ldpc.m
@@ -23,12 +23,12 @@ endfunction
 % Gray coded QPSK modulation function
 
 function symbol = qpsk_mod(two_bits)
-    two_bits_decimal = sum(two_bits .* [1 2]); 
+    two_bits_decimal = sum(two_bits .* [2 1]); 
     switch(two_bits_decimal)
-        case (0) symbol =  1+j;
-        case (1) symbol = -1+j;
-        case (2) symbol =  1-j;
-        case (3) symbol = -1-j;
+        case (0) symbol =  1;
+        case (1) symbol =  j;
+        case (2) symbol = -j;
+        case (3) symbol = -1;
     endswitch
 endfunction
 
@@ -56,9 +56,30 @@ function frameout = insert_uw(framein, uw)
         pout += 2;
         luw -= 2;
     end
+endfunction
+
+% removes a unique word from a frame of bits.  The UW bits are spread
+% throughout the input frame 2 bits at a time.
+
+function frameout = remove_uw(framein, lvd, luw)
+
+    spacing = 2*lvd/luw;
+
+    frameout = [];
+
+    pin = 1; pout = 1;
+    while (luw)
+        %printf("pin %d pout %d luw %d  ", pin, pout, luw);
+        %printf("pin+spacing-1 %d lvd %d lframein: %d\n", pin+spacing-1, lvd, length(framein));
+        frameout(pout:pout+spacing-1) = framein(pin:pin+spacing-1);
+        pin  += spacing + 2; 
+        pout += spacing;
+        luw  -= 2;
+    end
 
 endfunction
 
+
 % builds up a sparse QPSK modulated version version of the UW for use
 % in UW sync at the rx
 
diff --git a/codec2-dev/octave/ldpcenc.m b/codec2-dev/octave/ldpcenc.m
index 9773e79f..9d7dde0b 100644
--- a/codec2-dev/octave/ldpcenc.m
+++ b/codec2-dev/octave/ldpcenc.m
@@ -27,6 +27,7 @@ mapping = 'gray';
 demod_type = 0;
 decoder_type = 0;
 max_iterations = 100;
+EsNo = 10;
 
 vocoderframesize = 52;
 nvocoderframes = 8;
@@ -58,8 +59,8 @@ for nn = 1: Nframes
 end
 fclose(fc);
 
-printf("framesize: %d data_bits_per_frame: %d code_bits_per_frame: %d\n", ...
-        framesize, code_param.data_bits_per_frame,  code_param.code_bits_per_frame);
+%printf("framesize: %d data_bits_per_frame: %d code_bits_per_frame: %d\n", ...
+%        framesize, code_param.data_bits_per_frame,  code_param.code_bits_per_frame);
 
 % rx simulation (separate later)
 
@@ -71,7 +72,7 @@ lpackedmodem = 72/8;
 mod_codeword = zeros(1, code_param.code_bits_per_frame/2);
 lmod_codeword = code_param.code_bits_per_frame/2;
 
-for m=1:16
+for m=1:8
 
     % read in one modem frame at a time
 
@@ -89,8 +90,28 @@ for m=1:16
     mod_codeword(1:lmod_codeword-length(mod_unpackedmodem)) = mod_codeword(length(mod_unpackedmodem)+1:lmod_codeword);
     mod_codeword(lmod_codeword-length(mod_unpackedmodem)+1:lmod_codeword) = mod_unpackedmodem;
 
-    look_for_uw(10*mod_codeword(1:length(mod_uw)), mod_uw)
+    uw_sync = look_for_uw(mod_codeword(1:length(mod_uw)), mod_uw);
+    if (uw_sync)
+        % force UW symbols as they are known (is this needed?)
+
+        % LDPC decode
+
+        detected_data = ldpc_dec(code_param, max_iterations, demod_type, decoder_type, mod_codeword, EsNo);
+
+        % unpack payload data, removing UW
+
+        vd_rx = remove_uw(detected_data(1:code_param.data_bits_per_frame), length(vd), length(uw));
+
+        % measure BER
+
+        error_positions = xor(vd, vd_rx);
+        Nerrs = sum(error_positions);
+        if Nerrs>0, fprintf(1,'x'),  else fprintf(1,'.'),  end
+
+        % save packed payload data to disk
+    end
 end
 
+fprintf(1,'\n')
 fclose(fc);
 
-- 
2.25.1