From: drowe67 <drowe67@01035d8c-6547-0410-b346-abe4f91aad63>
Date: Mon, 30 Dec 2013 23:36:11 +0000 (+0000)
Subject: improvements to LDPC dec sync state machine
X-Git-Url: http://git.whiteaudio.com/gitweb/?a=commitdiff_plain;h=280f622cf49a4e182d745f2d2c959e6a98af4019;p=freetel-svn-tracking.git

improvements to LDPC dec sync state machine

git-svn-id: https://svn.code.sf.net/p/freetel/code@1350 01035d8c-6547-0410-b346-abe4f91aad63
---

diff --git a/codec2-dev/octave/ldpc.m b/codec2-dev/octave/ldpc.m
index 917b7efa..2e9cf125 100644
--- a/codec2-dev/octave/ldpc.m
+++ b/codec2-dev/octave/ldpc.m
@@ -102,15 +102,16 @@ endfunction
 
 % Uses the UW to determine when we have a full codeword ready for decoding
 
-function found_uw = look_for_uw(mem_rx_symbols, mod_uw)
+function [found_uw corr] = look_for_uw(mem_rx_symbols, mod_uw)
     sparse_mem_rx_symbols = mem_rx_symbols(find(mod_uw));
 
     % correlate with ref UW
 
     num = (mem_rx_symbols * mod_uw') .^ 2;
     den = (sparse_mem_rx_symbols * sparse_mem_rx_symbols') * (mod_uw * mod_uw');
-
-    found_uw = abs(num/(den+1E-6)) > 0.8;
+    
+    corr = abs(num/(den+1E-6));
+    found_uw = corr > 0.8;
 endfunction
 
 
diff --git a/codec2-dev/octave/ldpcenc.m b/codec2-dev/octave/ldpcenc.m
index 9d7dde0b..d32cc7da 100644
--- a/codec2-dev/octave/ldpcenc.m
+++ b/codec2-dev/octave/ldpcenc.m
@@ -17,6 +17,8 @@ ldpc;
 
 % Start simulation
 
+rand('state',1);
+
 rate = 3/4; 
 framesize = 576;  
 
@@ -28,6 +30,7 @@ demod_type = 0;
 decoder_type = 0;
 max_iterations = 100;
 EsNo = 10;
+Eprob = 0.18;
 
 vocoderframesize = 52;
 nvocoderframes = 8;
@@ -72,11 +75,13 @@ 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=1:8
-
-    % read in one modem frame at a time
+Terrs = 0; Ferrs = 0; Tbits = 0; Tframes = 0; nerr = [];
+corr = []; n = 0;
+sync_state = 0; sync_count = 0;
 
-    packedmodem = fread(fc,lpackedmodem,"uchar");
+[packedmodem, count] = fread(fc,lpackedmodem,"uchar");
+while (count == lpackedmodem)
+    n++;
     unpackedmodem = unpackmsb(packedmodem);
 
     j = 1;
@@ -85,13 +90,22 @@ for m=1:8
         j += 1;
     end
 
+    erasures = rand(1,length(mod_unpackedmodem))<Eprob; 
+    mod_unpackedmodem(erasures) = 0;
+
     % keep buffer of one entire codeword
 
     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;
 
-    uw_sync = look_for_uw(mod_codeword(1:length(mod_uw)), mod_uw);
+    [uw_sync corr(n)] = look_for_uw(mod_codeword(1:length(mod_uw)), mod_uw);
     if (uw_sync)
+      sync_state = 1;
+    end
+
+    if (sync_state && (sync_count == 0))
+        Tframes++;
+
         % force UW symbols as they are known (is this needed?)
 
         % LDPC decode
@@ -106,12 +120,29 @@ for m=1:8
 
         error_positions = xor(vd, vd_rx);
         Nerrs = sum(error_positions);
-        if Nerrs>0, fprintf(1,'x'),  else fprintf(1,'.'),  end
+        if Nerrs>0, fprintf(1,'x'); Ferrs++; ,  else fprintf(1,'.'),  end
+        Tbits += length(vd);
+        Terrs += Nerrs;
+        nerr(Tframes) = Nerrs;
 
         % save packed payload data to disk
     end
-end
 
-fprintf(1,'\n')
+    if (sync_state)
+        sync_count++;
+        if (sync_count == 8)
+            sync_count = 0;
+        end
+    end
+
+    % read in one modem frame at a time
+
+    [packedmodem, count] = fread(fc, lpackedmodem, "uchar");
+end
 fclose(fc);
 
+fprintf(1,"\nFrames: %d bits: %d errors: %d BER = %f FER = %f\n", Tframes, Tbits, Terrs, Terrs/Tbits, Ferrs/Tframes);
+subplot(211)
+plot(corr);
+subplot(212)
+plot(nerr);