From 776ec79a98316dadcf4aeaa0f568f2b37c743067 Mon Sep 17 00:00:00 2001
From: drowe67 <drowe67@01035d8c-6547-0410-b346-abe4f91aad63>
Date: Tue, 31 Dec 2013 03:18:34 +0000
Subject: [PATCH] first pass at working separate decoder program, needs a bit
 of a cleanup

git-svn-id: https://svn.code.sf.net/p/freetel/code@1352 01035d8c-6547-0410-b346-abe4f91aad63
---
 codec2-dev/octave/ldpcdec.m | 127 ++++++++++++++++++++++++++++++++++++
 1 file changed, 127 insertions(+)
 create mode 100644 codec2-dev/octave/ldpcdec.m

diff --git a/codec2-dev/octave/ldpcdec.m b/codec2-dev/octave/ldpcdec.m
new file mode 100644
index 00000000..0b75aefd
--- /dev/null
+++ b/codec2-dev/octave/ldpcdec.m
@@ -0,0 +1,127 @@
+% ldpcdec.m
+% David Rowe 31 Dec 2013
+% 
+% LDPC decoder test program, given a file of QPSK symbols (IQIQ floats), 
+% performs frame sync, decodes, and measures BER.
+
+% Start CML library
+
+currentdir = pwd;
+addpath '/home/david/tmp/cml/mat'    % assume the source files stored here
+cd /home/david/tmp/cml
+CmlStartup                           % note that this is not in the cml path!
+cd(currentdir)
+
+% Our LDPC library
+
+ldpc;
+
+% Start simulation
+
+rand('state',1);
+
+rate = 3/4; 
+framesize = 576;  
+
+mod_order = 4; 
+modulation = 'QPSK';
+mapping = 'gray';
+
+demod_type = 0;
+decoder_type = 0;
+max_iterations = 100;
+EsNo = 10;
+Eprob = 0.15;
+
+vocoderframesize = 52;
+nvocoderframes = 8;
+nbitspermodemframe = 72;
+
+code_param = ldpc_init(rate, framesize, modulation, mod_order, mapping);
+code_param.code_bits_per_frame = 576;
+
+data = [];
+r = []; 
+
+% Encoder: Generate simulated vocoder data, insert UW, and LPDC encode ---------------
+
+Nframes = 100;
+uw = [1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0];
+
+% repeat same simulated vocoder data to ease testing
+
+vd = round( rand( 1, vocoderframesize*nvocoderframes) );
+
+% Decoder: Sync with LDPC frames, LDPC decode, strip off UW, measure BER -------
+
+fm=fopen("modcodeword.bin","rb");
+
+mod_uw = build_mod_uw(uw, 2*length(vd)/length(uw));
+
+mod_codeword = zeros(1, code_param.code_bits_per_frame/2);
+lmod_codeword = code_param.code_bits_per_frame/2;
+
+Terrs = 0; Ferrs = 0; Tbits = 0; Tframes = 0; nerr = [];
+corr = []; n = 0;
+sync_state = 0; sync_count = 0;
+
+[mod_unpackedmodem_float32, count] = fread(fm,nbitspermodemframe, "float32");
+while (count == nbitspermodemframe)
+    n++;
+
+    mod_unpackedmodem = mod_unpackedmodem_float32(1:2:nbitspermodemframe) + j*mod_unpackedmodem_float32(2:2:nbitspermodemframe);
+    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 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
+
+        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'); Ferrs++; ,  else fprintf(1,'.'),  end
+        Tbits += length(vd);
+        Terrs += Nerrs;
+        nerr(Tframes) = Nerrs;
+
+        % save packed payload data to disk
+    end
+
+    if (sync_state)
+        sync_count++;
+        if (sync_count == 8)
+            sync_count = 0;
+        end
+    end
+
+    % read in one modulated modem frame at a time
+
+    [mod_unpackedmodem_float32, count] = fread(fm, nbitspermodemframe, "float32");
+end
+
+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);
-- 
2.25.1