From e3aff8e06999bbd38097d78ef91f33f7dee53836 Mon Sep 17 00:00:00 2001
From: drowe67 <drowe67@01035d8c-6547-0410-b346-abe4f91aad63>
Date: Tue, 24 Apr 2018 03:37:09 +0000
Subject: [PATCH] fixed bug in amplitude estimator that improved LDPC dec perf
 - Octave code

git-svn-id: https://svn.code.sf.net/p/freetel/code@3521 01035d8c-6547-0410-b346-abe4f91aad63
---
 codec2-dev/octave/ldpc.m         | 8 ++------
 codec2-dev/octave/ofdm_dev.m     | 8 ++++----
 codec2-dev/octave/ofdm_ldpc_rx.m | 4 ++--
 codec2-dev/octave/ofdm_lib.m     | 2 +-
 4 files changed, 9 insertions(+), 13 deletions(-)

diff --git a/codec2-dev/octave/ldpc.m b/codec2-dev/octave/ldpc.m
index d337394e..e05cb084 100644
--- a/codec2-dev/octave/ldpc.m
+++ b/codec2-dev/octave/ldpc.m
@@ -74,19 +74,15 @@ endfunction
 
 
 function [detected_data paritychecks] = ldpc_dec(code_param, max_iterations, demod_type, decoder_type, r, EsNo, fading)
-    if nargin == 6
-      fading = ones(1, length(r));
-    end
-
     symbol_likelihood = Demod2D( r, code_param.S_matrix, EsNo, fading);
-         
+    
     % initialize the extrinsic decoder input
 
     input_somap_c = zeros(1, code_param.code_bits_per_frame );
     bit_likelihood = Somap( symbol_likelihood, demod_type, input_somap_c );
     
     input_decoder_c = bit_likelihood(1:code_param.code_bits_per_frame);
-
+    
     [x_hat paritychecks] = MpDecode( -input_decoder_c, code_param.H_rows, code_param.H_cols, ...
                               max_iterations, decoder_type, 1, 1);
     [mx mx_ind] = max(paritychecks);
diff --git a/codec2-dev/octave/ofdm_dev.m b/codec2-dev/octave/ofdm_dev.m
index 109b0a7a..15f2f88b 100644
--- a/codec2-dev/octave/ofdm_dev.m
+++ b/codec2-dev/octave/ofdm_dev.m
@@ -309,7 +309,7 @@ function [sim_out rx states] = run_sim(sim_in)
 
       lnew = min(Nsam-prx,states.nin);
       rxbuf_in = zeros(1,states.nin);
-
+      
       if lnew
         rxbuf_in(1:lnew) = rx(prx:prx+lnew-1);
       end
@@ -370,7 +370,7 @@ function [sim_out rx states] = run_sim(sim_in)
       st = (f-1)*Nbitsperframe/bps + 1;
       en = st + Nbitsperframe/bps - 1;
       r = rx_np(st:en); fade = rx_amp(st:en);
-
+      fade
       % optional LDPC decode
      
       if ldpc_en
@@ -1084,9 +1084,9 @@ more off;
 
 init_cml('~/cml/');
 
-%run_single 
+run_single 
 %run_curves
 %run_curves_estimators
 %acquisition_histograms(0, 0)
-acquisition_test(Ntests=3, EbNodB=100, foff_hz=0)
+%acquisition_test(Ntests=3, EbNodB=100, foff_hz=0)
 %sync_metrics('freq')
diff --git a/codec2-dev/octave/ofdm_ldpc_rx.m b/codec2-dev/octave/ofdm_ldpc_rx.m
index 19178d63..870c18f2 100644
--- a/codec2-dev/octave/ofdm_ldpc_rx.m
+++ b/codec2-dev/octave/ofdm_ldpc_rx.m
@@ -29,7 +29,7 @@ function ofdm_ldpc_rx(filename, interleave_frames = 1, error_pattern_filename)
   mod_order = 4; bps = 2; modulation = 'QPSK'; mapping = 'gray';
   demod_type = 0; decoder_type = 0; max_iterations = 100;
 
-  EsNo = 10; % TODO: fixme
+  EsNo = 3; % TODO: fixme
   printf("EsNo fixed at %f - need to est from channel\n", EsNo);
   
   init_cml('~/cml/');
@@ -149,7 +149,7 @@ function ofdm_ldpc_rx(filename, interleave_frames = 1, error_pattern_filename)
 
       rx_np_de = gp_deinterleave(rx_np);
       rx_amp_de = gp_deinterleave(rx_amp);
-
+      
       % Interleaver Sync:
       %   Needs to work on any data
       %   Use indication of LDPC convergence, may need to patch CML code for that
diff --git a/codec2-dev/octave/ofdm_lib.m b/codec2-dev/octave/ofdm_lib.m
index e975ef41..6dbbb091 100644
--- a/codec2-dev/octave/ofdm_lib.m
+++ b/codec2-dev/octave/ofdm_lib.m
@@ -454,7 +454,7 @@ function [rx_bits states aphase_est_pilot_log rx_np rx_amp] = ofdm_demod(states,
     aphase_est_pilot_rect += sum(rx_sym(2+Ns+1,cr)*pilots(cr)');
 
     aphase_est_pilot(c) = angle(aphase_est_pilot_rect);
-    aamp_est_pilot(c) = abs(aphase_est_pilot_rect/12);
+    aamp_est_pilot(c) = abs(aphase_est_pilot_rect/6);   % amplitude is estimated over 6 rows of pilots
   end
  
   % correct phase offset using phase estimate, and demodulate
-- 
2.25.1