new me eff d/c and filtering works with freq offset

git-svn-id: https://svn.code.sf.net/p/freetel/code@1717 01035d8c-6547-0410-b346-abe4f91aad63

diff --git a/codec2-dev/octave/fdmdv.m b/codec2-dev/octave/fdmdv.m
index aee46816c11d0e16d68c042116dcaedbf456b884..8fecdacc9153d088f3df010ca714a07fe693b8f2 100644 (file)
--- a/codec2-dev/octave/fdmdv.m
+++ b/codec2-dev/octave/fdmdv.m
@@ -282,7 +282,6 @@ function rx_filt = rx_filter(rx_baseband, nin)
   global rx_filter_memory;
   global Nfilter;
   global gt_alpha5_root;
-  global Fsep;
 
   rx_filt = zeros(Nc+1,nin*P/M);
 
@@ -300,6 +299,64 @@ function rx_filt = rx_filter(rx_baseband, nin)
 endfunction
 
 
+% Combined down convert and rx filter, more memort efficentut less intuitive design
+
+function rx_filt = down_convert_and_rx_filter(rx_fdm, nin)
+  global Nc;
+  global M;
+  global P;
+  global rx_fdm_mem;
+  global phase_rx;
+  global freq;
+  global freq_pol;
+  global Nfilter;
+  global gt_alpha5_root;
+
+  % update memory of rx_fdm
+
+  rx_fdm_mem(1:Nfilter+M-nin) = rx_fdm_mem(nin+1:Nfilter+M);
+  rx_fdm_mem(Nfilter+M-nin+1:Nfilter+M) = rx_fdm(1:nin);
+
+  for c=1:Nc+1
+
+     % now downconvert using current freq offset to get Nfilter+nin
+     % baseband samples.
+     % 
+     %           Nfilter              nin
+     % |--------------------------|---------|
+     %                             |
+     %                         phase_rx(c)
+     %
+     % This means winding phase(c) back from this point
+     % to ensure phase continuity
+
+      wind_back_phase = -freq_pol(c)*Nfilter;
+     phase_rx(c)     =  phase_rx(c)*exp(j*wind_back_phase);
+    
+     % down convert all samples in buffer
+
+     rx_baseband = zeros(1,Nfilter+M);
+     st  = Nfilter+M;      % end of buffer
+     st -= nin-1;          % first new sample
+     st -= Nfilter;        % first sample used in filtering
+ 
+     for i=st:Nfilter+M
+        phase_rx(c) = phase_rx(c) * freq(c);
+       rx_baseband(i) = rx_fdm_mem(i)*phase_rx(c)';
+     end
+ 
+     % now we can filter this carrier's P symbols
+
+     N=M/P;
+     k=1;
+     for i=1:N:nin
+       rx_filt(c,k) = rx_baseband(st+i-1:st+i-1+Nfilter-1) * gt_alpha5_root';
+       k+=1;
+     end
+  end
+endfunction
+
+
 % LPF and peak pick part of freq est, put in a function as we call it twice
 
 function [foff imax pilot_lpf_out S] = lpf_peak_pick(pilot_baseband, pilot_lpf, nin)
@@ -1020,20 +1077,28 @@ tx_filter_memory = zeros(Nc+1, Nfilter);
 global rx_filter_memory;
 rx_filter_memory = zeros(Nc+1, Nfilter);
 
+global rx_fdm_mem;
+       rx_fdm_mem = zeros(1,Nfilter+M);
+
 % phasors used for up and down converters
 
 global freq;
-freq = zeros(Nc+1,1);
+       freq = zeros(Nc+1,1);
+global freq_pol;
+       freq_pol = zeros(Nc+1,1);
 for c=1:Nc/2
   carrier_freq = (-Nc/2 - 1 + c)*Fsep + Fcentre;
-  freq(c) = exp(j*2*pi*carrier_freq/Fs);
+  freq_pol(c)  = 2*pi*carrier_freq/Fs;
+  freq(c)      = exp(j*freq_pol(c));
 end
 for c=Nc/2+1:Nc
   carrier_freq = (-Nc/2 + c)*Fsep + Fcentre;
-  freq(c) = exp(j*2*pi*carrier_freq/Fs);
+  freq_pol(c)  = 2*pi*carrier_freq/Fs;
+  freq(c)      = exp(j*freq_pol(c));
 end
 
-freq(Nc+1) = exp(j*2*pi*Fcentre/Fs);
+freq_pol(c)  = 2*pi*Fcentre/Fs;
+freq(Nc+1) = exp(j*freq_pol(c));
 
 % Spread initial FDM carrier phase out as far as possible.  This
 % helped PAPR for a few dB.  We don't need to adjust rx phase as DQPSK

diff --git a/codec2-dev/octave/fdmdv_ut.m b/codec2-dev/octave/fdmdv_ut.m
index 247e4b99bf2ae4d189e8d0ae618fa218da1d9782..19b8c0b0e96e1861d3e34c682f9cb590cafadeb5 100644 (file)
--- a/codec2-dev/octave/fdmdv_ut.m
+++ b/codec2-dev/octave/fdmdv_ut.m
@@ -14,7 +14,7 @@ fdmdv;               % load modem code
 
 frames = 100;
 EbNo_dB = 7.3;
-Foff_hz = 0;
+Foff_hz = 10;
 modulation = 'dqpsk';
 hpa_clip = 150;
 
@@ -27,7 +27,6 @@ rx_phase_log = 0;
 rx_timing_log = 0;
 tx_pwr = 0;
 noise_pwr = 0;
-rx_fdm_mem = zeros(1,Nfilter+M);
 rx_fdm_log = [];
 rx_baseband_log = [];
 rx_bits_offset = zeros(Nc*Nb*2);
@@ -165,12 +164,7 @@ for f=1:frames
   S=fft(spec_mem.*hanning(Nspec)',Nspec);
   SdB = 0.9*SdB + 0.1*20*log10(abs(S));
 
-  % Delay
-
-  %rx_fdm_delay(1:Ndelay-M) = rx_fdm_delay(M+1:Ndelay);
-  %rx_fdm_delay(Ndelay-M+1:Ndelay) = rx_fdm;
-  rx_fdm_delay = rx_fdm;
-
+ 
   % -------------------
   % Demodulator
   % -------------------
@@ -178,70 +172,26 @@ for f=1:frames
   % frequency offset estimation and correction, need to call rx_est_freq_offset even in sync
   % mode to keep states updated
   
+  [pilot prev_pilot pilot_lut_index prev_pilot_lut_index] = get_pilot(pilot_lut_index, prev_pilot_lut_index, M);
+  [foff_coarse S1 S2] = rx_est_freq_offset(rx_fdm, pilot, prev_pilot, M);
+
   if sync == 0
-    foff = foff_course;
+    foff = foff_coarse;
   end
+  
   foff_log = [ foff_log foff ];
   foff_rect = exp(j*2*pi*foff/Fs);
   
   for i=1:M
     foff_phase *= foff_rect';
-    rx_fdm_delay(i) = rx_fdm_delay(i)*foff_phase;
+    rx_fdm(i) = rx_fdm(i)*foff_phase;
   end
 
 if 1
-
-  nin = M;
-
-  % update memory of rx_fdm
-
-  rx_fdm_mem(1:Nfilter+M-nin) = rx_fdm_mem(nin+1:Nfilter+M);
-  rx_fdm_mem(Nfilter+M-nin+1:Nfilter+M) = rx_fdm_delay(1:nin);
-
-  for c=1:Nc+1
-
-     % now downconvert using current freq offset to get Nfilter+nin
-     % baseband samples.
-     % 
-     %           Nfilter              nin
-     % |--------------------------|---------|
-     %                             |
-     %                         phase_rx(c)
-     %
-     % This means winding phase(c) back and fwd from this point
-     % to ensure phase continuity
-
-     freq_pol        =  atan2(imag(freq(c)), real(freq(c)));
-     wind_back_phase = -freq_pol*Nfilter;
-     phase_rx(c)     =  phase_rx(c)*exp(j*wind_back_phase);
-    
-     % down convert all samples in buffer
-
-     rx_baseband = zeros(1,Nfilter+M);
-     st  = Nfilter+M;      % end of buffer
-     st -= nin-1;          % first new sample
-     st -= Nfilter;        % first sample involved in filtering
- 
-     for i=st:Nfilter+M
-        phase_rx(c) = phase_rx(c) * freq(c);
-       rx_baseband(i) = rx_fdm_mem(i)*phase_rx(c)';
-     end
- 
-     % now we can filter this carrier's P symbols
-
-     N=M/P;
-     k=1;
-     for i=1:N:nin
-       rx_filt(c,k) = rx_baseband(st+i-1:st+i-1+Nfilter-1) * gt_alpha5_root';
-       k+=1;
-     end
-  end
-
+  % more memory efficient but more complex
+  rx_filt = down_convert_and_rx_filter(rx_fdm, M);
 else
-
-  % baseband processing
-
-  rx_baseband = fdm_downconvert(rx_fdm_delay(1:M), M);
+  rx_baseband = fdm_downconvert(rx_fdm, M);
   rx_baseband_log = [rx_baseband_log rx_baseband];
   rx_filt = rx_filter(rx_baseband, M);
 end
@@ -259,7 +209,8 @@ end
   else
     rx_symbols_log = [rx_symbols_log rx_symbols];
   endif
-  foff -= 0.5*ferr;
+  foff -= 0.5*foff_fine;
+  
   prev_rx_symbols = rx_symbols;
   sync_bit_log = [sync_bit_log sync_bit];