More work on the octave 4FSK mod/demod

git-svn-id: https://svn.code.sf.net/p/freetel/code@2320 01035d8c-6547-0410-b346-abe4f91aad63

diff --git a/codec2-dev/octave/fsk4.m b/codec2-dev/octave/fsk4.m
index 77bedb97ab1e3ebeafbb2a8eb7bfc5a48dc6e014..f5590fa23deabc09c865708db031b4663b61c7ab 100644 (file)
--- a/codec2-dev/octave/fsk4.m
+++ b/codec2-dev/octave/fsk4.m
@@ -7,7 +7,7 @@ fm;
 
 % Frequency response of the DMR raised cosine filter 
 % from ETSI TS 102 361-1 V2.2.1 page 111
-fsk4_rcf_resp = @(f) 1.0*(f<=1920) - cos((pi*f)/1920).*1.0.*(f>1920 & f<=2880);
+global fsk4_rcf_resp = @(f) 1.0*(f<=1920) - cos((pi*f)/1920).*1.0.*(f>1920 & f<=2880);
 
 %Maximum positive deviation of amy 4FSK symbol
 global fsk4_max_deviation = 1944;
@@ -18,6 +18,7 @@ global fsk4_symbols = [-1944 -648 648 1944];
 function fsk4_states = fsk4_init(fsk4_states,Rs)
     global fsk4_max_deviation;
     global fsk4_symbols;
+    global fsk4_rcf_resp;
 
     Fs = fsk4_states.Fs = 48000;  %Sample rate
     Rs = fsk4_states.Rs = Rs;     %Symbol rate
@@ -41,7 +42,22 @@ function fsk4_states = fsk4_init(fsk4_states,Rs)
 
 endfunction 
 
-function [tx, tx_filt] = fsk4_mod(fsk4_states, tx_symbols)
+function d = idmp(data, M, offset)
+    d = zeros(1,length(data)/M);
+    for i = 1:length(d)
+      d(i) = sum(data(1+(i-1)*M:i*M));
+    end
+endfunction
+
+function [tx, tx_filt] = fsk4_mod(fsk4_states, tx_bits)
+  hbits = tx_bits(1:2:length(tx_bits));
+  lbits = tx_bits(2:2:length(tx_bits));
+  %Pad odd bit lengths
+  if(length(hbits)!=length(lbits))
+    lbits = [lbits 0]
+  end
+  tx_symbols = lbits + hbits*2 + 1;
+  hist(tx_symbols);
   M = fsk4_states.M;
   nsym = length(tx_symbols);
   nsam = nsym*M;
@@ -51,18 +67,48 @@ function [tx, tx_filt] = fsk4_mod(fsk4_states, tx_symbols)
     tx_stream(1+(i-1)*M:i*M) = fsk4_states.symmap(tx_symbols(i));
   end
   tx_filt = filter(fsk4_states.tx_filter, 1, tx_stream);
+  tx_filt = tx_filt / max(tx_filt);
   tx = analog_fm_mod(fsk4_states.fm_states, tx_filt);
 endfunction
 
+%non-coherent demod based on a paper I found on IEEE xplore. Paper claims it is ~1db under coherent.
+% I don't think it works
+% Paper is titled "ALL- DIGITAL PSEUDO- COHERENT (PC) FSK MODEMS"
+function sym = fsk4_demod_thing(fsk4_states, rx)
+  global fsk4_symbols;
+  Fs = fsk4_states.Fs;
+  t = (1:length(rx));
+  shiftup = exp(j*2*pi*(1/4)*t);
+
+  rx_up = real(rx.*shiftup);
+  symup = fsk4_symbols + Fs/4;
+  sym1m = exp(j*2*pi*(symup(1)/Fs)*t).*rx_up;
+  sym2m = exp(j*2*pi*(symup(2)/Fs)*t).*rx_up;
+  sym3m = exp(j*2*pi*(symup(3)/Fs)*t).*rx_up;
+  sym4m = exp(j*2*pi*(symup(4)/Fs)*t).*rx_up;
+  sym1m = idmp(sym1m,10); sym1m = (real(sym1m).^2+imag(sym1m).^2);
+  sym2m = idmp(sym2m,10); sym2m = (real(sym2m).^2+imag(sym2m).^2);
+  sym3m = idmp(sym3m,10); sym3m = (real(sym3m).^2+imag(sym3m).^2);
+  sym4m = idmp(sym4m,10); sym4m = (real(sym4m).^2+imag(sym4m).^2);
+  sym = sym1m*-3 + sym2m*-1 + sym3m*1 + sym4m*3;
+  plot(abs(sym)(1:2000));
+  hist(sym(1:2:length(sym)),30);
+endfunction
 
+%incoherent demod loosly based on another paper. Works, more or less.
+% Paper is titled "Design and Implementation of a Fully Digital 4FSK Demodulator"
+function sym = fsk4_demod_fmrid(fsk4_states, rx)
+  afmd = analog_fm_demod(fsk4_states.fm_states,rx);
+  sym = afsym = idmp(afmd,10);
+  for i=(1:length(afsym))
+    
+  end
+  eyediagram(afsym,4);
+  %todo: write the thing that finds the symbols in the even/odd integrator output.
+endfunction
 
 
 
 
 
 
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