shallow zip-file copy from codec2 e9d726bf20

1 files changed, 35 insertions, 0 deletions

diff --git a/octave/qam16.m b/octave/qam16.m
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+++ b/octave/qam16.m
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+% qam16.m
+% David Rowe May 2020
+%
+% Octave QAM16 functions
+
+1;
+
+function symbol = qam16_mod(constellation, four_bits)
+    bits_decimal = sum(four_bits .* [8 4 2 1]);
+    symbol = constellation(bits_decimal+1);
+endfunction
+
+function four_bits = qam16_demod(constellation, symbol, amp_est=1)
+    assert (amp_est != 0);
+    symbol /= amp_est;
+    dist = abs(symbol - constellation(1:16));
+    [tmp decimal] = min(dist);
+    four_bits = zeros(1,4);
+    for i=1:4
+      four_bits(1,5-i) = bitand(bitshift(decimal-1,1-i),1);
+    end
+endfunction
+
+function test_qam16_mod_demod(constellation)
+    for decimal=0:15
+      tx_bits = zeros(1,4);
+      for i=1:4
+        tx_bits(1,5-i) = bitand(bitshift(decimal-1,1-i),1);
+      end
+      symbol = qam16_mod(constellation, tx_bits);
+      rx_bits = qam16_demod(constellation,symbol);
+      assert(tx_bits == rx_bits);
+    end
+endfunction
+