sova.htm

这是log-map或者说是软输出维特比算法的一个实现。

class=GramE>SOVADEC(</span> MSG, LLR, TRELLIS, WIN )<o:p></o:p></span></p>

<p class=MsoNormal align=left style='text-align:left;mso-pagination:widow-orphan;
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lang=EN-US style='font-size:12.0pt;font-family:宋体;mso-bidi-font-family:宋体;
mso-font-kerning:0pt'>%<span style='mso-spacerun:yes'>&nbsp;&nbsp; </span>where
MSG is the soft input (codeword), LLR is a priori information<o:p></o:p></span></p>

<p class=MsoNormal align=left style='text-align:left;mso-pagination:widow-orphan;
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lang=EN-US style='font-size:12.0pt;font-family:宋体;mso-bidi-font-family:宋体;
mso-font-kerning:0pt'>%<span style='mso-spacerun:yes'>&nbsp;&nbsp; </span>per
bit about the bits (log likelihood ratios), TRELLIS is the <o:p></o:p></span></p>

<p class=MsoNormal align=left style='text-align:left;mso-pagination:widow-orphan;
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lang=EN-US style='font-size:12.0pt;font-family:宋体;mso-bidi-font-family:宋体;
mso-font-kerning:0pt'>%<span style='mso-spacerun:yes'>&nbsp;&nbsp;
</span>trellis structure describing the <span class=SpellE>convolutional</span>
encoder used to <o:p></o:p></span></p>

<p class=MsoNormal align=left style='text-align:left;mso-pagination:widow-orphan;
tab-stops:45.8pt 91.6pt 137.4pt 183.2pt 229.0pt 274.8pt 320.6pt 366.4pt 412.2pt 458.0pt 503.8pt 549.6pt 595.4pt 641.2pt 687.0pt 732.8pt'><span
lang=EN-US style='font-size:12.0pt;font-family:宋体;mso-bidi-font-family:宋体;
mso-font-kerning:0pt'>%<span style='mso-spacerun:yes'>&nbsp;&nbsp; </span><span
class=GramE>encode</span> the original information message.<o:p></o:p></span></p>

<p class=MsoNormal align=left style='text-align:left;mso-pagination:widow-orphan;
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lang=EN-US style='font-size:12.0pt;font-family:宋体;mso-bidi-font-family:宋体;
mso-font-kerning:0pt'>%<span style='mso-spacerun:yes'>&nbsp;&nbsp; </span><o:p></o:p></span></p>

<p class=MsoNormal align=left style='text-align:left;mso-pagination:widow-orphan;
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lang=EN-US style='font-size:12.0pt;font-family:宋体;mso-bidi-font-family:宋体;
mso-font-kerning:0pt'>%<span style='mso-spacerun:yes'>&nbsp;&nbsp; </span><span
class=GramE>The</span> output of the function is the vector containing the soft
<o:p></o:p></span></p>

<p class=MsoNormal align=left style='text-align:left;mso-pagination:widow-orphan;
tab-stops:45.8pt 91.6pt 137.4pt 183.2pt 229.0pt 274.8pt 320.6pt 366.4pt 412.2pt 458.0pt 503.8pt 549.6pt 595.4pt 641.2pt 687.0pt 732.8pt'><span
lang=EN-US style='font-size:12.0pt;font-family:宋体;mso-bidi-font-family:宋体;
mso-font-kerning:0pt'>%<span style='mso-spacerun:yes'>&nbsp;&nbsp;
</span>estimates of the originally encoded information. The implementation<o:p></o:p></span></p>

<p class=MsoNormal align=left style='text-align:left;mso-pagination:widow-orphan;
tab-stops:45.8pt 91.6pt 137.4pt 183.2pt 229.0pt 274.8pt 320.6pt 366.4pt 412.2pt 458.0pt 503.8pt 549.6pt 595.4pt 641.2pt 687.0pt 732.8pt'><span
lang=EN-US style='font-size:12.0pt;font-family:宋体;mso-bidi-font-family:宋体;
mso-font-kerning:0pt'>%<span style='mso-spacerun:yes'>&nbsp;&nbsp; </span>is
able to perform decoding using any trellis structure <span class=SpellE>compatibile</span><o:p></o:p></span></p>

<p class=MsoNormal align=left style='text-align:left;mso-pagination:widow-orphan;
tab-stops:45.8pt 91.6pt 137.4pt 183.2pt 229.0pt 274.8pt 320.6pt 366.4pt 412.2pt 458.0pt 503.8pt 549.6pt 595.4pt 641.2pt 687.0pt 732.8pt'><span
class=GramE><span lang=EN-US style='font-size:12.0pt;font-family:宋体;mso-bidi-font-family:
宋体;mso-font-kerning:0pt'>%<span style='mso-spacerun:yes'>&nbsp;&nbsp;
</span>with the standard <span class=SpellE>Matlab</span> POLY2TRELLIS
function.</span></span><span lang=EN-US style='font-size:12.0pt;font-family:
宋体;mso-bidi-font-family:宋体;mso-font-kerning:0pt'><o:p></o:p></span></p>

<p class=MsoNormal align=left style='text-align:left;mso-pagination:widow-orphan;
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lang=EN-US style='font-size:12.0pt;font-family:宋体;mso-bidi-font-family:宋体;
mso-font-kerning:0pt'>%<o:p></o:p></span></p>

<p class=MsoNormal align=left style='text-align:left;mso-pagination:widow-orphan;
tab-stops:45.8pt 91.6pt 137.4pt 183.2pt 229.0pt 274.8pt 320.6pt 366.4pt 412.2pt 458.0pt 503.8pt 549.6pt 595.4pt 641.2pt 687.0pt 732.8pt'><span
lang=EN-US style='font-size:12.0pt;font-family:宋体;mso-bidi-font-family:宋体;
mso-font-kerning:0pt'>%<span style='mso-spacerun:yes'>&nbsp;&nbsp; </span>WIN
describes the size of the trellis buffer used to perform the<o:p></o:p></span></p>

<p class=MsoNormal align=left style='text-align:left;mso-pagination:widow-orphan;
tab-stops:45.8pt 91.6pt 137.4pt 183.2pt 229.0pt 274.8pt 320.6pt 366.4pt 412.2pt 458.0pt 503.8pt 549.6pt 595.4pt 641.2pt 687.0pt 732.8pt'><span
class=GramE><span lang=EN-US style='font-size:12.0pt;font-family:宋体;mso-bidi-font-family:
宋体;mso-font-kerning:0pt'>%<span style='mso-spacerun:yes'>&nbsp;&nbsp; </span><span
class=SpellE>Viterbi</span> algorithm.</span></span><span lang=EN-US
style='font-size:12.0pt;font-family:宋体;mso-bidi-font-family:宋体;mso-font-kerning:
0pt'> Thus, the decoder estimates the best path through<o:p></o:p></span></p>

<p class=MsoNormal align=left style='text-align:left;mso-pagination:widow-orphan;
tab-stops:45.8pt 91.6pt 137.4pt 183.2pt 229.0pt 274.8pt 320.6pt 366.4pt 412.2pt 458.0pt 503.8pt 549.6pt 595.4pt 641.2pt 687.0pt 732.8pt'><span
lang=EN-US style='font-size:12.0pt;font-family:宋体;mso-bidi-font-family:宋体;
mso-font-kerning:0pt'>%<span style='mso-spacerun:yes'>&nbsp;&nbsp; </span>the
trellis and searches back within this buffer at every decoding<o:p></o:p></span></p>

<p class=MsoNormal align=left style='text-align:left;mso-pagination:widow-orphan;
tab-stops:45.8pt 91.6pt 137.4pt 183.2pt 229.0pt 274.8pt 320.6pt 366.4pt 412.2pt 458.0pt 503.8pt 549.6pt 595.4pt 641.2pt 687.0pt 732.8pt'><span
class=GramE><span lang=EN-US style='font-size:12.0pt;font-family:宋体;mso-bidi-font-family:
宋体;mso-font-kerning:0pt'>%<span style='mso-spacerun:yes'>&nbsp;&nbsp;
</span>time instant.</span></span><span lang=EN-US style='font-size:12.0pt;
font-family:宋体;mso-bidi-font-family:宋体;mso-font-kerning:0pt'><o:p></o:p></span></p>

<p class=MsoNormal align=left style='text-align:left;mso-pagination:widow-orphan;
tab-stops:45.8pt 91.6pt 137.4pt 183.2pt 229.0pt 274.8pt 320.6pt 366.4pt 412.2pt 458.0pt 503.8pt 549.6pt 595.4pt 641.2pt 687.0pt 732.8pt'><span
lang=EN-US style='font-size:12.0pt;font-family:宋体;mso-bidi-font-family:宋体;
mso-font-kerning:0pt'>%<span style='mso-spacerun:yes'>&nbsp;&nbsp; </span><span
class=GramE>If</span> WIN is omitted, the trellis of length N+1 (where N is the
size<o:p></o:p></span></p>

<p class=MsoNormal align=left style='text-align:left;mso-pagination:widow-orphan;
tab-stops:45.8pt 91.6pt 137.4pt 183.2pt 229.0pt 274.8pt 320.6pt 366.4pt 412.2pt 458.0pt 503.8pt 549.6pt 595.4pt 641.2pt 687.0pt 732.8pt'><span
lang=EN-US style='font-size:12.0pt;font-family:宋体;mso-bidi-font-family:宋体;
mso-font-kerning:0pt'>%<span style='mso-spacerun:yes'>&nbsp;&nbsp; </span>of
the decoded message) is used.<o:p></o:p></span></p>

<p class=MsoNormal align=left style='text-align:left;mso-pagination:widow-orphan;
tab-stops:45.8pt 91.6pt 137.4pt 183.2pt 229.0pt 274.8pt 320.6pt 366.4pt 412.2pt 458.0pt 503.8pt 549.6pt 595.4pt 641.2pt 687.0pt 732.8pt'><span
lang=EN-US style='font-size:12.0pt;font-family:宋体;mso-bidi-font-family:宋体;
mso-font-kerning:0pt'>%<o:p></o:p></span></p>

<p class=MsoNormal align=left style='text-align:left;mso-pagination:widow-orphan;
tab-stops:45.8pt 91.6pt 137.4pt 183.2pt 229.0pt 274.8pt 320.6pt 366.4pt 412.2pt 458.0pt 503.8pt 549.6pt 595.4pt 641.2pt 687.0pt 732.8pt'><span
lang=EN-US style='font-size:12.0pt;font-family:宋体;mso-bidi-font-family:宋体;
mso-font-kerning:0pt'>%<span style='mso-spacerun:yes'>&nbsp;&nbsp; </span><span
class=GramE>For</span> the estimation of the reliability information only the
second<o:p></o:p></span></p>

<p class=MsoNormal align=left style='text-align:left;mso-pagination:widow-orphan;
tab-stops:45.8pt 91.6pt 137.4pt 183.2pt 229.0pt 274.8pt 320.6pt 366.4pt 412.2pt 458.0pt 503.8pt 549.6pt 595.4pt 641.2pt 687.0pt 732.8pt'><span
lang=EN-US style='font-size:12.0pt;font-family:宋体;mso-bidi-font-family:宋体;
mso-font-kerning:0pt'>%<span style='mso-spacerun:yes'>&nbsp;&nbsp; </span>best
path (competitor) is used, even if there are more than two<o:p></o:p></span></p>

<p class=MsoNormal align=left style='text-align:left;mso-pagination:widow-orphan;
tab-stops:45.8pt 91.6pt 137.4pt 183.2pt 229.0pt 274.8pt 320.6pt 366.4pt 412.2pt 458.0pt 503.8pt 549.6pt 595.4pt 641.2pt 687.0pt 732.8pt'><span
class=GramE><span lang=EN-US style='font-size:12.0pt;font-family:宋体;mso-bidi-font-family:
宋体;mso-font-kerning:0pt'>%<span style='mso-spacerun:yes'>&nbsp;&nbsp;
</span>paths merging at a particular state.</span></span><span lang=EN-US
style='font-size:12.0pt;font-family:宋体;mso-bidi-font-family:宋体;mso-font-kerning:
0pt'><o:p></o:p></span></p>

<p class=MsoNormal align=left style='text-align:left;mso-pagination:widow-orphan;
tab-stops:45.8pt 91.6pt 137.4pt 183.2pt 229.0pt 274.8pt 320.6pt 366.4pt 412.2pt 458.0pt 503.8pt 549.6pt 595.4pt 641.2pt 687.0pt 732.8pt'><span
lang=EN-US style='font-size:12.0pt;font-family:宋体;mso-bidi-font-family:宋体;
mso-font-kerning:0pt'>%<o:p></o:p></span></p>

<p class=MsoNormal align=left style='text-align:left;mso-pagination:widow-orphan;
tab-stops:45.8pt 91.6pt 137.4pt 183.2pt 229.0pt 274.8pt 320.6pt 366.4pt 412.2pt 458.0pt 503.8pt 549.6pt 595.4pt 641.2pt 687.0pt 732.8pt'><span
lang=EN-US style='font-size:12.0pt;font-family:宋体;mso-bidi-font-family:宋体;
mso-font-kerning:0pt'>%<span style='mso-spacerun:yes'>&nbsp;&nbsp; </span><span
class=GramE>The</span> output of the decoding algorithm is of the following
form<o:p></o:p></span></p>

<p class=MsoNormal align=left style='text-align:left;mso-pagination:widow-orphan;
tab-stops:45.8pt 91.6pt 137.4pt 183.2pt 229.0pt 274.8pt 320.6pt 366.4pt 412.2pt 458.0pt 503.8pt 549.6pt 595.4pt 641.2pt 687.0pt 732.8pt'><span
lang=EN-US style='font-size:12.0pt;font-family:宋体;mso-bidi-font-family:宋体;
mso-font-kerning:0pt'>%<span
style='mso-spacerun:yes'>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; </span>out =
sign(<span class=SpellE>inp</span>) * log( P(<span class=SpellE>inp</span>=1|out)
) / log( P(<span class=SpellE>inp</span>=-1|out) )<o:p></o:p></span></p>

<p class=MsoNormal align=left style='text-align:left;mso-pagination:widow-orphan;
tab-stops:45.8pt 91.6pt 137.4pt 183.2pt 229.0pt 274.8pt 320.6pt 366.4pt 412.2pt 458.0pt 503.8pt 549.6pt 595.4pt 641.2pt 687.0pt 732.8pt'><span
lang=EN-US style='font-size:12.0pt;font-family:宋体;mso-bidi-font-family:宋体;
mso-font-kerning:0pt'>%<o:p></o:p></span></p>

<p class=MsoNormal align=left style='text-align:left;mso-pagination:widow-orphan;
tab-stops:45.8pt 91.6pt 137.4pt 183.2pt 229.0pt 274.8pt 320.6pt 366.4pt 412.2pt 458.0pt 503.8pt 549.6pt 595.4pt 641.2pt 687.0pt 732.8pt'><span
lang=EN-US style='font-size:12.0pt;font-family:宋体;mso-bidi-font-family:宋体;
mso-font-kerning:0pt'>% See also: POLY2TRELLIS, CONVENCO, VITDEC<o:p></o:p></span></p>

<p class=MsoNormal align=left style='text-align:left;mso-pagination:widow-orphan;
tab-stops:45.8pt 91.6pt 137.4pt 183.2pt 229.0pt 274.8pt 320.6pt 366.4pt 412.2pt 458.0pt 503.8pt 549.6pt 595.4pt 641.2pt 687.0pt 732.8pt'><span
lang=EN-US style='font-size:12.0pt;font-family:宋体;mso-bidi-font-family:宋体;
mso-font-kerning:0pt'><o:p>&nbsp;</o:p></span></p>

<p class=MsoNormal align=left style='text-align:left;mso-pagination:widow-orphan;
tab-stops:45.8pt 91.6pt 137.4pt 183.2pt 229.0pt 274.8pt 320.6pt 366.4pt 412.2pt 458.0pt 503.8pt 549.6pt 595.4pt 641.2pt 687.0pt 732.8pt'><span
lang=EN-US style='font-size:12.0pt;font-family:宋体;mso-bidi-font-family:宋体;
mso-font-kerning:0pt'>%% (c) 2003 Adrian <span class=SpellE>Bohdanowicz</span><o:p></o:p></span></p>

<p class=MsoNormal align=left style='text-align:left;mso-pagination:widow-orphan;
tab-stops:45.8pt 91.6pt 137.4pt 183.2pt 229.0pt 274.8pt 320.6pt 366.4pt 412.2pt 458.0pt 503.8pt 549.6pt 595.4pt 641.2pt 687.0pt 732.8pt'><span
lang=EN-US style='font-size:12.0pt;font-family:宋体;mso-bidi-font-family:宋体;
mso-font-kerning:0pt'>%% $Id: <span class=SpellE>sovadec.m<span class=GramE>,v</span></span>
1.16 2003/06/15 14:57:29 <st1:City w:st="on"><st1:place w:st="on"><span
  class=SpellE>adrian</span></st1:place></st1:City> Exp $<o:p></o:p></span></p>

<p class=MsoNormal align=left style='text-align:left;mso-pagination:widow-orphan;
tab-stops:45.8pt 91.6pt 137.4pt 183.2pt 229.0pt 274.8pt 320.6pt 366.4pt 412.2pt 458.0pt 503.8pt 549.6pt 595.4pt 641.2pt 687.0pt 732.8pt'><span
lang=EN-US style='font-size:12.0pt;font-family:宋体;mso-bidi-font-family:宋体;
mso-font-kerning:0pt'><o:p>&nbsp;</o:p></span></p>

<p class=MsoNormal align=left style='text-align:left;mso-pagination:widow-orphan;
tab-stops:45.8pt 91.6pt 137.4pt 183.2pt 229.0pt 274.8pt 320.6pt 366.4pt 412.2pt 458.0pt 503.8pt 549.6pt 595.4pt 641.2pt 687.0pt 732.8pt'><span
lang=EN-US style='font-size:12.0pt;font-family:宋体;mso-bidi-font-family:宋体;
mso-font-kerning:0pt'><span style='mso-spacerun:yes'>&nbsp;&nbsp;&nbsp; </span><span
class=GramE>enc</span> = trellis2enc( <span class=SpellE>trl</span> );<o:p></o:p></span></p>

<p class=MsoNormal align=left style='text-align:left;mso-pagination:widow-orphan;