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Jordan Sherer
Executable
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<HTML><HEAD>
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<TITLE> Support Programs </TITLE>
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</HEAD><BODY>
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<H1> Support Programs </H1>
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The following programs provide support for testing and performance
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assessment.
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<P><A NAME="rand-src"><HR><B>rand-src</B>: Generate random message bits.
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<BLOCKQUOTE><PRE>
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rand-src <I>source-file seed n-bits</I>
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</PRE></BLOCKQUOTE>
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<P>Creates a file of random messages bits called
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<TT><I>source-file</I></TT>, which is suitable for testing the
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correctness and performance of other programs. The bits in the file
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are independent, and are equally likely to be 0 or 1. They are
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generated pseudo-randomly based on <TT><I>seed</I></TT>. The actual
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random number seed used will be <TT><I>seed</I></TT> times 10 plus 2,
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so that the stream of pseudo-random numbers will not be the same as
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any that might have been used by another program.
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<P>The <TT><I>n-bits</I></TT> argument specifies the number of bits to
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produce. It can be a single number, or it can consist of a block size
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and a number of blocks, written with <TT>x</TT> separating these
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numbers, with no spaces. Each block is written as a single line, with
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the bits in the block represented by the characters '0' and '1', with
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no intervening spaces. If the bit count is given by a single number,
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the block size is assumed to be one.
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<P><B>Example:</B> The following command produces a file containing
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3 blocks, each consisting of 15 random bits, produced using the pseudo-random
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number stream identified by the <TT><I>seed</I></TT> of 17:
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<UL><PRE>
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<LI>rand-src rsrc 17 15x3
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</PRE></UL>
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The contents of the file <TT>rsrc</TT> after this command might be something
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like the following:
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<BLOCKQUOTE><PRE>
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111011000110000
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010010110010111
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100000000000111
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</BLOCKQUOTE></PRE>
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<P><A NAME="verify"><HR><B>verify</B>: Verify that decoded blocks are
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codewords, and that they match the source.
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<BLOCKQUOTE><PRE>
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verify [ -t ] <I>pchk-file decoded-file</I> [ <I>gen-file</I> [ <I>source-file</I> ] ]
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</PRE></BLOCKQUOTE>
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<P>Checks whether or not the blocks in <TT><I>decoded-file</I></TT>
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are codewords, according to the parity check matrix in
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<TT><I>pchk-file</I></TT>. If <TT><I>gen-file</I></TT> is specified,
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the message bits of the blocks are also checked against the
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corresponding blocks of <TT><I>source-file</I></TT>, or against zero
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if <TT><I>source-file</I></TT> is not given. (Normally, one would
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leave out <TT><I>source-file</I></TT> only if the <A
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HREF="channel.html#transmit"><TT>transmit</TT></A> command was used
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with an argument specifying that zeros are to be transmitted, rather
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than a file of encoded data.)
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<P>A summary of the results is displayed on standard error, giving the
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total numbers of blocks, the number with parity check errors, and, if
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<TT><I>gen-file</I></TT> was specified, the number of blocks with
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source errors and the number with errors of both kinds. If
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<TT><I>gen-file</I></TT> was specified, a second
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summary line displays the bit error rate from
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comparing the decoded message bits with the true message bits (zeros
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if no <TT><I>source file</I></TT> was given).
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<P>If the <B>-t</B> option is given, block-by-block results are
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printed on standard output in two or three columns, giving the block
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number (from zero), the number of parity check errors for that block,
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and the number of errors in source bits. The last column is omitted
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if <TT><I>gen-file</I></TT> is not specified. The columns are
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preceded by a line of headers, so the file is suitable for reading
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into the S-Plus or R statistics packages, with a command such as
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<BLOCKQUOTE><PRE>
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data <- read.table(<I>file</I>,header=T)
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</PRE></BLOCKQUOTE>
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<P>Warning messages are displayed on standard error if the number of
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bits in <TT><I>decoded-file</I></TT> is not a multiple of the block
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length, or if <TT><I>source-file</I></TT> is too short. Newlines
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in these files are ignored, even though they would normally occur
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at the ends of blocks.
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<HR>
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<A HREF="index.html">Back to index for LDPC software</A>
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</BODY></HTML>
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