100 lines
2.6 KiB
C
100 lines
2.6 KiB
C
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/* CHANNEL.C - Procedures and variables regarding channels. */
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/* Copyright (c) 1995-2012 by Radford M. Neal.
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*
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* Permission is granted for anyone to copy, use, modify, and distribute
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* these programs and accompanying documents for any purpose, provided
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* this copyright notice is retained and prominently displayed, and note
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* is made of any changes made to these programs. These programs and
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* documents are distributed without any warranty, express or implied.
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* As the programs were written for research purposes only, they have not
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* been tested to the degree that would be advisable in any important
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* application. All use of these programs is entirely at the user's own
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* risk.
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*/
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <math.h>
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#include "channel.h"
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/* GLOBAL VARIABLES. Declared in channel.h. */
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channel_type channel; /* Type of channel */
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double error_prob; /* Error probability for BSC */
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double std_dev; /* Noise standard deviation for AWGN */
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double lwidth; /* Width of noise distribution for AWLN */
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/* PARSE A COMMAND-LINE SPECIFICATION OF A CHANNEL. Takes a pointer to an
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argument list and an argument count; returns the number of arguments that
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make up a channel specification at this point in the command line. Returns
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zero if the argument list does not start with a channel specification.
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Returns -1 if there seems to be a channel specification here, but it's
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invalid.
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Sets the variables declared in channel.h to the type and parameters of
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the channel.
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*/
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int channel_parse
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( char **argv, /* Pointer to argument list */
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int argc /* Number of arguments in list */
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)
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{
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char junk;
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if (argc==0) return 0;
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if (strcmp(argv[0],"bsc")==0 || strcmp(argv[0],"BSC")==0)
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{
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channel = BSC;
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if (argc<2 || sscanf(argv[1],"%lf%c",&error_prob,&junk)!=1
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|| error_prob<=0 || error_prob>=1)
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{ return -1;
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}
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else
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{ return 2;
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}
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}
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else if (strcmp(argv[0],"awgn")==0 || strcmp(argv[0],"AWGN")==0)
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{
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channel = AWGN;
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if (argc<2 || sscanf(argv[1],"%lf%c",&std_dev,&junk)!=1
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|| std_dev<=0)
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{ return -1;
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}
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else
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{ return 2;
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}
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}
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else if (strcmp(argv[0],"awln")==0 || strcmp(argv[0],"AWLN")==0)
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{
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channel = AWLN;
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if (argc<2 || sscanf(argv[1],"%lf%c",&lwidth,&junk)!=1
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|| lwidth<=0)
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{ return -1;
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}
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else
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{ return 2;
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}
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}
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else
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{
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return 0;
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}
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}
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/* PRINT USAGE MESSAGE REGARDING CHANNEL SPECIFICATIONS. */
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void channel_usage(void)
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{
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fprintf(stderr,
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"Channel: bsc error-probability | awgn standard-deviation | awln width\n");
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}
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