1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
|
/* CapacityTableLookup returns the instantaneous capacity for a particular
channel realization by using a precalculated AWGN capacity table.
Since the table does not generally contain capacity values for the exact
SNR, linear interpolation is used to estimate the value.
The calling syntax is:
cap = CapacityTableLoookup( EsNo_AWGN, capacity_AWGN, slope, gamma )
Outputs:
cap = The instantaneous capacity, a column vector with same number of
rows as gamma.
EsNo_AWGN = The SNR values stored in the table
capacity_AWGN = The AWGN capacity values stored in the table.
slope = The slope of the AWGN capacity curve.
gamma = The instantaneous SNRs for the channel realization.
Each row correpsonds to a distinct codeword,
And the columns correspond to the blocks of that codeword.
Copyright (C) 2005, Matthew C. Valenti
Last updated on Dec. 25, 2005
Function CapacityTableLookup is part of the Iterative Solutions
Coded Modulation Library. The Iterative Solutions Coded Modulation
Library is free software; you can redistribute it and/or modify it
under the terms of the GNU Lesser General Public License as published
by the Free Software Foundation; either version 2.1 of the License,
or (at your option) any later version.
This library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with this library; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
*/
#include <math.h>
#include <mex.h>
#include <Matrix.h>
#include <stdlib.h>
/* main function that interfaces with MATLAB */
void mexFunction(
int nlhs,
mxArray *plhs[],
int nrhs,
const mxArray *prhs[] )
{
/* declare variables */
double *SNR_table, *capacity_table, *slope, *gamma, *output_p;
int table_entries, trial_size, blocks, i, j, index_below;
double max_SNR, min_SNR, max_cap, this_gamma, cap;
/* Check for proper number of arguments */
if ((nrhs < 4 )||(nlhs > 1)) {
mexErrMsgTxt("Usage: cap = CapacityTableLoookup( EsNo_AWGN, capacity_AWGN, slope, gamma )");
}
/* first input is the SNR values in the table */
SNR_table = mxGetPr( prhs[0] );
table_entries = mxGetN( prhs[0] );
/* second input is the capacity values in the table */
capacity_table = mxGetPr( prhs[1] );
if ( mxGetN( prhs[1] ) != table_entries )
mexErrMsgTxt( "Table sizes don't match" );
/* third input is the slope */
slope = mxGetPr( prhs[2] );
if ( mxGetN( prhs[2] ) != table_entries-1 )
mexErrMsgTxt( "slope vector is wrong size" );
/* fourth input is the snr values */
gamma = mxGetPr( prhs[3] );
trial_size = mxGetM( prhs[3] );
blocks = mxGetN( prhs[3] );
/* create output */
plhs[0] = mxCreateDoubleMatrix( trial_size, 1, mxREAL );
output_p = mxGetPr( plhs[0] );
/* determine minimum and maximum values */
min_SNR = SNR_table[0];
max_SNR = SNR_table[table_entries-1];
max_cap = capacity_table[table_entries-1];
for (j=0;j<trial_size;j++) {
cap = 0;
for (i=0;i<blocks;i++) {
this_gamma = gamma[j+i*trial_size];
/*printf( "Gamma = %f\n", this_gamma ); */
if ( this_gamma >= max_SNR ) {
cap += max_cap;
} else if ( this_gamma > min_SNR ) {
/* need to interpolate */
index_below = 0;
while ( SNR_table[index_below] < this_gamma )
index_below++;
index_below--;
cap += capacity_table[index_below] + slope[index_below]*( this_gamma - SNR_table[index_below] );
}
}
output_p[j] = cap;
}
return;
}
|
