/usr/share/octave/packages/communications-1.1.1/prbs_iterator.m is in octave-communications-common 1.1.1-1.
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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 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 | ## Copyright (C) 2006 Muthiah Annamalai <muthiah.annamalai@uta.edu>
##
## This program is free software; you can redistribute it and/or modify it under
## the terms of the GNU General Public License as published by the Free Software
## Foundation; either version 3 of the License, or (at your option) any later
## version.
##
## This program 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 General Public License for more
## details.
##
## You should have received a copy of the GNU General Public License along with
## this program; if not, see <http://www.gnu.org/licenses/>.
## This function generates the output bits from the PRBS
## state, for the number of iterations specified.
##
## First argument is the PRBS structure obtained from prbs_generator.
## PRBS iterations is specified in the second argument.
## PRBS start state is taken from the prbs.sregs.
##
## Second argument of the output is PRBS structure with a new
## state. This allows usage like:
##
## [ seq, prbs ] = prbs_iterator( prbs, niterations );
##
## while the state of the PRBS is updated.
##
## Example: If you had a PRBS shift register like the diagram
## below with 4 registers we use representation by polynomial
## of [ 1 2 3 4], and feedback connections between [ 1 3 4 ].
## The output PRBS sequence is taken from the position 4.
##
## +---+ +----+ +---+ +---+
## | D |----| D |---| D |---| D |
## +---+ +----+ +---+ +---+
## | | |
## \ / /
## [+]---------------+------+
## 1 + 0.D + 1.D^2 + 1.D^3
##
## The code to implement this PRBS will be
## prbs=prbs_generator([1 3 4],{[1 3 4]},[1 0 1 1]);
## x = prbs_iterator(prbs,15)
##
## See Also: This function is to be used along with functions
## prbs_iterator, prbs_generator and prbs_sequence.
function [outputseq, prbs] = prbs_iterator (prbs, iterations = 2^(prbs.reglen)-1)
if ( nargin < 1 || nargin > 2 )
print_usage;
endif
outputseq=zeros(1,iterations);
nstate=zeros(1,prbs.reglen);
## For each iteration, shift the output bit. Then compute the xor pattern of connections.
## Finally apply feedback the stuff. Insert the computed pattern.
for itr=1:iterations
## save output.
outputseq(itr)=prbs.sregs(prbs.reglen);
## compute the feedback.
for itr2=1:prbs.conlen
val=0;
L=length(prbs.connections{itr2});
for itr3=2:L
val=bitxor(val,prbs.sregs(prbs.connections{itr2}(itr3)));
endfor
nstate(prbs.connections{itr2}(1))=val;
endfor
## rotate the output discarding the last output.
prbs.sregs=[0 prbs.sregs(1:prbs.reglen-1)];
## insert the feedback.
for itr2=1:prbs.conlen
prbs.sregs(itr2)=nstate(itr2);
nstate(itr2)=0; # reset.
endfor
endfor
endfunction
##
## TEST CASES FOR PRBS.
##
##
## 2^31 -1 : D31 + D28 + 1 =0 inverted
## 2^23 -1 : D23 + D18 + 1 = 0 ,
## 2^15 -1 : D15 + D14 + 1 = 0,
## 2^10 -1 : D10 + D7 + 1 = 0,
## 2^7 -1 : D7 + D6 + 1 = 0,
## 2^4 -1 : D3 + D2 + 1 = 0,
##
## +---+ +----+ +---+ +---+
## | D |----| D |---| D |---| D |
## +---+ +----+ +---+ +---+
## | | |
## \ / /
## [+]---------------+------+
## 1 + 0.D + 1.D^2 + 1.D^3
##
##
## prbs=prbs_generator([1 3 4],{[1 3 4]},[1 0 1 1]);
## x = prbs_iterator(prbs,15)
## y = prbs_iterator(prbs,30)(16:end)
## z = prbs_sequence(prbs)
## exit
## break
##
## Multiple Tap, Simple Sequence Generator.
##
## n=10;
## k=8;
## inits=round(abs(rand(1,n)*1.0))
## prbs=prbs_generator([n 1],{[1 2 k n-1 n]},inits);
## prbs_iterator(prbs,1023)
## prbs_seqlength(prbs,inits)
##prbs=prbs_generator([1 2 3],{[1 2 3]},[1 1 1]);
##prbs_iterator(prbs,7)
##
## 2^4 -1 : D4 + D1 + 1 = 0,
##
## +---+ +----+ +---+ +---+
## | D |----| D |---| D |---| D |
## +---+ +----+ +---+ +---+
## | | |
## \ / /
## [+]---------------+------+
## 1 + 0.D + 1.D^2 + 1.D^3
##
##prbs=prbs_generator([1 3 4],{[1 2 4]},[1 0 1 1]);
##prbs_iterator(prbs,16)
##prbs_iterator(prbs,32)
##prbs=prbs_generator([7],{[1 7 6]},[1 0 0 1 0 0 0]);
##y=prbs_iterator(prbs,128);
##x=prbs_iterator(prbs,256);
|