Home > freetb4matlab > comm > prbs_generator.m

prbs_generator

PURPOSE ^

%

SYNOPSIS ^

function prbs=prbs_generator(polynomial,connections,initstate)

DESCRIPTION ^

% 
% (C) 2006 Muthiah Annamalai <muthuspost@gmail.com>
%
% Implement book keeping for a Pseudo-Random Binary Sequence ( PRBS )
% also called as a Linear Feedback Shift Register.
% 
% Given a polynomial create a PRBS structure for that polynomial.
% Now all we need is to just create this polynomial and make it work.
% polynomial must be a vector containing the powers of x and an optional
% value 1. eg: x^3 + x^2 + x + 1 must be written as [3 2 1 0]
% all the coefficients are either 1 or 0. It generates only a Binary ...
% sequence, and the generator polynomial need to be only a binary
% polynomial in GF(2).
% 
% connections, contains a struct of vectors where each vector is the
% connection list mapping its vec(2:end) elements to the vec(1) output.
% 
% 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 with a start state of [1 0 1 1]
% will be:
% 
% prbs=prbs_generator([1 3 4],{[1 3 4]},[1 0 1 1]);
% x = prbs_sequence(prbs) %gives 15
% 
% prbs_iterator( prbs, 15 ) %15 binary digits seen
% [ 1   1   0   1   0   1   1   1   1   0   0   0   1   0   0 ]
% 
% See Also: This function is to be used along with functions
% prbs_iterator, and prbs_sequence.
%

CROSS-REFERENCE INFORMATION ^

This function calls: This function is called by:
Generated on Sat 16-May-2009 00:04:49 by m2html © 2003