Thread: [Octave-cvsupdate] SF.net SVN: octave:[5705] trunk/octave-forge/main/comm/inst

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Revision: 5705
          http://octave.svn.sourceforge.net/octave/?rev=5705&view=rev
Author:   gnumuthu
Date:     2009-04-13 22:16:33 +0000 (Mon, 13 Apr 2009)

Log Message:
-----------
PRBS : Pseudo Random Binary sequence generator

Added Paths:
-----------
    trunk/octave-forge/main/comm/inst/prbs_generator.m
    trunk/octave-forge/main/comm/inst/prbs_iterator.m
    trunk/octave-forge/main/comm/inst/prbs_sequence.m

Added: trunk/octave-forge/main/comm/inst/prbs_generator.m
===================================================================

--- trunk/octave-forge/main/comm/inst/prbs_generator.m	                        (rev 0)
+++ trunk/octave-forge/main/comm/inst/prbs_generator.m	2009-04-13 22:16:33 UTC (rev 5705)
@@ -0,0 +1,50 @@
+## 
+## (C) 2006 Muthiah Annamalai <mut...@gm...>
+##
+## 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.
+## 
+function prbs=prbs_generator(polynomial,connections,initstate)
+  prbs.reglen=max(polynomial);
+  prbs.polynomial=polynomial;
+  prbs.sregs=initstate;
+  prbs.connections=connections;
+  prbs.conlen=length(connections);
+  return
+end


Property changes on: trunk/octave-forge/main/comm/inst/prbs_generator.m
___________________________________________________________________
Added: svn:executable
   + *

Added: trunk/octave-forge/main/comm/inst/prbs_iterator.m
===================================================================
--- trunk/octave-forge/main/comm/inst/prbs_iterator.m	                        (rev 0)
+++ trunk/octave-forge/main/comm/inst/prbs_iterator.m	2009-04-13 22:16:33 UTC (rev 5705)
@@ -0,0 +1,125 @@
+## 
+## (C) 2006 Muthiah Annamalai <mut...@gm...>
+## 
+## 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.
+##
+## 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_iterator(prbs,iterations)
+  if ( nargin < 2 )
+    iterations=2^(prbs.reglen)-1;
+  end
+  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)));
+      end
+      nstate(prbs.connections{itr2}(1))=val;
+    end
+    
+    ## 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.
+    end
+    
+  end
+  return;
+end
+
+##
+##  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);


Property changes on: trunk/octave-forge/main/comm/inst/prbs_iterator.m
___________________________________________________________________
Added: svn:executable
   + *

Added: trunk/octave-forge/main/comm/inst/prbs_sequence.m
===================================================================
--- trunk/octave-forge/main/comm/inst/prbs_sequence.m	                        (rev 0)
+++ trunk/octave-forge/main/comm/inst/prbs_sequence.m	2009-04-13 22:16:33 UTC (rev 5705)
@@ -0,0 +1,73 @@
+## 
+## (C) 2006 Muthiah Annamalai <mut...@gm...>
+## 
+## Implement book keeping for a Pseudo-Random Binary Sequence ( PRBS )
+## also called as a Linear Feedback Shift Register.
+## 
+## For the given PRBS in a intial state, compute the PRBS sequence length.
+## Length is period of output when the PRBS state is same as 
+## the start state of PRBS.
+## 
+## 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_sequence(prbs) #gives 15
+## 
+
+## See Also: This function is to be used along with functions 
+## prbs_generator.
+## 
+function itrs=prbs_sequence(prbs)
+  if nargin < 1
+    error("usage: prbs_sequence(prbs struct ); \
+	create the prbs sequence using prbs_generator() function. \
+	This function generates the ML length sequence of 1 period\
+	and returns to the user.")
+  end
+  nstate=zeros(1,prbs.reglen); 
+  itrs=0;
+  inits = prbs.sregs;
+  
+  ## For each iteration, shift the output bit. Then compute the xor pattern of connections. 
+  ## Finally apply feedback the stuff. Insert the computed pattern.
+  while( true )
+    itrs = itrs + 1;
+    
+    ## 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)));
+      end
+      nstate(prbs.connections{itr2}(1))=val;
+    end
+    
+    ## 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.
+    end
+    
+    if(isequal(prbs.sregs,inits))
+      break;
+    end
+  end
+
+  return;
+end


Property changes on: trunk/octave-forge/main/comm/inst/prbs_sequence.m
___________________________________________________________________
Added: svn:executable
   + *


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Thread: [Octave-cvsupdate] SF.net SVN: octave:[5705] trunk/octave-forge/main/comm/inst

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