delay.m

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%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%  Property of Freescale
%  Freescale Confidential Proprietary
%  Freescale Copyright (C) 2005 All rights reserved
%  ------------------------------------------------------------------------
%  $RCSfile: delay.m.rca $
%  $Date: Sun Oct 22 03:19:41 2006 $
%  Target: Matlab
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%  802.16-2004 OFDMA PHY - Continuous time delay
%
%   Description: y = delay(x,t0,fs,OutLen) introduces a continuous 
%                time delay to the input vector x.
%
%   Output:
%       y => Matrix of delayed versions of input vector, x. One
%            column for each delay specified in the vector, t0.
%            A transient is present at the begining of each 
%            output column lasting for 5+floor(t0*fs) samples. 
%            The algorithm exhibits a low pass response but preserves 
%            50% of the input Nyquist bandwidth. It is recommended 
%            that the input signal use a 2X oversample rate for 
%            this reason.
%
%   Inputs:
%       x => Input vector.
%       t0 => Vector of delays in seconds to be introduced into
%             the input vector. Positive and negative delays are
%             supported. Delays can also be zero.
%       fs => Sample rate in Hz.
%       OutLen => Optional parameter that specifies the length of
%                 the output vector. Defaults to the length of x.
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
function y=delay(x,t0,fs,OutLen)

thresh = 1e-6;

if nargin==3
    OutLen=length(x);
end

% Make the input vector a column.
[R C]=size(x);
if R==1,
    x=transpose(x);
end

for k=1:length(t0),

% Convert time delay in seconds to sample periods

    n0=-t0(k)*fs;
    frac_n0=n0-round(n0);
    int_n0=round(n0);

% Implement integer delay
    x2=x;
    if int_n0<=0
        x2=[zeros(-int_n0,1); x(1:length(x)+int_n0)];
    elseif int_n0>0
        x2=[x(1+int_n0:length(x)); zeros(int_n0,1)];
    end

% Implement fractional delay
     if 0
    %if  abs(frac_n0) > thresh,
% Raised cosine shape in the frequency domain
        n=[-5+frac_n0:1:5+frac_n0];
        B=1/3;
        fsT=2*(1-B);
        h=sinc(n/fsT).*cos(pi*B*n/fsT)./(1-(2*B*n/fsT).^2);
        h=h/sum(h);
        temp=filter(h,1,[x2; zeros(5,1)]);
    
% Remove transient from the begining (filter delay)
        size(y);
        size(temp);
        y(:,k)=temp(6:end);
    else
        y(:,k)=x2;
    end
end

% Set desired length

TailLen=OutLen-size(y,1);
if TailLen >= 0
    y=[y; zeros(TailLen,size(y,2))];
else
    y=y(1:OutLen,:);
end