makepulse.m

MIMO and VBLAST( please see the documentation)

function pulse = makepulse(shape,cutoff,time,samples,rolloff,varargin)

%MAKEPULSE Modulation impulse design.
%   PULSE = MAKEPULSE(SHAPE,CUTOFF,TIME,SAMPLES,ROLLOFF) returns 
%   samples of desired SHAPE of modulation impulse. Possible values for 
%   SHAPE are 'SqRRC'|'Rect' a square-root raised cosine and rectangular
%   shape respectively. CUTOFF corresponds to the impulse shortening
%   in sense of CUTOFF * SAMPLES where TIME denotes a symbol duration. For
%   example if CUTTOFF = 8 than MAKEPULSE gives the impulse of total
%   length equals to 8 * SAMPLES + 1. A one sample is added to ensure
%   symbol symetry and correct sampling.AMPLES corresponds to the number
%   of samples per symbol. When a 'SqRRC' option is chosen than a ROLLOFF
%   factor must be specified; 0 < ROLLOFF < 1. All the impulses are
%   designed to have a unit energy.
%
%   PULSE = MAKEPULSE(...,'EchoOn') toggles function internal echo on. 
%
%   See also MODUL.

%   Copyright 2001-2002 Kamil Anis, [e-mail]
%   Dept. of Radioelectronics, 
%   Faculty of Electrical Engineering
%   Czech Technical University in Pragu
%   $Revision: 2.0 $  $Date: 2002/10/23 17:33:28 $
%   --
%   <additional stuff should go here>


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switch shape
case 'Rect'
  pulse = linspace(1 / sqrt(cutoff * time),...
      1 / sqrt(cutoff * time),samples * cutoff);
    
case 'SqRRC'
	singul = time / (4 * rolloff);
	tt = linspace(-cutoff * time / 2,...
          cutoff * time / 2,samples * cutoff + 1);
	
	z = find(tt == 0);
	k = find(abs(tt) == singul);
	
	% Checking for singularities...
  if (isempty(z) == 0) & (isempty(k) == 0) % zero & non-zero singularity
      n = [find(tt < -singul),find((tt > -singul) & (tt < 0)),...
        find((tt > 0) & (tt < singul)),find(tt > singul)];
      t = tt(n);
          
      pulse(n) = (1 ./ (sqrt(time) .* (1 - (4. * rolloff ./...
        time) .^ 2 .* t .^2))) .* ((sin((1 - rolloff) .* pi .* t ./...
        time) ./ (pi .* t ./ time)) + (4 .* rolloff .*...
        cos((1 + rolloff) .* pi .* t ./ time) ./ pi));

			pulse(z) = (1 / sqrt(time)) * (1 - rolloff + 4 * rolloff / pi);	
			
			pulse(k) = rolloff * ((-2 + pi) * cos(pi / (4 * rolloff)) +...
        (2 + pi) * sin(pi / (4 * rolloff))) / (pi * sqrt(2) *...
        sqrt(time));
  
  elseif (isempty(k) == 0) % non-zero singularity
		n = [find(tt < -singul),find(abs(tt) < singul),find(tt > singul)];
		t = tt(n);
            
		pulse(n) = (1 ./ (sqrt(time) .* (1 - (4 .* rolloff ./...
      time) .^ 2 .* t .^ 2))) .* ((sin((1 - rolloff) .* pi .* t ./...
      time) ./ (pi .* t ./ time)) + (4 .* rolloff .*...
      cos((1 + rolloff) .* pi .* t ./ time) ./ pi));
		
		pulse(k) = rolloff * ((-2 + pi) * cos(pi / (4 * rolloff)) + (2 + pi) *...
      sin(pi / (4 * rolloff))) / (pi * sqrt(2) * sqrt(time));
      
	elseif isempty(z) == 0 % zero singularity
		n = [find(tt < 0),find(tt > 0)];
    t = tt(n);
          
		pulse(n) = (1 ./ (sqrt(time) .* (1 - (4 .* rolloff ./...
      time) .^ 2 .* t .^ 2))) .* ((sin((1 - rolloff) .* pi .* t ./...
      time) ./ (pi .* t ./ time)) + (4 .* rolloff .*...
      cos((1 + rolloff) .* pi .* t ./ time) ./ pi));
		
		pulse(z)=(1 / sqrt(time)) * (1 - rolloff + 4 * rolloff / pi);
          
  else % no singularity found
    t = tt;
   
    pulse = (1 ./ (sqrt(time) .* (1 - (4 .* rolloff ./...
      time) .^ 2 .* t .^ 2))) .* ((sin((1 - rolloff) .* pi .* t ./...
      time) ./ (pi .* t ./ time)) + (4 .* rolloff .*...
      cos((1 + rolloff) .* pi .* t ./ time) ./ pi));
	end 
end 

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if (isempty(varargin) == 0) & (varargin{end} == 'EchoOn')
	[indent,gap,name] = iprompt('MAKEPULSE:');
	
	str1 = num2str(length(pulse));
	str2 = num2str(rolloff);
	
	disp(' ');
	disp([name,gap,str1,' samples of ',shape,...
		' impulse generated; roll-off -> ',str2,'.']);
	disp(' ');
end