raised_cosine.m

这个程序主要是实现空时编码的matlab编解码仿真。

function h = raised_cosine(Q, b, trunc)

%   function h = raised_cosine(Q, b, trunc)
%
%	Output:
%	h           - Raised-cosine shaped pulseform.
%   
%   Input:
%	Q           - Oversample-factor.
%   b           - Beta, the roll-off factor. Set to 0.22 if not specified.
%   trunc       - Decides how many periodes in raised-cosine before truncation.
%   
%   Short Theoretical Background for the Function:
%
%   The raised-cosine function is given by:
%   x(t) = sinc(t/T)*cos(pi*Beta*t/T) / (1 - 4*Beta^2*t^2/T^2);
%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%     
%%% Function part of simulation for Space-Time
%%% coding project, group Grey-2001.
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
%   Author: Stefan Uppg錼d
%   Date: 2001-04-06
%   Version: 1.0
%   Revision (Name & Date & Comment):
%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

if nargin < 3
  trunc = 5;
end

if nargin < 2
  b = 0.22;
end

% The symbol time T is assumed to be unity.

T = 1*Q;
t = -trunc*Q:1:trunc*Q;

h = ( cos(b*pi*t/T) .* sinc(t/T) ) ./ ...  
    (1-4*b^2*t.^2/T^2);

% Normalize

h = h / sqrt(h*h');