combiner.m

这个程序主要是实现空时编码的matlab编解码仿真。

function [combined_signal]=combiner(alpha1, theta1, alpha2, theta2, sampled_inphase_signal, sampled_quad_signal, model)

%   [combined_signal]=combiner(alpha1, theta1, alpha2, theta2, sampled_inphase_signal, sampled_quad_signal, model)
%
%   Output:
%   combined_signal         - The combined signal using Alamouti algorithm
%   
%   Using the channelmodel h = alpha * exp(theta), h1 and h2 are
%   channels over which the information is sent via antenna 1 and 2.
%
%	alpha1                  - Channel 1
%   theta1                  -
%   alpha2                  - Channel 2
%   theta2                  -
%   
%   sampled_inphase_signal  - Inphase signal which has been downsampled in reciever.
%   sampled_quad_signal     - Quadrature dito.
%
%   model		            - 0: no Alamouti coding, 1: Alamouti coding
%
%   Short Theoretical Background for the Function:
%
%   This funcion combines signals sent from two different
%   antennas, using the Alamouti algorithm and the estimates
%   from the channel estimator.
%   s0 = h1* r0 + h2 r1*
%   s1 = h2* r0 - h1 r1*, where r0 is recieved signal at time (0,T) and r1 at time (T,2T).
%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%     
%%% Function part of simulation for Space-Time
%%% coding project, group Grey-2001.
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
%   Author: Stefan Uppg錼d
%   Date: 2001-03-23
%   Version: 1.0
%   Revision (Name & Date):
%   FH 2001-04-02       more efficient combining without for...
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

received = complex(sampled_inphase_signal,sampled_quad_signal);
s = zeros(1,length(received));

if model == 0 				% This case, no Alamouti, compensating for phase only.
   
    s = exp(j*(-theta1)) * received;
elseif model == 1           % Alamouti coding
    
    odd = received(1:2:end);
    even = received(2:2:end);

    s(1:2:end) = alpha1 * exp(j*(-theta1)) * odd + alpha2 * exp(j*theta2) * conj(even);
    s(2:2:end) = alpha2 * exp(j*(-theta2)) * odd - alpha1 * exp(j*theta1) * conj(even);
end

combined_signal = s;