correlation.m

alamouti 空频分组码---在时变信道下SFBC-OFDM

% Correlation between C(n,k)
function Ec = Correlation (n_1, k_1, n_2, k_2, d, M, N, fm, fs)

% order of C(n,k)
%n_1 = 0;k_1 = 0;
%n_2 = 2;k_2 = 2;

% parameters
%d = 1;                                              % Tao_rms/T
%M = 12;                                             % Number of paths
%N = 128;                                            % Number of subcarries
%fm = 1000;                                          % Maximum Doppler Spread
%fs = 800000;                                        % Sampling Rate 1/T

% besselJ function
J = besselj(0, 2*pi*fm/fs*(0:N-1));

% caculation of Ec
Temp = 0;
for l_1 = 0:(N-1)
    for l_2 = 0:(N-1)
       Temp = Temp + J(abs(l_1-l_2)+1) * exp(sqrt(-1)*2*pi*(l_1*(n_1-k_1)-l_2*(n_2-k_2))/N);
    end
end
Ec = Temp/N/N ...
    *( (1-exp(-1/d))*(1-exp(-M/d)*exp(-sqrt(-1)*2*pi*M*(n_1-n_2)/N)) )/( (1-exp(-M/d))*(1-exp(-1/d)*exp(-sqrt(-1)*2*pi*(n_1-n_2)/N)));