function get_X_pinv_2x2(chantype,sampletime)
% get Pseudoinverse of X
% X: time domain transimitter matrix

PwNorm=sqrt(2048/1702);

switch chantype,
    case 1,     % SUI-1 Channel
        tau = [0 0.4 0.9];      % tap delay in us
    case 2,     % SUI-2 Channel
        tau = [0 0.4 1.1];
    case 3,     % SUI-3 Channel
        tau = [0.0 0.4 0.9];
    case 4,     % SUI-4 Channel
        tau = [0 1.5 4];
    case 5,     % SUI-5 Channel
        tau = [0 4 10];
    case 6,     % SUI-6 Channel
        tau = [0 14 20];
    otherwise,
        error('Unrecognized channel model');
end
L=max(round(tau/sampletime))+1;

% -----------2x2 MIMO Preamble-----------
load Wk_preamble.mat;
preamdata_tx1=zeros(1,1703);
preamdata_tx2=zeros(1,1703);
preamdata_tx1(2:2:end)=sqrt(2)*sqrt(2)*2*(0.5-Wk_preamble(2:2:end));    % first sqrt(2)--3 dB Boost, second sqrt(2)-- unitary symbol power
preamdata_tx2(1:2:end)=sqrt(2)*sqrt(2)*2*(0.5-Wk_preamble(1:2:end));    % Antenna 1 use even subcarriers, Antenna 2 use odd ones
preamdata_tx1(852)=0;  % DC carrier
preamdata_tx2(852)=0;
pream_tx1_freq=[zeros(1,173),preamdata_tx1,zeros(1,172)]*PwNorm;
pream_tx2_freq=[zeros(1,173),preamdata_tx2,zeros(1,172)]*PwNorm;
% IFFT
pream_tx1_time=sqrt(2048)*ifft(fftshift(pream_tx1_freq),2048);
pream_tx2_time=sqrt(2048)*ifft(fftshift(pream_tx2_freq),2048);

% Generate Tx 1 convolutional matrix
x1_row=[pream_tx1_time(1),pream_tx1_time(end:-1:end-L+2)];
x1_column=pream_tx1_time;
x1=toeplitz(x1_column,x1_row);

% Generate Tx 2 convolutional matrix
x2_row=[pream_tx2_time(1),pream_tx2_time(end:-1:end-L+2)];
x2_column=pream_tx2_time;
x2=toeplitz(x2_column,x2_row);

X=[x1,x2];

X_pinv=pinv(X);

switch chantype,
    case 1,     % SUI-1 Channel
        save X_pinv_sui1.mat X_pinv;
    case 2,     % SUI-2 Channel
        save X_pinv_sui2.mat X_pinv;
    case 3,     % SUI-3 Channel
        save X_pinv_sui3.mat X_pinv;
    case 4,     % SUI-4 Channel
        save X_pinv_sui4.mat X_pinv;
    case 5,     % SUI-5 Channel
        save X_pinv_sui5.mat X_pinv;
    case 6,     % SUI-6 Channel
        save X_pinv_sui6.mat X_pinv;
    otherwise,
        error('Unrecognized channel model');
end