% STTD MIMO encoder and modulator

function [y, Tx] = mimo_en(D,M,L,bit_n)

% D : dec_data
% L : chip_data Length
% bit_n : bit number / symbol
% M : Modulation M - QAM

% Tx : encoded data
% Tx_1 : transmitted data through the antenna 1
% Tx_2 : transmitted data through the antenna 2
% num_Tx : number of transmit antenna 


% variable in MIMO
Tx = zeros(L/bit_n, 1); 
% Tx_1 = zeros(L/bit_n, 1);
% Tx_2 = zeros(L/bit_n, 1);
% 
a = modem.qammod('M', M, 'SymbolOrder', 'Gray');
y = modulate(a, D);
scale = modnorm(y, 'avpow', 1);
y_s = scale * y;

Tx = y_s;
% s1 = y_s(1:2:end);        % 圈薦鍋擄 單撈磐
% s2 = y_s(2:2:end);        % 婁薦鍋擄 單撈磐
% 
% diversity encoding
% 1 column : 救拋唱 1   2 column : 救拋唱 2
% Tx(1:2:end, :) = [s1 s2];
% Tx(2:2:end, :) = [-conj(s2) conj(s1)];
% % 
% Tx_1 = Tx(:, 1);        % 救拋唱 1
% Tx_2 = Tx(:, 2);        % 救拋唱 2
%