% Channel Capacity of LTE mode 5 with the eNodeB with 2 antennas and 2
% single antenna users using the scheduling algorithm of aligning
% interference in the opposite quadrant


% clear;
% clc;
% close all;
% warning off all
% format('long');

% LTE with scheduling in opposite quadrant or without scheduling
%sigmasq_x2_all = 0:0.1:1;
%for i = 1:length(sigmasq_x2_all)

M1=4;% QAM on first antenna
M2=4;% QAM on second antenna
SNR = 0:9;
N_channel = 1000;  % No of channel realizations
N_noise = 100;  % No of noise realizations

alpha_1 =zeros(length(SNR),N);
beta_1 =zeros(length(SNR),N);
alpha_2 =zeros(length(SNR),N);
beta_2 =zeros(length(SNR),N);
chcap_lte_sch1 = zeros(length(SNR),N);
chcap_lte_sch2 = zeros(length(SNR),N);
chcap_lte_sch = zeros(length(SNR),N);

for v=1:length(SNR)
    seed(1) = 13579;
    seed(2) = 24680;
    rand('state', seed(1));
    randn('state', seed(2));
    N0=10^(-SNR(v)/10);
    sigmasq_x1 = 0.5;
    sigmasq_x2 = 0.5;
    [stream1]=sqrt(sigmasq_x1)*mapping(M1);     %x1   1x648
    [stream2]=sqrt(sigmasq_x2)*mapping(M2);     %x2   1x648
    for k=1:N %channel loop
        fprintf('v=%d,k=%d\n',v,k);
        [h1 h2]=channel;
        H=[h1 h2];  %first row is the channel to user-1 and second row is the channel to user-2
        match_precoder_norm=(1/sqrt(2))*[H(1,:)'/norm(H(1,:)) H(2,:)'/norm(H(2,:))]; %Frobenius norm is 1
        lte_precoder=[(match_precoder_norm(1,1))'*match_precoder_norm(:,1)  (match_precoder_norm(1,2))'*match_precoder_norm(:,2)];
        lte_precoder_norm=[lte_precoder(:,1)/lte_precoder(1,1)  lte_precoder(:,2)/lte_precoder(1,2)];
        lte_std_precoder=[1 -1 sqrt(-1) -sqrt(-1)];
        [val pos]=min([-real(lte_precoder(2,1))  real(lte_precoder(2,1))  -imag(lte_precoder(2,1))   imag(lte_precoder(2,1))]);
        lte_precoder_norm1=[1;lte_std_precoder(pos)];
        [val pos]=min([-real(lte_precoder(2,2))  real(lte_precoder(2,2))  -imag(lte_precoder(2,2))   imag(lte_precoder(2,2))]);
        lte_precoder_norm2=[1;lte_std_precoder(pos)];
        lte_precoder_qtz_orig=(1/sqrt(4))*[ lte_precoder_norm1   lte_precoder_norm2];
        %Scheduling to put interference in the opposite quadrant
        lte_precoder_qtz1=[ lte_precoder_qtz_orig(1,1)   lte_precoder_qtz_orig(1,2); lte_precoder_qtz_orig(2,1)   -lte_precoder_qtz_orig(2,1)];  %For opposite precoder
        lte_precoder_qtz2=[ lte_precoder_qtz_orig(1,1)   lte_precoder_qtz_orig(1,2); -lte_precoder_qtz_orig(2,2)   lte_precoder_qtz_orig(2,2)];  %For opposite precoder
        alpha_1(v,k)=H(1,:)*lte_precoder_qtz1(:,1);
        beta_2(v,k)=H(1,:)*lte_precoder_qtz1(:,2);
        beta_1(v,k)=H(2,:)*lte_precoder_qtz2(:,1);
        alpha_2(v,k)=H(2,:)*lte_precoder_qtz2(:,2);
        
        logsum_lte_sch1=0;
        logsum_lte_sch2=0;
        for l=1:10 %noise loop
            z=sqrt(N0)*sqrt(1/2).*(randn(1,1)+sqrt(-1)*randn(1,1));
            for s1=1:M1
                x1=stream1(s1);
                for s2=1:M2
                    x2=stream2(s2);
                    y_lte1=alpha_1(v,k)*x1+beta_2(v,k)*x2+z;
                    y_lte2=beta_1(v,k)*x1+alpha_2(v,k)*x2+z;
                    den_lte_sch1=0;
                    den_lte_sch2=0;
                    %For first stream
                    for t=1:M2
                        x2_d=stream2(t);
                        den_lte_sch1=den_lte_sch1+exp((-1/N0)*norm(y_lte1-H(1,:)*lte_precoder_qtz1(:,1)*x1-H(1,:)*lte_precoder_qtz1(:,2)*x2_d)^2);
                    end
                    % For second stream
                    for t=1:M1
                        x1_d=stream1(t);
                        den_lte_sch2=den_lte_sch2+exp((-1/N0)*norm(y_lte2-H(2,:)*lte_precoder_qtz2(:,1)*x1_d-H(2,:)*lte_precoder_qtz2(:,2)*x2)^2);
                    end
                    neu_lte_sch1=0;
                    neu_lte_sch2=0;
                    for g=1:M1;
                        x1_dd=stream1(g);
                        for h=1:M2
                            x2_dd=stream2(h);
                            neu_lte_sch1=neu_lte_sch1+exp((-1/N0)*norm(y_lte1-H(1,:)*lte_precoder_qtz1(:,1)*x1_dd-H(1,:)*lte_precoder_qtz1(:,2)*x2_dd)^2);
                        end
                    end
                    %For second stream
                    for g=1:M2;
                        x2_ddd=stream2(g);
                        for h=1:M1
                            x1_ddd=stream1(h);
                            neu_lte_sch2=neu_lte_sch2+exp((-1/N0)*norm(y_lte2-H(2,:)*lte_precoder_qtz2(:,1)*x1_ddd-H(2,:)*lte_precoder_qtz2(:,2)*x2_ddd)^2);
                        end
                    end
                    logsum_lte_sch1=logsum_lte_sch1+log2(neu_lte_sch1/den_lte_sch1);
                    logsum_lte_sch2=logsum_lte_sch2+log2(neu_lte_sch2/den_lte_sch2);
                end
            end
        end
        
        chcap_lte_sch1(v,k)=log2(M1)-logsum_lte_sch1/(M1*M2*N_noise);
        chcap_lte_sch2(v,k)=log2(M2)-logsum_lte_sch2/(M1*M2*N_noise);
        chcap_lte_sch(v,k)=log2(M1)-logsum_lte_sch1/(M1*M2*N_noise)+log2(M2)-logsum_lte_sch2/(M1*M2*N_noise);
        
    end
    
end
%end

%save QPSK_QPSK_lte_Mode5.mat;