Couldn't debug "your objective function is not a scalar"

Hello Everyone,
When I run my code in Matlab, I get the error message “your objective function is not a scalar”. I am new to CVX, please help me to solve this problem. Below is my Matlab code:

clc; 
M = 2;
K = 10;
N = 8; 
B_total = 20 *10^6; % in hertz
P_total = 100; % in watt 
QoS_req = 10*10.^6; %in bps
for i = 1:M
    b_initial(i) = 2;
    for j = 1:K;
        w_initial(:,:,i,j) = complex(randn(N,1),randn(N,1));
        h(:,:,i,j) = complex(randn(N,1),randn(N,1));
        SINR_initial(i,j) = 1024; 
        y_initial(i,j) = 1;
    end 
end
cvx_begin
    a= 0;
    variables b(M) x(M,K) y(M,K) SINR(M,K);
    variable w(N,1,M,K) complex;
    whos
    maximize (x)
    subject to
        for i = 1:M
            H =[];
            c=[];
            for j = 1:K
                a = a + pow_pos(norm(w(:,1,i,j),2),2);
                log(1+SINR(i,j))./log(2) >= y(i,j);
                2*(b(i)+y(i,j))*(b_initial(i)+y_initial(i,j))-(b_initial(i)+y_initial(i,j)).^2 >= 2*x(i,j) +b(i).^2+y(i,j).^2;
                H = h(:,:,i,j)*h(:,:,i,j)';
                for l = 1:K
                    if l~=j
                        c = c+ ((h(:,:,i,j)'*w(:,1,i,l))*(h(:,:,i,j)'*w(:,1,i,l))');
                    end
                end
                log(1+SINR(i,j))./log(2) >= (QoS_req)*inv_pos(b(i));
                c+b(i)*10^(-11) <= ((2*w(:,1,i,j)'*H*w_initial(:,1,i,j))./(SINR_initial(i,j)) - SINR(i,j)*((w_initial(:,1,i,j)'*H*w_initial(:,1,i,j))./(SINR_initial(i,j)).^2));
            end
        end
        sum(b) <= B_total;
        a <= P_total;
cvx_end

Thanking you for your help.

Your objective function is a matrix. The objective function needs to evaluate to s scalar.

Thank you for your help.