# ERROR: Cannot perform the operation: {concave} ./ {real affine}

(Hassan Fawaz) #1

Hello,
I tried reading the previous responses to people with the same problem, but it did not help me a lot. I believe the problem is convex (maximizing a concave function subject to linear constraints) so I don’t think that is a problem here.
The code:

> cvx_begin
> cvx_solver mosek
> variable pUL(5,30)
> expression objective
> ULUtility=cvx(zeros(5,30));
>  for j=1:5
>         for sc=1:30
>            if round(W(i,j,sc))==1
>               ULUtility(i,sc)=((10/log(10))*log(pUL(i,sc)*BS_antenna_gain*UE_antenna_gain*X(Mobile_user(I).ID,t)./(A*(sigma_2+(pDL1(j,sc)/SIC)))))/(pUL(i,sc)*UE_antenna_gain*UE_antenna_gain*Y(Mobile_user(J).ID,t)./D);
>            else
>               ULUtility(i,sc)=0;
>            end
>         end
>      end
> objective=sum(sum(ULUtility));
>               maximize (objective)
>               subject to
>               sum(pUL(i,:))<=0.25;
>               for sc=1:N_sc
>                   if sum(W(i,:,sc))==1
>                      pUL(i,sc)>=0.001;
>                   end
>               end
>              pUL(i,isc)>=0.01;
>               cvx_end

eh it’s not clean but all the non-optimization values in this equation are defined. The problem is obviously with the Objective (sum of ULUtility). But idek

(Mark L. Stone) #2

Have you proven that

ULUtility(i,sc)=((10/log(10))*log(pUL(i,sc)*BS_antenna_gain*UE_antenna_gain*X(Mobile_user(I).ID,t)./(A*(sigma_2+(pDL1(j,sc)/SIC)))))/(pUL(i,sc)*UE_antenna_gain*UE_antenna_gain*Y(Mobile_user(J).ID,t)./D);

is concave? If so, how? If it is concave, it will require a reformulation in order to be enterded into CVX in accordance with its DCP rules/

(Hassan Fawaz) #3

Thank you ! I did find the problem it’s bad