The argument of trace must be square. That requirements applies to MATLAB expressions (i.e., numerical arguments) and to CVX expressions… W is 2 by 1, so trace(W) produces an error message,
I suggest you re-read whatever paper you found this in, and think through what input data makes sense.
Also, note that it is perfectly fine to include the statement maximize 0;
in your CVX code. However, it does nothing, and can be omitted. maximize 0 (or any constant) , or minimize 0 (or any constant) has the same effect as not having a maximize statement or minimize statement, namely, to specify a feasibility problem, which is solved if any feasible solution is returned by the solver.
When G is 1 by m, as you have then G*W is a scalar, so you can take the norm or trace of that (although if G were n by m, with n > 1, it might make a more interesting example). Also, norm (in any norm) can be applied to an argument of any dimension.
If you are getting an error, you need to show a complete reproducible example, with all inputs, and show the complete output, including error messages. You might benefit from brushing up on MATLAB basics before trying to use CVX.