CST Boundary condition

I want to simulate a monopole antenna, provided with a ground plane.
Can someone please explain what settings to be put in 'boundary conditions' and 'background material' in CST Microwave Studio.... considering I want it to simulate anechoic chamber surrounding.

Set your boundaries to open (add space) in all directions and set your background material to normal.

hi bannay,
i want to understand the physical meaning of the boundary conditions and the cases which i set it to ( open add space) or to ( electric, magnetic, conducting wall and open )
thnx in advance