Antennas Concentrated in a Single Point
The antenna pattern is based on the assumption of radiation from a single point (therefore they are only valid in larger distances (several wavelengths) to the antennas. In the near filed different approaches are used to determine the radiated field (for example, FEM and MoM). Due to this single point radiator concept, the propagation can be approximated with spherical waves (and different gains in different directions).
If the distances to obstacles are several wavelengths (what is true for the frequencies in cellular wireless (more than 800 MHz) and the configurations supported with MASC, the local wavefront is nearly planar and the well-known equations to compute the reflection, penetration and diffraction losses can be applied.