Abstract: An apparatus collects, from mobile stations, first information indicating communication qualities of communications between the mobile stations and base stations, in association with position information indicating a position of each of the mobile stations, and determines, based on the first information for each of zones corresponding to the position information, whether a handover communication of a first mobile station to a first zone is unavailable. Upon determining that the handover communication of the first mobile station to the first zone is unavailable, the apparatus specifies the first zone as an unavailable area. When availability of the handover communication to a second zone, which is adjacent to the first zone of the unavailable area, is not defined yet and the second zone is adjacent to a plurality of the first zones determined as the unavailable area, the apparatus estimates the second zone as the unavailable area.