The present invention relates to a mobile network (10) organized into a plurality of location areas and service areas gathering a geographically homogeneous set of cells of the mobile network, with gathering of the femtocells into specific additional service areas. The arrival of a received phone call intended to a user equipment (14) coupled to a femtocell (30) triggers a location step, with communication to the switching center of a rough location comprising the service area codes SAC and location area codes LAC corresponding to the femtocell, and of a fine location comprising unique data, such as IP address and INSEE code, of identification of the Internet box (20) associated to the femtocell. The femtocells may hence operate in open mode, each femtocell being able to be coupled to any user equipment registered with the mobile network operator.