Disclosed is a method of determining the validity of service announcements in a cellular mobile network, wherein a multimedia broadcast/multicast service (MBMS) is provided, a service area (SA) is defined by the availability of a specific broadcast/multicast service which availability is announced in each cell, and the method comprises: generating a service announcement area identification (SAA id) which is the same for cells with identical service announcements; and checking by a user entity (UE) upon arrival in a new cell which service announcement is valid by receiving the service announcement area identification (SAA id). Also disclosed are a corresponding system and user entity.