A heterogeneous communication system comprises a plurality of heterogeneous access networks and a core network connecting the heterogeneous access networks. An admission server of the core network receives resource indications indicative of an estimated resource usage for a given communication service and a given access point of an access network. The admission server furthermore determines and stores current resource availability indications for access points. When a communication session request comprising a communication service indication and an access point identification is received, the admission server determines an estimated resource requirement for the communication sessions based on the resource indications. The admission server then determines whether to allow the communication session dependent on the resource availability for the access point and the estimated resource requirement for the communication service.