The capacity and coverage of a packet-based conversational service in a mobile communications system is increased by efficiently provisioning resources for packets that have different length headers transported over the radio interface during the period over which the service is provided. A radio bearer or connection is established between a mobile radio and a radio network to support a packet-based conversational service. The radio bearer or connection is normally configured with radio resources to deliver a particular quality of service assuming that the packet headers will be highly compressed. The length of packets to be transmitted via the radio bearer is checked. Those packets which are longer because of less header compression are detected. Processing is performed to minimize or reduce that impact on system capacity or coverage when the detected packets are transmitted over the radio bearer or connection.