The invention relates to a method and apparatus for controlling one or more characteristics of a service received by a mobile station in a mobile communications network across a radio communications link with a dynamically varying bandwidth. Bandwidth-sensing data packets are created for the purpose of determining changes in the bandwidth available across the link and transmissions of bandwidth-sensing data packets across the link are monitored. If timing information generated from the monitored transmissions indicates a change in the bandwidth, then one or more characteristics of the service received can be altered. With this new measure of the available bandwidth, the service received by a mobile station can be managed more intelligently, for example by instructing a bandwidth control function to alter the bandwidth available across the link, by instructing a handover control function to control a handover of the link from one fixed node to another fixed node, or by altering a data rate of the service data packets.