Admission control and QoS adaptation are the basics of service management in mobile networks characterized by limited resources and bandwidth fluctuation. The link bit rate was the only factor considered by most of research efforts to control admission and to adapt mobile services. Moreover, most of adaptation proposals did not account for interference, which represents a important limiting issue of network performance. This paper proposes a new approach of admission control and service adaptation that takes into account, not only both bandwidth and loss rate requirements, but also user mobility with the objective of maximizing the number of admitted services while limiting signalling overhead and interference to neighbour cells. The simulation of a third generation mobile network has allowed the comparison of other schemes with the proposed approach. The latter outperformed the proposals of equal priority, guard channel capacity and request-based reservation with respect to the number of admitted services. Moreover, our service degradation and enhancement scheme further improved the admission probability, when compared to the rate-based borrowing approach, in indoor and outdoor environments.