1 This work has been partially supported by the IST Project MOBIVAS. ABSTRACT The transport mechanisms of Internet have an inherent drawback, which is due to their generality. Internet has to support a broad range of services (data, audio, video, etc.) on top of a unique protocol stack. On the other hand, it is well known, that there is a high potential for QoS and efficiency improvement if joint source and channel coding are used. Utilization of this potential is especially attractive in the case of interactive multimedia transmitted over wireless channels. In this paper we present the Mobile Adaptation System (MAS), which supports the dynamic deployment of boosters for flow selective link level packet treatment in wireless Internet access. These boosters use the knowledge of the importance of individual packets, or relations among packets in order to optimise the link layer transmission. We discuss our approach using as example a speech property based (SPB) booster for improvement of the perceptual quality of Voice over IP transmission in Wireless LANs.