This paper lists various limitations in 2.5G, 3G cellular networks regarding services, and contrasts this to a characterization of fourth-generation wireless networks (4G). In order to investigate 4G’s feasibility, costeffectiveness, necessary functionality, and its potential with respect to services we created a testbed by adding wireless extensions to a public Gigabit IPnetwork, which was further enhanced with VoIP/SIP to deliver interoperability with existing services and to enable mobile multimedia applications. We present our experiences and analyze the cost-effectiveness of providing (wireless) access to existing voice services in this testbed, how and where these services and end-users can be hosted, and how interworking with services over other networks can be arranged. Furthermore, we present a service architecture to negotiate adaptive mobile multimedia communication, with minimal shared service knowledge, which enables applications to adapt to and make optimal use of the heterogeneous mobile infrastructure. We demonstrate the latter by presenting results from building a mobile-aware media-player, and extend it further to take into account the user’s context. In conclusion, we show the feasibility and cost-effectiveness of building 4G networks and provisioning of adaptive mobile multimedia applications by extending the emerging broadband infrastructure with existing wireless LANs.