## 1 Introduction  
In the framework of the most advanced telecommunication systems and projects the following kinds of _horizontal_ interoperations are being pursued: service/content interoperation and transport interoperation (this last including physical interoperation, MAC interoperation and network interoperation):  
1. The _service/content interoperation_ allows the users to benefit, in a fully context-aware fashion, of heterogeneous services/contents provided by heterogeneous service/content providers. The target is to allow users (i) to discover the services/contents, even provided by heterogeneous service/content providers, which are appropriate for them in the present context, (ii) to aggregate the services/contents in order to create personalized services/contents meeting their expectations, (iii) to distribute the aggregated services/contents to properly selected people. Several research projects have defined SoA-based _service and content convergence layers_ able to assure such interoperations. For instance, the FP6 Daidalos I and II IP projects [1] as for the service interoperation and the FP7 P2P-Next IP project [2] as for the content interoperation, have developed (i) advanced ontologies allowing a formal description of services/contents and (ii) basing on such ontological service/content descriptions, the procedures for context aware discovery, composition, re-composition and distribution of services/contents. * The _transport interoperation_ allows to assure interoperation among heterogeneous access networks (in the following, also referred to as \"underlying networks\" or \"underlying technologies\", or \"networks\"). The transport interoperation includes at least the _physical interoperation_ (layer 1)_, the MAC interoperation_ (layer 2) and the _network interoperation_ (layer 3). The target of these interoperations is to satisfy the requirements of users equipped with multi-mode terminals, in terms of Quality of Service (QoS), security and mobility, when roaming across heterogeneous underlying networks. Several research projects [3] have defined, at various layers (ranging from physical to network layer), _transport convergence layers_ able to assure such interoperations. For instance, the FP7 IP OMEGA project [4] is implementing a \" convergence layer\" which, based on the monitoring of some appropriate parameters of the heterogeneous wireless underlying networks, takes appropriate control provisions aiming at achieving a flexible and efficient selection of the underlying networks which should support the connections (in particular, a connection can be supported even by more than one underlying network), as well as an optimized real-time routing of the packets among the selected (possibly heterogeneous) underlying networks (load balancing). Although several research projects have already achieved valuable results in the framework of horizontal interoperation and optimization, at content, service, network, MAC, and physical levels, in general they have dealt with them in a separate, uncoordinated fashion: this particularly applies to service/content interoperations versus transport interoperations. No research project has still attempted to draw an unifying and coordinated perspective of all the horizontal interoperations; in other words, no research project has still attempted to add a _vertical interoperation and optimization_ to the horizontal interoperations. In this respect, this paper outlines an innovative architecture which achieves the collapsing of the service/content and transport convergence layers.