In a network environment where the presence of heterogeneous wireless accesses is becoming more and more likely, it becomes critical to achieve an efficient management of the available radio resources. This is one of the main objectives which are being pursued by the Ambient Networks project. One of the main distinctive aspects of this work is that it is going further of state of the art, since the goal is to assess the feasibility of the proposed solution by means of a prototype based on existing ('off-the-shelf) devices and technologies. In this paper we describe the main characteristics of the multi radio access architecture which is being specified in the framework of the aforementioned project, encompassing two main entities: the Multi Radio Resource Management and the Generic Link Layer. Furthermore, we also describe the interfaces that have been specified to be used between them and we discuss how the architecture is mapped onto a software implementation.