"The present document contains the result from the study of introduction of support for A-interface over IP. High level areas that are studied are e.g. potential placement of transcoders in the core network@ effective bandwidth utilisation at the A-interface@ impact on call related messages@ payload formats. The following items shall be covered in the study: In the target solution it is wanted to transfer compressed speech as far as possible end-to-end to achieve efficient transport and speech quality. The possibility to free GERAN from handling all kind of transcoders shall be studied@ and the architecture might place Codecs in the core network. Impacts/changes on current A-interface procedures resulting from placing transcoders in the core network as well as in the BSS shall be studied@ e.g. impacts on the assignment and handover procedures. In addition to allow compressed speech over the A-interface the study shall provide further solution for effective bandwidth utilisation at the A interface@ which means it shall describe multiplexing of RTP flows and how this will be negotiated between the BSS and CN nodes. The study shall describe a solution for ""true end-to-end Codec negotiation""@ which considers on a call basis the preference/situation of the radio network. It shall be studied how call related messages have to be adapted@ e.g. transfer of Codec related information@ identification of calls/sessions. The study shall describe the wanted payload formats and other relevant user plane parameters like packetization time etc."