Deploying IP Multimedia Subsystem (IMS) services in future mobile networks

The Third Generation Partnership Project (3GPP) has proposed the Long Term Evolution and System Architecture Evolution (LTE/SAE) as the next stage of technologies aimed at overcoming the limitation in the existing 2G and 3G networks while driving mobile networks towards 4G standardisation. Although a new architecture has been proposed for the LTE/SAE, however, some technologies from the existing 2G and 3G frameworks are reused to allow for smooth transition and backward compatibility. One of such technologies is the service delivery framework know as the IP Multimedia Subsystem (IMS). In this paper, we investigate and report our early-trials findings on the integration of the IMS and the LTE/SAE architecture specifically looking at key parameters such end-to-end call quality, QoS parameters, IP connectivity and session management. This was achieved by firstly critically analysing key 3GPP and non-3GPP approaches of deploying telephony services over LTE/SAE while making various recommendations based on a wide range of existing research work in the field. In order to demonstrate the recommendations suggested, a high level prototype of the Evolved Packet Core (EPC) prototype was modeled and developed. The EPC model was then integrated with the FOKUS Open IMS Core and deployed on our testbed while carrying out various Quality of Service (QoS) related experimental tests. Our results shows that even though an EPC controlled IMS session generates more packets for initial signaling, it will in the long-run lead to a reduction in bandwidth consumption by the client due to the fragmentation of SIP messages. This in return makes available additional bandwidth for the integration of additional service such as presence and high-resolution video to existing voice services.