Advanced Multicast and Broadcast Content Distribution in Mobile Cellular Networks Michael Knappmeyer Mobile & Ubiquitous Systems Group, CCCS Research University of the West of England Bristol, UK Björn Ricks, Ralf Tönjes Faculty of Engineering and Computer Science University of Applied Sciences Osnabrück Osnabrück, Germany Adel Al-Hezmi Fraunhofer Institute FOKUS Berlin, Germany Abstract—Recently 3GPP (Third Generation Partnership Project) has standardised MBMS (Multimedia Broadcast Multicast Services) enabling broadcast and multicast transmissions over GPRS (General Packet Radio Service) and UMTS (Universal Mobile Telecommunications System). Hence it makes an efficient usage of radio resources possible. 3GPP and 3GPP2 introduced the specification of IMS (IP Multimedia Subsystem) and MMD (Multimedia Domain), receptively, which both are responsible for resource, admission and charging control. It allows for cost efficient and flexible provision of enriched multimedia services over IP networks. Up to now the controlling IMS and MBMS are separated subsystems sharing no common interfaces. This paper introduces both systems and depicts ongoing standardisation activities regarding their interworking. Finally, it proposes a service provision architecture and describes required signalling flows which enable the provision of multicast streaming using the MBMS specifications not only as access bearer technology. Thus, we present a step towards the evolution of IMS enabling it with multicast and broadcast capabilities. Keywords- Multimedia Streaming, Multicast, Broadcast, Mobile Cellular Networks, MBMS IMS Integration, IMS Signalling, Service Architecture, Content Distribution I. INTRODUCTION The evolution of mobile cellular networks focuses on the provision of enriched multimedia services and the support of QoS (Quality of Service) guarantees. The Network Operators envisage a cost efficient distribution of contents to large recipient groups and would like to add location based and context aware functionalities. MBMS and IMS are the most promising European candidates for fulfilling their requirements of ubiquitous availability, user interactivity and personalisation. Regarding the trend of distributing user generated content, they furthermore enable a subscribed user to become CP (Content Provider) himself. MBMS (as specified in 3GPP Release 6) primarily cares for efficient utilisation of radio resources while IMS was developed to control multimedia sessions based on IP delivery, i.e. it provides admission and policy control. Moreover, IMS offers the possibility of easy and flexible service creation by using service enablers. Each enabler offers a set of basic functionalities and by their composition and extension, novel services and applications can be generated individually. Some of them are standardised by OMA (Open Mobile Alliance), e.g. a service enabler providing broadcast functionalities entitled BCAST [1]. In this paper we present a promising approach of combining the advantages of both MBMS and IMS by designing an integrated service provisioning framework and defining common service enablers. This work has been conducted within the European IST project C-MOBILE that aims at enhancing MBMS at the RAN (Radio Access Network) and at the CN (Core Network) for systems beyond 3G. With this regard C-MOBILE is working on the provisioning of interactive and personalised mobile services with QoS and mobility support as well as ensuring a smooth migration path for the following 3GPP releases. The next section gives a brief overview of the reference technologies. Section III analyses the functionalities of both IMS and MBMS and proposes the derived integrated architecture. The most relevant signalling flows are depicted on the basis of an exemplary case study before section IV finally draws a summarising conclusion. II. REFERENCE TECHNOLOGY OVERVIEW A. 3GPP Multimedia Broadcast Multicast Service (MBMS) In Release 6 3GPP standardised MBMS [2][3][4] to support efficient broadcast and multicast IP packet delivery in existing UMTS and GPRS networks. Concerning the RAN point-to-multipoint transmissions in downlink direction are introduced in order to save radio resources. MBMS allows two modes of operation: the broadcast mode and the multicast mode. In broadcast mode, transmissions take place regardless of user presence in a defined area, whereas in multicast mode solely those areas are supplied where subscribers need to be served. Consequently, MBMS multicast mode is associated with subscription and authorisation prior to group joining. This work was supported by the European IST project C-MOBILE which aims at enhancing MBMS for systems beyond 3G.