Mobility Support of Multi-User Services in Next Generation Wireless Systems Luis Veloso University of Coimbra lmveloso@dei.uc.pt Paulo Mendes NTT DoCoMo Euro-Labs mendes@docomolab-euro.com Edmundo Monteiro University of Coimbra edmundo@dei.uc.pt Abstract The substantial advancement and proliferation of wireless technologies leads to the need to efficiently manage user mobility. Furthermore, the simultaneously emerging of services like video- conference, radio and TV has emphasized the importance to deliver content to several simultaneous receivers. This way, one of the key challenges to deploy multi-user services in the next generation wireless systems is the support of seamless mobility of multi- user services. In this paper the functioning of the Seamless Mobility of Users for Media Distribution Services (SEMUD) proposal is presented. This mobility management technique possesses two operation modes. To provide seamless mobility the standard mode resorts on the collaboration between caches (located in the base stations) and buffers (located in the mobile nodes). The enhanced mode introduces mobility prediction and messages for context transfer between access routers. A performance analysis is given to corroborate the merits of the proposal. 1. Introduction Several wireless technologies have been developed to satisfy the different requirements and expectations of users. On the other hand, the size reduction, low cost affordability and increase in the autonomy of electronic devices have leaded for the development of portable devices. The wide spread utilization of these handheld devices and the astounding development of wireless technologies demands for the seamless mobility of users. Furthermore, the simultaneously emergence of several applications like video-conference, radio and TV has emphasized the importance to deliver content to several simultaneous receivers. In this context, the multicast technique arises as the appropriate method to forward information simultaneously to several receivers (denominated multicast group). Its development leaded to the standardization of several multicast protocols by the IETF (Internet Engineering Task Force). Nevertheless, the various multicast proposals were initially developed and optimized for fixed networks. That is, they were not aimed to support seamless mobility of users. Consequently, it is necessary to overcome this limitation of the IP multicast routing, and provide mobility support in the next generation wireless systems. This way, one of the challenges in the next generation mobile networks and the objective of the present work is the development of a mobility management technique that provides seamless mobility of multicast data between different access technologies. This work presents the functioning of the Seamless Mobility of Users for Media Distribution Services (SEMUD) mechanism. This proposal aims to support the movement of users between different locations without packet losses and with reduced latency. This mobility management technique possesses two operation modes. To provide seamless mobility the standard mode is based on the collaboration between caches (located in the base stations) and buffers (located in the mobile nodes). Additionally, the enhanced mode of the mechanism described in this paper includes mobility prediction and messages for context transfer between access routers. This proposal was developed under the QoS Architecture for Multi- user Mobile Multimedia (Q3M) project [1]. This project aims to develop a platform for publish- subscribe services over an IP-based mobile system and results from the collaboration between the University of Coimbra and the NTT DoCoMo Euro-Labs. The remainder of this document is organized as follows. Section 2 gives a survey of the related work and section 3 presents the SEMUD mechanism with special emphasis to the enhanced functionality. Following, the simulation scenario and experimental results are presented in the section 4. Finally, the conclusions are presented in the section 5. 9 1-4244-1338-6/07/$25.00/©2007 IEEE