Naoki Imai

A media synchronization method for real-time group communication in a multiple device environment

This paper proposes a media synchronization method for real-time group communication within a multiple device environment. The method controls the output time of each media unit received at multiple devices and synchronizes them, even if the arrival time of the media unit temporarily fluctuates. This fluctuation is caused by variation in bandwidth and the network delay between different access networks. This paper also evaluates the system performance, in terms of aspects such as the average time of difference between the output and input times of each media unit, in order to confirm the effectiveness of the proposal.

Flexible and seamless service migration for real-time communication with ubiquitous and heterogeneous networked resources

We present a service initiation and migration system for real-time communication services in a ubiquitous networking environment. The key concepts are: (1) the isolation of a few functions as common components with SIP protocol from realtime applications; (2) the incorporation of service migration into service initiation so that users can change resources at any time during communication; and (3) service negotiation which enables all user requests and situations to he reflected in the service. Therefore, users can enjoy real-time communication even when they face resource heterogeneity and changeable situations in the ubiquitous networking environment. The implementation of this system and the experimental results are also described, which demonstrate that users can switch devices and applications seamlessly without terminating the session.

Extension of Service Migration Method for Video on Demand Service

We studied a service migration method using Session Initiation Protocol (SIP) to dynamically switch resources (i.e., devices, access networks and media) for interactive communication services such as chat, Voice over IP (VoIP) and video telephony according to user’s requirements. In this paper, we extend the method to incorporate the Video On Demand (VOD) service. In the extension, a VOD server and VOD clients are assumed to be SIP User Equipments (UEs), and SIP sessions for a Real Time Streaming Protocol (RTSP) and a Real-time Transport Protocol (RTP) among them are controlled separately. It allows not only switching VOD clients seamlessly but also assigning different roles to different VOD clients, e.g. a user can control the playback mode from a cellular phone as a remote controller while rendering content on a TV. We implemented a system based on the proposal and conducted measurements to evaluate the processing delay consumed by the session control.

Implementation and evaluation of a collaborative content play method in a home network

Digital network appliances supporting DLNA (Digital Living Network Alliance) have been gaining wide acceptance in home networks (HNWs). To enhance the entertainment experiment in the HNW, we propose a collaborative content play method that automatically plays the user-selected content (e.g. music, photo) as main-content and other kinds of content to suit the mood of the main-content as sub-content in the same timing. Moreover, we show the performance evaluation of the proposed method in experimental test bed using multiple digital network appliances supporting DLNA.

A unified resource switching for real-time communication in a ubiquitous networking environment

Person-to-person communication on digital networks has begun to play an important role in our daily life. In a ubiquitous networking environment where we will be surrounded by more and more networked devices, real-time communication should be performed using appropriate devices, applications, and network. Moreover, when our situation changes, resources must be switched dynamically without breaking down the ongoing session. In this paper, we present a unified resource switching mechanism that supports network, device, application, and composite switching. Resource switching can be executed even in a session initiation phase because this is designed based on the SIP protocols. The implementation of the prototype and the experimental results are also described in the paper.