Cheng Suan Lee

Performance Study on Location-Assisted and Bluetooth-Assisted Session Transfer for VoIP Application

With the increasing use of small, lightweight, powerful and multi-radio devices, and the omnipresence of wireless networks such as WiFi, the pave to ubiquitous computing is gradually emerged and realized. Ubiquitous computing allows users to access their services using any device, anytime, anywhere in a very flexible manner based on the current context. In particularly, services could be started on one device that attaches to one network and later be easily switched to another device connected to another network, commonly known as session mobility. In this paper, we describe our concept of seamless session transfer for real-time application such as VoIP and IPTV, and our prototype implementation of such concept using both WiFi and Bluetooth approaches, with qualitative and quantitative performance comparison.

Seamless handover between unicast and multicast multimedia streams

With the deployment of heterogeneous networks, mobile users are expecting ubiquitous connectivity when using applications. For bandwidth-intensive applications such as Internet Protocol Television (IPTV), multimedia contents are typically transmitted using a multicast delivery method due to its bandwidth efficiency. However, not all networks support multicasting. Multicasting alone could lead to service disruption when the users move from a multicast-capable network to a non-multicast network. In this paper, we propose a handover scheme called application layer seamless switching (ALSS) to provide smooth real-time multimedia delivery across unicast and multicast networks. ALSS adopts a soft handover to achieve seamless playback during the handover period. A real-time streaming testbed is implemented to investigate the overall handover performance, especially the overlapping period where both network interfaces are receiving audio and video packets. Both the quality of service (QoS) and objective-mapped quality of experience (QoE) metrics are measured. Experimental results show that the overlapping period takes a minimum of 56 and 4 ms for multicast-to-unicast (M2U) and unicast-to-multicast (U2M) handover, respectively. The measured peak signal-to-noise ratio (PSNR) confirms that the frame-by-frame quality of the streamed video during the handover is at least 33 dB, which is categorized as good based on ITU-T recommendations. The estimated mean opinion score (MOS) in terms of video playback smoothness is also at a satisfactory level.

Prototype implementation of a connection handover system for video streaming with different delivery methods

With the emergence of multimode terminals and the deployment of multiple access networks, users are expecting ubiquitous and seamless connectivity across heterogeneous networks when using IP-based applications. For bandwidth intensive IP-based application such as Internet Protocol Television (IPTV), the multimedia contents are usually transmitted via multicast delivery for reason of efficiency. However, not all networks support multicast. Hence, multicast video delivery could lead to service disruption when users move from a network with multicast support to another network that is not. In this paper, we propose a system called Application Layer Switching System (ALSS) that focuses on switching video transmission between multicast and unicast delivery methods. More specifically, we study the overlapping period needed by the mobile terminal to achieve smooth video playback for different videos during connection handover.

Real-time application Session Transfer over IP Multimedia Subsystem (IMS) Network

Living in a world surrounded by multiple devices such as smart phone, laptop, desktop PC and even tablet, it is important for the user to seamlessly transfer his/her session across these devices in a ubiquitous manner according to user preferences. While most of the systems either rely on realtime location tracking of the target device, or require users to remember the contact or IP address of the target device for the transfer, we propose in this paper an automated session transfer mechanism leveraging on the registration information which are readily found in the IP Multimedia Subsystem (IMS) core. We explain in this paper the system architecture and signaling flow of our prototype implementation. Results showed that our proposed mechanism for session transfer over both wired and wireless access network took 202ms and 388ms respectively, which stays within the ITU-T recommendation of 150ms to 400ms overall delay. (4 pages)

Prototype implementation of a presence-based multimedia session sharing system

Emailing has been and it is still continue to be the most common way for many people to share information using texts and/or with attachments. More popular alternatives nowadays are using the Instant Messengers (IM) and online community networks which convey presence information and provide higher degree of interactions with richer multimedia experience. However, these existing systems involve human intervention onto updating the status information, e.g. the presence status message is manually entered and remains unchanged until the next manual update. A more sophisticated presence system would be those which can determine a users status automatically, with the objective to enable more interactions including indirect contents sharing. In this paper, we present the prototype implementation of a presence-based multimedia session sharing system. This proposed system helps users to publish their session dynamically, and enable their buddies/contacts to join the same session as to consume the contents. We envisaged that the proposed system would help service providers to advertise and promote their contents at lower cost with a viral effect.