Nobuyasu Nakajima

Handoff delay analysis and measurement for SIP based mobility in IPv6

This paper describes the session initiation protocol (SIP) based mobility in IPv6 and its performance in our laboratory testbed. For real-time mobile multimedia communication, we use SIP for signaling protocol as well as for supporting terminal mobility. While performance study for real-time mobile communication refers to several factors and their measurements, we analyze here only the handoff delay due to node mobility. In particular, we are interested to examine the delay incurred when a mobile node moves to a new link and perform the duplicate address detection (DAD) and router selection, and analyze the delay in each case. We notice that the IPv6 Linux implementation provides substantial amount of delay during node movement, which severely affects the performance of real-time applications. Therefore, we modify the Linux kernel and compare with the unaltered one. Finally, we conclude that a faster handoff is achievable in SIP based terminal mobility with intelligent modifications to unaltered Linux kernel.

Implementing a testbed for mobile multimedia

In an effort to realize wireless Internet telephony and multimedia streaming in a highly mobile environment a testbed emulating a wireless Internet has been built. This allows the setting up of multimedia calls between IP mobiles and integration between IP and PSTN end-points in a wireless environment. Different functionalities and components involved with the wireless Internet streaming multimedia have been prototyped and experimented in the testbed. These include signaling, registration, dynamic binding, location management as well as supporting the QoS features for the mobile users. This paper describes some of the components of the testbed and highlights the experiences while building this testbed which could be beneficial to some who plan to build a similar testbed to realize several features and capabilities of Mobile Wireless Internet, before actually bringing to the market.

Realizing mobile wireless Internet telephony and streaming multimedia testbed

Streaming real-time multimedia content over the Internet is gaining momentum in the communications, entertainment, music and interactive game industries as well as in the military. In general, streaming applications include IP telephony, multimedia broadcasts and various interactive applications such as multi-party conferences, collaborations and multiplayer games. Successfully realizing such applications in a highly mobile environment, however, presents many research challenges. In order to investigate such challenges and demonstrate viable solutions, we have developed an experimental indoor and outdoor testbed laboratory. By implementing standard IETF protocols into this testbed, we have demonstrated the basic functionalities required of the mobile wireless Internet to successfully support mobile multimedia access. These requirements include signaling, registration, dynamic configuration, mobility binding, location management, Authentication Authorization and Accounting (AAA), and quality of service over a variety of radio access network (RAN) technologies (e.g. 802.11b, CDMA/GPRS). In this paper, we describe this testbed and discuss important design issues and tradeoffs. We detail the incorporation and inter-relation of a wide catalog of IETF protocols-such as SIP, SAP, SDP, RTP/RTCP/RTSP, MGCP, variants of Mobile-IP, DRCP, HMMP, PANA, and DSNP-to achieve our goals. We believe that the results and experiences obtained from this experimental testbed will advance the understanding of the pertinent deployment issues for a Mobile Wireless Internet.

SDL-Net: a wireless access link to broadband multimedia networks

SDL-Net (Super high speed DownLink Network) is proposed as a wireless access link to a broadband multimedia network, and its basic features are described. In the SDL-Net, the transmission data rate in downlink is 30 to 300 times faster than the transmission data rate in uplink. With this asymmetric architecture, most of multimedia personal communication services are realized through hand-held portable multimedia terminals. The SDL-Net is economically constructed by additionally installing high speed downlink transmitters in existing narrowband personal communication networks. By combining high speed downlink with narrowband links, both seamless CBR services such as voice communication and spot beam VBR services such as electronic publishing are realized.

Broadband multi-media communication system with asymmetric wireless access link, SDL-Net

SDL-Net (super high speed downlink network) is proposed as a wireless access link to a broadband multi-media network, and its physical-layer and datalink-layer protocols are described. In SDI-Net, the transmission data rate in the downlink is 100 to 1000 times faster than the transmission data rate in the uplink. Since the backward channel is much narrower than the forward channel, a sophisticated ARQ technique is indispensable for errorless data transmission through such an asymmetric air interface. Considering the ARQ scheme and the transmission quality in the downlink, the downlink throughput and the uplink traffic are investigated for large file transfer services such as an electronic publishing. The round trip delay which is one of the important performance measures, is analyzed. The backbone networks for the SDL-Net are also discussed.

Advanced aggregate computation for large data visualization

Large data visualization and analysis faces challenges related to performance, operability, degree of discrimination, etc. In this paper, an advanced aggregate computation is proposed to solve these issues from three aspects. By virtue of visualization-based data separation and aggregation, a large dataset is mapped to a visualization-based small dataset for efficient visualization while keeping operability of data. A minimum size of visual primitives for aggregated data is defined to ensure visibility of important but tiny information. And a D3-based rendering implementation improves the performance of consecutive visualizations.

Distributed aggregate computation between server and client for interactive visualization

A visualization system is frequently challenged by large volume of datasets to be processed. The situation becomes more serious when visual feedback is required to be responsive. In this paper, an adaptive approach is proposed to efficiently distribute aggregate computation load between server and client for interactive visualization. This proposal combines available computing power on both server and client sides. Additionally, adaptively shifts part of the aggregate computation load to and fro for achieving interactive rate of large data visualization. An experimental prototype confirmed that that proposed method improves interactive rate of large data visualization.