Morihiko Tamai

UbiREAL: realistic smartspace simulator for systematic testing

In this paper, we propose a simulator for facilitating reliable and inexpensive development of ubiquitous applications where each application software controls a lot of information appliances based on the state of external environment, users contexts and preferences. The proposed simulator realistically reproduces behavior of application software on virtual devices in a virtual 3D space. For this purpose, the simulator provides functions to facilitate deployment of virtual devices in a 3D space, simulates communication among the devices from MAC level to application level, and reproduces the change of physical quantities (e.g., temperature) caused by devices (e.g., air conditioners). Also, we keep software portability between virtual devices and real devices. As the most prominent function of the simulator, we provide a systematic and visual testing method for testing whether a given application software satisfies specified requirements.

Advancing interactive collaborative mediums through tele-immersive dance (TED): a symbiotic creativity and design environment for art and computer science

The Tele-immersive Dance Environment (TED) is a geographically distributed, real-time 3-D virtual room where multiple participants interact independent of physical distance. TED, a highly interactive collaborative environment, offers digital options with multiple viewpoints, enhancing the creative movement composition involved with dance choreography. A symbiotic relationship for creativity and design exists between dance artists and computer scientists as the tele-immersive environment is analyzed as a creativity and learning tool. We introduce the advancements of the interactive digital options, new interface developments, user study results, and the possibility of a computational model for human creativity through Laban Movement Analysis.

Energy-aware video streaming with QoS control for portable computing devices

We propose an energy-aware video streaming system for portable computing devices, in which the video can be played back for the specified duration within the remaining battery amount. To save power, we introduce techniques (i) to reduce playback quality of a video at an intermediate proxy and (ii) to shorten working time of the network I/F card using periodic bulk transfer of the video data on the wireless LAN. To enable playback for the specified duration, we have developed a power consumption model for portable devices using parameters on playback quality, playback duration, battery amount, and so on. We have also developed an algorithm to assign different playback quality among multiple video segments based on the users preference.within the battery amount. Our experiments using PDAs and laptop PCs on 802.11b WLAN show that our system achieves less than 6 prediction error in playback duration while adapting playback quality among video segments.

DTN MapEx: Disaster area mapping through distributed computing over a Delay Tolerant Network

Disaster area map generation and sharing are critical to disaster response operations. In post-disaster contexts however, cloud-based mapping services and data may be unavailable because of network challenges. Disruption Tolerant Network (DTN) architectures have been proposed for data sharing in challenged networks. However, map generation may be too complex for individual DTN nodes given their limited computing resources. To generate and share maps of disaster areas, we present DTN MapEx, a distributed computing system for mapping that operates over a DTN. DTN MapEx distributes disaster map data and map generation tasks to multiple nodes to minimize individual computational loads. In the system, responders and volunteers act as mobile sensing nodes. They log the GPS traces of their traversed paths and collect disaster area map data such as the coordinates, images, and assessments of points-of-interest. The mobile nodes then route their collected data and a task request through the DTN to pre-deployed, fixed Computing Nodes. The Computing Nodes aggregate the data to generate a map and opportunistically route it back to the network. To reduce complexity, mapping tasks and data are divided amongst Computing Nodes based on their current computational load. Computing Nodes periodically update the DTN about their current loads. Mobile nodes use these updates in deciding where to allocate their task requests and data. In this paper, we present the design of DTN MapEx and perform initial evaluations on its feasibility in disaster scenarios.

SakuraSensor: quasi-realtime cherry-lined roads detection through participatory video sensing by cars

In this paper, we propose SakuraSensor, a participatory sensing system which automatically extracts scenic routes information from videos recorded by car-mounted smart-phones and shares the information among users in quasirealtime. As scenic routes information, we target flowering cherries along roads since the best period of flowering cherries is rather short and uncertain from year to year and from place to place. To realize SakuraSensor, we face two technical challenges: (1) how to accurately detect flowering cherries and its degree, and (2) how to efficiently find good places of flowering cherries (PoIs) using the participatory sensing technique. For the first challenge, we develop an image analysis method for detecting image pixels that belong to flowering cherries. To exclude artificial objects with similar color to flowering cherries, we also employ fractal dimension analysis to filter out unnecessary image areas. For the second challenge, we propose a method called k-stage sensing. In this method, the interval for sensing (taking a still image and applying the image analysis) by each car is dynamically shortened so that the roads near the already found PoIs are more densely sensed. We implemented SakuraSensor consisting of client-side software for iOS devices and server-side software for a cloud server and conducted experiments to travel cherry-lined roads and record videos by several cars. As a result, we confirmed that our method can identify flowering cherries at about 74 % precision and 84 % recall. We also confirmed that our k-stage sensing method could achieve the comparable PoI detection rate with half sensing times compared to a conventional method.

Resource-aware service composition for video multicast to heterogeneous mobile users

In this paper, we propose a method to deliver video for multiple wireless mobile users with different quality requirements. In the proposed method, we assume several proxies and wireless access points in the network. There are overlay links between these nodes, and certain amounts of bandwidths are reserved in advance. Each proxy is capable of executing multiple transcoding services and forwarding services. The original video sent from the server is transcoded into various quality by these services, and delivered to user nodes with the required quality along the service delivery paths. In this paper, we propose an algorithm to construct the service delivery paths which minimize the weighted sum of computation power for transcoding and the bandwidth consumed on physical links on the overlay network. The proposed method can treat user mobility where each user node moves to a range of another access point. Also, users of the proposed system can change quality requirements anytime. Through experiments with simulations, we show the usefulness of our method.

View control interface for 3D tele-immersive environments

The 3D tele-immersive (3DTI) environments are emerging as the next generation technique for telecommunication. In this paper, we present a novel and generic interface for view control in 3D environments. The interface uses Wii Remote, a wireless controller for a video game console. It allows the user to manipulate the virtual camera and 3D objects intuitively with buttons and through motions (pitch and roll). We conducted user studies to evaluate the interface with a professional dancer and average audiences. The results demonstrate that the Wii Remote interface is much better suited to view control in 3DTI environments since it is much easier to use, more effective, and more accurate than the conventional mouse-based interfaces.

MTcast: robust and efficient p2p-based video delivery for heterogeneous users

In this paper, we propose a new video delivery method called MTcast (Multiple Transcode based video multicast) which achieves efficient simultaneous video delivery to multiple users with different quality requirements by relying on user nodes to transcode and forward video to other user nodes. In MTcast, each user specifies a quality requirement for a video consisting of bitrate, picture size and frame rate based on the users environmental resource limitation. All users can receive video with the specified quality (or near this quality) along a single delivery tree. The main characteristics of MTcast are in its scalability, high user satisfaction degree in received video quality, short startup latency and robustness against node failure. Through simulations, we have confirmed that MTcast can achieve much higher user satisfaction degree and robustness against node failure than the layered multicast method.

A trigger-based dynamic load balancing method for WLANs using virtualized network interfaces

We propose a method for dynamic load balancing in wireless LANs (WLANs), which adapts association topology dynamically based on traffic conditions, while keeping the handoff overhead negligible using virtualized wireless network interfaces (WNICs). In large-scale WLANs, there are many locations that each station (STA) can discover multiple access points (APs). In these locations, the conventional approach to the AP selection in which each station connects to the AP with the strongest Received Signal Strength Indication (RSSI) may suffer from imbalanced load among APs. To address this issue, a number of AP selection schemes have been proposed, which achieve load balancing by changing some STA-AP associations. However, since stations cannot communicate during handoff, frequent changes of STA-AP associations will result in serious deterioration of the communication quality. Therefore, in the existing schemes, we face a problem that it is difficult to decide appropriate timing of association changes. Nevertheless, this problem was not considered as a major concern in the literature. In this paper, we propose a method for trigger-based dynamic load balancing in WLANs. In the proposed method, to minimize the handoff overhead, the WNIC on a station is virtualized and connected to multiple APs simultaneously. Using this approach, we propose a method that continuously monitors changes in traffic conditions and that switches STA-AP associations at appropriate timing based on the monitored results. We evaluate the effectiveness of our method in terms of aggregated throughput and fairness using the ns-3 simulator. Compared with the result in the traditional AP selection method, aggregated throughput is improved by about 11%, while increasing the Jains fairness index by about 19% in our method.

Distributed market broker architecture for resource aggregation in grid computing environments

In order to allow every user to extract aggregated computational power from idle PCs in the Internet, we propose a distributed architecture to achieve a market based resource sharing among users. The advantages of our proposed architecture are the following: (i) aggregated resources can be bought by one order; (ii) resource prices are decided based on market principles; and (iii) the load is balanced among multiple server nodes to make the architecture scalable w.r.t. the number of users. Through simulations, we have confirmed that the proposed method can mitigate the load at each server node to a great extent.