Keiichi Yasumoto

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.

Getting urban pedestrian flow from simple observation: realistic mobility generation in wireless network simulation

In order for precise evaluation of MANET applications, more realistic mobility models are needed in wireless network simulations. In this paper, we focus on the behavior of pedestrians in urban areas and propose a new method to generate a mobility scenario called Urban Pedestrian Flows (UPF). In the proposed method, we classify pedestrians in a simulation field into multiple groups by their similar behavior patterns (simply called flows hereafter, which indicate how they move around geographic points). Given the observed road density in the target field, we derive using linear programming techniques how many pedestrians per minute follow each flow. Using the derived flows, we generate a UPF scenario which can be used in network simulators. In particular, we have enhanced a network simulator called MobiREAL, which has been developed in our research group, so that we can generate and use the UPF scenario. MobiREAL simulator has three main facilities: the behavior simulator, network simulator and animator. The behavior simulator can generate/delete mobile nodes according to the UPF scenario. The network simulator can simulate MANET protocols and applications. The animator offers elegant visualization of simulation traces as well as graphical user interfaces for facilitating derivation of UPF scenarios. Through several case studies, we show similarity of the derived flows to the observed ones, as well as the metrics that characterize the mobility of the scenario.

A distributed event delivery method with load balancing for MMORPG

In this paper, we propose a new distributed event delivery method for MMORPG (Massively Multiplayer Online Role Playing Games). In our method, the whole game space is divided into multiple sub spaces with the same size and some player nodes are selected as responsible nodes to deliver game events occurring in their responsible sub spaces. Our method includes (1) a load balancing mechanism which allows each responsible node for the crowded sub space to dynamically construct a tree of multiple nodes and deliver events along the tree to reduce event forwarding overhead per node, (2) a technique to reduce end-to-end event delivery delay by dynamically replacing nodes in the tree, and (3) a technique to efficiently and seamlessly switch sub spaces to be observed while each players view moves around in the game space. Through experiments, we show that our method achieves practical performance for MMORPG.

A Method for Sharing Traffic Jam Information using Inter-Vehicle Communication

In this paper, we propose a method for cars to autonomously and cooperatively collect traffic jam statistics to estimate arrival time to destination for each car using inter-vehicle communication. In the method, the target geographical region is divided into areas, and each car measures time to pass through each area. Traffic information is collected by exchanging information between cars using inter-vehicle communication. In order to improve accuracy of estimation, we introduce several mechanisms to avoid same data to be repeatedly counted. Since wireless bandwidth usable for exchanging statistics information is limited, the proposed method includes a mechanism to categorize data, and send important data prior to other data. In order to evaluate effectiveness of the proposed method, we implemented the method on a traffic simulator NETSTREAM developed by Toyota Central R&D Labs, conducted some experiments and confirmed that the method achieves practical performance in sharing traffic jam information using inter-vehicle communication

MobiREAL simulator-evaluating MANET applications in real environments

In this paper, we propose a probabilistic rule-based model to describe behavior of mobile nodes for accurately evaluating performance of MANET applications. The proposed model allows us to describe how mobile nodes change their destinations, routes and speeds/directions based on their positions, surroundings (e.g. neighboring nodes), information obtained from applications, and so on. We have designed and developed a network simulator called MobiREAL based on the proposed methodology. Through experiments, we show importance to simulate MANET applications in realistic environments.

Urban pedestrian mobility for mobile wireless network simulation

In order to perform precise evaluation of MANET applications in the real world, realistic mobility models are needed in wireless network simulation. In this paper, we propose a new method to create urban pedestrian flows (UPF) mobility scenarios, which reproduce the walking behavior of pedestrians in urban areas. From given densities of pedestrians observed at several points, our method derives a UPF mobility scenario that reproduces the walking behavior of pedestrians consistent with the observed densities, using linear programming techniques. We have developed a network simulator MobiREAL to design and evaluate MANET protocols and applications with this realistic mobility model. MobiREAL provides various functions and tools including a mobility model to describe the behavior of individual nodes, a GUI to assist with automatic generation of UPF mobility scenarios and a visualization tool. We have conducted some experiments using the MobiREAL simulator. Through the experiments, we have investigated the influence of node mobility on the performance of MANET protocols and have shown the usefulness of our method and the MobiREAL simulator.

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.

A personal tourism navigation system to support traveling multiple destinations with time restrictions

We propose a personal navigation system (called PNS) which navigates a tourist through multiple destinations efficiently. In our PNS, a tourist can specify multiple destinations with desired arrival/stay time and preference degree. The system calculates the route including part of the destinations satisfying tourists requirements and navigates him/her. For the above route search problem, we have developed an efficient route search algorithm using a genetic algorithm. We have designed and implemented the PNS as a client-server system so that the portable device users can use the PNS through the Internet. Experiments using general map data and PDAs show that our PNS can calculate a semioptimal route almost in real-time.

Formal Techniques for Networked and Distributed Systems – FORTE 2008

Thank you for reading formal techniques for networked and distributed systems forte 2004 24th ifip wg 612 international conference madrid spain september 27 3

Distance and time based node selection for probabilistic coverage in People-Centric Sensing

Aiming to achieve sensing coverage for a given Area of Interest (AoI) in a People-Centric Sensing (PCS) manner, we propose a concept of (α, T)-coverage of the target field where each point in the field is sensed by at least one node with probability of at least α during the time period T. Our goal is to achieve (α, T)-coverage by a minimal set of mobile sensor nodes for a given AoI, coverage ratio α, and time period T. We model pedestrians as mobile sensor nodes moving according to a discrete Markov chain. Based on this model, we propose two algorithms: the inter-location and inter-meeting-time algorithms, to meet a coverage ratio α in time period T. These algorithms estimate the expected coverage of the specified AoI for a set of selected nodes. The inter-location algorithm selects a minimal number of mobile sensor nodes from nodes inside the AoI taking into account the distance between them. The inter-meeting-time selects nodes taking into account the expected meeting time between the nodes. We conducted a simulation study to evaluate the performance of the proposed algorithms for various parameter setting including a realistic scenario on a specific city map. The simulation results show that our algorithms achieve (α, T)-coverage with good accuracy for various values of α, T, and AoI size.