Hirozumi Yamaguchi

GVGrid: A QoS Routing Protocol for Vehicular Ad Hoc Networks

In this paper, we present a QoS routing protocol called GVGrid for multi-hop mobile ad hoc networks constructed by vehicles, i.e., vehicular ad hoc networks (VANETs). GVGrid constructs a route on demand from a source (a fixed node or a base station) to vehicles that reside in or drive through a specified geographic region. The goal of GVGrid is to maintain a high quality route, i.e. a robust route for the vehicles movement. Such a route can be used for high quality communication and data transmission between roadsides and vehicles, or between vehicles. The experimental results have shown that GVGrid could provide routes with longer lifetime, compared with an existing routing protocol for VANETs

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.

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.

Ad-hoc Localization in Urban District

In this paper, we present a range-free ad-hoc localization algorithm called UPL (Urban Pedestrians Localization), for positioning mobile nodes in urban district. The design principle of UPL is two-fold. (1) We assume that location seeds are deployed sparsely due to deployment-cost constraints. Thus most mobile nodes cannot expect to meet these location seeds frequently. Therefore, each mobile node in UPL relies on location information received from its neighboring mobile nodes in order to estimate its area of presence. The area of presence of each mobile node becomes inexact as it moves, but it is helpful to reduce the areas of presence of the other mobile nodes. (2) To predict the area of presence of mobile nodes accurately under mobility, we employ information about obstacles such as walls, and present an algorithm to calculate the movable areas of mobile nodes considering obstacles. This also helps to reduce each nodes area of presence. The experimental results have shown that by the above two ideas UPL could achieve 8 m positioning error in average with 10 m of radio range.

Cooperative Vehicle Positioning via V2V Communications and Onboard Sensors

This paper presents a vehicular positioning system in which multiple vehicles cooperatively calibrate their positions and recognize surrounding vehicles with their GPS receivers and ranging sensors. The proposed system operates in a distributed manner and works even if all vehicles nearby do not or cannot participate in the system. Each vehicle acquires various pieces of positioning information with different degrees of accuracies depending on the sources and recency of information, and compiles them based on likelihood derived from estimated accuracies to minimize estimation errors. A simulation based performance evaluation given in the paper shows that the proposed system improves the estimation accuracy by 85% on average with respect to the standalone GPS receiver, and recognizes about 70% surrounding vehicles with an error of 1m.

Cost-conscious geographic multicast on MANET

In this paper, we propose a location-aware multicast protocol on MANET called MgCast (multiCAST or multiple geographical regions). Given a source node and a set of geographical destination regions, MgCast constructs and maintains a routing tree from the source to nodes which reside in the regions, in a decentralized manner. Our aim is to pursue trade-off between the route discovery ratio, the number of route request messages and the number of links of the tree. The experimental results have shown that MgCast could achieve a good balance between these metrics.

Synthesis of protocol entities specifications from service specifications in a Petri net model with registers

In general, the services of a distributed system are provided by some cooperative protocol entities. The protocol entities must exchange some data values and synchronization messages in order to ensure the temporal ordering of the events which are described in a service specification of the distributed system. It is desirable that a correct protocol entity specification for each node can be derived automatically from a given service specification. In this paper, we propose an algorithm which synthesizes a correct protocol entity specification automatically from a service specification in a Petri Net model with Registers called PNR model. In our model, parallel events and selective operations can be described naturally. The control flow of a service specification must be described as a free-choice net in order to simplify the derivation algorithm, however, many practical systems can be described in this class. In our approach, since each protocol entity specification is also described in our PNR model, we can easily understand what events can be executed in parallel at each protocol entity.

Survey of Real-time Processing Technologies of IoT Data Streams

Recently, Internet of Things (IoT) has been attracting attention due to its economical impact and high expectations for drastically changing our modern societies. Worldwide by 2022, over 50 billion IoT devices including sensors and actuators are predicted to be installed in machines, humans, vehicles, buildings, and environments. Demand is also huge for the real-time utilization of IoT data streams instead of the current off-line analysis/utilization of stored big data. The real-time utilization of massive IoT data streams suggests a paradigm shift to new horizontal and distributed architecture because existing cloud-based centralized architecture will cause large delays for providing service and waste many resources on the cloud and on networks. Content curation, which is the intelligent compilation of valuable content from IoT data streams, is another key to fully utilize and penetrate IoT technologies. In this paper, we survey the emerging technologies toward the real-time utilization of IoT data streams in terms of networking, processing, and content curation and clarify the open issues. Then we propose a new framework for IoT data streams called the Information Flow of Things (IFoT) that processes, analyzes, and curates massive IoT streams in real-time based on distributed processing among IoT devices.

CLIPS: Infrastructure-free collaborative indoor positioning scheme for time-critical team operations

Indoor localization has attracted much attention recently due to its potential for realizing indoor location-aware application services. This paper considers a time-critical scenario with a team of soldiers or first responders conducting emergency mission operations in a large building in which infrastructure-based localization is not feasible (e.g., due to management/installation costs, power outage, terrorist attacks). To this end, we design and implement a collaborative indoor positioning scheme (CLIPS) that requires no preexisting indoor infrastructure. We assume that each user has a received signal strength map for the area in reference. This is used by the application to compare and select a set of feasible positions, when the device receives actual signal strength values at run time. Then, dead reckoning is performed to remove invalid candidate coordinates eventually leaving only the correct one which can be shared amongst the team. Our evaluation results from an Android-based testbed show that CLIPS converges to an accurate set of coordinates much faster than existing noncollaborative schemes (more than 50% improvement under the considered scenarios).