Tadashige Iwao

Dynamic Data Forwarding in Wireless Mesh Networks

Unreliable wireless links can cause frequent link (and route) failures, creating a major challenge for routing protocols who need to constantly repair routes and find alternate paths. In this paper we propose DADR (Distributed Autonomous Depth-first Routing), a new distributed distance-vector routing protocol designed to adapt quickly to changing link conditions while minimizing network control overhead. In our algorithm, when a link fails, data packets are rerouted through an alternate next hop, and the information about the failed link is propagated with the data packet; therefore, routes are updated dynamically and with little overhead. We have implemented DADR on several link-layer technologies and deployed it in different applications, including AMI deployments in Japan; all implementations resulted in reliable networks that were easy to set up, maintain, and resilient to changing conditions.

Comparison of data forwarding mechanisms for AMI networks

Advance Metering Infrastructure (AMI) networks are often deployed under challenging and unreliable conditions. One of the issues for the transmission of data packet in these unreliable networks is the routing of packets, because routing paths may behave differently from the time when the route is discovered to the time when a data packet is forwarded. In addition, control packets may get lost and give routers an inconsistent view of the network. While previous research has focused on designing the control-plane of routing protocols to deal with the AMI network conditions, there is comparatively a smaller amount of research on the advantages of new data forwarding mechanisms designed for unreliable networks. This paper introduces a set of data forwarding mechanisms inspired by distributed depth-first search algorithms, and designed for the challenging conditions of large-scale unreliable networks envisioned by smart-grid deployments. These forwarding mechanisms use data packets to detect loops, update routing tables, and perform rerouting of data packets through alternate paths, recovering thus, packets that would have been normally dropped due to failures at the link layer. We perform simulations based on a real field AMI deployment to evaluate the performance of the proposed mechanisms. We also provide the evaluation results for the data forwarding mechanisms that have been implemented in a real AMI network.

Flexible Multi-agent Collaboration Using Pattern Directed Message Collaboration of Field Reactor Model

In this paper, we propose a flexible multi-agent model, called Field Reactor Model (FRM) for open system environment such as ubiquitous computing. FRM unifies indirect communication with an abstract medium and pattern-oriented message communication. The collaboration method among agents is pattern directed message collaboration that yields functional relations among patterns of agents. The pattern directed message collaboration enables agents on heterogeneous platforms to create collaboration each other and supports to change collaboration dynamically. We describe how to apply the computation scheme originated from dataflow to the pattern directed message collaboration. Also, we show the flexibility of FRM with an example of file format translations.

Ubiquitous computing with service adaptation using peer-to-peer communication framework

Mobile devices and wireless network infrastructures will be leading users to seamlessly use peer-to-peer services and ubiquitous computing by the growing of the infrastructures. In order to realize to use peer-to-peer services and ubiquitous services seamlessly, a new framework that enables users to use peer-to-peer services and ubiquitous computing is required. Hence, this paper describes a new ubiquitous computing framework, called VPC on KODAMA, using a peer-to-peer mechanism. Virtual Private Community (VPC) is an execution environment for peer-to-peer services, and provides a framework for definition of peer-to-peer services. Peer-to-peer services in VPC are defined as policy packages that have necessary elements to provide the services. Peer-to-peer services are offered in communities by collaboration among roles that are assigned to users. KODMA provides a network infrastructure for agents. Agents in KODAMA have their own community, and represent the communities. Communities have a hierarchy structure by agents residing in other agents communities. Agents have message filtering policy, and refuse messages that are against the policy. By unifying VPC and KODAMA, a new framework that enables services to define roles and their behavior and to manage logical relationship among communities is provided. VPC on KODAMA enables users to use peer-to-peer services and appliances seamlessly with their mobile devices.

Collaboration among agents in logical network of peer-to-peer services

Mobile devices will have enough power to provide various kinds of services on themselves in the Internet. In these services, users buy and sell products by peer-to-peer contact on streets and shops. In order to realize the peer-to-peer services, we need a platform that satisfies the following requirements: describing a service independent of its location, and providing a service under dynamically changing network environment. This paper proposes a new framework, called virtual private community (VPC), for such services. VPC provides flexible collaboration and a new computation framework for the flexible collaboration, in order to realize such services.

Large Scale Peer-to-Peer Experiments with Virtual Private Community (VPC) Framework

This paper describes service models for peer-to-peer services in a mobile environment. These days, mobile devices such as PDAs and mobile telephones have the power and the capability to support a variety of services independently. In the near future, peer-to-peer services, for mobile devices in a mobile environment, will be commonplace. However, the performance of these devices is not comparable to those of PCs. The CPU performance of mobile devices is ten times less than those of PCs. Likewise, the data storage capacity of mobile devices is quite limited. Thus, it is difficult for these devices to provide peer-to-peer services such as file sharing and the access of CPU power. Hence, we propose suitable peer-to-peer service models for mobile devices. We have performed a large-scale experiment, with six hundred participants. This paper also contains the results and discussions of this experiment.

A control model of multi-purpose sensor networks by policies

This paper describes a new framework of policy control sensor networks. Sensor networks are shared by various applications, and have many nodes. Hence, sensor networks need to have ability to accept various applications, and to deploy application modules to nodes easily. Sensor nodes should have appropriate application modules. A framework that is based on VPC on KODAMA enables sensor nodes to have appropriate modules by assignment rules in a policy. When users only put application policies to sensor networks, sensor nodes propagate the policies and perform appropriate roles in the applications. This paper also shows that sensor networks with policies change behavior corresponding to detected active RFID tags as an example.

An information notification model with VPC on KODAMA in an ubiquitous computing environment, and its experiment

The notification of useful information to users is necessary to keep them aware of their environment and is of particular benefit in a ubiquitous computing environment. However, the amount and nature of information to be provided depends on circumstances. Too much information will confuse users. Systems used to disseminate information in a ubiquitous computing environment should not provide all information to all users, and should instead modify information disseminated depending on circumstances and context. In addition, systems designed for use in a ubiquitous computing environment need a security function for various reasons including privacy protection. For these reasons, we have developed an information dissemination model, called VPC on KODAMA. The model enables systems to provide an appropriate amount of information to users depending on circumstances and contains a security function. Using this model, we performed a large-scale experiment involving approximately one thousand participants. This paper contains the results of and discussions regarding this experiment.

Testing of Multi-agent-based System in Ubiquitous Computing Environment

Agent technology is ready to shift from the stage in which agent architectures are proposed to the stage in which applications working in the real world are developed. Accordingly, we have developed an agent-based application integrating VPC and KODAMA, as an example of a system where agents can behave effectively in the real world. VPC on KODAMA is a framework for actualizing a ubiquitous computing environment. VPC on KODAMA has a mechanism that assigns services to user agents according to their profiles. Using VPC on KODAMA, we developed an information notification system. This system sends advertisement e-mail tailored to user profiles, including user location, to the user’s cellular phone. We have conducted a large-scale experiment in shopping malls. The results of this experiment show that agent technology is effective for applications in ubiquitous computing environments.

You've Got Mail From Your Agent: A Location and Context Sensitive Agent System

The best way to evaluate a new technology such as the agent-oriented programming paradigm is to test it in the real world. In this article, we illustrate how multiagent systems can be deployed to analyse, design and implement a location- and context-dependent information system in a shopping mall. Our goal in this application was to help people by making personalised information available where and when it is needed in a way that disturbs them as little as possible and protects their privacy as much as possible. By employing the VPC communication framework on the KODAMA agent platform, we were able to build a shopping-support system as a collection of interacting, autonomous, flexible agents, with support functions capable of dynamically adapting services to client location and preferences as well as environment changes. Here we will give a close view of the system, examine application scenarios and discuss the pros and cons that emerged from the results of a large-scale experiment.