Yoshiaki Kakuda

An adaptive multihop clustering scheme for highly mobile ad hoc networks

A clustering scheme for ad hoc networks is aimed at managing a number of mobile devices by utilizing hierarchical structure of the networks. In order to construct and maintain an effective hierarchical structure in ad hoc networks where mobile devices may move at high mobility, the following requirements must be satisfied. (1) The role of each mobile device for the hierarchical structure is adaptive to dynamic change of the topology of the ad hoc networks. The role of each mobile device should thus change autonomously based on the local information. (2) The overhead for management of the hierarchical structure is small. The number of mobile devices in each cluster should thus be almost equivalent. This paper proposes an adaptive multihop clustering scheme for highly mobile ad hoc networks. The results obtained by extensive simulation experiments show that the proposed scheme does not depend on mobility and node degree of mobile devices in the network, which satisfy the above requirements.

A routing protocol for finding two node-disjoint paths in computer networks

In this paper, we present a routing protocol for finding two node-disjoint paths between each pair of nodes in a computer network. In the proposed protocol, each node in the network has the same procedure, which is driven by local information with respect to the network topology such as an adjacent node on a spanning tree in the network. Thus, the execution of the protocol can continue after changes of the network topology and load. The concept of spanning tree-based kernel construction is introduced to synchronize procedures under the distributed control of the protocol. The routing scheme based on the protocol possesses the enhanced capabilities of alternate routes and load splitting, which cope with failures and load variations in the network. Furthermore, even if topology changes occur which damage the obtained disjoint paths, the paths themselves can be updated efficiently.

An Automobile Control Method for Alleviation of Traffic Congestions Using Inter-Vehicle Ad Hoc Communication in Lattice-Like Roads

Since losing costs and spending time which are caused by traffic congestions are large, methods for alleviation of traffic congestions are required. So far, some methods (ex. car navigation system or vehicle information and communication system (VICS), which shows a route that avoids points of traffic congestion) have been developed as commercial products. These commercial products could cause other traffic congestions by the following mechanism. When a traffic congestion is recognized by the products, the method installed in the products tries to find a route where travelling time becomes shortest. As a result, many drivers, who equip the products, choose the same route. It causes other traffic congestions on the route. We intend to achieve an automobile control system where each driver obtains traffic information adaptively and it helps to alleviate traffic congestions. For such automobile control system, in this paper we propose an automobile control method for alleviation of traffic congestion using inter-vehicle ad hoc communication in lattice-like roads. In the proposed method, each automobile broadcasts information of the automobile, the information is relayed in multi-hop transmissions, and each automobile obtains information of automobiles. The automobile can therefore calculate an appropriate route based on the obtained information. Also, this paper presents simulation evaluations on the proposed method.

Mobile Agents for Service Discovery in Ad Hoc Networks

Recently sophisticated protocols for routing in ad hoc networks have been proposed, but there is still little work on service discovery in such volatile environments. In this paper a mobile agent-based scheme for service discovery in ad hoc networks is introduced. Mobile agents are traveling through the network, collecting the dynamically changing service information. The travel route and the number of travel agents are adjusted according to the information state and the change of network topology. In a quantitative analysis the proposed algorithm is compared with the flooding scheme. The usefulness of the approach is proved by an implementation for mobile devices using J2ME and Bluetooth.

Secure decentralized data transfer against node capture attacks for wireless sensor networks

In wireless sensor networks, sensor nodes have limited computational power and memory size. The data is vulnerable to attack due to the nature of the systems, so maintaining confidentiality is an important problem. Most security methods are based on common or public key cryptosystems. However, these methods have problems with encryption of data. When nodes try to encrypt data, they must preestablish keys. When nodes send data to the sink node, all of the exchanged information will concentrate in the sink node. This creates a single point of failure. In this paper, we propose a new distribution method resilient against node capture attacks using the Secret Sharing Scheme. In addition, we will confirm the ability of our method to improve resiliency against node capture attacks, comparing it with TinySec, which is the major security architecture of wireless sensor networks. Also, we compare the resiliency to existing pairwise key establishment methods.

An Inter-domain Routing for Heterogeneous Mobile Ad Hoc Networks Using Packet Conversion and Address Sharing

In ad hoc networks, a diversity of routing protocols exists. Each network selects a routing protocol suitable for its own environment such as a vehicular ad hoc network (VANET), a wireless mesh network, or a mobile ad hoc network (MANET) that consists of pedestrians. Generally, since there is no interoperability between different routing protocols in ad hoc networks, the communication between different networks is impossible. Therefore, in this paper, we propose Ad hoc Traversal Routing (ATR) to provide interoperability between different networks. Because of ATR, any two nodes in different networks can seamlessly communicate with each other. ATR connects two different networks to each other by converting control messages from one network to another network and adding the node address of different networks into the routing table for routing protocols. In addition, we conduct simulation experiments to evaluate the performance of ATR in heterogeneous wireless network environment that consists of a vehicle ad hoc network, a wireless mesh networks, and a mobile ad hoc network.

Fault-tolerant scheduling algorithm for distributed real-time systems

In a distributed real-time system, tolerance to faults on processing nodes in the system is achieved by means of redundant nodes and a fault-tolerant scheduling algorithm. Since redundant nodes increase total failure rate of the system, the number of such redundant nodes should be small. This paper proposes a procedure for fault-tolerant scheduling, which realizes fault-tolerance via a small number of redundant nodes. The procedure is based on such a technique that allows multiple copies of a task to be executed concurrently. It achieves efficient utilization of nodes by forcing copies being executed to terminate immediately after having obtained the first result of these copies. A fundamental scheduling algorithm, into which the procedure is incorporated, is defined and its simulation results are shown.<<ETX>>

Improvement of assurance including security for wireless sensor networks using dispersed data transmission

Assurance networks are one of the essential technologies of New-generation Networks. Assurance is defined as the capability of guaranteeing functional and non-functional system properties such as dependability, security, timeliness and adaptability to heterogeneous and changing requirements. Assurance is essential for sustainable networks and this research focused specifically on providing assurance for WSNs. Node capture attacks are one prospective kind of attack on WSNs. To reduce negative effect of node capture attacks, we have previously proposed secure decentralized data transfer. In this proposed method, it was assumed that multiple paths were in place. In this paper as well, we again propose using the multipath routing method. To make multiple paths fit our previously proposed method, we have modified ATR (Augmented Tree Based Routing). We have conducted simulation experiments using our proposed method in a network simulator. The results show that our previously proposed method is effective in both cases in which the network size is small or large. In addition, we conducted other simulation experiments to measure several aspects of the assurance of our method. We measured in terms of varying parameters such as node densities, distance between the source and the destination nodes, and so on. Additionally, our method is more assured than the single path-based method.

A Self-Configurable New Generation Children Tracking System Based on Mobile Ad Hoc Networks Consisting of Android Mobile Terminals

Hiroshima City Children Tracking System is a safety support system for children based on ad hoc network technologies. Field experiments have been conducted in cooperation with an elementary school in Hiroshima. In this paper, we propose a new generation children tracking system which is based on experiences and findings of the field experiments for Hiroshima City Children Tracking System. Our proposed system consists of Android terminals which has Wireless LAN device and Bluetooth device with the ad hoc communication function. Our system manages groups of Android terminals using Autonomous Clustering technique. In this paper, we show the system requirements for our children tracking system and describe the implementation features to satisfy the system requirements. Finally, we provide some preliminary implemented results for our proposed system.

An Efficient On-Demand Hierarchical Routing Protocol Based on Autonomous Clustering for Mobile Ad Hoc Networks

In order to make routing efficient for large-scaled ad hoc networks, we have proposed the autonomous clustering scheme and the hierarchical routing called Hi-AODV based on the autonomous clustering. Since, in the current autonomous clustering, a tree rooted at a clusterhead which manages a cluster is constructed for each cluster, data and control packets always pass through the clusterhead in the hierarchical routing and the overhead of the clusterhead becomes much higher. Therefore, in order to reduce the number of data and control packets which each clusterhead handles, this paper proposes an efficient on-demand hierarchical routing protocol based on the autonomous clustering for ad hoc networks