In a huge earthquake, disaster notification system may cease to function due to the damage of communication cables, etc. Therefore, in this study, we assume a wireless mesh network using LPWA that operates independently from existing infrastructures such as the Internet. Disaster notification to first responders must be delivered reliably and with low latency. Flooding is a possible way to obtain redundancy. However, flooding increases the number of messages, and there is concern that increased latency due to time slot control. In this study, we focus on Plumtree that is a fault-tolerant and message-reducing algorithm and consider its application to the disaster notification wireless mesh network. Specifically, we propose a method to enable unicast notification to the first responder node by extending Plumtree. In the proposed method, each node has an additional routing table to keep the direction of the first responder node. Experimental results show that the number of hops in the proposed method is sufficiently small for message loss rates up to 5 %. Even when the loss rate is 50 %, the number of hops is less than approximately two and a half times compared to the shortest path tree.

Structured overlays enable the construction of application-level networks from multiple nodes, and the decentralized searching of data in the network. One such structured overlay is the skip graph, which supports range queries. Each node in a skip graph has multi-level shortcut links. The degree of each node is O(log N) on a network with N nodes. The paper, proposes Ballistic Skip Graph, a structured overlay that reduces the degree of each node to O(1) by limiting the number of shortcut links to a randomly selected single level while supporting range queries. Because the nodes are not grouped, the proposed method requires no extensive reconfiguration of the network when nodes join or leave. An evaluation experiment confirmed that the average routing table size is confined to a small constant.

In Skip Graph, a structured overlay, each node constructs its routing table by choosing connected nodes based on its membership vector. However, membership vectors are determined randomly; therefore, nodes do not always form an ideal topology. This can cause the route length to be long. Therefore, we propose Self-Refining Skip Graph, a structured overlay where each node refines its routing table toward an ideal Skip Graph topology. Our proposed method has shorter route length as approaching to an ideal topology while maintaining the robustness derived from the mechanism of membership vectors. Our evaluation confirms that the topology approaches to an ideal one and that the route length becomes shorter than that in Skip Graph.

We are designing authentication framework for a regional network with concerns on fast authentication and disaster robustness. To achieve this goal, we previously proposed a proactive and distributed authentication framework (PDAF). In this paper, to enhance the robustness of PDAF, we add temporary registration and authentication procedures in a disaster scenario and the distributed regional network key server (RNKS) mechanism. Meanwhile, we optimize PDAF messaging through reducing redundancy to improve the performance. The proposed PDAF is a fully distributed design, which is intrinsically more robust than the existing authentication framework. In particular, we implement the PDAF over an existing regional network and measure the performance of PDAF. This shows that network scale and offered traffic load do not influence the PDAF's authentication time, which is usually around 31 ms under our experiment environment, because neighboring networking devices directly authenticate end devices.

Delaunay overlay networks have a Delaunay graph structure, which has spatial locality. This feature is useful for distributed spatial computing, distributed geographical database systems, and geometric routing networks. An incremental construction method of these networks is proposed. The existing method assumes that each communication node can create overlay connections using IDs with all other nodes via underlay networks. Yet this method cannot be used for deploying underlay networks. To solve this problem, the existing method is enhanced by using detour paths for spatial neighbor-connected networks. We propose a detour path construction procedure, which is useful for introducing position-based heuristic routing to L3 networks, DTNs, and database networks.

Nerve Net is a concept of regional wireless access platform where multiple service providers can provide their own services with the shared use of the network and sensors, making various context-aware services practical. It works as the nervous system of the human beings. Densely located, interconnected access points with database and data processing unit will provide mobility to terminals without a location server and will enable secure sensor data transport on a highly reliable, managed mesh network. The motivation, concept, architecture, system configuration, and preliminary performance results of Nerve Net are introduced.

A managed wireless mesh for infrastructure-level, stable regional mesh network has been studied. NerveNet, which we have been proposing, is a concept of future regional platform network that covers local regions and provides various context-aware services with the shared use of sensors and actuators. The managed wireless mesh developed for materializing NerveNet features auto-configuration of multiple, different routes between any two base stations for high capacity and reliability. The managed wireless mesh of ten base stations was implemented on PCs and commercial L2 switches. Performance evaluation showed that route switching after one or two link failures had been detected was completed in no later than 70 milliseconds while it takes a few to tens of seconds with existing adhoc routing-based mesh networks. It was also shown that the restart of the network took only about three minutes, enabling urgent recovery of communication in emergency situations.

A managed wireless mesh for infrastructure-level, stable regional mesh network has been studied. NerveNet, which we have been proposing, is a concept of future regional platform network that covers local regions and provides various context-aware services with the shared use of sensors and actuators. The managed wireless mesh developed for materializing NerveNet features auto-configuration of multiple, different routes between any two base stations for high capacity and reliability. The managed wireless mesh of ten base stations was implemented on PCs with commercial L2 switches. Performance evaluation showed that route switching after a link failure had been detected was completed in no later than 70 milliseconds while it takes a few to tens of seconds with existing ad hoc routing-based mesh networks.

A new-generation access network should be able to transport various kinds of dynamically changing sensor information about specific localities or private individuals to different destination servers in a secure manner for processing so that the various processed information can be used in an integrated manner to provide advanced context-aware services. After classifying the various kinds of sensor information related to individuals, we propose a communication architecture in which sensors placed in the environment, mobile terminals owned by users, and the new generation access network operate cooperatively. It features secure transport of sensor information via mobile terminals by establishing communication channels to sensors and the sensor database.

We start systematical analysis on the performance of managed mesh network (MMN), which provides communication function in the concept of community service platform in a local region. Towards the performance evaluation framework for MMN, we herein analyze the capacity provision of one base station (BS) under the constraints of physical transmission rate and available spectrum using queueing theory. In the related work of capacity analysis on mesh network, most of them have not put effort on the determination of exact capacity, or they investigated backhaul mesh network, which is different from MMN. Some other researchers investigated the architecture similar to MMN, but they have not investigated actual traffic processed in the transmission queue. Our modeling solves these problems and determines the exact capacity provided by each BS in an MMN. At the same time, we perform extensive simulations to verify the correctness of our modeling under a set of scenarios with different main parameters. After model verification, we apply our modeling results to a city and show how the capacity of one user at peak time changes with the deployment cost.

This paper identifies communication system functions and technologies that a local region, individuals living in that region, and various communities to which each individual belongs require and propose a community communication service platform for providing those functions and technologies. To provide a variety of services suited to the characteristics of a region or community, the local region itself or individuals, communities, or organizations that are not the conventional telecommunications carriers should be able to deploy, operate, and manage the communications network within that region and should be able to easily construct and provide various services on it. The proposed system, which is based on open specifications, establishes logical paths with a many-to-many mesh topology on a physical wireless mesh network to implement multiple services each of which uses the paths based on its own policy.

This paper proposes a method for extracting the ROI using geometric computations, to obtain information of commonly-interested objects by multiple users. The authors use P2P Delaunay Network to share the regional information shot by cameras with peers, and extract the most intersecting area of camera ranges as ROI. In P2P Delaunay Network, nodes and edges refer to as computers and their connections. This proposed method can construct P2P Delaunay Network using locations of mobile devices as GPS phones or PDAs equipped with a camera, and process computations distributively with these devices. Thereby, a P2P Delaunay network can be constituted, without using the computer resource of other settlements. The method first partitions the plane and assigns the partitions to nodes according to their locations using P2P Delaunay Network. Then, each camera propagates its camera range information to nodes, and each node thus processes computation distributively. The node which has received multiple camera range information computes the intersecting area within its Voronoi region. Finally, the ROI can be determined, by computing the most intersecting area among all nodes. The authors examine the proposed method by evaluating the frequency of region partitioning and data transfer for each node through numerical simulation.