A vehicular delay/disruption tolerant network (VDTN) is efficient in keeping communications in sintuations where natural disasters, such as earthquakes and tsunami, occur. We have implemented a VDTN-based information-sharing system with multiple radio communications, such as digital convenience radio (DCR) and Wi-Fi. The information-sharing system enables firefighters and medical staff to share medical records and the state of the disaster damage via the network. The system requires to authenticate users individually to prevent falsification or circulation of incorrect information by malicious or ignorant users. WPA2-EAP is a major authentication mechanism for enterprise systems. It, however, requires many management frame exchanges to establish a secure link and reduces time to exchange data frames. Thus, we have proposed using the IEEE 802.11ai (FILS) together with WPA2-EAP for the system. In this paper, we report the results of field experiments to measure the FILS performance on a VDTN system. Our experiment results show that FILS shortens the initial link setup times between passing vehicles to around 130 ms, which is about 10 times shorter than WPA2-EAP, and FILS increases the amount of transmitted data up to around 33 MB more than using WPA2-EAP.

Most of natural disaster events have caused damage to the basic infrastructure. This leads to impossibility for victims and rescuers to communicate through the Internet. Wireless Mesh Networks (WMNs) and Moveable and Deployable Resource Unit (MDRU) are two popular solutions for recovery of the communication system. Based on the concept of wireless mesh network, the NerveNet is a disaster-resilient mesh-topology network which is strong against failures in disaster. Moreover, vehicles are considered as a key component in which MDRU can be deployed. In this paper, we propose a disaster-resilient communication framework for heterogeneous vehicular network (HetVNet). The proposed framework integrates NerveNet with the traditional network. We also show our implementation of the network switching algorithm for selecting either NerveNet or LTE for the HetVNet. The real experiments were conducted using the campus shuttle buses in Chulalongkorn University. The results show that the proposed framework can operate well in normal scenario, HetVNet scenario, and disaster scenario. Specifically, in the disaster situation where LTE network is not available, all of the data traffic is transferred via NerveNet. In the normal situation where NerveNet and LTE networks are available, the data traffic can be transferred over both of them.

When a large-scale disaster occurs and the usual communication infrastructure is disconnected, Internet access becomes impossible, and information cannot be exchanged. However, using edge servers, each terminal can upload and view information. Therefore, we consider an environment construction that enables information exchange by edge servers keeping information synchronized. In this paper, we construct an application that accepts and aggregates requests for items that are required for materials other than those provided at the time of disaster and shares information with goods wholesalers.

SNS websites and messages have become a regular part of daily life. However, some large-scale disasters such as earthquakes could damage network cables and equipment and cause network failures. Despite the assistance of information related to disasters and support that is effective for controlling the situation and offering help, it is possible that frequently used SNS messages and websites will become unreachable in a disaster area. Moreover, in a disaster area, the network could break into several sub-networks because of the damage of the backbone network. It is possible that the sub-networks can provide network services in a smaller area range without connecting to the Internet. Therefore, this paper proposes a decentralized SNS system that could solve two major problems during large-scale disasters. First, it describes a stable and continuous SNS network for the affected population and helpers without the influence of networks in the disaster region. Second, it proposes a reliable method to share synchronized data across the affected areas. In this case, a reliable method to control connections among shelters, whether newly built shelters or shelters that lost connection during the disaster, should also be considered. This paper shows the effectiveness of the proposed decentralized SNS system using XMPP to provide SNS for refugees and helpers in each shelter under an emergency of network failure. The connection control among shelters has also been examined and was designed to provide secure connections and data synchronization for this decentralized SNS system.

We propose a novel communication system for an emergency fire response team, which provides Internet service on the way to and in the disaster area. The system is composed of a multi-interface mobile ad-hoc network (MANET) router, a Global Positioning System (GPS) receiver, and two Wi-Fi interfaces with directional antennas, which can be easily attached to the roof of a vehicle. The front-side Wi-Fi interface of the vehicle is operated in the infrastructure mode, and the rear-side interface is operated in the access point mode. Different channels are assigned to each AP interface of the vehicles. Infrastructure-mode Wi-Fi interfaces automatically scan and connect to an appropriate AP interface and create MANET links. Some experiments using this wireless system with the WINDS satellite mobile earth station and nine fire engines were conducted in Ebetsu, Hokkaido. We measured the TCP throughput and confirmed that a throughput of more than 10 Mbps was able to be obtained by most of the node pairs. In addition, high-vision video streaming was able to be successfully transmitted to the streaming server on the Internet through MANET and satellite communication links while they were platooning.

In recent years, disasters happened in many places, and resulted in power shortage and communication interruption. The Wireless Mesh Networks (WMNs) constituted by Renewable Energy-enabled Base Station (REBS) is regarded as a powerful solution in post-disaster recovery, for its energy harvesting ability and the ready-made facilities. However, this solution needs to address several challenges such as unstable power supply, limited bandwidth and long-term optimization. In this paper, we focus on the issue of energy efficiency when realizing the maximal network throughput in a period of time, by the combination of energy usage and network data distribution. To this end, we firstly analyze the unique features of REBS and its associated network in disaster area. Then a throughput-maximization problem is proposed in order to figure out the maximal network throughput. Based on the maximal value, we count out the most energy-efficiency result while guaranteeing the maximal network throughput. We formulate the proposed model into a two-stage Mixed-Integer Linear Programming (MILP) problem and solve it by branch-and-bound algorithm. Simulation results demonstrate our considered two-stage energy efficient scheme strikes a balance between network throughput and its associated energy consumption, and outperforms the existing schemes.

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.

We target energy efficiency of municipal access networks. A municipal access network typically provides coverage for city-wide area, and is characterized by diverse and dynamic traffic profiles. Most existing approaches to energy savings adapt network state to traffic variation. However, these approaches fail to capture the potential of energy savings by exploiting the traffic that has already existed in the network. We study network dimensioning for municipal mesh access networks to save energy by rearranging existing traffic and adjusting link rate. The problem of energy-efficient network dimensioning is formulated using mixed integer linear programming. We also propose an efficient heuristic algorithm that consists of both traffic engineering and link-rate adaptation. Numerical experimental results show that our scheme is more effective than link-rate adaptation in saving energy, and achieves a good balance between energy efficiency and resource efficiency.

Wireless/wired hybrid network offers a promising solution to future broadband access. Exploiting the potential of a hybrid network requires an integrated effort on network design and optimization. We discuss the inter-network traffic and intra-network traffic that commonly exist in an access network, and study to improve transmission efficiency for the two types of traffic. We propose a three-step holistic design and optimization: 1) optimizing the locations of gateway access points (GAP) to reduce wireless hops traffic needs to travel before reaching the wired part; 2) connecting GAPs by "shortcuts" to reduce wireless hops for intra-network traffic; and 3) routing with infrastructure awareness to optimize transmission. In particular, we propose a novel idea of "Virtual Channel" using only existing wired infrastructure to achieve inter-GAP connectivity. Simulation experiments show that a combination of these three steps jointly reduces transmission cost in hybrid networks, with a good scalability when network size grows.

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.

OLSRv2 is being standardized in the IETF MANET (Mobile Ad hoc Network) working group. OLSRv2 uses the common packet format, that is also being standardized in the MANET WG. It is necessary to validate the OLSRv2 protocol specification by implementing OLSRv2. In addition, OLSRv2 has a great capability to reduce message size compared to OLSR. This is due to address compression. The change of control message size directly affects the total network performance, but how much it affects the various parameters are dependent on the network scale, number of nodes, and address compression implementation. In this context, we have implemented the OLSRv2 protocol, which can run as a real-time protocol or in the QualNet simulator. In addition, we added link disconnection feedback function from MAC layer to OLSRv2 modifying wireless LAN device driver. In this paper our OLSRv2 implementation detail is introduced, and OLSRv2 performance is compared with OLSR by using both a 50 node testbed built in Niigata university and also in the Qualnet simulator. In addition, IP address compression effect is analyzed in the simulator, and the performance of OLSRv2 with link layer disconnection feedback is evaluated in the testbed.