SOS Message Distribution for Searching Disaster Victims

This chapter presents the design and implementation of the SOSCast application which enables SOS message distribution for searching victims in a disaster-damaged area. During catastrophic disasters such an earthquake or tsunami, people may be injured or trapped in fallen buildings and debris. In situations like these, it is critical that rescue operations must be done within the first 72 h to save many lives. It is also during these events where communication infrastructures are severely damaged, and thus, makes it difficult for victims to ask for help due to the absence of communication channels. By using the SOSCast application in such scenario, victims are able to exchange SOS messages automatically by communicating directly among smartphones with less operation. By collecting these SOS messages, rescuers can find the existences of the victims as mapped on their smartphones. We have shown in our preliminary experiment within a residential area that SOSCast is capable of determining the existence of a propagator based on the collected SOS messages

Data Delivery Method Based on Neighbor Nodes’ Information in a Mobile Ad Hoc Network

This paper proposes a data delivery method based on neighbor nodes’ information to achieve reliable communication in a mobile ad hoc network (MANET). In a MANET, it is difficult to deliver data reliably due to instabilities in network topology and wireless network condition which result from node movement. To overcome such unstable communication, opportunistic routing and network coding schemes have lately attracted considerable attention. Although an existing method that employs such schemes, MAC-independent opportunistic routing and encoding (MORE), Chachulski et al. (2007), improves the efficiency of data delivery in an unstable wireless mesh network, it does not address node movement. To efficiently deliver data in a MANET, the method proposed in this paper thus first employs the same opportunistic routing and network coding used in MORE and also uses the location information and transmission probabilities of neighbor nodes to adapt to changeable network topology and wireless network condition. The simulation experiments showed that the proposed method can achieve efficient data delivery with low network load when the movement speed is relatively slow

Calibration of Smartphone-Based Weather Measurements Using Pairwise Gossip

Accurate and reliable daily global weather reports are necessary for weather forecasting and climate analysis. However, the availability of these reports continues to decline due to the lack of economic support and policies in maintaining ground weather measurement systems from where these reports are obtained. Thus, to mitigate data scarcity, it is required to utilize weather information from existing sensors and built-in smartphone sensors. However, as smartphone usage often varies according to human activity, it is difficult to obtain accurate measurement data. In this paper, we present a heuristic-based pairwise gossip algorithm that will calibrate smartphone-based pressure sensors with respect to fixed weather stations as our referential ground truth. Based on actual measurements, we have verified that smartphone-based readings are unstable when observed during movement. Using our calibration algorithm on actual smartphone-based pressure readings, the updated values were significantly closer to the ground truth values

Studies on measurement-based path selection in multi-homed wireless networks

https://library.naist.jp/mylimedio/dllimedio/show.cgi?bookid=100040521&oldid=74697博士 (Doctor)工学 (Engineering)博第365号甲第365号博士（工学）奈良先端科学技術大学院大

VOIP TECHNOLOGIES

350 Halama

Rate Adaptation Mechanism with Available Data Rate Trimming and Data Rate Information Provision for V2I Communications

We study a rate adaptation mechanism for improving communication performance between a connected vehicle and a roadside unit (RSU) using Wi-Fi during movement in a vehicle-to-infrastructure (V2I) environment. Wi-Fi communication provides various attractive services to connected vehicles during movement. However, as a connected vehicle is generally moving at high speed, the communication performance with an RSU that works as an access point is degraded because wireless link quality fluctuates abruptly and continuously. We then propose a rate adaptation mechanism employing the following two main features to mitigate such deterioration in communication performance: available data rate trimming and data rate information provision. To alleviate degradation of communication, the former avoids usage of excessively low data rates and the latter then provides data rate information suitable for channel quality from a dataset of adequate data rates based on the vehicle's location and speed. However, the data rate information provided from a dataset may not always be appropriate because of various indefinite factors such as multipath fading and shadowing. Thus, the proposed method also employs a measurement-based function to compensate for such a drawback of the dataset. Simulation experiments evaluate communication performance for 10, 60, and 100 km/h in single-vehicle and multiple-vehicles cases. Simulation results showed that the proposed method overall provides superior communication performance in situations involving more than one vehicle, in comparison with existing counter- and sample-based methods

A Unified Handover Management Scheme Based on Frame Retransmissions for TCP over WLANs

In ubiquitous networks based on Wireless Local Area Networks (WLANs) with limited individual coverage, mobile nodes will be likely to traverse different WLANs during TCP communication. An effective handover management scheme for achieving seamless and efficient communication throughout the handover operation is therefore crucial. To achieve this, the following three requirements are essential: (i) early initiation of handover, (ii) elimination of communication interruption upon handover, (iii) selection of an optimal WLAN. The handover scheme proposed in this study employs frame retransmission over WLAN as an indicator of link degradation, and a handover manager (HM) on the transport layer obtains the number of frame retransmissions on the MAC layer using a cross-layer architecture in order to achieve (i) and (iii). Then, it also employs multi-homing in order to achieve (ii). Simulations demonstrate that the proposed scheme can satisfy all of the three requirements and is capable of maintaining TCP performance throughout the handover operation