Telecommunications
Post-disaster networking, IoT

Age-effective information updating over intermittently
connected MANETs
Division of Electrical, Electronic and Infocommunications Engineering, Graduate School of Engineering
Assistant Professor Yoshiaki Inouehttps://researchmap.jp/q_yoshiaki/

Telecommunications

Abstract
Immediately after the occurrence of a natural disaster, communication infrastructure such as wireless base stations may become
unavailable. Even under such circumstances, it is important tokeep continuous operation of Internet of Things (IoT) based monitoring systems for rapid information acquisition and enhanced
safety. The Delay/Disruption/Disconnection Tolerant Networking(DTN) technology has been studied extensively as a method torealize remote communication without relying on infrastructure.
However, these studies have been conducted without targeting theuse for monitoring systems. In particular, investigations on the key
design factors, such as the frequency of sensing data transmission, have not been addressed so far. In this study, we establisheda method to mathematically analyze the system from the viewpointof “information freshness,” which is of key importance when applying the DTN technology to monitoring systems.

▍ Significance of the research and Future perspective
Although numerous research efforts are currently put on enhancing functions of cities using IoT from a variety of perspectives,enough attention has not been paid to their continuation in emergency situations such as immediately after the occurrence of a natural disaster. Also, while DTN technology has long been studied as
a communication method for emergencies, its use for monitoring,
the key application of the IoT, has remained largely unexplored. Itis expected that this study will serve as a springboard for further
research on the continuity of IoT systems during emergencies.

▍ Background & Results
As exemplified by the term Internet of Things (IoT), recent years
have seen a growing interest in utilizing information sensed by numerous devices to improve the safety and convenience of our daily
lives. The concept of incorporating such functions throughout anentire city is known as the smart city, and it is expected to transform our lives in the near future. Toward the realization of the smart
city, efforts are being made in various fields, such as miniaturization and enhancement of sensing devices, development of communication infrastructure for information aggregation, and machinelearning technology for analyzing collected information.
While these studies aim to enhance functions of the city during“normal” times of daily life, it is desirable to maintain such enhanced functions, even if only partially, during “emergencies” suchas immediately after the occurrence of a natural disaster. In particular, it is important to assume a scenario in which communication
infrastructure such as wireless base stations become unavailable.
The Delay/Disruption/Disconnection Tolerant Networking (DTN)
technology has been studied for a long time as a technology torealize remote communication in situations where communication
infrastructure is unavailable. In DTN, information is delivered to thedestination by repeating exchanges of copies of the transmitted
information between nearby mobile devices; it is called the epidemic routing as it behaves like an infectious disease. Conventional research on DTN has mainly focused on the delivery of a single
message from a source device to a destination device. However,in the context of the smart city mentioned above, it is necessary
for source devices to periodically send out sensing data according
to some interval, and in this case, it is important to maintain high“freshness” of the information held by the destination device. Our
study is the first to provide a mathematical method to analyze theinformation freshness in DTN systems, where we derived somenew mathematical results for infinite-server queueing models, andwe characterized the information freshness in DTN systems bycombining these results with Markov analysis.

A DTN-based monitoring system

Information sampling schemes

P a t e n t
Tr e a t i s eInoue, Yoshiaki; Kimura, Tomotaka. Age-Effective Information Updating over Intermittently Connected MANETs, IEEE Journal on Selected Areas inCommunications. 2021, 39(5), p. 1293-1308. doi: 10.1109/JSAC.2021.3065031

URL
K e y w o r d post-disaster networking, IoT, delay/disruption/disconnection tolerant networking (DTN), age of Information (AoI)