Dr. Shintaro Mori’s official website

Ⅰ. Introduction

Senior researchers have devoted much effort to technological innovation to use limited frequency resources (radio spectrum) effectively in the research field of wireless communications and networks. However, the explosive increase of IoT devices in the future cannot be directly associated with greenhouse gas emissions, but it could be a major concern in a sustainable society. It is necessary to continue to promote the development of technologies that improve energy efficiency and efficient and secure design to develop information-centric wireless sensor networks (ICWSNs). In addition, developing the elemental technologies that can be used as the seeds for smart cities, especially disaster-resistant smart cities, must be considered in this field.

The key feature of this study is that information-centric networking (ICN) scheme is applied to wireless sensor networks (WSNs). ICN was researched and developed as a replacement for the next-generation Internet technology. This is an essential element of next-generation wireless network technology. Since ICWSNs have a pull-type structure, they have great potential for a wide range of new applications compared to conventional push-type systems. On the other hand, it is crucial to improve the structural drawbacks that increase energy consumption, which this research and development aims to accomplish.

As the next-generation wireless network technology deployed on the next-generation wireless communication system (5G/B5G), our contributions to the frontier wireless communication technologies in ICWSN are to provide scalability, autonomy, and decarbonization. The results of this project are academically significant as it aims to achieve international competitiveness and further academic development in an innovative research field by publishing research results in conferences and journals with a strong global presence.

The technological innovations and applications obtained through this project will significantly contribute to the knowledge necessary to achieve a sustainable, disaster-resistant smart city. We believe that producing these seeds is of great social significance. Implementing and developing hardware devices that can perform in practical environments is socially significant. It provides a vision for the technological needs of the industrial field, and it is also helpful for developing new technologies to enrich people's lives through industry-academia-government collaboration.

Ⅱ. Related Studies

In previous grant-funded studies, we conducted fundamental studies on ICWSNs, including the development of efficient and reliable caching methods, their application to disaster-resistant smart cities, and further development. In addition, the paper that outlined the research topic was accepted at a high-level international conference.

Ⅲ. Research and Development Items

To realize a green ICWSN, we will develop a technology to reduce energy consumption and establish the technology as a seed through evaluation based on hardware experiments using a testbed.

In this project, we focus on introducing the ICN technique into WSNs, and we propose it as a novel technology. ICN is developed as a next-generation Internet architecture, and its feature is that individual data are managed as named data rather than IP addresses. In ICWSNs, there is potential for reducing the overall system energy consumption and making more efficient use of radio spectrum as data transfer can be reduced (caching scheme), unnecessary data transmission can be reduced (pull-type network design), and protocol overhead can be eliminated (no need for addresses). However, in the nodes that consist of ICWSNs, the hardware resources, such as batteries and computing resources, are limited. Furthermore, there are technical issues with adapting ICN, i.e., ICN designed for wired networks (next-generation Internet), against WSNs.

In the R&D item in FY2023, we focus on validating the energy-saving effect in comparison with the conventional framework in terms of traffic reduction and latency improvement to the introduction of the proposed framework. In the previous studies, we developed the ICWSN testbed, constructed a prototype network, and evaluated the fundamental performance in the laboratory. Then, we conducted test experiments for medium- to long-term operation. Based on the knowledge obtained there, we plan to implement and develop hardware devices that can meet the demands in a practical environment regarding energy consumption. From these studies, we demonstrate the effectiveness of the proposed method and identify issues that need to be overcome for future implementation. The outcomes of this study will be submitted to academic conferences in domestic and international societies where researchers of wireless communication and networks participate to enhance the quality of the research. In addition, we will accelerate the development of the proposed system for the next fiscal year.

The development of energy-saving technology in FY2024 aims to simply overcome the disadvantages (increasing energy consumption) in ICWSNs compared to conventional WSNs. The proposed scheme has advantages, such as improving network performance. This indicator is widely accepted, as it is based on the same perspective in the base stations for next-generation mobile communication systems. However, in terms of academic contribution, we believe it is an exaggeration to describe it as a technical improvement. In particular, in WSNs, it is necessary to deal with and consider the dynamic wireless environment due to the addition and removal of wireless nodes, movement, and propagation environment changes. From this situation, to demonstrate academic novelty, we will develop a method in which the neighboring nodes cooperate to act as if there were virtual nodes. Thanks to this mechanism, the proposed scheme can overcome the structural disadvantage of ICWSN by using the sleep mode to reduce energy consumption. The outcomes of this R&D item will be published in academic conferences like in FY2023. In addition, since academic contribution is a research theme that crosses multiple fields of application, it will be widely presented to the academic societies.

As a significant outcome of this project, we aim to develop a technique for reducing the overall energy consumption in WSNs, a key elemental technology for green ICWSNs. In addition, this experiment includes an evaluation of a testbed that has been implemented in practical environments, such as a Restful data common infrastructure and connectivity with existing devices, for smart city applications. Therefore, the findings and challenges identified through this project are innovative and competitive fundamental academic results. The development of technological seeds is another outcome of this project. In other words, when we regard this project as Phase 0 for future deployment, We hope that the results of this project will be developed and used as a milestone for meeting the technological needs of the industry (Phase 1) and introducing advanced technology to projects that enhance people's social lives through industry-academia-government collaboration (Phase 2). In light of this scenario, the testbed implementation in FY2024 should be developed and evaluated in a manner that provides the knowledge necessary for future research and development.

Ⅳ. Findings and Results

This study's outcomes include identifying the proposed scheme's potential as a technological seed for future social application. As a proof of concept, we also focused on solving practical implementation issues by actively developing testbeds and operational experiments. In order to achieve a green ICWSN, we developed a technology to reduce the framework's overall energy consumption. We can establish the perspective of this project as a seed based on hardware experiments using testbeds, as follows. The novelty of this study is that we focus on ICWSN. Since the data transfer in the ICWSN can reduce the data transmission distance (caching design), reduce unnecessary data transmission (pull-type network design), and reduce protocol overhead (no need for addresses), the system contributes to reducing overall energy consumption, and at the same time, it is expected to achieve effective use of radio spectrum.

In the R&D item in FY2023, we compared the energy-saving technology of ICWSN with the system designed based on the conventional framework. For the increase in power consumption due to the introduction of the proposed scheme, the effect of improving the network performance (traffic reduction, latency improvement) was compared and evaluated. As shown in Fig. 1, the proposed model for power consumption assumes four states: active, transmitting, receiving, and sleeping. In the active status, the device performs more sophisticated tasks such as sensing, sensing data generation, caching, and calculation/analysis. Wireless data transmission requires more energy than computation, but sleep mode consumes the least energy.

Figure 2 shows a numerical example based on the power consumption model described above. Computer simulation was developed using the C++ language. The simulation parameters were determined based on the measured values of the hardware devices. For the data transmission rate per unit time, ν and λ in the cases where 0, 10, 20, 30, 40, and 50, the proposed scheme can improve the performance by 37.2, 35.4, 33.7, 32.0, 30.2, and 28.5%, respectively, but the power consumption increases by 3.62, 3.30, 3.08, 2.91, 2.78, and 2.67 times, respectively. The reason for increasing energy consumption is that the proposed scheme consumes more energy to distribute cached data over a wider area. From this perspective, the general data caching policy considers the freshness and popularity of data, and the retrieved data is unbalanced. Therefore, the results should improve in a practical scenario compared to the completely random scenario presented in this paper. On the other hand, the proposed scheme is effective when the frequency of the data generation and data retrieval environment is relatively lower.

In the R&D item in FY2024, we consider the dynamic wireless environment due to the joining and leaving of wireless nodes, movement, and propagation environment changes in WSNs. In light of this situation, we investigated energy-saving technology for blockchain-based cashing methods to emphasize their academic novelty clearly. We introduce blockchain into the proposed scheme because the decentralized, traceable and immutable ledger can be provided without the need for a centralized and trustworthy node. At the same time, the data verification process in blockchain requires a massive computer calculation (mining work) based on PoW (Proof of Work), which cannot be performed by wireless nodes due to hardware limitations.

The proposed scheme uses a lightweight method based on PoET (Proof of Elapsed Time) to address the abovementioned issues. In the proposed scheme, each node has a timer, and the first node that reaches the specified waiting time is determined to be the winner. Unlike the original PoET method, the data verification procedure of the proposed scheme rotates the coordinator among the nodes. This approach ensures fairness between nodes and eliminates the single point of failure caused by the coordinator. As a detailed procedure, the validator broadcasts a request message with a signature, the coordinator verifies the message, and then replies with the latest block index and a random waiting time. The validator waits until the waiting time has elapsed and then determines which node will be given the privilege of block approval as the winner. The winner node broadcasts the verified block with an identifier and proof of validity, and other nodes append it to the blockchain. The blockchain might fork if two or more nodes are selected as winners in the same waiting time. However, the proposed scheme is being deployed in the area of regional smart cities. Therefore, such a situation is negligible for a sufficiently small scale.

Regarding the robustness of the proposed scheme, it is not valid if malicious verification is performed. However, the proposed scheme solves this problem by rotating the verification nodes based on a randomized selection. Since malicious nodes are mutually exclusive, it can analyze the history of the winner node in the blockchain. On the other hand, regarding the energy consumption of the proposed scheme, the validator can switch to an idle or sleep state while waiting, reducing both the computer resources and energy consumption. Specifically, it was found that energy consumption could be reduced by 30.7% (when idle) and 59.0% (when sleeping) if the processing time for the PoW and PoET consensus methods were assumed to be the same.

As an outcome of this research and development, the experimental evaluation includes an evaluation of a testbed with a smart city application as a case study, including a Restful data common infrastructure and connectivity with existing devices, such as an urban operating system. Therefore, the findings and issues identified through this research and development are novel and superior fundamental study findings in universities, and the technology seeds produced by this research are another outcome of this research. Aiming to make such developments, we carried out testbed development and evaluation that can provide the knowledge necessary for future research and development.

Specifically, as a smart city as a service platform, we developed and evaluated the implementation of ICWSN for future smart city applications. Here, we developed a test field with a reliable, zero-touch testbed device and evaluated network performance. It was constructed as a wireless communication system based on millimeter wave band communication for broadband communication. In addition, using the developed platform, we can demonstrate the feasibility of our proposed scheme through the experimental results of network performance.

Ⅴ. Conclusion and Future Work

The results of this research and development include identifying the developed system as a technology seed for future practical applications, and we also tackled the problem of practical deployment through the active testing and development of testbeds and operational experiments. In order to achieve a green ICWSN, we developed a technology to reduce the energy consumption of the entire framework, and we could establish it as a technology seed based on an evaluation using hardware experiments with a testbed. In the future outlook, we will further expand the findings of this study and work to introduce the latest technology to meet the technological needs of the industrial field and promote projects that contribute to improving people's social lives through industry-academia-government collaboration. To this purpose, we have applied for four competitive research grants as the primary applicants and have been accepted for two.