グエン キエン

This paper proposes the maximum efficiency tracking for the multi-receiver wireless power transmission (WPT) system. The proposed system is designed to satisfy zero-voltage switching (ZVS) for load variations and coil misalignment, regulating the output voltage. The control strategy for the multiple-receiver WPT system is suggested in this paper. The experiment with the two-receiver WPT system is conducted to show the effectiveness of the proposed system.

This paper presents a design procedure for wireless power transfer (WPT) systems with the load-independent class-E inverter family. The design procedure guarantees that the WPT system will achieve constant output and soft switching in response to load variations without particular control, which can apply not only single-hop single-output but multi-hop multi-output WPT system designs. It is analytically explained that a WPT-system output type is determined by properly selecting inverter, rectifier, and coupling resonant structure. As a concrete design example, we designed the three-hop three-output WPT system for installation into a robot arm. Experimental results exemplified the validity and usefulness of the established procedure.

Multipath communication is a well-developed technology that enhances communication effectiveness and resilience. Moreover, it can flexibly utilize network resources through load balancing among available paths. However, traditionally, deploying such load balancing functions on network devices is costly due to the required configuration changes and complicated signaling mechanisms on the devices' control planes. Programming Protocol-independent Packet Processors (P4) has recently emerged as a programming language that enables programmability on the data plane, with the potential to relieve such issues in multipath communication. This work introduces and implements three P4-based multipath schedulers that can split traffic over several paths in wireless networks. The first is P4-based Random Splitting, which distributes traffic randomly. The second is P4-based Weighted Round Robin, with path scheduling based on weights in accordance with path capability. The last is P4-based Dynamic Weighted Round Robin (DWRR), which can improve bandwidth utilization by shifting the weights following dynamic changes in the available bandwidth (i.e., when congestion occurs). We have extensively evaluated the implementation of these three P4-based schedulers in a Mininet-WiFi/P4 environment with User Datagram Protocol (UDP) traffic. The results show that these schedulers can achieve multipath communication with the designed scheduling mechanisms.

When deploying the IoT-Blockchain system on an infrastructure-based network (e.g., Wi-Fi), we will face the single point of failure problem (e.g., failure of an access point harm the whole system). Using ad-hoc routing protocols can avoid such a problem, and the system can recover the communication automatically if an IoT device fails. This paper investigates the recovery time of two routing protocols (i.e., Optimized Link State Routing (OLSR) and a Better Approach To Mobile Ad-hoc Network (BATMAN)) in an IoT-Blockchain system after a network failure happened without and with a blockchain connection. We have used mininet-wifi and private Ethereum blockchain to build the IoT-Blockchain, where we deployed the two routing protocols. The evaluation results show that the performance of BATMAN is better than OLSR's. Specifically, the recovery time of BATMAN is 8.485, 7.355 seconds faster than OLSR when not having and having a blockchain connection, respectively.

Blockchain technologies have been emerging with the potential to disrupt many fields (e.g., cryptocurrencies replacing the traditional ones, enabling trustworthy voting, etc.). The Internet of Things (IoT) has been predictably strengthened when integrating to the private blockchain, such as Ethereum. In an IoT deployment with private Ethereum, a thorough understanding of the latency is a critical issue that has not been adequately understood in the literature. Motivated by that, this work aims to comprehend the latency performance in the IoT Ethereum with two popular consensus algorithms: Proof-of-Work (PoW) and Proof-of-Authority (PoA). Initially, we clarify different latency segments from transaction submission to execution, namely the transaction lifecycle in a private blockchain. We then consider the three related latency metrics: transactionoriented latency, mining time, and block-oriented latency in the PoW case. With PoA, the mining time’s consideration is omitted since the mining process is not necessary. After that, we construct a realistic private Ethereum IoT network (i.e., using a laptop and seven Raspberry Pi 3b+ nodes) and a large-scale emulated one with 30 nodes. We write and deploy a smart contract to read and write data to the blockchain and measure the latencies in various scenarios. The measurement results reveal the values of transaction-oriented and block-oriented latency with PoW, PoA in both the actual and emulated networks. Moreover, we derive the expected value for the PoW’s mining time by fitting the probabilities to an exponential curve.

This paper presents a design method of a two-hop wireless power transfer (WPT) system for installing on a robot arm. The class-E inverter and the class-D rectifier are used on the transmission and receiving sides, respectively, in the proposed WPT system. Analytical equations for the proposed WPT system are derived as functions of the geometrical and physical parameters of the coils, such as the outer diameter and height of the coils, winding-wire diameter, and number of turns. Using the analytical equations, we can optimize the WPT system to obtain the design values with the theoretically highest power-delivery efficiency under the size limitation of the robot arm. The circuit experiments are in quantitative agreement with the theoretical predictions obtained from the analysis, indicating the validity of the analysis and design method. The experimental prototype achieved 83.6% power-delivery efficiency at 6.78 MHz operating frequency and 39.3 W output power.

The fifth generation of mobile wireless networks (5G) will provide an infrastructure with abundant and reliable connectivity for innovative and complicated applications. In 5G, 5G mobile devices, which will have improved computing resources for such applications, play an essential role. However, the network stack of 5G devices may continue to be borrowed from 4G legacy operating systems, thereby degrading user experience. In this paper, we posit that 5G users should have flexibility in utilizing networks and gain more awareness of network selection. To this end, we exploit network softwarization technologies to empower 5G devices. We then devise 5GSoft, a novel softwarized networking stack on each 5G mobile device. 5GSoft includes wireless virtualization to relax the dependence on hardware, thereby enabling sharing and multiple access. The 5GSoft device can concurrently exploit surrounding wireless networks using software-defined networking. Finally, the 5GSoft device is aware of network selection for each application process by applying network namespace. Qualitative evaluation of 5GSoft, in comparison to other approaches, highlights its effectiveness in terms of awareness and flexibility provision. Moreover, real experiments show that the virtualization in 5GSoft has negligible overhead.

This chapter studies the congestion control of Multipath TCP (MPTCP) in a heterogeneous wireless network with LTE and Wi-Fi (i.e., the canonical use case ofMPTCP). In such a network, an MPTCP-capable mobile device uses two wireless links for data transferring to an application server. We conduct an experimental study of the four congestion control algorithms, namely balia, olia, lia, wvegas. We aim to reveal three critical issues that may be appeared when deploying MPTCP in the networks. First, we evaluate how the algorithms are backward compatible with the environment with only a single path. The evaluation results indicate that except wvegas, the three others are compatible. Second, we observe how the network selection for the initial subflow of an MPTCP connection affects the overall performance. While all the algorithms have a similar initialization time, their throughput values are substantially different. In the case of olia, the throughput with Wi-Fi selection is more than 200% the one with LTE selection. Finally, we investigate the impact of buffer size at a receiver on the MPTCP performance. Our evaluation shows that selecting the suitable buffer size can gain theMPTCP throughput up to 2.4 times.

負荷非依存動作は，制御を行うことなく負荷変動に対して一定出力電圧かつソフトスイッチングを達成する．制御機構が不要となることで，DC-DCコンバータや無線電力伝送システムの簡素化が期待される．近年，E級整流器に負荷非依存動作を実装した負荷非依存E級整流器が提案されたが，その解析はまだなされていない．本論文では，E級同期整流器の波形式を解析的に与え，負荷非依存動作を達成するための条件を明らかにする．更に，負荷非依存E級同期整流器の電力出力容量，入力インピーダンス，電力変換効率を解析的に導出する．回路実験と解析結果が定量的一致することにより，解析の妥当性を示す．

In a three-Tier Vehicle to X (V2X) network, a vehicle can offload the computational tasks to the edge computing component at a roadside unit (RSU) or a base station with cloud computing (gNB). Moreover, an RSU can also offload to gNB, forming three offloading paths: vehicle-To-RSU, vehicle-To-gNB, and RSU-To-gNB. This paper aims to minimize the offloaded tasks' average latency while dealing with the network dynamic. Note that the existing works assume the fixed network parameters, hence have failed to address the dynamic. As a solution, we use the multi-Agent multi-Armed bandits (MBA) learning for offloading that can adapt to the network dynamic and optimize the latency. More importantly, we propose a new MBA offloading scheme with an exploration mechanism based on the Sigmoid function. We conduct an extensive evaluation to evaluate and show the superiority of our proposal. First, the proposed Sigmoid exploration mechanism reduces the tasks' average latency by 35% compared to a basic MBA using negative rewarding. Second, the simulation results show our proposed offloading algorithm shortens the task latency by 18.5% on average and 56.9% in the best case, compared to the state-of-The-Art.

This paper proposes a load-independent zero-current switching (ZCS) parallel-resonant inverter along with its analytical expressions and a design method. The proposed inverter achieves constant output voltage amplitude and ZCS against load variations, which are called the load-independent operation in this paper. The analytical expressions provide design equations for achieving the load-independent operation. The analytical expressions and the design equations were verified from the quantitative agreements between the experimental measurements and analytical predictions.

Guaranteeing delay performance is an essential issue in a Wi-Fi network since it has increasingly conveyed a huge amount of Internet application traffic. This paper introduces our continuous effort in delay-guaranteed provision for Wi-Fi networks. More specifically, we have introduced the previously proposed delay-guaranteed mechanism that uses the advantage of SDN technology. In this work, we evaluate the mechanism in a new environment considering several TCP flows. The evaluation results show that the SDN-based algorithm effectively controls the delay values of multiple flows. Moreover, the sharing bandwidth between the flows is fair with negligible overhead.

This paper proposes a parallel resonant power oscillator that has the load-independent characteristic. The proposed oscillator is the first parallel-resonant power oscillator for high frequency operations. In addition, it achieves the constant output voltage and the soft switching against the load variations without any control. The feedback network for generating a driving signal does not have a resonant structure and its function is not affected by the self-oscillation frequency. Therefore, the proposed oscillator also has a self-tuning function for the resonant-filter component tolerances. Because of the above characteristics, the proposed oscillator is expected to be used in many applications such as a transmitter of the wireless power transfer systems.

In an IEEE 802.11 Distributed Coordination Function–based wireless network with multiple hops, a node operates on its own with several predefined data rates (i.e. following modulation and coding schemes). Moreover, the IEEE 802.11 Distributed Coordination Function node’s communication is characterized by transmission and carrier-sensing distances. The transmission one is, in general, reverse proportional to the data rate. Meanwhile, the carrier distance keeps constant regardless of the modulation and coding scheme. Therefore, when a node has a high transmission rate, within its carrier-sensing range, the number of nodes may increase. The previous works have not yet extensively investigated the impact of data rates on such a scenario. This article addresses that issue aiming to quantify the network performance of the multi-hop IEEE 802.11 networks. As a solution, we propose the mathematical expressions, which consider data rates, for end-to-end throughputs, as well as delays in the network with string topology. We confirm the expressions’ correctness by presenting the quantitative agreements between the analytical and simulation results.

Medical delivery drones are gradually becoming an inseparable part of smart human society, especially with the emergence of 5G and existing internet of things (IoT). A wide range of medical facilities can be leveraged via drone-based delivery aspects. Being a nascent stage of development, this field of application faces significant drawbacks from reliable and secure e-healthcare. In this paper, we discuss the importance of blockchain to improve decentralization, privacy, and consensus-aware medical product delivery by the drones. We firstly review the background of blockchain, 5G-IoT ecosystem and unmanned aerial vehicles (UAVs). Secondly, we review existing UAVs capable of performing medial delivery. We also find whether such drones are technically viable to work accordance to the 5GIoT era. Thirdly, we propose a modified multi-modal aspect behind medical delivery drones under the 5G-IoT assisted blockchain ecosystem. Fourthly, we propose an architecture comprising 5G, IoT, blockchain, and medical delivery drones with extraterrestrial communication support from satellites. Lastly, we discuss key open research challenges and provide a future road map.

The IEEE 802.11ad technology, which is a member of the IEEE 802.11 family, promisingly extends the operation of Wi-Fi networks to the unlicensed 60 GHz band. In such a case, the Wi-Fi network can support the throughput of multi-gigabit per second, potentially support various emerging applications. Since the Transport Control Protocol (TCP) plays a vital role in Wi-Fi networks, it is necessary to understand the TCP performance in that multi-Gbps condition. This paper investigates the performance of popular TCP variants on the IEEE 802.11ad wireless link. We conduct the experiments with TCP CUBIC, CDG, BBR, which are typically loss-based, delay-based, and model-based TCP congestion control algorithms, in different loss conditions. The results show that in a no-loss scenario, CUBIC and CDG keep good throughput at the cost of high TCP latency. Meanwhile, BBR has excellent performance even under the high loss scenario.

There has recently been an increasing number of blockchain applications in different realms. Among the popular blockchain technologies, Ethereum is an emerging platform featuring smart contracts with the public Ethereum associated to the Ether currency. Besides, the private Ethereum has been gaining interest due to its applicability to the Internet of Things. An Ethereum blockchain network includes distributed records that are immutable and transparent through replicating among network nodes. Ethereum manages information in blocks that are submitted to the chain as transactions. This paper aims to characterize latency performance in the private Ethereum blockchain network. Initially, we clarify two perspectives of latency according to the lifecycle of transactions (transaction-oriented and block-oriented latency). We then construct a real private blockchain network with a laptop and Raspberry Pi 3b+ for the latency measurement. We write and deploy a smart contract to read and write data to the blockchain and measure the latencies in a baseline and realistic scenario. The experiment results reveal the latencies-hop correlation, as well as the latencies’ relation in different workloads. Moreover, the blockchain network spends averagely 63.92 ms (except the mining time) to take one transaction into effect in one hop.