• Journal of information and communication convergence engineering
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• 제17권2호
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• pp.105-116
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• 2019

Recently, there has been an increase in research on wireless sensor networks (WSNs) because they are easy to deploy in applications such as internet-of-things (IoT) and body area networks. However, WSNs have constraints in terms of power, quality-of-service (QoS), computation, and others. To overcome the power constraint issues, wireless energy harvesting has been introduced into WSNs, the application of which has been the focus of many studies. Additionally, to improve system performance in terms of achievable rate, cooperative networks are also being explored in WSNs. We present a review on current research in the area of energy harvesting in WSNs, specifically on the application of simultaneous wireless information and power transfer (SWIPT) in a cooperative sensor network. In addition, we discuss possible future extensions of SWIPT and cooperative networks in WSNs.

• Journal of Communications and Networks
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• 제13권2호
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• pp.142-148
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• 2011

Because currently available wireless technologies are not appropriate for wireless body area networks (WBANs), the IEEE 802.15.6 standard was introduced by the IEEE 802.15.6 Task Group to satisfy all the requirements for a monitoring system that operates on, in, or around the human body. In this work, we develop an analytical model for evaluating the performance of an IEEE 802.15.6-based WBAN under saturation condition and a noisy channel. We employ a three-dimensional Markov chain to model the backoff procedure as specified in the standard. Probability generating functions (PGFs) are used to compute the performance descriptors of the network. The results obtained from the analytical model are validated by simulation results. Our results indicate that under saturation condition, the medium is accessed by the highest user priority nodes at the vast majority of time while the other nodes are starving.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제9권5호
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• pp.1733-1751
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• 2015

The IEEE 802.15.4 standard not only provides a maximum of seven guaranteed time slots (GTSs) for allocation within a superframe to support time-critical traffic, but also achieves ultralow complexity, cost, and power in low-rate and short-distance wireless personal area networks (WPANs). Real-time wireless body area sensor networks (WBASNs), as a special purpose WPAN, can perfectly use the IEEE 802. 15. 4 standard for its wireless connection. In this paper, we propose an adaptive GTS allocation scheme for real-time WBASN data transmissions with different priorities in consideration of low latency, fairness, and bandwidth utilization. The proposed GTS allocation scheme combines a weight-based priority assignment algorithm with an innovative starvation avoidance scheme. Simulation results show that the proposed method significantly outperforms the existing GTS implementation for the traditional IEEE 802.15.4 in terms of average delay, contention free period bandwidth utilization, and fairness.

• 한국정보통신학회논문지
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• 제18권4호
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• pp.839-847
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• 2014

최근 컴퓨터 기술의 발전으로 웨어러블 컴퓨터 기술이 개발되고 있다. 이는 HCI (human-centric interface)기술과 유비쿼터스 컴퓨팅 기술을 기반으로 한다. 웨어러블 컴퓨터 시스템은 WiMedia PHY/MAC 기술과 결합된 USB 기술로 WUSB (wireless universal serial bus) 기술을 사용하여 구성할 수 있다. 본 논문은 U-Health 기능을 지원하는 무선 웨어러블 컴퓨터시스템을 구성하기 위해 WUSB기술과 WBAN (wireless body area networks) 기술을 결합한 통신시스템 구조에 초점을 맞추었다. 이를 위해 WBAN 망에서 WUSB 통신 구간을 할당하는 통신 구조를 제안한다. 제안하는 통신구조에서 WUSB 통신 구간은 WBAN Privated Period를 사용한다. 성능 평가에서는 WBAN 통신 점유율에 따른 WUSB 통신 수율을 이론적인 분석과 시뮬레이션을 통해 비교 분석하여 WUSB over WBAN 통신의 효율성을 평가하였다.

• 한국정보통신학회논문지
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• 제18권7호
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• pp.1619-1627
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• 2014

웨어러블 컴퓨터 시스템은 WiMedia PHY/MAC 기술과 결합된 USB 기술로 WUSB (wireless universal serial bus) 기술을 사용하여 구성할 수 있다. 본 논문은 U-Health 기능을 지원하는 무선 웨어러블 컴퓨터시스템을 구성하기 위해 WUSB기술과 IEEE 802.15.6 WBAN (wireless body area networks) 기술을 결합한 통신시스템 구조에 초점을 맞추었다. 그리고 IEEE 802.15.6 기반 WUSB 통신 구조에서 시각동기 통신 기술을 제안하였다. 제안하는 시각동기 구조는 WBAN Polling Access 구조를 활용하고 Time Stamp를 사용한 시각동기 미들웨어를 결합한다. 성능 평가에서는 WBAN Polling Access를 적용한 시각동기 성능 및 시각동기 미들웨어를 추가한 성능을 비교분석하여, WUSB over IEEE 802.15.6 통신구조에서 제안한 시각동기 방식의 효율성을 평가하였다.

• 한국정보통신학회논문지
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• 제18권7호
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• pp.1610-1618
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• 2014

웨어러블 컴퓨터 시스템은 WiMedia PHY/MAC 기술과 결합된 USB 기술로 WUSB (wireless universal serial bus) 기술을 사용하여 구성할 수 있다. 본 논문은 U-Health 기능을 지원하는 무선 웨어러블 컴퓨터시스템을 구성하기 위해 WUSB기술과 IEEE 802.15.6 WBAN (wireless body area networks) 기술을 결합한 통신시스템 구조에 초점을 맞추었다. 그리고 IEEE 802.15.6 기반 WUSB 통신 구조에서 저전력 Hibernation 통신 구조를 제안하였다. 제안하는 Hibernation 구조는 WBAN Wakeup Period 및 Wakeup Phase 메시지 필드들을 사용하여, WBAN의 주기적인 Inactive 구간에서 WUSB 통신 구간을 할당한다. 성능 평가에서는 WBAN Wakeup Period에 따른 성능 및 WUSB 통신량에 따른 성능을 비교분석하여, WUSB over IEEE 802.15.6 통신구조에서 제안한 Hibernation 구조의 효율성을 평가하였다.

• 한국정보통신학회논문지
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• 제18권5호
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• pp.1087-1095
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• 2014

최근 컴퓨터 기술의 발전으로 웨어러블 컴퓨터 기술이 개발되고 있다. 이는 HCI (human-centric interface)기술과 유비쿼터스 컴퓨팅 기술을 기반으로 한다. 웨어러블 컴퓨터 시스템은 WiMedia PHY/MAC 기술과 결합된 USB 기술로 WUSB (wireless universal serial bus) 기술을 사용하여 구성할 수 있다. 본 논문은 U-Health 기능을 지원하는 무선 웨어러블 컴퓨터시스템을 구성하기 위해 WUSB기술과 IEEE 802.15.6 WBAN (wireless body area networks) 기술을 결합한 통신시스템 구조에 초점을 맞추었다. 그리고 IEEE 802.15.6 기반 WUSB 통신 구조에서 서로 다른 전송 우선 순위를 갖는 U-health WBAN 트래픽 및 WUSB트래픽의 QoS를 차등화하기 위한 통신 구조를 제안하였다. 제안내용 및 성능 평가에서는 단일 클래스 및 다중 클래스 환경에서 U-health WBAN 및 WUSB 트래픽의 수율 성능을 분석하여, WUSB over IEEE 802.15.6 통신구조에서 QoS 차등화 효율성을 평가하였다.

• Journal of Communications and Networks
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• 제17권4호
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• pp.419-427
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• 2015

There have been increases in the elderly population worldwide, and this has been accompanied by rapid growth in the health-care market, as there is an ongoing need to monitor the health of individuals. Wireless body area networks (WBANs) consist of wireless sensors attached on or inside the human body to monitor vital health-related problems, e.g., electrocardiograms (ECGs), electroencephalograms (EEGs), and electronystagmograms (ENGs). With WBANs, patients' vital signs are recorded by each sensor and sent to a coordinator. However, because of obstructions by the human body, sensors cannot always send the data to the coordinator, requiring them to transmit at higher power. Therefore, we need to consider the lifetime of the sensors given their required transmit power. In the IEEE 802.15.6 standard, the transmission topology functions as a one-hop star plus one topology. In order to obtain a high throughput, we reduce the transmit power of the sensors and maintain equity for all sensors. We propose the multiple-hop transmission for WBANs based on the IEEE 802.15.6 carrier-sense multiple-access with collision avoidance (CSMA/CA) protocol. We calculate the throughput and variance of the transmit power by performing simulations, and we discuss the results obtained using the proposed theorems.

• Journal of information and communication convergence engineering
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• 제12권1호
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• pp.14-18
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• 2014

A recent major development in computer technology is the advent of wearable computer systems. Wearable computer systems employ a wireless universal serial bus (WUSB), which refers to a combination of USB with the WiMedia wireless technical specifications. In this study, we focus on an integrated system of WUSB over wireless body area networks (WBANs) for wireless wearable computer systems. However, current WBAN MACs do not have well-defined quality of service (QoS) mapping and resource allocation mechanisms to support multimedia streams with the requested QoS parameters. To solve this problem, we propose a novel QoS-aware time slot allocation method. The proposed method provides fair and adaptive QoS provisioning to isochronous streams according to current traffic loads and their requested QoS parameters by executing a QoS satisfaction algorithm at the WUSB/WBAN host. The simulation results show that the proposed method improves the efficiency of time slot utilization while maximizing QoS provisioning.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제7권8호
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• pp.1805-1824
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• 2013

Recently, the use of wireless body area networks (WBAN) has been increasing rapidly in medical healthcare applications. WBANs consist of smart nodes that can be used to sense and transmit vital data such as heart rate, temperature and ECG from a human body to a medical centre. WBANs depend on limited resources such as energy and bandwidth. In order to utilise these resources efficiently, a very well organized medium access control (MAC) protocol must be considered. In this paper, a new, adaptive and energy-efficient MAC protocol, entitled isMAC, is proposed for WBANs. The proposed MAC is based on multi-channel communication and aims to prolong the network lifetime by effectively employing (i) a collision prevention mechanism, (ii) a coordinator node (WCN) selection algorithm and (iii) a transmission power adjustment approach. The isMAC protocol has been developed and modelled, by using OPNET Modeler simulation software. It is based on a networking scenario that requires especially high data rates such as ECG, for performance evaluation purposes. Packet delay, network throughput and energy consumption have been chosen as performance metrics. The comparison between the simulation results of isMAC and classical IEEE 802.15.4 (ZigBee) protocol shows that isMAC significantly outperforms IEEE 802.15.4 in terms of packet delay, throughput and energy consumption.