• Journal of information and communication convergence engineering
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• 제16권3호
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• pp.135-141
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• 2018

Wireless sensor networks (WSN) are composed of a large number of sensor nodes. Battery-powered sensor nodes have limited coverage; therefore, it is more efficient to transmit data via multi-hop communication. The network lifetime is a crucial issue in WSNs and the multi-hop routing protocol should be designed to prolong the network lifetime. Prolonging the network lifetime can be achieved by minimizing the power consumed by the nodes, as well as by balancing the power consumption among the nodes. A power imbalance can reduce the network lifetime even if several nodes have sufficient (battery) power. In this paper, we propose a routing protocol that prolongs the network lifetime by balancing the power consumption among the nodes. To improve the balance of power consumption and improve the network lifetime, the proposed routing scheme adaptively controls the transmission range using a power control according to the residual power in the nodes. We developed a routing simulator to evaluate the performance of the proposed routing protocol. The simulation results show that the proposed routing scheme increases power balancing and improves the network lifetime.

• Journal of Communications and Networks
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• 제9권3호
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• pp.265-273
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• 2007

This paper expands an analytical performance model of 802.11 to accurately estimate throughput and energy demand of 802.11-based wireless sensor network (WSN) when sensor nodes employ Reed-Solomon (RS) codes, one of block forward error correction (FEC) techniques. This model evaluates these two metrics as a function of the channel bit error rate (BER) and the RS symbol size. Since the basic recovery unit of RS codes is a symbol not a bit, the symbol size affects the WSN performance even if each packet carries the same amount of FEC check bits. The larger size is more effective to recover long-lasting error bursts although it increases the computational complexity of encoding and decoding RS codes. For applying the extended model to WSNs, this paper collects traffic traces from a WSN consisting of two TIP50CM sensor nodes and measures its energy consumption for processing RS codes. Based on traces, it approximates WSN channels with Gilbert models. The computational analyses confirm that the adoption of RS codes in 802.11 significantly improves its throughput and energy efficiency of WSNs with a high BER. They also predict that the choice of an appropriate RS symbol size causes a lot of difference in throughput and power waste over short-term durations while the symbol size rarely affects the long-term average of these metrics.

• 대한산업공학회지
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• 제37권3호
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• pp.180-190
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• 2011

Efficient energy consumption is a critical factor for deployment and operation of wireless sensor networks (WSNs). To achieve energy efficiency there have been several hierarchical routing protocols that organize sensors into clusters where one sensor is a cluster-head to forward messages received from its cluster-member sensors to the base station of the WSN. In this paper, we propose a self-organized clustering method for cluster-head selection and cluster based routing for a WSN. To select cluster-heads and organize clustermembers for each cluster, every sensor uses only local information and simple decision mechanisms which are aimed at configuring a self-organized system. By these self-organized interactions among sensors and selforganized selection of cluster-heads, the suggested method can form clusters for a WSN and decide routing paths energy efficiently. We compare our clustering method with a clustering method that is a well known routing protocol for the WSNs. In our computational experiments, we show that the energy consumptions and the lifetimes of our method are better than those of the compared method. The experiments also shows that the suggested method demonstrate properly some self-organized properties such as robustness and adaptability against uncertainty for WSN's.

• 대한전자공학회논문지TC
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• 제43권8호
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• pp.77-83
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• 2006

본 논문에서는 무선 센서 네트워크에서 Directed Diffusion을 이용하여 데이터를 신뢰성 있게 전달하는 기법을 제안하였다. 각각의 노드는 자신의 이웃에 대한 정보만을 유지하고 있으나 Interest의 전파 과정을 이용하여 종단간의 전달 신뢰성을 계산함으로써 도달가능성이 높은 경로를 선택하여 전송하는 메커니즘이다. 링크의 에러율과 노드의 개수 변화에 따른 실험을 통하여 제안 방식이 데이터 전달 신뢰성을 향상시킨다는 사실을 확인하였다. 또한, 부가적인 효과로서 트래픽 부하가 분산되고 에너지 소비가 감소되어 네트워크 수명이 연장됨을 알 수 있었다.

• Journal of Communications and Networks
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• 제16권4호
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• pp.465-474
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• 2014

Wireless sensor network (WSN) is considered to be one of the most important research fields for ubiquitous healthcare (u-healthcare) applications. Healthcare systems combined with WSNs have only been introduced by several pioneering researchers. However, most researchers collect physiological data from medical nodes located at static locations and transmit them within a limited communication range between a base station and the medical nodes. In these healthcare systems, the network link can be easily broken owing to the movement of the object nodes. To overcome this issue, in this study, the fast link exchange minimum cost forwarding (FLE-MCF) routing protocol is proposed. This protocol allows real-time multi-hop communication in a healthcare system based on WSN. The protocol is designed for a multi-hop sensor network to rapidly restore the network link when it is broken. The performance of the proposed FLE-MCF protocol is compared with that of a modified minimum cost forwarding (MMCF) protocol. The FLE-MCF protocol shows a good packet delivery rate from/to a fast moving object in a WSN. The designed wearable platform utilizes an adaptive linear prediction filter to reduce the motion artifacts in the original electrocardiogram (ECG) signal. Two filter algorithms used for baseline drift removal are evaluated to check whether real-time execution is possible on our wearable platform. The experiment results shows that the ECG signal filtered by adaptive linear prediction filter recovers from the distorted ECG signal efficiently.

• 전기학회논문지
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• 제65권1호
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• pp.122-127
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• 2016

In this paper, new spectrum sensing schemes based on analog/RF front-end processing are introduced for IoT wireless sensor networks. While the conventional approaches for wireless channel cognition have been issued in signal processing area, the RF spectrum cognition concept makes it feasible to achieve cognitive wireless sensor networks (C-WSNs). The spectrum cognition at RF processing is categorized as four kinds of sensing mechanisms. Two recent reseaches are described as promising candidates for the C-WSN. One senses spectrum by the frequency discriminating receiver, the other senses and detects from the frequency selective super-regenerative receiver. The introduced systems with simple and low-power RF architectures play dual roles of channel sensing and demodulation. simultaneously. Therefore, introduced spectrum sensing receivers can be one of the best candidates for IoT wireless sensor devices in C-WSN environments.

• 디지털융복합연구
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• 제11권12호
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• pp.367-380
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• 2013

무선센서 네트워크에서 안전한 데이터 수집은 중요한 보안이슈 중에 하나이다. 일반적으로 안전한 데이터 수집이란 데이터 자체의 보안과 안전한 전송 경로 확보를 의미한다. 본 논문은 이와 같은 관점에서 무선센서 네트워크에서 안전한 데이터 수집 프로토콜을 제안한다. 제안하는 프로토콜은 계층형 센서네트워크를 고려한 계층형 키 보안 기법과 안전을 보장할 수 있는 전송경로 설정을 핵심적으로 제시한다. 프로토콜은 네트워크 부하를 최소화 할 수 있도록 최적화 되었으며 네트워크 공격으로 인해 발생하는 문제점을 효과적으로 차단한다. 성능평가 결과 제안하는 프로토콜은 네트워크 퍼포먼스를 고려한 데이터 수집에 효율적이다. 데이터 수집 시 안전을 확보하기 위한 보안 분석 역시 검증해 보았다.

• 한국인터넷방송통신학회논문지
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• 제10권2호
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• pp.151-157
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• 2010

MEMS(Micro Electro-Mechanical Systems) 분야의 급격한 발전은 저비용의 정보 처리 센싱 능력을 갖춘 센서의 발전에 박차를 가했다. 이러한 기술의 흐름은 강력하고 높은 확장성을 가지는 WSNs(Wireless Sensor Networks)을 위하여 더 많은 센서 간 연결을 위한 연구가 진행되고 있는 실정이다. WSNs의 자원부족, Ad-hoc 배치방법, 보다 광대해지는 규모는 센서 간 통신에서 안전성을 보다 중요한 문제로 인식하게 하고 있다. 센서 네트워크의 주요 고려사항은 에너지 효율이기 때문에, 보안 기술은 통신에서의 보안 특징과 그것을 수행하기 위해 계산해야하는 오버헤드 간 균형을 맞춰야한다. 본 논문에서는 새로운 보안 인식 다중경로 위치기반 라우팅 프로토콜을 개발하기 위하여 위치정보와 전송확률을 결합한다. 네트워크 시뮬레이터(ns-2)를 실행한 결과 보다 나은 성능을 얻을 수 있음을 알 수 있다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제12권12호
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• pp.5744-5764
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• 2018

In Wireless Sensor Networks (WSNs) for Internet of Things (IoT) environment, fault tolerance is a most fundamental issue due to strict energy constraint of sensor node. In this paper, a robust energy saving data dissemination protocol for IoT-WSNs is proposed. Minimized energy consumption and dissemination delay time based on signal strength play an important role in our scheme. The representative dissemination protocol SPIN (Sensor Protocols for Information via Negotiation) overcomes overlapped data problem of the classical Flooding scheme. However, SPIN never considers distance between nodes, thus the issue of dissemination energy consumption is becoming more important problem. In order to minimize the energy consumption, the shortest path between sensors should be considered to disseminate the data through the entire IoT-WSNs. SPMS (Shortest Path Mined SPIN) scheme creates routing tables using Bellman Ford method and forwards data through a multi-hop manner to optimize power consumption and delay time. Due to these properties, it is very hard to avoid heavy traffic when routing information is updated. Additionally, a node failure of SPMS would be caused by frequently using some sensors on the shortest path, thus network lifetime might be shortened quickly. In contrast, our scheme is resilient to these failures because it employs energy aware concept. The dissemination delay time of the proposed protocol without a routing table is similar to that of shortest path-based SPMS. In addition, our protocol does not require routing table, which needs a lot of control packets, thus it prevents excessive control message generation. Finally, the proposed scheme outperforms previous schemes in terms of data transmission success ratio, therefore our protocol could be appropriate for IoT-WSNs environment.

• Journal of Communications and Networks
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• 제11권4호
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• pp.350-358
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• 2009

In a wireless sensor network (WSN) setting, this paper presents a distributed decision-making framework and illustrates its application in an online structural health monitoring (SHM) system. The objective is to recover a damage severity vector, which identifies, localizes, and quantifies damages in a structure, via distributive and collaborative decision-making among wireless sensors. Observing the fact that damages are generally scarce in a structure, this paper develops a nonlinear 0-norm minimization formulation to recover the sparse damage severity vector, then relaxes it to a linear and distributively tractable one. An optimal algorithm based on the alternating direction method of multipliers (ADMM) and a heuristic distributed linear programming (DLP) algorithm are proposed to estimate the damage severity vector distributively. By limiting sensors to exchange information among neighboring sensors, the distributed decision-making algorithms reduce communication costs, thus alleviate the channel interference and prolong the network lifetime. Simulation results in monitoring a steel frame structure prove the effectiveness of the proposed algorithms.