• Journal of the Korea Society of Computer and Information
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• v.13 no.4
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• pp.127-132
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• 2008

Wireless sensor network technologies applicable to various industrial fields are rapidly growing. Because it is difficult to change a battery for the once distributed wireless sensor network, energy efficient design is very critical. In order to achieve this purpose in network design, a number of studies have been examining the energy efficient routing protocol. The sensor network consumes energy in proportion to the distance of data transmission and the data to send. Cluster-based routing Protocols such as LEACH-C achieve energy efficiency through minimizing the distance of data transmission. In LEACH-C, however, the total distance between the nodes consisting the clusters are considered important in constructing clustering. This paper examines the cluster-head-selection-algorithm that reflect the distance between the base station and the cluster-head having a big influence on energy consumption. The Proposed method in this paper brought the result that the performance improved average $4{\sim}7%$ when LEACH-C and the base station are located beyond a certain distance. This result showed that the distance between cluster-head and the base station had a substantial influence on lifetime performance in the cluster-based routing protocol.

• The Journal of the Korea Contents Association
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• v.12 no.1
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• pp.48-58
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• 2012

With the development of sensing devices and wireless communication technologies, wireless sensor networks are composed of a large number of sensor nodes that are equipped with limited computing performance and restricted communication capabilities. Besides, the sensor nodes are deployed in hostile or unattended environments. Therefore, the wireless sensor networks are vulnerable to security. In particular, the fatal damage may be occurred when data are exposed in real world applications. Therefore, it is important for design requirements to be made so that wireless sensor networks provide the strong security. However, because the conventional security schemes in wired networks did not consider the limited performance of the sensor node, they are so hard to be applied to wireless sensor networks. In this paper, we propose a secure multipath transmission scheme based on one-way hash functions in wireless sensor networks considering the limited performance of the wireless sensor nodes. The proposed scheme converts a sensor reading based on one of one-way hash functions MD5 in order to make it harder to be cracked and snooped. And then, our scheme splits the converted data and transfers the split data to the base station using multi-path routing. The experimental results show that our proposed scheme consumes the energy of just about 6% over the existing security scheme.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.8
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• pp.1507-1514
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• 2015

Non-orthogonal multiple access (NOMA) is a promising candidate for 5G networks. NOMA achieves superior spectral efficiency than conventional orthogonal multiple access (OMA), as in NOMA multiple users uses the same time and frequency resources. Multiple-input-multiple-output (MIMO) is one another promising technique that can enhance system performance. In this paper we present a spectral and energy efficient multiple antenna based NOMA scheme, known as spatially modulated NOMA. In the proposed scheme the cell edge users are multiplexed in spatial domain, which means the information to cell edge users is conveyed using the transmit antenna indices. In NOMA the performance of cell edge users are deeply effected as it treats signals of others as noise. The proposed scheme achieves superior spectral efficiency than the conventional NOMA. The number of decoding steps involved in decoding NOMA signal reduces by one as cell edge user is multiplexed in spatial domain. The proposed scheme is more energy efficient as compare to conventional NOMA. All of the three gains high spectral, energy efficiency and one step reduction in decoding comes at cost of multiple transmit antennas at base station.

• The KIPS Transactions:PartC
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• v.15C no.5
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• pp.383-390
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• 2008

The mobile sink is most suitable to guarantee the real time processing to events in ubiquitous environment. However it brings many challenges to wireless sensor networks. In particular, the question of how to transfer the collected data to the mobile sink is an important topic in the aspect of effective management of wireless sensor nodes. In this paper, a new data dissemination model is proposed. Since this method uses the home agent and the access node concepts, it provides reliable and efficient data delivery to mobile sink with minimum overhead. In this proposed method, the information of the mobile sink which is constantly moving is informed only to the home agent node and the access node, instead of all sensor nodes. Thus, the collected data from sensor nodes are transferred to the fixed home agent and it sends these data to the mobile sink. Since the confliction phenomenon between data packets in wireless networks could be reduced, the success ratio of data arriving in the mobile sink is highly enhanced. In our experiments, the proposed method reduces the number of broadcast packets so that it saves the amount of energy consumed for transmitting and receiving the data packets. This effect contributes to prolong the lifetime of the wireless sensor networks operated by batteries.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.4
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• pp.1272-1277
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• 2010

Target detection and tracking wireless sensor network must have various signal processing ability. Wireless sensor nodes need to light weight signal processing algorithm because of energy constraints and communication bandwidth constraints. General signal processing algorithm of wireless sensor node consists of de-noising, received signal strength computation, feature extraction and signal compression. Wireless sensor network life-time and performance of target detection and classification depend on sensor node signal processing. In this paper, we propose energy efficient signal processing algorithm using wavelet transform. The proposed method estimates exact target position.

• Convergence Security Journal
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• v.7 no.2
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• pp.107-118
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• 2007

Distributed wireless sensor network in various environment have characteristic that is surveillance of environment-element and offering usefully military information but there is shortcoming that have some secure risks. Therefore secure service must be required for this sensor network safety. More safe and effective techniques of node administration are required for safe communication between each node. This paper proposes effective cluster-header and clustering techniques in suitable administration techniques of group-key on sensor network. In this paper, first each node transmit residual electric power and authentication message to BS (Base-Station). BS reflects "Validity Authentication Rate" and residual electric power. And it selects node that is more than these regularity values by cluster header. After BS broadcasts information about cluster header in safety and it transmits making a list of information about cluster member node to cluster header. Also, Every rounds it reflects and accumulates "Validity Authentication Rate" of former round. Finally, BS can select more secure cluster header.

• The Journal of Society for e-Business Studies
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• v.14 no.4
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• pp.75-94
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• 2009

Since XML emerged as a standard for data exchange on the web, it has been established as a core component in e-Commerce and efficient query processing over XML data in ubiquitous computing environment has been also receiving much attention. Recently, the techniques were proposed whereby an XML document is fragmented into XML fragments to be streamed and the mobile clients receive the stream while processing queries over it. In processing queries over an XML fragment stream, the average access time significantly depends on the order of fragments in the stream. As such, for query performance, an efficient organization of XML fragment stream is required as well as the indexing for energy-efficient query processing due to the reduction of tuning time. In this paper, a technique of XML fragment stream organization based on query frequencies, fragment size, fragment access frequencies, and an active XML-based indexing scheme are proposed. Through implementation and performance experiments, our techniques were shown to be efficient compared with the conventional XML fragment stream organizations.

• Proceedings of the Korean Society of Computer Information Conference
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• 2019.01a
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• pp.107-108
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• 2019

모바일 엣지 컴퓨팅(Mobile Edge Computing, MEC)은 높은 컴퓨팅 성능을 요구하는 작업을 모바일 장치에서 가까운 MEC 서버로 오프로딩함으로써 모바일 서비스에 높은 계산 요구량을 효율적으로 제공할 수 있는 기술로 부상하였다. 본 논문에서는 실행 대기 시간과 장치 에너지 소비를 줄이기 위해 여러 가지의 독립적 작업을 통해 MEC 시스템에 대한 작업 오프로드 일정 및 전송 에너지 할당을 최적화하는 기법을 제안한다. 시뮬레이션 결과로 MEC 시스템에서 사용 가능한 무선 및 계산 리소스가 상대적으로 균형 잡혀있는 경우 작업 오프로딩 일정이 더 중요하다는 것을 확인했다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2012.05a
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• pp.241-244
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• 2012

In mobile ad-hoc networks, it should be the most important issue to reduce the power consumption of communications, because the resource of a node is limited in these networks. In existing cluster-based routing protocols, cluster headers participate in almost all communication processes. Therefore the lifetime of the cluster header is shortened and it does not have the effective route. In the proposed cluster-based routing protocol, the cluster header transmits a control packet which gives the route information to member nodes. This makes that the cluster header decreases the number of participating in communications, and that node members do not have to communicate trough the cluster header. This results in extending the lifetime of the cluster header, and having the effective route, data transmission rate and improved stability of routes.

• Journal of Korea Society of Industrial Information Systems
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• v.11 no.2
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• pp.48-62
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• 2006

In recent years, wireless sensor networks(WSNs) have emerged as a new fast-growing application domain for wireless distributed computing and embedded systems. Recent Progress in computer and communication technology has made it possible to organize wireless sensor networks composed tiny sensor nodes. Furthermore, ad-hoc network protocols do not consider the characteristics of wireless sensor nodes, making existing ad-hoc network protocols unsuitable for the wireless sensor networks. First, we propose power-aware routing protocols based on energy-centered routing metrics. Second, we describe power management techniques for wireless sensor nodes using the spatial locality of sensed data. Many nodes can go into a power-down mode without sacrificing the accuracy of sensed data. Finally, combining the proposed techniques, we describe an overall energy-efficient protocol for data collection. Experimental results show that the proposed routing protocol can extend the routing path lifetime more than twice. The average energy consumption per sensing period is reduced by up to 30%.