• KSII Transactions on Internet and Information Systems (TIIS)
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• v.13 no.4
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• pp.1961-1974
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• 2019

In this letter, a harmonic-mean-based dual-antenna selection scheme at relay node is proposed in two-way relaying networks (TWRNs). With well-designed distributed orthogonal concatenated Alamouti space-time block code (STBC), a dual-antenna selection problem based on the instantaneous achievable sum-rate criterion is formulated. We propose a low-complexity selection algorithm based on the harmonic-mean criterion with linearly complexity $O(N_R)$ rather than the directly exhaustive search with complexity $O(N^2_R)$. From the analysis of network outage performance, we show that the asymptotic diversity gain function of the proposed scheme achieves as $1/{\rho}{^{N_R-1}}$, which demonstrates one degree loss of diversity order compared with the full diversity. This slight performance gap is mainly caused by sacrificing some dual-antenna selection freedom to reduce the algorithm complexity. In addition, our proposed scheme can obtain an extra coding gain because of the combination of the well-designed orthogonal concatenated Alamouti STBC and the corresponding dual-antenna selection algorithm. Compared with the common-used selection algorithms in the state of the art, the proposed scheme can achieve the best performance, which is validated by numerical simulations.

• Journal of Integrative Natural Science
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• v.11 no.4
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• pp.197-203
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• 2018

Long Term Evolution-Advanced (LTE-A) is the next drive in the broadband mobile communication, which allows operators to improve networks performance and service capabilities. LTE-A targets the peak data rates of 1Gbps in the downlink and 500Mbps in the uplink. This requirement is only fulfilled by a transmission bandwidth of up to 100MHz. However the accessibility of such large part of the contiguous spectrum is uncommon in practice. Therefore LTE-A uses some new features on top of the existing LTE standards to provide very high data rate transmission. Some of the most significant features introduced in LTE-A are carrier aggregation, heterogeneous network enhancement, coordinated multipoint transmission and reception, enhanced multiple input and multiple output, and development relay nodes with universal frequency reuse. This review paper presents an overview of the above mentioned LTE-A key features and functionalities. Based on this review, in the conclusion we discuss the current technical challenges for future broadband mobile communication systems.

• Proceedings of the Korea Inteligent Information System Society Conference
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• 2001.01a
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• pp.45-49
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• 2001

Korean government and companies have given a lot of their efforts to exchange electronic documents between themselves and their partners. As the results of them. Korean EDI standards were made by Korean EDIFACT Committee and the standards have been used by companies and governmental organization in Korea. However, Korean export customs clearance EDI system is based on VAN(Value Added Network) and one VAN company ha monopolistic right to relay EDI documents to Korean Customs Service. Therefor is leads to a lot of problems such as inconvenient software, expensive transmission fee and the difficulty of connection with the in-house systems of user companies. To solve these problems, a few good solutions and systems have been suggested and one of them is the Internet EDI. we will suggest a new export customs clearance EDI system running on the Web. This system is basically an Internet EDI system, but we have developed this system using XML instead of HTML, XML is a new markup language with merit such as isolating data from style of documents. This system consists of 7 modules, schema/style/template management, XML/EDI document management, XML/EDI transformation, EDI transmission, certification management and log management. Also this system can be used with other traditional EDI systems that have UN/EDIFACT standards. We will discuss the advantages and disadvantages of XML/EDI system for customs clearance. The development of this system will be a leading study for XML/EDI standards in export clearance EDI system.

• Proceedings of the Korea Information Processing Society Conference
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• 2010.11a
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• pp.988-991
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• 2010

본 논문에서는 현재 3GPP에서 진행되고 있는 차세대 이동통신 기술 표준, 즉 LTE 시스템의 하향링크 전송방식의 수신성능을 향상시키기 위해 기지국(BS)과 단말(MS) 사이에 릴레이(RS) 설치를 제안하고, BS의 위치와 설치된 RS의 거리를 각각 500m, 1000m로 하고 RS의 전송방식을 OFDMA와 SC-FDMA를 선택함으로써 수신성능을 높이기 위한 연구를 수행 하였다. 연구결과 RS의 위치가 BS와 가까울수록 RS에서는 SC-FDMA를 사용하는 것이 좋게 나왔고, 반대로 BS와 RS의 거리가 멀어질수록 RS에서는 OFDMA를 사용하는 것의 성능이 좋은 것으로 나왔다. 또한 BS와 MS 거리의 중심지역에서는 그 상황에 맞는 전송방식을 사용함으로써 시스템의 수신성능을 향상시킬 수 있었다. 본 논문에서 시뮬레이션 한 결과를 토대로 실제 LTE 시스템에 적용하였을 때, 셀 커버지지를 확장 시켜 시스템 전체의 수신성능을 향상 시킬 수 있을 것으로 보였다.

• Review of KIISC
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• v.33 no.4
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• pp.13-22
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• 2023

Controller area network (CAN) 네트워크로 대표되는 자동차 내부네트워크와 비교하여 자동차 스마트키 시스템은 상대적으로 소수의 연구가 진행되어오고 있다. 하지만, 현실 세계에서는 스마트키 시스템의 취약점으로 인해 많은 피해사례가 발생하고 있다. 대표적으로, 2010년 NDSS 학회에 소개된 신호 중계 공격 (signal relay attack)은 현재까지도 수많은 자동차 절도 사건들에 악용되고 있다. 이와 같은 문제를 근본적으로 해결하기 위해 초광대역 통신(ultra-wideband communication, UWB)을 사용한 디지털 키 (Digital Key) 기술이 일부 최신 자동차들에 탑재되고 있다. 하지만, 2022년USENIX Security 학회에서 애플, 삼성과 같은 글로벌 기업이 채택한 high rate pulse repetition frequency (HRP) UWB 측위 시스템에 대한 거리 단축 공격 (distance reduction attack)이 가능함이 소개되었다. 이는 디지털 키 시스템 또한 신호중계 공격과 같은 보안 위협에 노출될 수 있다는 점을 시사한다. 본 논문에서는 자동차 스마트키 시스템을 대상으로 수행된 공격 연구 사례들을 살펴본다. 먼저, remote keyless entry (RKE) 시스템 및 passive keyless entry and start (PKES) 시스템으로 대표되는 기존 스마트키 시스템을 대상으로 하는 보안 위협에 대해 살펴본다. 다음으로 차세대 스마트키 시스템으로 주목받고 있는 디지털키 시스템을 구성하는 초광대역 통신기술의 동작 원리 및 이에 대한 보안위협 연구 동향을 살펴본다.

• Journal of Digital Contents Society
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• v.8 no.3
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• pp.323-328
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• 2007

Communication systems beyond 3G should provide more than 100 Mbps for wireless access. In addition to smart antennas, wireless multi-hop networks are proposed to increase the cell size and throughput. For example, Zigbee technology is expected to provide low cost and low power connectivity and can be implemented in wireless mesh networks larger than is possible with Bluetooth. Also, home embedded system using wireless mesh network is one of the key market areas for Zigbee applications. If the line-of-sight path is shadowed by home obstacles, a direct connection between the access point (AP) and the node is not possible at high frequencies. Therefore, by using multi-hop relay scheme the end node can be reached to AP. In this paper, the relaying of data between the AP and the end node is investigated and the throughput and PER(Packet Error Rate) are evaluated in multi-hop wireless mesh networks by using DSSS/BPSK system.

• Journal of Korea Society of Industrial Information Systems
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• v.16 no.1
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• pp.37-48
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• 2011

Sensor networks monitor the environment, collect sensed data, and relay the data back to a collection point. Although sensor nodes have very limited hardware resources, they require an operating system that can provide efficient resource management and various application environments. In addition, the wireless sensor networks require the code update previously deployed to patch bugs in program and to improve performance of kernel service routines and application programs. This paper presents EPRCU (Easy to Perform Remote Code Update), a new operating system for wireless sensor nodes, which has enhanced functionalities to perform remote code update. To achieve an efficient code update, the EPRCU provides dynamic memory allocation and program memory management. It supports the event-driven kernel, which uses priority-based scheduling with the application of aging techniques. Therefore, the proposed operating system is not only easy to perform wireless communication with the remote code update but also suitable for various sensor network applications.

• The KIPS Transactions:PartC
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• v.17C no.6
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• pp.459-464
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• 2010

Due to the application-specific nature of wireless sensor networks, the sensitivity to such a requirement as data reporting latency may vary depending on the type of applications, thus requiring application-specific algorithm and protocol design paradigms which help us to maximize energy conservation and thus the network lifetime. In this paper, we implement and evaluate a novel delay-adaptive sensor scheduling scheme for energy-saving data gathering which is based on a two phase clustering (TPC), in wireless sensor networks. The TPC is implemented on sensor Mote hardwares. With the help of TPC implemented, sensors selectively use direct links for control and forwarding time critical sensed data and relay links for data forwarding based on the user delay constraints given. Implementation study shows that TPC helps the sensors to increase a significant amount of energy while collecting sensed data from sensors in a real environment.

• Journal of Korea Multimedia Society
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• v.16 no.10
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• pp.1196-1203
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• 2013

In general, the cost of transceiver for wireless network configuration is more expensive than that for wired network. However, in case of environmental management system in a tunnel, the cost can be minimized by adopting low rate tranceiver because the amount of the exchanged data for tunnel monitoring is very small. When the obtained data from sensor node is sent directly to the corresponding command node, there is no need to consider routing problem of the data transfer. However in this case, sensor nodes are required to be implemented with high power transmitter and experience high energy consumption. To tackle this problem, relay nodes can be used to transfer the data of tunnel monitoring, and suitable routing protocols for selecting optimum path are needed. Therefore, in this paper, we propose a routing algorithm and a self-configuration protocol for environment management system in tunnel.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2015.05a
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• pp.113-115
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• 2015

In this paper, we proposed an algorithm based on movement prediction using rate of change of the attribute information of nodes what is called WRC(Weighted Rate Control) in delay tolerant networks(DTNs). Existing DTN routing algorithms based on movement prediction communicate by selecting relay nodes increasing connectivity with destination node. Thus, because the mobile nodes are in flux, the prediction algorithms that do not reflect the newest attribute information of node decrease reliability. In this paper, proposed algorithm approximate speed and direction of attribute information of node and analysis rate of change of attribute information of node. Then, it predict movement path of node using proposed weight. As the result, proposed algorithm show that network overhead and transmission delay time decreased by predicting movement path of node.