• Journal of the Korea Convergence Society
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• v.9 no.8
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• pp.33-39
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• 2018

In the Internet of Things (IoT) era, objects are connected to each other by wired and wireless networks, and information is exchanged whenever necessary. Channel and network environments change over time; thus, a carrier sensing function that identifies whether signals containing information are present in the channel is essential. The carrier sensing circuit of a wireless communication system determines the receiver sensitivity, and the receiver sensitivity is closely related to the service coverage and service quality of the system. As the receiver sensitivity decreases, the service coverage increases but it becomes sensitive to noise. However, as the receiver sensitivity increases, the service coverage decreases but it becomes insensitive to the noise. Therefore, carrier sensing design and optimization are very important from the viewpoint of the receiver sensitivity and noise sensitivity. This paper proposes an effective carrier sensing technique from the viewpoint of the receiver sensitivity for the long range IoT.

• Journal of KIISE:Computer Systems and Theory
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• v.26 no.11
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• pp.1414-1428
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• 1999

ATM/B-ISDN 신호 프로토콜과 같은 통신 프로토콜의 상호운용성을 시험하기 위한 시험경우를 생성하는 알고리즘이 제안되었다 1]. 현재까지 상호운용성 시험경우 도출을 자동화하거나 이에 대한 커버리지를 분석한 경우는 없다. 본 논문은 1]에서 제안한 알고리즘을 프로그램으로 구현하여 TCP 연결설정 프로토콜에 적용하고 결과를 분석한다. 이 과정에서 (1) TCP 연결설정 프로토콜의 3방향 핸드 쉐이킹 부분을 다루지 못했던 기존의 알고리즘을 개선하고, (2) 개선된 알고리즘을 프로그램으로 구현하여 TCP 연결설정 프로토콜의 상호운용성 시험경우를 도출하고, (3) 생성된 상호운용성 시험경우를 트랜지션 커버리지 관점에서 분석하고, (4) 향상된 트랜지션 커버리지를 얻기 위하여 알고리즘 확장 방안을 제시한다.Abstract A test derivation method suitable for testing interoperability for the class of communication protocols like the ATM/B-ISDN signaling protocol was proposed 1]. Up to now, there is no work on automating derivation of the interoperability test suite and analyzing its coverage. In this paper, we implement the algorithm proposed by 1], apply it to the Transmission Control Protocol (TCP), and analyze its results. In this process, we (1) improve the algorithm that is not applicable to the TCPs three-way handshaking, (2) implement the improved algorithm as a program and derive an interoperability test suite automatically from a given pair of TCP FSMs, (3) analyze generated interoperability test suite in view of transition coverage, and (4) present a method in order to extend the algorithm for better transition coverage.

• Journal of IKEEE
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• v.26 no.4
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• pp.693-704
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• 2022

5G service uses mid-band (n78) than existing mobile communication frequencies, so it is necessary to improve 5G coverage by utilizing low-band frequencies below 2 GHz. To this end, the application of Dynamic Spectrum Sharing technology of LTE and 5G-NR system using most of the low-band frequencies is required. In this paper, signaling overhead factors for DSS application and RF issues for terminal implementation are derived, and signaling overhead ratios from the respective perspectives of 5G-NR and LTE for the 1.8GHz band (50MHz width) that can utilize wide-bandwidth among low-band frequencies are estimated. Also handset RF issues were analyzed. Based on the analysis results, if DSS technology using low band is applied, it is expected that excellent 5G service quality can be provided due to 5G coverage improvement when LTE traffic quickly migrates to 5G-NR.

• Journal of Advanced Navigation Technology
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• v.28 no.3
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• pp.362-368
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• 2024

In this paper, we investigated the performance of directional and omnidirectional precoding schemes when transmitting to improve downlink performance in massive MIMO. Omnidirectional precoding was used to broadcast a common signal, such as a synchronization or control signal, to all users. The main purpose of omnidirectional precoding is to design the precoding matrix so that the signal transmitted in the downlink is the same in all directions and emitted with maximum energy. We propose a flexible omnidirectional precoding method for full-dimensional massive MIMO that can set the spatial coverage range to less than 120 degrees. The constraints of omnidirectionality of all antennas, equal transmit power, and maximum transmit rate are used to design the encoding matrix of the proposed method. The performance was evaluated in terms of spatial coverage by considering changing the spatial coverage of the antenna array by changing the distance between neighboring antennas in the antenna array.

• Information and Communications Magazine
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• v.33 no.4
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• pp.86-91
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• 2016

커버리지를 확대하고 다이버시티 이득의 극대화를 통해 전송 신뢰도를 높이는데 효과적인 무선 중계기술은 많은 연구자의 높은 관심을 받아왔으며 그동안의 주요 연구결과를 바탕으로 3GPP Release 10에 LTE/LTE-A를 위한 중계기술로 표준화되기에 이르렀다. 본고에서는 LTE/LTE-A를 위한 중계기술이 표준기술로 포함된 Release 10을 중심으로 중계 시스템의 전반적인 구조를 소개하고 중계 절차 및 주요 네트워크 프로토콜을 살펴본다.

• Electronics and Telecommunications Trends
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• v.32 no.1
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• pp.46-53
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• 2017

넓은 커버리지를 요구하는 응용이 늘면서 서비스 지연에 민감하지 않은 소량의 데이터를 전달하기에 적합한 LPWA 네트워크 기술이 주목받고 있다. 본고는 LPWA 네트워크기술을 시장과 밀접한 관련을 갖고있는 무선 대역으로 구분하여, 비면허 대역 기술과 면허 대역 기술로 나누어 최근 개발 및 확산 동향을 살펴본다. 특히, 비면허 대역의 대표적인 기술인 Sigfox, LoRaWAN, PRMA 등의 기술을 다루었으며, 면허 대역의 기술로는 3GPP의 LTE기술을 중심으로 살펴본다. 또한, LPWA네트워크 기술과 관련하여 최근 진행 중인 IETF의 표준화 동향을 정리한다.

• Proceedings of the Korean Institute of Communication Sciences Conference
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• 2004.07a
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• pp.373-373
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• 2004

• Information and Communications Magazine
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• v.25 no.5
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• pp.38-46
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• 2008

협력 다이버시티 기술은 최근 수년간 MIMO(Multiple-Input-Multiple-Output) 기술의 실질적인 대안으로, 애드 혹 네트워크에서의 MIMO 기술로, 셀룰러 시스템에서의 커버리지 확장 기술로 주목을 받아 왔다. 따라서, 협력 다이버시티 기술은 응용 목표에 따라 방식이 다르게 존재하게 된다. 이 논문에서는 기존의 협력 다이버시티 기술들을 몇 가지 일관된 기준으로 분류하여 보고, 이 분야에서 미진한 연구방향으로 다중사용자 환경에서의 협력 다이버시티 기술과 다중 안테나 노드를 위한 협력 다이버시티 기술을 제시한다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2017.10a
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• pp.129-131
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• 2017

In the special situations such as the extension or construction of networks, network sharing can be a more favorable alternative. In this point, this research is to review the types and characteristics related to network sharing among mobile network operators(MNOs).

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.43 no.5 s.347
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• pp.113-120
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• 2006

This thesis deals with solutions such as coverage area extension, reduction of the shadow region and performance enhancement of handover caused by structural modification of WiBro network. The More far the distance of RAS(Radio Access Station) and SS(Subscriber Station) is in micro cell, the more bad the quality of channel environment becomes owing to radio interference. Consequently, it causes the deterioration of the throughput and also the deterioration of communication quality in many sides. In fact, most users of WiBro are located in the region, the QPSK region which is bad in point of channel quality. It brings the service complaint by user. We select RS(relay station) to solve the matter caused by channel environment in this cell, and extend coverage and improve the performance of handover call blocking.