• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• 제22권6호
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• pp.50-60
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• 2008

The ANSI/IEEE Std. 80-2000 method has been commonly used to design grounding system for the South Korea domestic market. However, the appropriateness of this method to the ground design environment has not yet been examined. This paper presents a new design grounding system method that complements the ANSI/IEEE Std. 80-2000 method, when the new method is a lied to thickness, dangerous voltage, and grid spaced computations for grounding conductors. Furthermore, this paper examines reliability and economic efficiency issues by comparing of the ANSI/IEEE Std. 80-2000 Annex B's case study with the original method.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• 제22권4호
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• pp.68-77
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• 2008

When we design the grounding grid, dangerous voltage IEEE Std. 80 method has been commonly used in the domestic area. However there is not appropriative examination of ground design environment. So in this paper, we examined of IEEE Std. 80 touch voltage method's marginal utility and we induced corrective factor for those problems by comparison between IEEE Std. 80 touch voltage value and simulation experimentation value. Moreover, Logistic model's corrective factor we proved the maximum accidental error has reduced less than 10[%].

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• 제27권5호
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• pp.54-60
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• 2013

There is increasing demand for practical groundings for small-area substations because of the recent revision of Korea's Electrotechnical Regulations, which necessitates the method of evaluating their safety. This paper proposes a practical mesh grounding system for 22.9kV substations and studies how to evaluate its safety. The proposed grounding system is proved to obey the safety criteria of ANSI/IEEE Std. 80 via ANSI/IEEE Std. 80 method and computer simulation.

• Journal of KIISE:Information Networking
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• 제37권3호
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• pp.249-253
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• 2010

Resource of wireless frequency bandwidth is gradually going to be deficient due to explosive increase of traffic and saturated non-licensed frequency band such as ISM. In the contrary, many licensed frequency bands are revealed to be low in utilization by several measurement based researches. To alleviate this inefficiency, a concept of cognitive radio is suggested. Cognitive radio lets non-licensed user exploit the licensed frequency band as long as non-licensed user does not interfere licensed user and as a result, it is possible to harness wireless frequency more efficiently. IEEE 802.22 is the first standard network with cognitive radio technology and it employs Two-Stage channel sensing mechanism to accomplish both enough licensed user protection and efficient channel utilization. In this paper, we analyze the overhead of Two-Stage channel sensing mechanism and identify the influence of channel sensing time to the overhead.

• Journal of IKEEE
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• 제22권3호
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• pp.651-657
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• 2018

IEEE 802.11 wireless LANs support 20, 40, 80 and 160MHz bandwidth transmission. In general, the data rate increases as the transmission bandwidth increases. However, the transmission power spectral density decreases, which may lead to increasing packet errors and retransmissions. In this paper, we derive a mathematical model of energy consumption with consideration of various factors such as transmission bandwidth, packet error rate and data size. Based on the model, we design a scheme to adapt a transmission bandwidth for each frame transmission. The scheme estimates packet error rates for different bandwidth cases, updates the table of energy consumption and selects the best bandwidth for the next transmission. The simulation study with VoIP traffic shows the energy consumption of the scheme under various environments.

• The Magazine of the IEIE
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• 제22권12호
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• pp.93-104
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• 1995

디지탈 회로를 구현한 칩 및 보드의 시험 비용을 줄이기 위하여 사용되는 스캔 설계 기술 동향에 대하여 기술하였다. 스캔 설계 기술은 칩 수준에서 먼저 적용되기 시작하였다. 회로의 모든 플립플롭을 스캔할 수 있도록 하는 완전 스캔이 먼저 개발되었고, 최근에는 플립플롭의 일부분만 스캔할 수 있도록 하는 부분 스캔 기술이 활발하게 논의되고 있다. 한편 보드의 시험에 있어서도 보드에 실장되는 칩의 밀도가 증가되고, 표면 실장 기술이 일반화됨에 따라 종래의 시험 기술로는 충분한 시험을 거치는 것이 불가능하게 되었다. 따라서, 칩에 적용되던 기법과 유사한 스캔 설계 기술이 적용되기 시작하였다. 이를 경계 스캔(Boundary Scan)이라고 하는데, 이 기술은 80년대 후반부터 본격적으로 논의되기 시작하였다. 1990년에는 이 기술과 관련된 IEEE의 표준이 제정되어 더욱 많이 적용되는 추세에 있다. 이 논문에서는 이러한 칩 및 보드의 시험을 쉽게하기 위한 스캔 설계 기법의 배경, 발전 과정 및 기술의 내용을 소개한다.

• Journal of Communications and Networks
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• 제13권1호
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• pp.32-42
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• 2011

Frequency reuse among relay stations (RSs) in a down-link access zone is widely adopted for throughput enhancement in IEEE 802.16j relay networks. Since the areas covered by the RSs or the base station (BS) may overlap, some mobile stations (MSs) at the border between two neighboring transmitting stations (RS or BS) using an identical frequency band may suffer severe interference or outage. This co-channel interference within the cell degrades the quality of service (QoS) fairness among the MSs as well as the system throughput. Exclusive use of a frequency band division (orthogonal resource allocation) among RSs can solve this problem but would cause degradation of the system throughput. We observe a trade-off between system throughput and QoS fairness in the previously reported schemes based on frequency reuse. In this paper, we propose a new frequency reuse scheme that achieves high system throughput with a high fairness level in QoS, positioning our scheme far above the trade-off curve formed by previous schemes. We claim that our scheme is beneficial for applications in which a high QoS level is required even for the MSs at the border. Exploiting the features of a directional antenna in the BS, we create a new zone in the frame structure. In the new zone, the RSs can serve the subordinate MSs at the border and prone to interference. In a 3-RS topology, where the RSs are located at points $120^{\circ}$ apart from one another, the throughput and Jain fairness index are 10.64 Mbps and 0.62, respectively. On the other hand, the throughput for the previously reported overlapped and orthogonal allocation schemes is 8.22 Mbps (fairness: 0.48) and 3.99 Mbps (fairness: 0.80), respectively. For a 6-RS topology, our scheme achieves a throughput of 18.38 Mbps with a fairness of 0.68; however, previous schemes with frequency reuse factors of 1, 2, 3, and 6 achieve a throughput of 15.24 Mbps (fairness: 0.53), 12.42 Mbps (fairness: 0.71),8.84 Mbps (fairness: 0.88), and 4.57 Mbps (fairness: 0.88), respectively.

• Journal of the Institute of Convergence Signal Processing
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• 제22권1호
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• pp.38-44
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• 2021

Wi-Fi provides some low-power connection solutions that other Bluetooth cannot provide, and at the same time brings many benefits. First, there is a potentially higher data rate: it can reach 230mbps. Wi-Fi coverage is also wider than competitors, and its operating frequency is also 5GHz, which is much less congested than 2.4GHz. Finally, it also supports IP networks, which is important if you want to send data to the cloud without complexity. The 802.11ac standard of the previous generation still accounts for most shipments (80.9%) and revenue (76.2%). However, there is a limit to accepting IoT devices that will continue to increase significantly in the future. To solve this problem, the new Wi-Fi 6 standard is expected to be the solution (IEEE 802.11ax) which is quickly becoming the main driving force of the wireless local area network (WLAN) market. According to IDC market research analysts, in the first quarter of 2020, independent access points (APs) supported by Wi-Fi 6 accounted for 11.8% of shipments, but 21.8% of revenue. In this paper, we have compared and analyzed the IoT connectivity, QoS, and security requirements of devices using Wi-Fi 6 network.