• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.6B
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• pp.553-558
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• 2009

There have been various research efforts to support the fairness between uplink and downlink of TCP streams in IEEE 802.11 networks. Existing methods, which have been effective for the fairness, however could not provide the solution for the unfairness caused by the situation in which a station which is having multiple TCP uplink streams monopolizes the uplink bandwidth. This paper proposes a method that AP allocates token buckets for each uplink TCP station. The proposed method is also able to support the fairness between the uplink and downlink. To remedy the underutilization which may happen under token bucket-based schemes, it allows the movement of redundant tokens among the token buckets. By controlling the token movements, it can balance the fairness and the utilization. Simulation results show that the proposed method is able to support the fairness of the TCP uplink stations, as well as the fairness between the uplink and downlink.

• Aerospace Engineering and Technology
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• v.1 no.2
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• pp.45-50
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• 2002

A conceptual design on the link budget of TC&R RF subsystem which transfers command and telemetry data as RF signal between the ground system and the 2005SAT spacecraft is presented in this paper. In order to perform the analysis of the link budget, we divided the analysis process into two processes, i.e., uplink and downlink process. For the uplink the power flux density at the spacecraft and the margin of the command receiver are calculated. In the case of the downlink the downlink EIRP and the margin of C/ No and Eb / No at the ground station are calculated. Through the uplink performance analysis, the power at the command receiver has well efficient margin, and the margin of C/ No and Eb / No is also fully proper for the downlink case.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2023.11a
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• pp.143-144
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• 2023

해양수산부가 구축한 초고속 해상무선통신망(LTE-Maritime)은 연안으로부터 최대 100km 해역을 항해하는 선박들에게 지능형 해상교통정보서비스(e-Nav)를 제공하기 위한 기반 통신 인프라다. 선박에서 e-Nav 서비스를 제공받기 위해 LTE-M. 무선설비는 선내 고정 설치되어 유선으로 연결된 표시장치와 연동이 필요하다. 이는 공간이 협소하고 밀폐된 소형선박에 설치의 어려움뿐 아니라 선내 센서를 비롯한 다양한 IoT 기기 등과의 연결성에 제약을 줄 수 있다. 또한 선박이 육상의 LTE-M. 기지국과 멀리 떨어질 경우, 다운링크에 비해 업링크 통신품질이 상대적으로 취약해져 긴급 조난 신호를 비롯한 위험상황의 전달에 문제가 발생될 수 있다. 본 연구에서는 LTE-M. 망의 무선설비 다각화 사업으로 추진·개발된 소형선용 WiFi 및 업링크 향상용 무선설비의 실해역 성능 시험 방안을 고찰하여, 선내 WiFi 무선 품질을 평가하기 위한 성능 지표를 비롯해 업링크 통신속도 개선 등을 확인하기 위한 상호운용성 성능 시험 방안을 제시하고자 한다.

• Proceedings of the Korea Contents Association Conference
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• 2017.05a
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• pp.175-176
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• 2017

현대사회에서 인터넷 이용은 인간으로서 기본적인 삶의 문제가 되어 매일 인터넷을 이용하지 않는 경우는 것의 없으며, SNS를 사용하면서 거의 매일 하이퍼링크를 하고 있다. 그러나 이러한 하이퍼링크가 합법적으로 업로드된 저작물에 연결되는 것에 대해서는 별로 문제가 되지 않지만, 불법적으로 업로드된 저작물에 링크를 하고, 이러한 링크를 관리하여 수익모델을 가지고 있는 개인 및 기업의 증가로 대한민국뿐만 아니라, 전세계적으로 저작권법적인 문제가 되고 있다. 본 논문에서는 미국, EU, 대한민국의 판례를 간략하게 정리하고, 현재까지 판례를 비판하며, 입법론을 제안해 보고자 한다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.4A
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• pp.329-336
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• 2011

This paper addresses the fairness issue between uplink and downlink traffic in IEEE 802.11 WLANs. Some solutions in existing work try to solve this issue by giving smaller minimum contention window (CWmin) value to an AP compared to stations. In contrast to the existing solutions, a proposed algorithm in this paper aims at finding CWmin values that not only provides fairness between uplink and downlink traffic among stations but also achieves high throughput. For this, in the proposed algorithm, an AP checks the number of stations that have uplink and downlink traffic, respectively. Based on this information, the AP calculates optimal CWmin values and announces it to stations. Our simulation results show that the proposed algorithm outperforms existing algorithms in terms of fairness and throughput.

• Proceedings of the Korean Society of Disaster Information Conference
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• 2023.11a
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• pp.204-206
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• 2023

본 연구는 현재 각 현장에서 사용되어지는 다양한 화재수신기의 DATA를 받기 위한 프로토콜 및 접점 포트 구현 및 통신3사(SKT, KT, LGU+)의 LPWA 모뎀을 통한 업링크 기능 또한 무선 업링크 전송 불가시 유선 업링크 기능을 구현하여, 어떠한 환경에서도 데이터를 서버로 전송할 수 있는 H/W 기술과 다양한 화재수신기의 Data를 수집/분석 전송할 수 있는 지능화한 S/W와 다양한 화재수신기의 데이터를 표준화하여 이를 적용한 펌웨어 고도화, 사용자 APP 및 UI를 개발하는데 목적이 있다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.16 no.11
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• pp.1084-1094
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• 1991

Upon introducing satellite communication system to korea, one of the important problems to copy with is the effect from the probable intentional interference i. e. jamming. In this paper, we have considered the M any PSK signal and the soft limiter type, which contains hard limiter, nonhnear satellite transponder in environments of uplink tone or noise jamming plus Gaussian noise and downlink Gaussian noise. Using the derived error rate equation, we have evaluated numerically the error performance of BPSK and QPSK system, and shown in figures in terms of upink and downink earner to jamming rater(CJR) and limiting level. From the results we have known that tone jamming effect on the error performance in BPSK and QPSK signals in nonlinear satelhie shnnel become less with increasing the uplink CNR and with decreasing the liniting level. And in a tone jamming, the limiting level affects hardly on the error performance of both BPSK and QPSK signals. When limiting leveri is zero, BPSK and QPSK signals show the best error rate performance.

• Journal of the Korea Society for Simulation
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• v.15 no.1
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• pp.27-33
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• 2006

To guarantee QoS (Quality of Service), routers should determine routing paths satisfying service requirements, based on link state information as well as network topology. Link status database (LSD) in routers should be efficiently managed to effectively reflect the current state of all links. However, there is a trade off between the exact reflection of the current link status and its update cost. For exactly reflecting the current link status, each router immediately notifies its neighbors that link state information is changed. This may degrade performance of the router due to the processing of link state update messages. On the other side, if the current link state information is not updated appropriately, a route setup request can be rejected because of the discrepancy between the current link state information and previously updated link state information in LSD. In this paper, we propose a traffic variation based link state update algorithm for adaptively controlling the generation of link state update messages and compare its performance with those of four existing algorithms by intensive simulations.

• Journal of Satellite, Information and Communications
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• v.9 no.1
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• pp.107-114
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• 2014

The satellite 2.1 GHz frequency bands, 1980-2010 MHz and 2170-2200MHz are allocated for mobile satellite service including satellite IMT, while it does not preclude the use of these bands for mobile services. The concept of an integrated satellite/terrestrial network has been introduced in worldwide because the terrestrial use in these bands adjacent to existing terrestrial IMT bands is attractive to provide mobile broadband services. The integrated satellite/terrestrial infrastructure with a high degree of spectrum utilization efficiency has the ability to provide both multimedia broadband services and public protection and disaster relief solutions. In addition, it is required to consider interference issues between the terrestrial and satellite components in order to reuse the same frequency band to both satellite and terrestrial component. This paper analyzes the interference for satellite uplink in the satellite/terrestrial integrated system and the interference reduction scheme for satellite uplink interfered by terrestrial user equipment.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.9A
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• pp.790-795
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• 2011

The need for broadband wireless data networks such as IEEE 802.16e WiMAX systems increases as a variety of wireless information devices like smart phones are adopted rapidly in everyday life. Since most of mobile applications employ TCP as their transport layer protocol, the performance improvement of TCP in WiMAX systems is crucial. This paper proposes an efficient method to transmit uplink piggyback ACK packets by exploiting the uplink packet buffering which happens because of the resource allocation scheme of the WiMAX systems. The proposed method can support not only the ACK filtering but also the merging of the piggyback ACK packets. As a result, the bandwidth reduction in the piggyback ACK packet transmission leads to the improvement of the downlink throughput. The simulation results show that the bandwidth for the ACK packets reduces more than 90%, and the downlink throughput increases at least 30%.