• Title/Summary/Keyword: multi-relay

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Comparison of Outage Probability Between Best-relay 2-hop Relaying and 3-hop Relaying (두 릴레이가 존재할 때 삼중 홉 중계와 베스트 릴레이 선택 후 이중 홉 중계 방식의 아웃티지 확률 비교)

  • Youn, You-Sun;Kim, Dong-Woo
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.35 no.1B
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    • pp.136-143
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    • 2010
  • In this paper, we investigate decode-and-forward (DF) relaying systems with a direct link between the source and the destination node. The objective of this paper is to determine the better relaying strategy between 3-hop DF relaying and dual-hop DF relaying with the best relay selection. Assuming Rayleigh fading channels, we present closed-form outage probability of the 3-hop relaying and the dual-hop relaying, respectively, and compare the performances by numerical investigation. Numerical results show that if the channel is poor, the outage performance of the 3-hop relaying is better than the dual-hop relaying.

Multiple-Relay-Assisted Spectral Efficient OFDMA Transmission System with Simple Channel Cyclicity Restoration (간단한 채널 주기성 복원이 포함된 다중 중계기 기반의 주파수 효율적인 OFDMA 전송 시스템)

  • Won, Hui-Chul
    • Journal of Korea Society of Industrial Information Systems
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    • v.20 no.6
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    • pp.1-10
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    • 2015
  • In this paper, we propose a spectral efficient orthogonal frequency division multiple access(OFDMA) transmission system using multiple relays for a shadow area. The performance of the proposed OFDMA system in a shadow area can be improved by applying space-frequency(SF) block code over relaying multi-path channels. A simple channel cyclicity restoration method is also added in the proposed OFDMA system without cyclic prefix(CP) to recover the destruction of channel cyclicity due to the lack of CP. Simulation results show that the proposed OFDMA system without CP is almost same as that of the conventional OFDMA system with sufficient CP, which increases the spectral efficiency of the system.

Spectral Efficient SF Block Coded Relay Transmission System without Cyclic Prefix for a Shadow Area (음영 지역을 위한 주기적 프리픽스 없는 주파수 효율적인 주파수 공간 블록 부호화 중계기 전송 시스템)

  • Won, Hui-Chul
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.16 no.11
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    • pp.7456-7462
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    • 2015
  • This paper proposes a spectral efficient space-frequency(SF) block coded single carrier-frequency division multiple access(SC-FDMA) transmission system in a relaying multi-path shadow area. The cyclic prefix(CP) is not used in the proposed system in order to prevent a loss of spectral efficiency due to the use of CP. The destruction of channel cyclicity due to the lack of CP is recovered at the receivers of relays and a destination station. Simulation results show that the performance of the proposed system without CP is almost same as that of the conventional system with full CP, thus increasing the spectral efficiency.

Performance Analysis of Single-frame Mode and Multi-Frame Mode in IEEE802.16j MMR System (IEEE802.16j MMR 시스템에서 Single-Frame 방식과 Multi-Frame 방식의 성능 분석)

  • Kim, Seung-Yeon;Kim, Se-Jin;Yoo, Chang-Jin;Ryu, Seung-Wan;Lee, Hyong-Woo;Cho, Choong-Ho
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.33 no.6B
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    • pp.403-410
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    • 2008
  • In this paper, we investigate the performance of MMR system in Non-transparent mode. The IEEE 802.16j MMR system has two node of operation, Single-frame (in band) and Multi-frame (out band) mode. In the analysis, we assume that channel interference between MR-BS and RS, or between RSs anywhere in the given area is ignored. The performance is presented in terms of the delay and the frame efficiency by varying number of RS and BS coverage to RS coverage ratio and the maximum coverage area of a BS by varying traffic density. Analytical results show that the Single-frame is more efficient than Multi-frame in frame efficiency and coverage extension.

Hybrid Three-Level DC/DC Converter using an Energy Recovery Snubber (에너지회생스너버를 적용한 하이브리드 3레벨 DC/DC 컨버터)

  • Heo, Ye-Chang;Joo, Jong-Seong;Harerimana, Elysee-Malon;Kim, Eun-Soo;Kang, Cheol-Ha;Lee, Seung-Min
    • The Transactions of the Korean Institute of Power Electronics
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    • v.22 no.1
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    • pp.36-43
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    • 2017
  • This paper describes a hybrid multi-output three-level DC/DC converter suitable for a wide, high-input voltage range of an auxiliary power supply for a high-power photovoltaic generating system. In a high-power photovoltaic generating system, the solar panel output voltage depends on solar radiation quantity and varies from 450Vdc to 1100Vdc. The proposed hybrid multi-output three-level DC/DC converter, which is an auxiliary power supply, would be used as power source for control printed circuit boards and relay and cooling fans in a high-power photovoltaic generating system. The proposed multi-output ($24V_{DC}/30A$, $230V_{DC}/5A$) hybrid three-level boost converter, which uses an energy recovery snubber, is controlled by variable-frequency and phase-shifted modulations and can achieve zero-voltage switching with all operating conditions of input voltage and load range. Experimental results of a 2kW prototype are evaluated and implemented to verify the performance of the proposed converter.

Development of ACL Modul For Agent Communication in Auto-Adaptive OCR Agent (자율적응형 과전류계전기 에이전트의 통신을 위한 ACL모듈 개발)

  • Oh, T.W.;Lee, S.J.;Choi, M.S.;Kim, K.H.;Lim, S.I.;Min, B.W.;Lee, H.W.
    • Proceedings of the KIEE Conference
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    • 2002.07a
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    • pp.193-195
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    • 2002
  • In this paper, a communication module is proposed to be applied to communication between over current relay (OCR) agents in multi agent protection system. A multi agent system can achieve a global goal beyond the ability of each individual agent by working together, in which it is the prerequisite for each agent to be able to exchange or share information or processing status with other agent. The proposed communication module is purposed to enable not only each agent to bring about its own goal, but also the whole protective system to provide much improved coordinated protection. It is applied to a self adaptive protection system for a distribution network using multi agent concept to show its effectiveness.

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A Study on Calculation of Protection Ratio for Frequency Coordination in Microwave Relay System Networks (M/W 중계 시스템 망의 주파수 조정을 위한 보호비 계산에 대한 연구)

  • Suh Kyoung-Whoan
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.17 no.2 s.105
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    • pp.139-147
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    • 2006
  • This paper suggests an efficient method of protection ratio calculation and shows some results applicable to frequency coordination in microwave(M/W) relay system networks, and the net filter discrimination(NFD) associated with Tx spectrum mask and overall Rx filter characteristics has been examined to obtain the adjacent channel protection ratio. The protection ratio comprises several factors such as C/N of modulation scheme, noise-to-interference ratio, multiple interference allowance, fade margins of multi-path and rain attenuation, and NFD. According to computed results for 6.7 GHz, 64-QAM, and 60 km at BER $10^{-6}$, fade margin and co-channel protection ratio are 41.1 and 75.2 dB, respectively. NFD for channel bandwidth of 40 MHz reveals 28.9 dB at the first adjacent channel, which results in adjacent channel protection ratio of 46.3 dB. In addition, NFD and protection ratio for different systems with channel bandwidth 20 and 40 MHz have been investigated to be used for actual M/W networks. The proposed method provides some merits of an easy calculation, systematic extension, and applying the same concept to frequency coordination in millimeter wave relay system networks.

An Approach for Multi-User Multimedia Requests Service to Overlay Multicast Trees (다중 사용자의 멀티미디어 요구 서비스를 위한 오버레이 멀티캐스트 트리의 구성과 복구 방안)

  • Kang, Mi-Young;Yang, Hyun-Jong;Nam, Ji-Seung
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.33 no.12B
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    • pp.1058-1065
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    • 2008
  • In the Internet, as computer resource is developed, multimedia data request being increase more and more. It is effective way that process both high capacity-data and real-time data. Overlay Multicast is an effective method for efficient utilization of system resources and network bandwidth without using hardware customization. Overlay Multicast is an effective method for multimedia data service to multi-users. Multicast tree reconstruction is required when a non-leaf host leaves or fails. In this paper, relay-frame interval is selected as revealed network-state with jitter. In our proposal, multi-user service control algorithm gives a delay effect in multimedia request time. The simulation results show that our proposal takes shorter period of time than the other algorithms to reconstruct a similar tree and that it is a more effective way to deal with a lot of nodes that have lost their multi-user nodes.

Navigation Augmentation in Urban Area by HALE UAV with Onboard Pseudolite during Multi-Purpose Missions

  • Kim, O-Jong;Yu, Sunkyoung;No, Heekwon;Kee, Changdon;Choi, Minwoo;Seok, Hyojeong;Yoon, Donghwan;Park, Byungwoon;Jee, Cheolkyu
    • International Journal of Aeronautical and Space Sciences
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    • v.18 no.3
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    • pp.545-554
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    • 2017
  • Among various applications of the High Altitude Long Endurance (HALE) Unmanned Aerial Vehicle (UAV), this paper has a focus on the Global Positioning System (GPS) utilizing pseudolite and its improved performance, particularly during the multi-purpose missions. In a multi-purpose mission, the HALE UAV follows a specified flight trajectory for both navigation applications and missions. Some of the representative HALE missions are remote exploration, surveillance, reconnaissance, and communication relay. During these operations, the HALE UAV can also be an additional positioning signal source as it broadcast signals using pseudolite. The pseudolite signal can improve the availability, accuracy, and reliability of the GPS particularly in areas with poor signal reception, such as shadowed regions between tall buildings. The improvement in performance of navigation is validated through simulations of multi-purpose missions of the solar-powered HALE UAV in an urban canyon. The simulation includes UAV trajectory generation at stratosphere and uses actual geographical building data. The results indicate that the pseudolite-equipped HALE UAV has the potential to enhance the performance of the satellite navigation system in navigationally degraded regions even during multi-purpose operations.

MLP-A(Multi Link Protection for Airborne Network Verifying) algorithms and implementation in multiple air mobile/verification links (다중 공중 이동/검증 링크에서의 MLP-A 알고리즘 및 구현)

  • Youn, Jong-Taek;Jeong, Hyung-jin;Kim, Yongi;Jeon, Joon-Seok;Park, Juman;Joo, Taehwan;Go, Minsun
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.26 no.3
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    • pp.422-429
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    • 2022
  • In this paper, the intermediate frequency transmission signal level between the network system-based baseband and RF unit consisting of multi-channel airborne relay devices and a lot of mission devices, which are currently undergoing technology development tasks, is kept constant at the reference signal level. Considering the other party's receiving input range, despite changes in the short-range long-range wireless communication environment, it presents a multi-link protection and MLP-A algorithm that allows signals to be transmitted stably and reliably through signal detection automatic gain control, and experiments and analysis considering short-distance and long-distance wireless environments were performed by designing, manufacturing, and implementing RF units to which MLP-A algorithms were applied, and applying distance calculation equations to the configuration of multiple air movements and verification networks. Through this, it was confirmed that a stable and reliable RF communication system can be operated.