• The Journal of the Korea institute of electronic communication sciences
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• v.8 no.3
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• pp.453-458
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• 2013

Aside from the issues like energy saving and maximizing network lifetime. WMSN has another issue to deal with: support of quality of service(QoS) which is required especially for handling real-time data such as object tracking and data gathering. This paper proposes a multipath routing algorithm considering the distance to sink node, energy level and link quality of neighbour nodes. Proposed algorithm supports multipath routing path with high quality links. Hence it helps to reduce a power consumption concentration that happens in particular set of nodes along the frequently selected route. It also specifies a service quality pattern and a service quality level depending on traffic pattern. By doing this, the proposed algorithm can realize a differentiated service with QoS guaranteed data transmission.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37B no.10
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• pp.921-928
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• 2012

In this paper, we propose a novel interference alignment transceiver for multi-cell MIMO downlink channels with arbitrary number of cells and users per cell. We design the receive beamformer to align the interference from undesired base stations to the effective inter-cell interference (ICI) channels. Subsequently, we design the transmit precoder which can nulllify the interference from the corresponding base station. The proposed transceiver design can attain the degrees of freedom (DOF) equal to the number of streams per user. Accordingly, we investigate conditions for the antenna configuration. From numerical results, we confirm that the proposed transceiver design can achieve higher DOF than the conventional scheme under equal antenna configuration.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.22 no.1
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• pp.96-103
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• 1997

We developed the prototype of 4-channel WDM link with erbium-doped fiber amplifiers. Bit rate of each channel was 2.5Gb/s. The unrepeatered transmission over 120km with DSF was achieved and the transmission length was extended to 240km using two EDFAs.

• Information and Communications Magazine
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• v.31 no.8
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• pp.84-91
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• 2014

본고에서는 최근 학계 및 산업계에서 활발히 연구되고 있는 간섭정렬 기술동향에 대해 소개한다. 특히 Signal Space 간섭정렬, Signal Scale 간섭정렬, Ergodic 간섭정렬의 기본 개념과 장단점 및 응용분야를 정리하였다. 또한 셀룰라 무선망에서의 간섭정렬에 대해 소개한다. 크게 단일안테나 환경과 다중안테나 환경에서의 간섭정렬로 나뉠 수 있으며, 각각의 경우에 대해 기술동향 및 주요 연구결과를 정리하였다. 마지막으로 최근 Reverse TDD, 즉 상향링크와 하향링크가 공존하는 환경에서의 간섭정렬을 통해 다중안테나 셀룰라 무선망의 자유도를 획기적으로 개선 할 수 있는 연구결과를 소개한다.

• Journal of Advanced Navigation Technology
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• v.18 no.3
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• pp.236-241
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• 2014

In a mobile ad hoc networks, multi-hop transmission is used to transfer data from source node to destination node and the routing protocol is the one of the important technical issues. The links between nodes can be unstable due to the changes of node location and channel conditions, and it can induce link error. To solve this problem, multipath routing was proposed. Multipath routing can reduce the data congestion and increase data throughput. In the multipath routing, however, each path can be interfered by the other path, and it can aggravate network performance. In this paper, we propose the multipath routing technique in the multi-rate MANET. The proposed multipath routing can avoid interference without the knowledge of node location. Simulation results show that the proposed multipath routing can reduce transmission delay and error.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.6B
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• pp.568-574
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• 2009

320km optical transmission link for 128 channel DWDM (dense wavelength-division-multiplexing) signals is simulated and fabricated. An optical fiber amplifier for the link is composed of a distributed Raman amplifier and dual C/L-band EDFAs which are optimized for the performances of an optical amplifier obtained from the simulation. Gain and NF of the optimized EDFAs are above 19dB and below 7.5dB, respectively. The resultant OSNRs (optical signal to noise ratios) of the link are average 25dB on each band.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.3C
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• pp.271-278
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• 2003

In this paper, we propose a new MLP based detector which has low circuit complexity and fast adaptation capability for CDMA downlink in frequency selective fading, and is easy for parameter optimization. The simplified structure of the proposed MLP is designed by making use of transmission characteristics of downlinks such that all users signals transmitted over same propagation paths and the number of channelization codes are limited. Significant performance improvement over Rake receiver can be obtained with the proposed MLP and the efficiency of the proposed MLP was compared with that of conventional MLP.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.1A
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• pp.1-9
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• 2005

We have studied the dispersion properties of a 40 channel x 10 Gbit/s wavelength division multiplexer(WDM) transmission link using standard single mode fiber with all EDFA amplification over 30 x 100 km spans. The dispersion map of the link was investigated by adding fiber sections with positive or negative dispersion at the transmitter, within each amplifier span, and at the receiver. Optimum combinations of these dispersive fiber lengths were attained to significantly enhance the overall transmission performance.

• Journal of Advanced Navigation Technology
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• v.25 no.4
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• pp.286-292
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• 2021

Dispersion maps of antipodal symmetric type for improvement of compensation effect in dispersion managed link combined with optical phase conjugation, which can compensate for the distorted wavelength division multiplexed (WDM) signals due to chromatic dispersion and nonlinear Kerr effects of single-mode fiber, were proposed. It was confirmed that the proposed all of antipodal symmetric dispersion maps was more effective to compensate for the distorted WDM channels than the conventional link of uniform type dispersion map. Especially, dispersion maps formed like the inversion of alphabet S were more advantageous as the distorted WDM channels were compensated than dispersion maps formed like alphabet S. It was expected that the variety of optical network topology was more expanded by applying the proposed antipodal symmetric dispersion maps into transmission link.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.7
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• pp.1293-1295
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• 2015

In this letter, an adaptive multi-antenna channel estimation scheme is proposed for uplink multiuser environments such as LTE-A systems to accurately estimate time-varying channels within an affordable complexity. It is confirmed that the proposed channel estimator can achieve accurate channel tracking performance even when various time-varying channel environments and traffic patterns are provided.