• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.7B
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• pp.517-527
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• 2012

This paper considers a cooperative communication system with a single relay node, where two-layer superposition coding and successive decoding is employed to reduce the expected distortion of a Gaussian source delivered. For the system, we propose a relay scheme which forwards an appropriate relay signal at the relay node, based on the local decoding result of layers and the decoding result of layers at the destination node fed back to the relay node. In the scheme, the relay signal is designed not only by applying decode-and-forward but also by applying amplify-and-forward to reduce the outage probability in final decoding of each layer. The performance of the proposed scheme is evaluated numerically in terms of the expected distortion at various relay locations using outage probabilities derived. The results show that the proposed scheme outperforms the conventional schemes in most cases of the relay location and the gain gets larger when the relay node is closer to the source node in particular.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.11A
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• pp.831-843
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• 2009

In this paper, we propose a new adaptive cooperation scheme with multi-relay nodes which achieves higher performance and spectral efficiency than that of some conventional cooperative schemes. The relay-selection is applied to choose the most potential relay among K ones. Afterward, the instantaneous signal-to-noise ratio (SNR) differences between S-D, S-R and R-D channels are considered for adaptive selection between the direct and the cooperation transmission strategy. In the proposed adaptive protocol, if the direct link is of high quality, the source will transmit to destination directly with all power consumption. Otherwise, the source broadcasts the signal with a lower power and requires the help of the chosen relay if it decodes correctly, else the source will transmit again with remaining power. Firstly, the spectral efficiency is derived by calculating the probability of each mode. Subsequently, the BER performance for the adaptive cooperation scheme is analyzed by considering each event that one of K relays is selected and then making the summation of all. Finally, the numerical results are presented to confirm the performance enhancement offered by the proposed schemes.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2012.07a
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• pp.371-372
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• 2012

본 논문은 협력 네트워크(cooperative network)에서 무선 채널의 보안성(security) 강화를 위한 자가 전파방해(self-jamming) 기반 기회적 중계(opportunistic relaying) 기법을 제안한다. 단일 송신 단말 (source)과 단일 수신 단말(destination)이 다중 중계 단말(relay)의 협력을 통해 송수신하는 이중 홉(dualhop) 네트워크에서 도청 단말(eavesdropper)에 의한 정보 절취를 최소화하기 위해 자가 전파방해 기법과 기회적 중계 기법을 결합한다. 이를 통해 무선 채널의 방송(broadcasting) 특성에 기인한 도청 용이성을 저하 시키고, 다중 중계 단말의 송신 전력을 최소화하여 협력 네트워크의 수명(lifetime)을 연장한다. 컴퓨터 모의실험 결과를 통해 제안된 기법이 다중 중계기가 있는 이중 홉 협력 네트워크에서 보안 전송률(secrecy rate)의 불능확률(outage probability) 성능을 제고함을 보인다.

• Proceedings of the Korean Information Science Society Conference
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• 2007.06d
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• pp.58-62
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• 2007

기존의 무선 Ad-hoc 네트워크의 연구는 라우팅기법에 중심으로 이뤄지고 있다. 그러나 기존의 연구들은 네트워크를 구성하는 각 요소들이 우호적이며 상호 협력적인 상황을 가정하여 연구가 이루어지고 있다. 그러나 최근 연구에는 안전한 통신을 보장하기 위한 보안 알고리즘의 필요성에 집중되고 있다. 무선 Ad-hoc 네트워크에서의 악의적인 노드를 식별하는 방안들은 정상적인 노드임에도 불구하고 거짓으로 신고했을 때 확인절차 없이 경로를 재탐색하여 최적의 경로를 변경시킴으로서 최적의 전송환경을 활용하지 못하는 문제점이 있다. 본 논문에서는 다중경로 기반의 보안경로 탐색 프로토콜인 MP-SAR 프로토콜을 이용하여 보안경로에서는 악의적인 노드를 검증하고, 유효한 최단경로를 통해 데이터전송을 하는 기법을 제안하고자 한다. 제안한 기법을 적용함으로써 노드에 대한 신고가 있을 때 확인과정을 거쳐 불필요하게 경로를 재탐색하는 과정을 줄일 수 있다.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.9 no.1
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• pp.34-41
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• 2010

In this paper, we analyze and simulate co-channel interference (CCI) mitigation method for cooperative communication systems employing decode-and-forward relays. In co-channel interference mitigation method, A source transmits signals that are encoded by orthogonal code. Then, the receiver can distinguish its own signals form the received signals by using the orthogonal code which is already known to the receiver. The orthogonal codes applied to this paper are orthogonal Gold codes. However, we can employ other codes, which have orthogonality, as the orthogonal code. In addition, we utilize a space time block coding (STBC) scheme for enhancing the system performance by obtaining additional array gain.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.1
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• pp.86-88
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• 2016

In a previous work, a simultaneous reporting scheme for cooperative spectrum sensing has been presented for a resource efficient transmission over a report channel. In this paper, we present a method of reducing transmission errors on the report channel for it and evaluate its performance by simulation.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.1A
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• pp.87-94
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• 2010

It is widely known that cooperative spectrum sensing in which secondary users scattered in some region collaborate to detect primary users can significantly reduce the performance degradation due to the fading phenomenon. Most of previous works on cooperative spectrum sensing are based on the assumption that the local spectrum sensing decisions of secondary users are statistically independent. However, there can be practically some statistical correlation between the local decisions of any two secondary users in close proximity, which is caused by shadowing effect. In order to evaluate the effect of this correlation on the performance of collaborative spectrum sensing, we assumed that, for the case that a primary user are active in the spectrum of interest, any two local decisions are statistically correlated to each other with some level of constant correlation and independent otherwise, and analyzed the achievable throughput with the degree of correlation varying. The results showed that, as the degree of correlation gets higher, the throughput increases for the case of the AND fusion rule and decreases for the OR fusion rule.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.11 no.1
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• pp.141-150
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• 2011

In this paper, we propose a Cross-Layer Cooperative Routing(CLCR) architecture to support transmission efficiency in mobile wireless sensor networks. The main features and contributions of the proposed architecture and method are as follows. First, the clustering which uses the location information of nodes is utilized as infrastructure. Second, a cross-layer strategy which uses the technologies of network layer, MAC layer, physical layer together to support transmission efficiency and channel efficiency for cooperative-aided routing and transmission. Third, we consider realistic approach in the view points of the mobile ad-hoc wireless sensor networks while conventional methods just consider fixed sensor network environments. The performance evaluation of the proposed method is performed via simulation using OPNET and theoretical analysis. The results of performance evaluation of the proposed CLCR show improvement of transmission efficiency by the proposed CLCR.

• Journal of KIISE
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• v.42 no.5
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• pp.671-680
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• 2015

Numerous clustering schemes have been proposed to increase energy efficiency in wireless sensor networks. Clustering schemes consist of a hierarchical structure in the sensor network to aggregate and transmit data. However, existing clustering schemes are not suitable for use in wireless multimedia sensor networks because they consume a large quantity of energy and have extremely short lifetime. To address this problem, we propose the Energy-Aware Cooperative Communication (EACC) method which is a novel cooperative clustering method that systematically adapts to various types of multimedia data including images and video. An evaluation of its performance shows that the proposed method is up to 2.5 times more energy-efficient than the existing clustering schemes.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2023.05a
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• pp.309-310
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• 2023

본 논문은 해상 항로 표지 내 탑재되는 다양한 해양 센서, 등명기, 전원 모듈을 분리하여 각각의 서브 플랫폼으로 관리하고 각각의 서브 플랫폼들은 통합적으로 운영하는 메인 플랫폼 구조를 갖는 계층적 형태의 스마트 항로표지 구조안을 제시한다. 제안된 구조안을 바탕으로 기존에 제공되는 다양한 장비 및 센서 뿐만 아니라 항로표지 신 서비스 요구사항에 따른 신규 센서의 확장 및 설치가 용이하며, 서브 플랫폼 별 독립적인 운영을 통한 전체 시스템의 안정성 향상 기대할 수 있다. 또한, 목적에 따른 숫자, 음성, 영상 등 다양한 형태의 데이터를 전송하기 위한 선택적 통신 플랫폼 구조를 제시함으로써 육상 정보협력시스템과의 원활한 정보 교환 체계를 구축할 수 있는 방안을 제안한다.