• Journal of Satellite, Information and Communications
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• v.7 no.2
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• pp.30-35
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• 2012

In this paper, we proposed spectrum sensing using cooperative relay to solve problem of sensing performance degradation due to CPE (Customer-Primise equipments) which causes low SNR (signal-to-noise ratio) problem. This system model is expected that cooperative relay scheme guarantees the high sensing performance by its diversity gain. Based on these backgrounds, in this paper, we apply to cooperative relay scheme to the CR (cognitive radio) system, and simulation results show comparison of the sensing performance combining method EGC and MRC.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.46 no.2
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• pp.38-45
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• 2009

In this paper, we propose an efficient cooperative diversity technique, which partition the codewords of each mobile and transmit portions of each codeword through independent fading channels using duo-binary turbo codes. A coded diversity technique can achieve high cooperative diversity gain by decoding and transmitting of the re-encoded signal, while this can also cause high performance degradation due to failure of the decoding. In this paper, we introduce various coded diversity technique using duo-binary turbo codes which are defined as channel coding schemes in the IEEE WiMax specification, and also demonstrate performance simulation results with the analysis. We also propose a cooperative diversity technique using rate-compatible duo-binary turbo codes, where user terminals with different parity symbols cooperate each other. Simulation results investigated in this paper reveal that the proposed scheme show high diversity gain at a reasonal SNR range.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2008.11a
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• pp.103-105
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• 2008

차세대 양방향데이터방송 (BIFS: BInary Format for Scenes) 서비스에서는 하향링크(downlink) 데이터 전송률에 상응하는 높은 상향링크(uplink) 데이터 전송률이 요구되고 있다. 이에 무선 전송 채널의 한정된 자원 환경 속에서 상향링크 전송용량 증대를 위한 주파수 효율성 제고 기술의 필요성이 대두되고 있다. 본 논문에서는 차세대 양방향데이터방송을 위한 다중 모바일(mobile) 사용자의 클러스터(cluster) 기반 상향링크 협동 다이버시티(cooperative diversity) 기법을 제안한다. 제안된 기법은 하나의 단일 안테나(single antenna) 방송 기지국과 다수의 단일 안테나 모바일 사용자가 있는 상향링크 시분할다중접속 (TDMA: Time Division Multiple Access) 시스템에서 데이터 지연허용(delay-tolerant)에 따라 클러스터를 구성하고 제곱 다이버시티 차수(square diversity order)의 협동 프로토콜(cooperative protocol)을 통해 높은 공간다이버시티 이득(spatial diversity gain)을 얻는다. 또한, 비대칭(asymmetric) 무선 채널 환경에서 공정성(fairness)을 보장한다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2012.10a
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• pp.626-628
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• 2012

In this paper, we propose a cooperative spectrum sensing scheme using the spatial diversity of secondary users (SUs). In our scheme, a SU makes an estimation whether the primary user (PU) is active or not using the signals from the other SUs. We know that the diversity order of miss detection probability increases as the number of SUs increases from the simulation result.

• 한국ITS학회:학술대회논문집
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• 2010.05a
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• pp.48-52
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• 2010

• Journal of Communications and Networks
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• v.10 no.2
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• pp.156-162
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• 2008

Cooperative relays can provide spatial diversity and improve performance of wireless communications. In this paper, we study subcarrier power allocation at the relays for orthogonal frequency division multiplexing (OFDM)-based wireless systems. For cooperative relay with amplify-and-forward (AF) and decode-and-forward (DF) algorithms, we investigate the impact of power allocation to the mutual information between the source and destination. From our simulation results on word~error-rate (WER) performance, we find that the DF algorithm with power allocation provides better performance than that of AF algorithm in a single path relay network because the former is able to eliminate channel noise at each relay. For the multiple path relay network, however, the network structure is already resistant to noise and channel distortion, and AF approach is a more attractive choice due to its lower complexity.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.44 no.1
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• pp.106-112
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• 2007

A new space-time cooperative communication relaying strategy with assistant or management terminals is proposed in multi-hop wireless communication systems. More than one relaying terminals are included in one cooperative group to share the state information such as frame error rate and channel information. Among the cooperative group, the best ones are selected to send bit information using space-time codes. An implementation for the proposed scheme is also presented using a TDMA cooperative protocol. Receive signal to transmit signal ratio($E_r/E_s$) and computer simulation show the strategy outperform the conventional cooperative system.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.1A
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• pp.109-114
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• 2007

A new space-time cooperative communication relaying strategy with assistant or management terminals is proposed in multi-hop wireless communication systems. More than one relaying terminals are included in one cooperative group to share the state information such as frame error rate and channel information. Among the cooperative group, the best ones are selected to send bit information using space-time codes. An implementation for the proposed scheme is also presented using a TDMA cooperative protocol. Receive signal to transmit signal ratio($E_r/E_s$) and computer simulation show the strategy outperform the conventional cooperative system.

• Journal of Communications and Networks
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• v.12 no.4
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• pp.358-365
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• 2010

We develop a low complexity cooperative diversity protocol for low energy adaptive clustering hierarchy (LEACH) based wireless sensor networks. A cross layer approach is used to obtain spatial diversity in the physical layer. In this paper, a simple modification in clustering algorithm of the LEACH protocol is proposed to exploit virtual multiple-input multiple-output (MIMO) based user cooperation. In lieu of selecting a single cluster-head at network layer, we proposed M cluster-heads in each cluster to obtain a diversity order of M in long distance communication. Due to the broadcast nature of wireless transmission, cluster-heads are able to receive data from sensor nodes at the same time. This fact ensures the synchronization required to implement a virtual MIMO based space time block code (STBC) in cluster-head to sink node transmission. An analytical method to evaluate the energy consumption based on BER curve is presented. Analysis and simulation results show that proposed cooperative LEACH protocol can save a huge amount of energy over LEACH protocol with same data rate, bit error rate, delay and bandwidth requirements. Moreover, this proposal can achieve higher order diversity with improved spectral efficiency compared to other virtual MIMO based protocols.

• The Journal of Korean Academic Society of Nursing Education
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• v.23 no.3
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• pp.241-251
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• 2017

Purpose: The purpose of this study is to examine how the acceptance of diversity of nursing college students affects creativity and to verify empirically the role of individual cooperative learning competency and unlearning competency in such influence relations. Methods: This study surveyed 209 nursing college students and analyzed the structured questionnaire data using SPSS WIN 21.0 and AMOS 18.0. Results: The results of this study were as follows. First, the creativity of the subjects showed significant correlations with all other variables. Second, diversity openness directly affected creativity. We also confirmed that diversity openness and cooperative learning competency have a positive effect on creativity through mediating unlearning competency. Conclusion: In order to enhance the creativity of nursing college students, diversity openness should be actively reflected in the curriculum. In addition, concrete teaching-learning strategies should be developed in order to increase and enhance the unlearning competency and cooperative learning competency of nursing students.