• Journal of Satellite, Information and Communications
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• v.5 no.2
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• pp.64-68
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• 2010

In this paper, we studied the novel synchronization algorithm for cooperative communication system over fading. We research mainly on the decode-and-forward scheme. Also, we inserted spreading sequence in origin data frame to control efficiently data synchronization. In mobile station, inserted spreading sequence in data frame passed through the corelation process. We had decide the delay value of received data through result of correlation process. In simulation, We applied that channel gain of three node had different value in various fading environment. Finally we will be possible to control the received data synchronization using result of corelation value in each node between relay to mobile station and base station to mobile station. The results of this paper can be applicable to the cooperative systems.

• The Journal of Korean Association of Computer Education
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• v.14 no.5
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• pp.97-104
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• 2011

Collaborative filtering is a methodology to recommend websites by obtaining data and opinions from the other users with similar tastes. During the past few years, this method has been used in various fields such as books, food, and movies in e-commerce systems. This study addresses the computation of similarity between users to determine items to be recommended in collaborative filtering systems. Previous studies measured similarity between users by treating each user's ratings independently without considering the distribution of the user's ratings. In contrast, this study measures similarity by utilizing position and rank information of each rating in the range of the user's ratings. The result of the experiments on the real datasets demonstrated that the proposed method improves the mean absolute error significantly, compared to the previous methods, especially when the predetermined range of ratings is large.

• Journal of Satellite, Information and Communications
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• v.5 no.1
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• pp.22-26
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• 2010

In this paper, we propose an effective method for detecting signals among multi-user in cooperative communication system. Spread sequence is inserted to NULL space of synchronization channel to synchronize between each user among frame formats of the cooperative communication and then transmitted. In the receiver, the wanted signal is detected by using correlation among the inserted spread sequences. As simulation results, correlations among the signals using Kasami/Walsh sequence in AWGN, Rician, and Rayleigh channel are shown. Using the simulation results in this paper, we expect a reliable cooperative communication.

• Annual Conference of KIPS
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• 2015.10a
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• pp.1618-1621
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• 2015

본 훈련 시스템은 재난유형별 국가재난대응시나리오 기반의 대응체계를 바탕으로 재난의 종류나 규모, 복잡성 등과 무관하게 유관기관의 재난관리 관계자를 위한 교육 평가를 통해 표준화된 교육 훈련 평가체계를 확립한다. 이를 위해 국내와 해외의 사례에서 조사된 내용의 특 장점 및 표출형태를 고려하여 재난대응역량 강화를 위한 재난 발생 시나리오 기반의 텍스트 위주의 훈련용 웹 시스템을 개발한다. 무엇보다도 현실적으로 지역의 위험과 위협을 대표하는 검증된 유형별 시나리오를 기반으로 예방(Mitigation) 대비(Preparedness) 대응(Response) 복구(Recovery) 단계의 복잡 다양한 재난상황에 대한 재난대응역량 및 상황대처 능력을 향상시키기 위한 훈련지원 교육으로 활용하기 위한 사용자 확장성이 유용한 훈련용 웹 시스템을 개발한다. 이를 통해 사전에 유관기관과의 협력강화를 위한 원활한 재난대응 협력체계 강화방안을 수립하고 재난현장 협력업무와 관련된 필요역량을 도출하는 등의 활동과, 이에 대한 실효성 있는 평가로 재난현장의 기관간 상호협력 능력을 제고할 수 있다. 또한 대응기관의 역량수준을 점검하고, 대응역량에 대해 부족한 부분을 보완하여 효율적 재난대비태세 구축하여, 재난피해를 최소화하는 효과를 기대할 수 있다.

• The KIPS Transactions:PartC
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• v.14C no.7
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• pp.597-602
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• 2007

In conventional cooperative communication data rate is 1/2 than non cooperative protocols. In this paper, we propose a full data rate DF (Decode and Forward) cooperative transmission scheme. Proposed scheme is based on time division multiplexing (TDM) channel access. When DF protocol has full data rate, it can not obtain diversity gain under the pairwise error probability (PEP) view point. If it increases time slot to obtain diversity gain, then data rate is reduced. The proposed algorithm uses orthogonal frequency and constellation rotation to obtain both full data rate and diversity order 2. Moreover, performance is analyzed according to distance and optimized components that affect the system performance by using computer simulation. The simulation results revealed that the cooperation can save the network power up to 7dB over direct transmission and 5dB over multi-hop transmission at BER of $10^{-2}$. Besides, it can improve date rate of system compared with the conventional DF protocol.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.3C
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• pp.255-263
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• 2010

In this paper, we present an efficient cooperative transmission scheme for high speed 60GHz WPAN system. In 60GHz, the cooperative transmission with relay is effective scheme because signals are exceedingly attenuated according to the distance and the transmission is impossible when there is no LOS between transmitter and receiver. Moreover, the reliability of signal in destination can be improved by receiving data from a relay as well as a transmitter. However, the overall data rate is reduced because transmission time is more required for relay. To solve this problem, we propose a cooperative transmission scheme with RS-CC serial concatenated codes. In the proposed cooperative transmission scheme, the relay can reduce the transmission data size because the only parity bits of systematic RS code are transmitted after encoding by CC. But the computational complexity is increased at the relay and the destination.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.12 no.4
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• pp.31-36
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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-Premises equipments) which causes low SNR (signal-to-noise ratio) problem. In cooperative communication system, AF (amplify-and-forward) and DF (decoded-and-forward) is widely used for relay mechanism. Also, it 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.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.7
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• pp.1397-1405
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• 2012

Cooperative communications play a important role in increasing frame transmission rate at wireless communication networks where frequency resource is strictly limited. In this paper, we did a research on how to select the helper nodes that are very import in cooperative communications. As a prelude study in this research field, we carried out performance comparison of three helper node selection schemes using computer simulation. The system throughput was used as the performance measure and the random way point mobility model, where every communicating nodes move around within the designated communication range, was used.

• Journal of Korea Game Society
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• v.12 no.4
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• pp.3-12
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• 2012

This study discusses how players make the mutually cooperative mechanism in Social Games. In SNG, many players exchange helps each other. That mechanism is not only one-off but also repetitive process. In the perspective of reciprocity in Evolutionary psychology and Mythology, this study analyzes mutual cooperation in several game texts most well known in the SNG field. According to the field study results, four cooperative mechanisms were extracted. These 4 principles apply to every digital game design for emerging of cooperative storytelling among players.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.7C
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• pp.435-442
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• 2011

The MIMO has weak points such as size and cost of systems and the complexity of hardware augment. Thus, the cooperative transmission techniques have been recently discussed briskly and it also solves problems by increase of shadowy area. However, limited cooperation scheme is utilized due to a single-antenna at the destination. The base station is simply equipped with multiple antennas. When the base station has multiple antennas, cooperative diversity and multiplexing schemes can be easily applied in the base station. To guarantee reliability with high throughput, a cooperative hybrid cyclic relay diversity transmission scheme is proposed which can use an arbitrary number of relays without rate loss and a modification of the base station. The presented results show that the proposed schemes can be effectively applied to the existing various MIMO-OFDM communication system.