• Proceedings of the Korean Institute of Communication Sciences Conference
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• 2004.07a
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• pp.31-31
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• 2004

• Information and Communications Magazine
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• v.25 no.5
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• pp.38-46
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• 2008

협력 다이버시티 기술은 최근 수년간 MIMO(Multiple-Input-Multiple-Output) 기술의 실질적인 대안으로, 애드 혹 네트워크에서의 MIMO 기술로, 셀룰러 시스템에서의 커버리지 확장 기술로 주목을 받아 왔다. 따라서, 협력 다이버시티 기술은 응용 목표에 따라 방식이 다르게 존재하게 된다. 이 논문에서는 기존의 협력 다이버시티 기술들을 몇 가지 일관된 기준으로 분류하여 보고, 이 분야에서 미진한 연구방향으로 다중사용자 환경에서의 협력 다이버시티 기술과 다중 안테나 노드를 위한 협력 다이버시티 기술을 제시한다.

• Proceedings of the Korea Information Processing Society Conference
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• 2003.05a
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• pp.39-42
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• 2003

셀룰러 네트워크의 발전과 카메라 부착이 가능한 핸드폰 증가와 같은 발전에 따라서 핸드폰에서 비디오 인코딩을 가능하게 하는 핸드폰에 대한 수요가 증가하고 있다. 그러나 현재의 시스템은 별도의 하드웨어 부착 없이는 핸드폰에서 비디오 인코딩을 하는 것이 불가능하다. 이 논문에서는 별도 하드웨어 부착 없이 가능한 소프트웨어 인코더를 설계/구현하고, 그에 따른 실험 결과와 문제점을 보여준다.

• Electronics and Telecommunications Trends
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• v.10 no.4 s.38
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• pp.57-83
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• 1995

이동통신과 관련된 표준은 코드리스폰과 셀룰러 이동전화에서 독립적으로 시작되어 PCS, UPT, FPLMTS의 통합된 규격으로 발전하고 있다. 본 고는 먼저 이동통신 발전동향에 대하여 기술하였고, 망구조 및 구성요소간의 통신 및 망간 통신에 필요한 시그널링, 지능망 그리고 지능망을 이용하여 가입자에게 제공되는 UPT 및 개인통신서비스에 대하여 기술하였다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38A no.5
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• pp.451-458
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• 2013

This paper proposes a cross-tier interference avoidance scheme to improve femtocell performance in single frequency heterogeneous cellular networks (SFHCN). The scheduled macrocell users located close femtocell base stations cause serious interference to those femtocells so that the performance of femtocell is dramatically deteriorated. To solve this problem, this paper proposes an interference avoidance scheme by reversing the uplink and downlink frames of such femtocells. After reversing the uplink and downlink frames, femtocell base station relays the macrocell user data as well as transmitting its own data. In the 1st relaying link, femtocell and macrocell users transmit their data respectively divided uplink frames and in the 2nd relaying link, femtocell base station transmit macrocell and femtocell data using a simultaneously superposition coding scheme. Computer simulation results confirm performance improvement of proposed scheme.

• Journal of IKEEE
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• v.13 no.4
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• pp.75-81
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• 2009

The cellular system in the next generation decreases the range of transmission of a signal as well as increases the rate of transmission adapting the method of multi-hop relaying with the relay. However, the fact of decreasing the range of transmission with the method of multi-hop relaying means increasing interferential amount in the outer cell; therefore, the deployment of the relay can affect to the function of the cellular system. In this thesis, the deployment of the relay is determined for the maximum rate of transmission, based on the transmission power of the relay and the variation of interferential amount. The condition to determine the deployment of the relay is analyzed with the mathematical model; in addition, its performance is verified through the result of a simulation. Based on the analysis of this thesis, the established deployment and transmission power of the relay to minimize the average outage probability exist. Furthermore, the relay contributes to enlargement of capacity of cells, decreasing the average outage probability in the situation of less severe interference between cells with reuse of frequency. However, the relay should be restrained in use in the situation of severe interference between cells due to the fact that the outage probability of inter-cells can be increased.

• Journal of Internet Computing and Services
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• v.11 no.3
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• pp.43-51
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• 2010

In this paper, we evaluate the system throughput and the method of optimal wireless resource allocation for the access zone (AZ) and relay zone (RZ) in downlink when the cell coverage is extended using the non-transparent Relay Station (RS) in a 2-hop cellular relay system based on IEEE802.16j, which uses the OFDMA-TDD structure. For the analyses, we first introduce the MAC (Media Access Control) frame structure in the non-transparent mode, then we investigate the interfering elements in both AZ and RZ for the network devices such as the Mobile Station (MS) and RS. Through computer simulation, we analyze the cell coverage extension and system throughput in terms of the distance between Base Station (BS) and RS, then we present the amount of the optimal allocation of wireless resource for the AZ and RZ in downlink using our results.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.5 s.108
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• pp.451-460
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• 2006

We have designed local exposure systems for long-time mice experiments in PCS and cellular frequency band(PCS: 1,762.5 MHz, cellular: 848.5 MHz). The fabricated systems are local exposure systems of carousel type, and 40 mice can be exposed at a time. In order not to give extra stress to the mice ender experiment, the systems were fabricated to meet the environmental conditions such as illumination, ventilation, noise etc. SAR measurement was performed using a temperature probe. Measurements at 3 points in the head of mouse cadaver and solid phantom were made, and it has been confirmed that the measurement results are in good agreement with the simulation results in the real exposure environment. The exposure systems are currently used for long-term mice experiments.

• The KIPS Transactions:PartC
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• v.11C no.2
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• pp.193-202
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• 2004

Handoff if the most Important feature for the user's mobility in a cellular communication system, which is related to resource reservation at nearby cells. For efficient resource reservation, mobility prediction has been reported as an effective means to decrease call dropping probability and to shorten handoff latency in wireless cellular environments. Several early proposed handoff schemes making use of tile user's movement history on a cell-by-cell basis work on the assumption that the user's movements are restricted to the indoor locations such as an office or a building. However, those algorithms cannot be applied to a micro-cell structure or a metropolis with complicated structure of roads. In this paper, to overcome those drawbacks we propose a new mobility prediction algorithm, which stores and uses the history of the user's positions within the current cell to predict the next cell.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.21 no.3
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• pp.537-542
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• 2017

In this paper, we propose a new scheduling scheme to reduce the complexity and overhead in TDD uplink cellular networks. In a TDD network, users can estimate the interference causing to neighboring BSs by measuring the signals transmitted from them. In the existing max SGIR scheduling scheme, each user calculates SGIR and feeds back to BS. Then, the BS selects a user having the largest SGIR value to transmit data. This scheme has a problem that as the number of BSs increases, the number of interference channels to be measured by the users increases, and thus the hardware and algorithm complexity of the user increases. We propose a max SmGIR (Signal-to-max generating interference ratio) scheduling scheme that can reduce the user complexity by predicting the SGIR value based on only the largest interference information. According to computer simulations, the proposed scheme has similar performance to the existing max SGIR scheme despite this low complexity.