• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.12
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• pp.2549-2558
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• 2015

The non-orthogonal multiple access (NOMA) is one of the fledging paradigms which next generation radio access technologies are sprouting toward. The NOMA with superposition coding (SC) in the transmitter and successive interference cancellation (SIC) at the receiver comes with many desirable features and benefits over orthogonal multiple access (OMA) such as orthogonal frequency division multiple access (OFDMA) adopted by Long-Term Evolution (LTE). In this paper, we study the recent research trends on NOMA in 5G systems. We discuss the basic concept of NOMA and explain its aspects of importance for future radio access. Then, we provide a survey of the state of the art in NOMA for 5G systems in a categorized manner. Further, we analyze the NOMA performances with numerical examples; and provide some avenues for future research on NOMA on a set of open issues and challenges.

• Journal of Korea Society of Industrial Information Systems
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• v.9 no.2
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• pp.89-95
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• 2004

CDMA is the way that more than one users can share the time and frequency at the same time and connect with multiple access in mobile communication. Multiple Access is indispensible for mobile communication because the limited frequency is able to be used by many users in mobile communication. CDMA is also applied to home network, military, business and medical sectors. This paper, presents a users should share limited frequency resource. CDMA module implemented with 8-layer PCB which consists of the Slice-board circuit, keeping Radio frequency characteristics and a slot type connector.

• The Magazine of the IEIE
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• v.33 no.12 s.271
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• pp.51-68
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• 2006

지난 수십 년간 인터넷망은 세계 도처를 연결하면서 인터넷 사용자의 수를 기하급수적으로 늘렸으며, 웹에서부터 P2P에 이르는 다양한 응용들을 지원하는 글로벌 인프라로 자리 메김 하였다. 기존 인터넷의 철학은 응용 서비스간의 품질 구분이 없이 공정히 사용하자는 철학에 근거해 인터넷 서비스 제공자의 접속료만 지불하고 사용하여 왔으며 인터넷에 초보 사용자에서부터 고급 사용자에 이르기까지 사용자의 능력에 맞게 다양한 정보를 제공하는 장이 되어왔었다. 이는 기존 인터넷 기반 서비스들이 품질에 차등적으로 요금이 지불되는 형태가 아니었기 때문에 가능했으나 최근 몇 년간은 다수의 서비스 제공자들이 인터넷 인프라의 고도화를 통해 IPTV, VoIP, Video Conferencing과 같은 통신, 방송 및 유선 무선 통합 서비스를 품질 차등적으로 제공하는 비즈니스 환경으로 변화를 시도 중에 있다. 이러한 큰 변화의 중심에는 해결해야 되는 다양한 기술적인 문제들이 남아 있으며, 이중 QoS 이슈는 문제의 핵심이다. QoS는 트랙픽 관리, 제어 및 모니터링 분야로 대별되는 본고에서는 이에 대한 해결책으로 제안 되고 있는 다양한 기술 및 표준에 대한 동향을 소개한다.

• Proceedings of the Korean Information Science Society Conference
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• 2001.04a
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• pp.487-489
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• 2001

인터넷과 무선 이동통신 등이 보편화되면서 두 기술을 접목한 WAP(Wireless Application Protocol)[1]이 등장하였으며, 다수의 사용자 요구를 동시에 효율적으로 처리하면서 다양한 문서 단말기로부터 요청을 신속하게 처리할 수 있는 WAP 게이트웨이(gateway)에 대한 연구가 여러 연구 그룹에서 수행되고 있다. WAP 스택은 이러한 연구 중의 가장 기본적인 기술이다. 본 논문에서는 Java의 기본적인 서비스인 멀티쓰레드를 이용하고, 컨테이너 유효 리소스의 효율적 관리를 위해 접속 풀링(connection pooling) 기능을 적용하여 UDP(User Datagram Protocol)[4], WTP(Wireless Transaction Protocol)[2], WSP(Wireless Session Protocol)[3] 계층을 설계한다. 설계 방법론은 UML(Unified Modeling Language)을 사용한다.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.22 no.6
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• pp.648-653
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• 2011

In this paper, coordinated space division multiple access(SDMA) technology is proposed to mitigate inter-cell interference by using partial channel state information in cooperative wireless communications system with limited feedback. Each AT selects an optimal cluster transmission mode and sends it back to a cluster scheduler, and at the cluster scheduler, ATs are scheduled within a AT group with the identical cluster transmission mode, and the optimal transmission mode and the corresponding scheduled ATs are determined to maximize scheduling priority. Also, in order to enhance multiuser diversity gain, an extended transmission feedback method is proposed to feed back multiple preferred cluster transmission modes at each AT. It is shown that the proposed coordinated SDMA scheme outperforms existing non-coordinated SDMA schemes in terms of the average system throughput.

• Journal of the Korea Computer Industry Society
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• v.5 no.5
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• pp.761-770
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• 2004

The multicarrier direct sequence code-division (MC-DS/CDMA) is a well-known multiple access and data transmission scheme that is applicable for various mobile and wireless communications. Particularly for modern, smart vehicles equipped with multiple sensors, MC-DS/CDMA is one of the possible means for giving the sensors to get connected one another for sending and receiving messages and control information. For intra-vehicalur communicaiton and networking applications, we have proposed a novel MC-DS/CDMA multiple access and data transmission scheme incorporating a new idea of inserting sub-symbol based cyclic prefixes for compromising inter-symbol interference. In the performance investigation of our MC-DS/CDMA, we have looked into system performances related to bandwidth utiltzation, coding gain, and multiple number of sensors. Since the channel delay is comparatively shorter inside of vehicle than any other general mobile channels, the proposed scheme can be a successful candidate for networking wireless sensors simultaneously operting in an intelligent vehicle.

• Journal of Korea Society of Industrial Information Systems
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• v.15 no.4
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• pp.7-15
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• 2010

This study proposes a rad o resource management scheme to maximize the performance of the LTE(Long Term Evolution) uplink, using SC-FDMA(Single Carrier-Frequency Division Multiple Access). Rather than the single-cell SC-FDMA system the existing studies are mainly concerning, this study focuses on multi-cell system which needs considering the interaction among cells. Radio resource management is divided into two phases, planning and operation phases. The former is for the master eNB(e-NodeB) to allocate RBs(radio bearer) to eNB, the latter for eNB to assign RBs to the mobiles in the cell. For each phase, an optimization model and greedy algorithm are proposed. Optimization models aim to maximize the system performance while satisfying the constraints for both QoS and RB continuity. The greedy algorithms, like generic ones, move from a solution to a neighboring one having the best objective value among neighboring ones. From the numerous numerical experiments, the performance and characteristics of the algorithms are analyzed. This study is expected to play a volunteering role in radio resource management for the multi-cell SC-FDMA system.

• Proceedings of the Korea Information Processing Society Conference
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• 2006.05a
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• pp.1203-1206
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• 2006

무선 인터넷이 보급됨에 따라 개인 휴대용 단말 장치(PDA)와 같은 모바일 PC를 이용하여 실시간으로 Server에 접속, 의료정보 및 환자 정보 등을 볼 수 있다. 여기서 PDA는 작은 몸체로 이동성 및 편리성 등이 PC보다 뛰어나지만, 처리 속도가 상대적으로 느리기 때문에 해상도가 큰 이미지, 높은 처리 속도를 요구하는 작업 등을 처리하기에는 효율성이 낮은 문제점이 있다. 또한 정보를 Display할 수 있는 액정이 매우 작아서 환자와 관련된 의료 영상 즉, MRI 사진이나 X-ray 사진 등을 자세히 보기에는 현재의 기술력으로는 매우 어렵다. 특히 다수의 PDA와 PC 클라이언트의 데이터 요청으로 인한 서버의 과부하 문제 또한 모바일 진료시스템의 발전에 걸림돌이 되고 있다. 따라서 본 논문에서는 처리 속도와 Display의 제한을 대처하기 위하여 모바일 다중처리 시스템과 작업 이양 시스템을 구성하기 위한 하나의 방법론을 제안한다.

• Journal of Convergence Society for SMB
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• v.6 no.3
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• pp.21-27
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• 2016

In this paper, we introduce the PB/MC-CDMA (Partial Block/Multi-Carrier-Code Division Multiple Access) system to mitigate inter-cell interference (ICI) and enhance user capacity in the small cell environment. In 5G mobile communications, the number of devices connected to the network is expected to increase exponentially with the expansion of the IoT (Internet of Things) services. In addition, each device is expected to be required by the various data rates by their content types. In LTE/LTE-A, there are some limitations that large scale connectivity and supporting various data rates. Therefore, we introduce a PB/MC-CDMA physical layer system which is suitable for the small cell environment, and evaluate the performance in the multi cell environment which is affected by ICI. Through computer simulation results, we demonstrate the effectiveness of PB/MC-CDMA for the small cell environment.

• Journal of Korea Multimedia Society
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• v.10 no.1
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• pp.66-73
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• 2007

SDR technology is a fundamental wireless access technology that combines and accommodates multiple wireless communication standards in one transceiver system through just modifying software using modular communication platforms without any hardware modifications for RF and IF signal processing on the basis of high performance DSP devices. Various communication systems that are designed under diverse and complex network environments require the communication platforms on the basis of SDR supporting reorganization to guarantee simple and fast communication interfaces among the respective wireless networks. This paper introduces a main idea on the implementation of platform on the basis of SDR and a communication platform is designed for experiments that is composed of a DSP board with TMS320C6713 CPU, a FPGA board processing IF signals, and a module with RF transceiver processing wireless LAN frequency bandwidth. Various modulation schemes(BPSK, QPSK, and 16QAM) used in communication systems are applied and tested on the designed platform and the test results shows that it is possible to design a reconfigurable communication terminal platform.