• Information and Communications Magazine
• /
• v.21 no.5
• /
• pp.70-79
• /
• 2004

최적 경로 서비스를 제공하기 위해서는 구간 통행속도, 구간 통행시간, 회전 정보, 혼잡도 등과 같은 교통정보가 필요하다. 또한, 고객에게 신뢰성 있는 최적 경로를 제공하기 위해서는 실시간 교통정보 수집은 반드시 필요하며, 이러한 실시간 교통정보 수집 방법들에 대한 고찰과 검토가 선행되어야 한다. 기존의 교통정보 수집방법을 살펴보면 지점검지 방식의 경우, 수집되는 정보가 검지기 설치 지점의 지점속도(Spot Speed)이므로 해당 링크를 주행한 통행속도(통행시간)의 대표값으로 채택하기에는 다소 무리가 있으며 구간검지 방식의 경우, 일반적으로 급격한 교통류 변동에 따른 대기행렬 검지가 늦다는 단점이 있다.(중략)

• Journal of Information Technology and Architecture
• /
• v.10 no.3
• /
• pp.305-313
• /
• 2013

Ground troops as part of the implementation of the real-time visualization of battlefield tactics to ensure the exchange of information sharing and situational awareness for the ground tactical data link system development is underway. However, with the existing inorganic KVMFbased weapon systems and tactics Quarterly problem occurs because the information has not been in development or in the development of future weapons systems based KVMF share battlefield information to enable interoperability building measures is presented.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.35 no.2C
• /
• pp.229-237
• /
• 2010

The conventional detection methods developed for spatially-multiplexed MIMO systems such as OSIC and QRD-M show performance difference for each user depending on the order of detection when they are applied to detection of multi-user signals in uplink multiuser systems based on collaborative spatial multiplexing. In this paper, a signal detection method for uplink multiuser systems based on collaborative spatial multiplexing is proposed to provide similar performance for each user while its performance is close to the case of ML detection. Compared with QRD-M method, computational complexity of the proposed signal detection method is similar in the case of QPSK, and significantly lower in the case of high modulation order with 16-QAM and 64-QAM.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.34 no.12A
• /
• pp.941-948
• /
• 2009

In the 3GPP LTE systems, SC-FDMA is adopted for the uplink owing to its good PAPR efficiency. In the frequency domain, however, the performance of SC-FDMA is degraded due to frequency selective fading. As a compromise, a Hybrid OFDMA/SC-FDMA was proposed in the LTE-Advanced systems. Hybrid scheme uses SC-FDMA in the edge of cell area, while it uses OFDMA nearby the base-station. In this paper, uplink relays based on hybrid scheme is proposed to increase the performance of the 3GPP LTE systems. With different positions of mobile and relay, the proposed scheme can adaptively select SC-FDMA or OFDMA to improve the link performance. Our simulation results show that the proposed scheme achieves a better performance in terms of end-to-end BER and power consumption.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.35 no.1C
• /
• pp.103-112
• /
• 2010

In this paper, we propose a coarse and fine frequency synchronization method which is suitable for the 3GPP(3rd Generation Partnership Project) LTE(Long Term Evolution) FDD(Frequency Division Duplexing) / TDD(Time Division Duplexing) dual mode system. In general, PSS(Primary Synchronization Signal) correlation based estimation method and CP(Cyclic Prefix) correlation based tracking loop are applied for coarse and fine frequency synchronization in 3GPP LTE OFDMA(Orthogonal Frequency Division Multiple Access) system, respectively. However, the conventional coarse frequency synchronization method has performance degradation caused by fading channel and squaring loss. Also, the conventional fine frequency synchronization method cannot guarantee stable operation in TDD mode because of signal power difference between uplink and downlink subframe. Therefore, in this paper, we propose enhanced coarse and fine frequency synchronization methods which can estimate more accurately in multi-path fading channel and high speed channel environments and has stable operation for TDD frame structure, respectively. By computer simulation, we show that the proposed methods outperform the conventional methods, and verify that the proposed frequency synchronization method can guarantee stable operation in 3GPP LTE FDD/TDD dual mode downlink receiver.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.38A no.5
• /
• pp.393-400
• /
• 2013

In conventional single-tier networks, downlink based association is the best association scheme for the uplink association because all macro base stations have the same physical specification. However, in uplink heterogeneous cellular networks, a downlink based cell association cannot be the best for uplink any more because of the difference of physical specification between the different base station. In this paper, we will propose a uplink based cell association scheme, and devise performance metric for describing a uplink performance in heterogeneous cellular networks. Then, we will discuss the necessity of the uplink based association by observing outage probability, delay constraint outage probability, delay constraint outage capacity.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.25 no.11A
• /
• pp.1642-1651
• /
• 2000

위성통신시스템에서의 10GHz이상의 Ku 또는 Ka 대역은 수십 dB의 크기를 갖는 강우에 의한 감쇠 현상이 심각하여 이러한 감쇠는 위성 링크의 심각한 성능 정하를 가져온다. 본 논문은 위성통신 링크 상에서의 강우 감쇠 보상을 위한 알고리즘을 제시하고, Ku 대역의 강우 감쇠 데이터를 사용한 시뮬레이션을 통하여 그 성능을 비교 분석하였다. 예측 기법 측면에서, 적응형 알고리즘을 적용한 기법과 신호 레벨 변화량에 근거한 예측 기법은 거의 동일한 예측 오차를 보였고, 따라서, 급속한 신호레벨 변화에 적응성을 요하지 않은 강우 감쇠 예측의 경우, 알고리즘 측면에서 비교적 간단한 예측 기법으로도 충분한 성능을 얻을 수 있음을 확인하였다. 또한, 제시된 전송 방식 결정 알고리즘은 기존의 임계값 기반 알고리즘에 비해 품질 저하율이 0.6%에서 0.01% 이하로 감소하였고, 거의 동일한 전송 효율을 가지면서 약 5배의 적은 전송 방식 전환을 요구한다.

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

• Proceedings of the Korean Information Science Society Conference
• /
• 2006.06c
• /
• pp.79-81
• /
• 2006

최근 이질 분산형태를 갖는 정보를 통합하는 방법으로서 웹 서비스 기술을 이용한 바이오 정보 시스템이 개발 구축되고 있다. 이러한 웹 서비스 기반 바이오 정보 시스템으로 Bio-MOBY. DDBJ, MyGrid Project 등을 들 수 있다. 그러나 이들 기존 시스템에서는 선택한 DB에 대한 accession 번호 검색을 지원하거나. 시스템에 등록된 서비스의 선택만이 허용되는 등 이용형태가 매우 제한적이다. 또한 서비스의 품질 평가 기능이 제공되지 않아 서비스의 관련성을 판별하지 못하며, 심지어 링크가 바르게 연결되지 않았거나, 작동하지 않는 서비스의 분별조차 불가능한 실정이다. 본 논문에서는 이러한 문제점을 해결하고자 서비스 검색과정에서 웹 서비스의 품질을 평가하고 평가된 품질을 기반으로 웹 서비스를 순위화해 사용자에게 제공하는 품질기반 UDDI를 제안한다. 이를 위해 우리는 Gene Ontology를 이용한 연관 키워드 검색방식과 키워드 기반의 서비스 품질 평가 방법을 제안하고, 본 방식의 유용성을 보인다.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.31 no.3A
• /
• pp.254-266
• /
• 2006

Recently, researches about downlink resource allocation algorithms applying SDMA to enhance the system throughput and cell coverage have begun. Most OFDM/SDMA based resource allocation algorithms have some limitations such that those only concentrate on maximizing the system throughput or can be applied in single cell environment. In this paper, we propose an OFDM/SDMA based downlink resource allocation algorithm which considers high layer QoS parameters suitable for the required data traffic and it also minimizes the system throughput loss and considers inter-cell interference from adjacent cells. so it can be adopted in multi-cell environment. We manifest the performance of the proposed algorithm in Ped A and SCME MIMO Channel Model.