• 한국통신학회논문지
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• 제40권5호
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• pp.809-811
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• 2015

In this paper, for the purpose of providing high data rate services, the multi-hop frame structure is designed for the underwater acoustic (UWA) short-range system which is proposed as a part of ocean surveillance and tracking network (OSTN). Under the measured underwater channel environment, the link-level system performance are also evaluated. Simulation results show not only the packet error rate (PER) comparisons, but the optimal modulation and coding scheme (MCS) levels for the orthogonal frequency division multiplexing (OFDM) based short-range UWA communications network.

• 정보와 통신
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• 제31권3호
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• pp.103-116
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• 2014

This paper proposes the design of Vehicular Cyber-Physical Systems (called VCPS) based on vehicular cloud for smart road networks. Our VCPS realizes mobile cloud computing services where vehicles themselves or mobile devices (e.g., smartphones and tablets of drivers or passengers in vehicles) play a role of both cloud server and cloud client in the vehicular cloud. First, this paper describes the architecture of vehicular networks for VCPS and the delay modeling for the event prediction and data delivery, such as a mobile node's travel delay along its navigation path and the packet delivery delay in vehicular networks. Second, the paper explains two VCPS applications as smart road services for the driving efficiency and safety through the vehicular cloud, such as interactive navigation and pedestrian protection. Last, the paper discusses further research issues for VCPS for smart road networks.

• 한국정보처리학회:학술대회논문집
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• 한국정보처리학회 2000년도 추계학술발표논문집 (하)
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• pp.1541-1544
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• 2000

본 논문은 이동 컴퓨팅 환경에서 실시간 데이터의 전송시 발생하는 패킷 손실에 관한 문제를 다룬다. 현재 인터넷 상에서의 실시간 데이터 전송은 주로 RTP/RTCP 프로토콜[1]을 이용하는데, 이 프로토콜은 안정된 전송을 보장받지 못하며, 따라서 패킷 손실을 피할 수 없다[2,3]. 특히, 제한된 무선 대역폭과 높은 BER(bit error rate) 특성을 갖는 이동 컴퓨팅 환경에서는 기존의 인터넷보다도 더 많은 패킷들이 손실될 수 있다. 본 논문에서는, 이동 컴퓨팅 환경에서 실시간 데이터 전송시 발생되는 패킷 손실 특성을, 길버트 모델에 기초하여 확률적으로 분석하고, 이를 기반으로 새로운 복구 방법을 제안한다. 제안하는 실시간 데이터의 복구 방법에서는 패킷에 부가하는 잉여 데이터의 개수를 가변적으로 조절함으로써, 사용 중인 네트워크의 패킷 손실 특성을 반영할 수 있다. 특히, 잉여 데이터들의 오프셋 값들을 비연속적으로 설정함으로써, 간헐적이거나 연속적인 패킷 손실 모두에 대처할 수 있는 특징이 있다.

• 한국정보처리학회:학술대회논문집
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• 한국정보처리학회 2016년도 춘계학술발표대회
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• pp.72-75
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• 2016

스마트폰, 센서, 소셜미디어, 웹 서비스 등으로부터 발생되는 데이터의 폭증으로 인하여 빅데이터의 분석 및 활용에 대한 요구가 커져가고 있다. 특히 스마트 기기의 발달과 사용자 이용 패턴의 변화로 인하여 스트림 데이터는 끊임없이 발생되고 있지만, 기존의 하둡을 이용한 분석 시스템은 응답시간이 지연되어 빠르게 결과를 조회할 수 없는 단점으로 인하여 데이터를 실시간으로 분석하여 바로 활용할 수 있는 시스템에 대한 요구가 점점 더 증가하면서 람다 아키텍쳐가 등장하였다. 람다 아키텍쳐는 데이터 처리 과정을 배치 레이어와 스피트 레이어로 나누고, 스피드 레이어에서는 배치 결과가 나오기 전까지 스트림으로 유입되는 데이터를 실시간으로 분석하여 가장 최근의 데이터를 빠르게 조회 할 수 있도록 결과를 제공한다. 본 논문에서는 람다 아키텍쳐를 활용하여 연속적으로 유입되는 대용량의 스트림 데이터를 효과적으로 처리하여 실시간 분석과 동시에 배치 분석을 제공하는 데이터 처리 시스템을 설계하고 구현한다.

• ETRI Journal
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• 제28권3호
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• pp.311-319
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• 2006

This paper presents a terminal-assisted frame-based packet reservation multiple access (TAF-PRMA) protocol, which optimizes random access control between heterogeneous traffic aiming at more efficient voice/data integrated services in dynamic reservation TDMA-based broadband access networks. In order to achieve a differentiated quality-of-service (QoS) guarantee for individual service plus maximal system resource utilization, TAF-PRMA independently controls the random access parameters such as the lengths of the access regions dedicated to respective service traffic and the corresponding permission probabilities, on a frame-by-frame basis. In addition, we have adopted a terminal-assisted random access mechanism where the voice terminal readjusts a global permission probability from the central controller in order to handle the 'fair access' issue resulting from distributed queuing problems inherent in the access network. Our extensive simulation results indicate that TAF-PRMA achieves significant improvements in terms of voice capacity, delay, and fairness over most of the existing medium access control (MAC) schemes for integrated services.

• ETRI Journal
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• 제30권4호
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• pp.495-505
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• 2008

This paper presents a parallel processing searcher structure for the initial synchronization of a direct sequence ultra-wideband (DS-UWB) system, which is suitable for the digital implementation of baseband functionalities with a 1.32 Gsample/s chip rate analog-to-digital converter. An initial timing acquisition algorithm and a data demodulation method are also studied. The proposed searcher effectively acquires initial symbol and frame timing during the preamble transmission period. A hardware efficient receiver structure using 24 parallel digital correlators for binary phase-shift keying DS-UWB transmission is presented. The proposed correlator structure operating at 55 MHz is shared for correlation operations in a searcher, a channel estimator, and the demodulator of a RAKE receiver. We also present a pseudo-random noise sequence generated with a primitive polynomial, $1+x^2+x^5$, for packet detection, automatic gain control, and initial timing acquisition. Simulation results show that the performance of the proposed parallel processing searcher employing the presented pseudo-random noise sequence outperforms that employing a preamble sequence in the IEEE 802.15.3a DS-UWB proposal.

• Journal of the Optical Society of Korea
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• 제11권3호
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• pp.93-96
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• 2007

We demonstrate a 240 km reach DWDM-PON at 8-Gb/s capacity based on wavelength-locked Fabry-Perot laser diodes and a bidirectional EDFA. We achieve a packet-error-free transmission in both the 64 upstream and 64 downstream channels, guaranteeing a 125 Mb/s symmetric data rate per user. There is no noticeable dispersion penalty. The power penalty due to the crosstalk induced by the DWDM transmission and detuning between AWGs is less than 1.2 dB, when the detuning is within ${\pm}0.12 nm$.

• 제어로봇시스템학회논문지
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• 제12궈1호
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• pp.23-27
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• 2006

As a pervasive healthcare application to help medication of elderly patients, the smart compliance monitors have been recently proposed. In this paper, we present a new smart drug/medicine pack (SDP) for ubiquitous medication monitoring, for which the packaging is either paper packet or blister pack. This ubiquitous compliance monitor is composed of several SDPs and a Bluetooth equipped PDA phone. The SDP is a wireless module that monitors the medication consumption unobtrusively by transmitting the sensed data of 'drug removal' events to the medical center and by reminding patients when they take a dose on their mobile phone. The communication between SDP modules and PDA is realized via Bluetooth. The PDA is basically embedded to indicate the medication record and to alert every prescribed medication time during treatment. Experimental results show that the proposed system works exactly when the SDPs are far within about 2 [m] from PDA.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2002년도 하계종합학술대회 논문집(1)
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• pp.287-290
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• 2002

This paper rotates to tile FPGA that is reffered to as the UTOSPI. The design goal of the FPGA is to convert the UTOPIA-3 bus interface to the SPI-3 bus interface, so that the SAR chips on the ATM interface board can be interfaced to the packet processor through this FPGA. We Propose a new architecture that has two Dual Port RAMs and flow control signals. To buffer data, the UTOSPI has a Dual port RAM in the receive direction and the same size of that in the transmit direction. This design has been implemented, compiled, and tested using a Xilinx Virtex-I XCV-300E FPGA.

• 전자공학회논문지B
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• 제32B권9호
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• pp.1162-1170
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• 1995

In this paper, we present a message transfer scheme for efficient message passing in the hierarchically structured multiprocessor computer SPAX(Scalable Parallel Architecture computer based on X-bar network). The message transfer scheme provides interface not only with operating system but also with end users. In order to transfer two types of control message and data message efficiently, it supports both of memory-mapped transfer and DMA-based transfer. Dual-port RAMs are used as message buffers, and control and status registers provide efficient programming interface. Interlaced parity scheme is adopted for error control. If any error is detected at receiving node, errored packet is resent by sender according to retry mechanism. In conjunction with retry mechanism, watchdog timers are used to protect infinite waiting and repeated retry. The proposed message transfer scheme can be applied to input/output nodes and communication connection nodes as well as processing nodes in the SPAX.