• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.12C
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• pp.1184-1191
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• 2009

We aim at frequency offset estimation for IEEE 802.15.4a ranging systems, where an impulse-radio ultra-wideband (IR-UWB) signal is exploited, By incorporating the property of the ternary code in the preamble, we derive a simplified maximum-likelihood (ML) estimation of the frequency offset. In addition, a closed form estimator for implementation is investigated. Simulation results and theoretical analysis verify our estimators in IEEE 802.15.4a IR-UWB packet-based ranging systems.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.19 no.1
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• pp.35-46
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• 1994

In this paper, the performance of DS/SS acquisition system over frequency nonselective Rician fading channel is analyzed by means of packet loss probability. The power ratio of the fading component to the specular compnent. seccessive constant fadong chips k. and correlation coefficient among k chipe are taken for channel parameters. The false alarm probabilities and detection probabilities are derived, and packet loss probability is evaluated in terms of these probablities in the stats transition diagram. From the results of the performance test, these exists the region of packet loss probability in crease because of autocorrelation sidelobe. As k increases, the packet loss probabolotoes decrease.

• Electronics and Telecommunications Trends
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• v.15 no.2 s.62
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• pp.15-31
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• 2000

IP 패킷스위칭을 수행할 수 있는 WDM 기반의 대용량 광패킷스위칭 시스템을 위해 입력광 신호 속도 10Gb/s의 16 x 단위 스위치로 구성되는 출력 버퍼링 방식의 방송 및 선택형스위치 구조가 제안되었다. 기존의 광소자는 광특성 때문에 집적광 집적화 논리회로(PCL)의 제작이 쉽지 않았으나 최근 세계적으로 어레이형 집적화 광소자의 개발 추세가 급속도로 진전되고 있어 대용량의 광교환기 시스템 구조는 기존의 교환기 시스템과 유사한 형태 및 구조가 가능하다.

• Journal of KIISE:Information Networking
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• v.29 no.6
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• pp.706-711
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• 2002

In this paper, we implement a diffserv-capable router on the linux system and evaluate its performance. The router supports the packet marking for the input finks that is different from the previous implementation. The edge diffserv-capable router can guarantee the performance of each class, even in a congested condition. We compare the performance of the diffserv-capable router with that of the normal router in terms of PDBs (per domain behaviors), which are defined with traffic conditioning rules and PHBs (per hop behaviors).

• Journal of the Institute of Convergence Signal Processing
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• v.1 no.2
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• pp.122-130
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• 2000

This paper mainly deals with the modified version of conventional PRMA(Packet Reservation Multiple Access). In the existing PRMA schemes, the occupied slot in the initial access state is not allowed to be reserved in the silent period and retrial of gaining the slot access has to pay additional packet dropping. Whereas in the modified model, we propose to utilize a control minislot that maintains slot reservation and this prevents additional packet drop occurrence since initial access, and this slightly improves the system performance.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.7 no.4
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• pp.97-106
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• 2008

This proposed system is a part of internal control system that national highway need to support their ITS information audit. This paper explains the design and implementation of a packet interceptor and a DB query analyzer. The packet interceptor sniffs users' query packets, and then the DB query analyzer parses the SQL queries and stores the users' DB access information such as SQL queries, access data and changing data. The information may be used as the evidences on internal control of users and users' accesses.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.41 no.9
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• pp.9-16
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• 2004

This paper proposes a performance analysis model of security servers comprising IPSec accelerators. The proposed model is based on a M/M1 queueing system with traffic load of Poisson distribution. The decoding delay has been defined to cover parameters characterizing hardware of security sorrels. Decoding delay values of a commercial IPSec accelerator are extracted yielding less than 15% differences from measured data. The extracted data are used to simulate the server system with the proposed model. The simulated performance of the cryptographic processor BCM5820 is around 75% of the published claimed level. The performance degradation of 3.125% and 14.28% are observed for 64byte packets and 1024byte packets, respectively.

• Journal of the Korea Society of Computer and Information
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• v.14 no.5
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• pp.149-156
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• 2009

Korean WiBro becomes international standard to IEEE 802.16e, and We are carrying out a WiBro network business from capital regions. We executed eavesdropping about voices and messenger program and the VoIP which frequently happened in WiBro networks at these papers. We have a lot in common with the Wireshark which is a packet collection and an analyzer, and We execute eavesdropping, and We reproduce eavesdropping data with bases to a SIP, H.263, TCP, UDP protocol through packets. In time of a copy of a packet negative the VoIP which verify time with bases, and was eavesdropped on integrity packet and a X-Lite call record, be matched that a packet is counterfeit forgery did not work, and We demonstrate, and verify integrity. The data which integrity was verified put in a seaming envelope, and we prepare so as it is to a liver of investigator, and execute, and to be able to do use to proof data after seaming in courts in order to utilize as criminal investigation data.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.19 no.4
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• pp.729-739
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• 1994

In a centralized spread-spectrum packet radio network, a random assignment -transmitter-based spreading code protocol(RA-T) is proposed which permits the contention mode only in the trasmission of a preamble while avoiding collision during the data packet transmission by assigning near-orthogonal spreading codes to each user. Compared to the conventional transmitter-based code scheme, this scheme allows reduction in receiver complexity when only a small number of distinct spreading codes are employed for the preamble transmission. Throughout theoretical and simulation results, it is shown that the use of the RA-T scheme with just two or three distinct codes for the preamble packet achieves most of the performance gain.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.20 no.8
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• pp.1438-1443
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• 2016

In this paper, we investigate the effect of multiple antennas at a relay node on the performance of physical-layer network coding (PNC) in the two-way relay channel (TWRC). We assume that two source nodes have a single antenna and the relay node has multiple antennas. We extend the conventional TWRC environment with a signle antenna at both relay and source nodes to the case of multiple antennas at the relay node. In particular, we consider two decoding strategies: separate decoding (SD) and direct decoding (DD). The SD decodes each packet from the two sources and performs the network coding with bit-wise exclusive OR (XOR) operation, while the DD decodes the network-coded packet from the two sources. Note that both decoding strategies are based on log-likelihood ratio (LLR) computation. It is shown that the bit error rate (BER) performance becomes significantly improved as the number of antennas at the relay node.