• Journal of Korea Society of Industrial Information Systems
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• v.15 no.2
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• pp.23-30
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• 2010

This paper presents implementation details of car communications system based on V2I2V model over broadband wireless networks including WCDMA, HSDPA and WiBro. Also, we measures the major performance metrics such as Round Trip Time, end-to-end latency and others between in-vehicle client and location management system by driving across urban areas in Daegu city. Analysis of experimental results would be helpful to consider the applicability of traffic safety services using V2I2V-based car communications over various broadband wireless networks.

• Proceedings of the Korean Information Science Society Conference
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• 2008.06d
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• pp.440-443
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• 2008

WCDMA 시스템에서 radio link간에 data를 주고 받고 신뢰성 있는 data를 검증하는 layer가 RLC이다. RLC에서는 전송 측에서 전송한 data가 수신 측에 잘 전송이 되었는지 status report를 확인을 받고 전송이 이루어지지 않았을 경우 재전송을 한다. 재전송 메커니즘에는 poll 및 status 관련 timer가 존재하면 이러한 파라미터값을 적절히 사용하지 않으면 불필요한 data의 재전송으로 인한 radio resource 낭비 및 시스템 throughput에 영향을 준다.

• Proceedings of the IEEK Conference
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• 2001.06a
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• pp.45-47
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• 2001

본 논문은 WCDMA 시스템의 역방향 링크에서의 빔포밍 적용에 관하여 기술하였다. 제안된 빔포밍 구조는 제어채널의 파일럿 심볼을 이용한 빔포밍 계수계산과 데이터 채널에 적용하는 분리구조를 가지고 있다. 적응 빔포밍의 대표적 방식인 LMS 알고리즘과steering 알고리즘을 적용하여 성능 분석과 시뮬레이션을 수행하였으며, 다양한 환경 변수에 따른 시뮬레이션 결과는 빔포밍 알고리즘의 구현과 설계에 있어 중요한 지침을 주리라 기대된다.

• Proceedings of the KIEE Conference
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• 2001.07d
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• pp.2502-2504
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• 2001

본 논문은 WCDMA 시스템의 역방향 링크에서의 빔포밍 적용에 관하여 기술하였다. 제안된 빔포밍 구조는 제어채널의 파일럿 심볼을 이용한 빔포밍 계수 계산과 데이터 채널에 적용하는 분리구조를 가지고 있다. 적응 빔포밍의 대표적 방식인 LMS 알고리즘과 steering 알고리즘을 적용하여 성능 분석과 시뮬레이션을 수행하였으며, 다양한 환경 변수에 따른 시뮬레이션 결과는 빔포밍 알고리즘의 구현과 설계에 있어 중요한 지침을 주리라 기대된다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2002.11a
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• pp.209-212
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• 2002

The realization for code domain analyzing system on WCDMA is presented. This system is realized with the RF, FPGA and DSP processor. The FPGA firgures out the scambling code, and DSP produces the power of code domain using OVSF. The experiment results allow the code domain power accuracy to keep $\pm$1dB low. This system leads to split the text, sound and image signal.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.3A
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• pp.269-276
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• 2008

In this paper, we analyze the M-WiMAX UL capacity limits under 2-Tier cell layout, considering the effects of random user position, path loss models, fading channel and adjacent channel interference from WCDMA system. In order to make the analysis approximate to the practical system capacity, we propose a MCS-based capacity analysis method considering the effects of PER requirement and the utilized MCS levels in M-WiMAX system. The proposed MCS-based method is validated through a system-level Monte Carlo simulation. Furthermore, a comparison between the conventional Shannon method and the proposed MCS-based method is presented and the optimum cell radius is suggested.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.2B
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• pp.125-136
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• 2002

It is very important to acquire the synchronization in a intercell asynchronous WCDMA system, and it is carried out through the three-step cell search process. The cell search can operate in a stepwise parallel manner, where each step works in pipelined operation, to reduce the cell search time. In case that the execution time is set to be the same in each step, excessive accumulations will be caused in both step 1 and step 3, because step 2 should take at least one frame for its processing. In general, the effect of post-detection integration becomes saturated as the number of the accumulations increases. Therefore, the stepwise parallel scheme does not give much enhancement. In this paper, the performance of the stepwise parallel processing for cell search in WCDMA system is analyzed over Rayleigh fading channels. Through the analysis, the effect of cell search parameters such as the number of accumulations in each step and the power ratio allocated among channels is investigated. In addition, the performance of the stepwise parallel cell search is improved by adjusting the execution time appropriately for each step and is compared with that of the conventional stepwise serial processing.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.11A
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• pp.1106-1112
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• 2007

As a demand for high speed uplink packet services increases, the WCDMA enhanced uplink, also known as high speed uplink packet access (HSUPA), has been specified in release 6 by 3GPP. This HSUPA will provide various types of multimedia services, such as real-time video streaming, gaming, VoIP, and FTP. Generally, the performance of HSUPA is dominated by scheduling policy. Therefore, it is required to design a scheduling algorithm considering the traffic characteristics to provide QoS guaranteed services in various traffic environments. In this paper, we propose a scheduling algorithm considering the traffic characteristics to guarantee QoS in a mixed traffic environment. Finally, the performance of the proposed scheduling algorithm is evaluated in terms of average packet delay, packet delay jitter, and system throughput using a system level simulator.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.4A
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• pp.429-438
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• 2004

In this paper, a decision-feedback coherent code tracking loop is designed for WCDMA systems and its performance is analyzed in terms of jitter variance considering the effect of phase and symbol estimation errors for both AWGN and fading environments. An analytical closed-form formula for jitter variance is Int derived for AWGN environments as a function of a pulse-shaping filter, timing offset, signal-to-interference ratio, and loop bandwidth while involving the phase estimation error and bit error rate, and the upper bound of jitter variance is derived for fading environments. Finally a second-order coherent code tracking loop is designed with the DPCH frame format #13 of the WCDHA forward link selected as a target system, and its performance is evaluated by the closed-form formula and compared with the simulation results for both AWGN and Rayleigh fading environments.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2005.05a
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• pp.230-237
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• 2005

WCDMA방식에서 채택한 AMR(Adaptive Multirate) 음성 코덱은 4.75kbps에서 12.2kbps까지 8개의 가변 출력률을 가진다. 기지국제어시스템(Radio Network Controller)은 무선망 상황에 따라 AMR 출력 모드를 가변적으로 조정해 줌으로써 높은 사용자 QoS와 효율적인 시스템 성능을 얻을 수 있다. 본 연구에서는 순방향 WCDMA 채널에서 세 가지의 AMR 출력 모드 할당 방식을 제안하고, 음성 사용자가 경험하는 QoS 만족도를 시스템 성능 척도로하여 제안된 방식들을비교 할 수 있는 분석적 방법을 제시한다. 실험 예제를 통해서 시스템 부하에 따른 시스템 성능 척도의 변화를 도시함으로써 최적의 AMR 모드 할당 방식을 결정하는 기준을 제시한다.