• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.6A
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• pp.600-606
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• 2004

An interleaving delay diversity scheme is investigated in this paperand the applications in the multi-code WCDMA system along with antenna selection diversity is proposed. The proposed algorithm utilizes interleaving and delayed duplicated transmission mechanism to mitigate the effect of noise and fading. The interleaved signal and the original signal are both transmitted at intervals to obtain time diversity without any increase in required capacity. By adjusting the number of retransmissions of the information signal properly, the system achieve the receive diversity efficiently. For transmission power efficiency the proposed system also applies antenna selection diversity. By computer simulation, it has been shown that the proposed algorithm achieves better performance than the conventional algorithms by more than 2dB.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.46 no.5
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• pp.104-108
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• 2009

In this paper, we investigate the performance of ARQ-aided downlink Time Switched Transmit Diversity (TSTD) in the WCDMA LCR-TDD system. Proposed TSTD system applies the ARQ scheme in which the receiver sends the response signal (ACK or NACK signal) to the transmitter and predicts the channel condition based on response signal after receiver checks the error, then it re-sends data. Simulation results demonstrate that the proposed TSTD scheme yields about 5.5dB performance gain, compared with the conventional TSTD in term of the frame error rate(FER) for a mobile speed of 3km/h and an FER value of 1%. In addition, 7% of throughput gain is shown when Eb/N0=7dB.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.44 no.10
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• pp.1-7
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• 2007

In WCDMA systems the down-link power allocation directly affects the cell deployment capacity, coverage, and system performances. Down-link power should be controlled at minimum but still satisfy the mobile stations' required signal to noise ratio. This paper mathematically proves that the down-link power allocation depends on the number of active mobile stations accessed to the base station. Therefore this paper proposes the dynamic down-link power allocation should be implemented to the WCDMA cellular systems.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.10 no.5
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• pp.53-59
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• 2011

In this paper wideband dipole antenna that is usable as PCS/WCDMA/WiBro/WiMax public relay station antenna is proposed. The proposed antenna that designed by using double ring structure improves bandwidth performance of existing dipole antenna to wideband performance. To verify wideband performance and isotropic radiation pattern of the proposed antenna, simulation and fabrication have progressed its radiation characteristic has measured and then compared with calculated result. Measured result is similar to calculated result and has gain of 2dB VSWR of 2:1 over 1.75~3GHz. It is considered that the dipole antenna that designed in this paper can be usable as PCS/WCDMA/WiBro/WiMax public relay station antenna.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.4A
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• pp.423-428
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• 2004

High-data rate and high speed communication techniques are required for wireless mobile communication systems to provide multimedia services. A multiple antenna technology may be used to meet this demand. In this paper, a method for performance improvement of a WCDMA downlink system using space time block coding is proposed in quasi-static Rayleigh fading channels. The proposed receiver uses the cross correlation matrix obtained by each finger corresponding to multi paths. To obtain maximum diversity gain, the inverse of cross correlation matrix and the Hermitian matrix of the channel matrix for each path arc computed, and then applied to received signals. Various simulation results show that the proposed receiver outperforms a conventional receiver in Rayleigh fading channels.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.1A
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• pp.16-24
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• 2010

High Speed Uplink Packet Access(HSUPA) is a WCDMA Release 6 technology which corresponds to High Speed Downlink Packet Access(HSDPA). Node B Supports fast scheduling, Hybrid ARQ(HARQ), short Transmission Time Interval(TTI) for high rate uplink packet data. It is very important to detect Iub congestion to improve end user's Quality of Service(QoS). This paper proposes Node B Congestion Detection(BCD) mechanism and suggests to use the hybrid of Transport Network Layer(TNL) congestion detection and BCD. It is shown that HSUPA user throughput performance can be improved by the proposed method even with small Iub bandwidth.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.1A
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• pp.16-23
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• 2008

In this paper, we propose a new code grouping interference cancellation(IC) receiver for multirate wideband code division multiple access(WCDMA) system based on orthogonal variable spreading factor(OVSF) code. The users are assigned different lengths of OVSF codes as a spreading code according to their data rates and divide the active users having same representative code split into a group for effective cancellation. The code grouping IC receiver performs cancellation between the groups first and cancellation within group. This proposed IC receiver can cancel the interferences using desired user's code information and then desired signals are detected. The results show that the large improvement in performance can be attained by groupwise IC scheme and we can make the effective systems compare to conventional ones.

• 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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• 2008.06a
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• pp.307-308
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• 2008

In this paper, we propose a mitigation method to reduce the effect of pilot interference at the wireless repeater. This improves the signal to interference ratio (SIR), and enables increased cell capacity and better bits error rates (BER) performance in the WCDMA systems. Simulation studies have been carried out to verify the proposed approach and we obtained promising results.