• Journal of the Institute of Electronics Engineers of Korea TC
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• v.47 no.10
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• pp.43-48
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• 2010

In general, in order to reduce an initial cell searching time, W-CDMA systems adopt a three-step cell search scheme: slot synchronization, frame synchronization, and primary scrambling code identification. We consider the second step (frame synchronization), in which a coherent detection using P-SCH (primary synchronization channel) is possible. In this paper, we propose a new coherent detection scheme, where a first order recursive filter is used to enhance channel estimation performance. Computer simulation results indicate that the detection performance of the proposed scheme can be robust over large range of frequency offset.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.23 no.5
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• pp.606-612
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• 2012

A highly efficient multi-mode balanced power amplifier(PA) structure is proposed for W-CDMA handset applications. The proposed PA has 2-stage amplifier configuration and the stage-bypass and load impedance switching techniques were applied to enhance power efficiency at medium power level as well as low output power level. Using the two techniques, four highly efficient power modes were realized. To demonstrate the usefulness of the proposed structure, a GaAs HBT balanced PA module was designed, fabricated, and measured.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.6A
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• pp.900-909
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• 2000

Adaptive array antennas are one of the most promising techniques for improving the capacity of CDMA mobile communication system. In this paper, the uplink and downlink capacity for asynchronous W-CDMA system with adaptive array antenna is analyzed when an angle estimation error is present. From the results, it is found that the capacities are decreased by the angle estimation error. Specifically, when 5 degrees of error is present at 9 element adaptive array, the capacities are found to decrease by 5.2% in the uplink and 11.6% in the downlink. Also, in this paper, an attempt for comparing the capacities on different channel environments has been made. However, it is found that the increase of the Rice factor hardly effects the capacity due to the power control.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.10 no.4
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• pp.183-191
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• 2010

In the recent digital communication systems, the performance of Turbo Code used as the error correction coding method depends on the interleaver size influencing the free distance determination and the iterative decoding algorithms of the turbo decoder. However, some iterations are needed to get a better performance, but these processes require a large time delay. Recently methods of reducing the number of iteration have been studied without degrading original performance. In this paper, the new method of combining ME (Mean Estimate) stopping criterion with SDR (sign difference ratio) stopping criterion among previous stopping criteria is proposed, and the fact of compensating each method's missed detection is verified. Faster decoding is realized that about 1~2 time iterations to reduced through adopting this method into serially concatenated both decoders. System Environments were assumed W-CDMA forward link system with intense MAI (multiple access interference).

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.5A
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• pp.611-617
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• 2000

Asynchronous mode W-CDMA system is kmown to be quite appropriate to the next generation mobile communication system, especially in a non-homogenious cellular architecture. In this case, however, each base station needs to use different spreading code for identification, so it is a demeanding task for a mobile terminal to find the best cell site and get an accurate code synchronization at the beginning of a communication. Since slow acquisition of a base station could mean the failure of initiation, a fast algorithm to accelerate the cell search process is essential. In this paper, a new cell search algorithm based on the binary code position modulation within the code block is proposed. Different cell sites are identified by different hopping code sequences, andeach position modulation is performed by the hopping code. The proposed algorithm is proved to make the cell search time in most places in a cell much shorter than the previous algorithms, and to make the receiver implementation simpler.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.6B
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• pp.601-609
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• 2002

In multi-path wireless channels with time-variant delay profile, a mobile station measures the received signal strength and report it to network which performs network control function such as handover. In order to improve the maximum ratio combining (MRC) gain, it also should search the strongest signal paths and measure their time offsets fast and exactly. This paper proposes some methods of fast and exactly measuring the multi-path signal strength and time offset. Since the W-CDMA system adopts antenna diversity technique for the next generation high speed packet access (HSDPA) service, we derive the optimum design parameter values for the proposed methods through computer simulations under the HSDPA conditions o( low speed of mobile, of no power control, and of multi-path wireless environment with transmit and receive antenna diversity. Finally, we prove the validity of the proposed methods by showing the improvement of the bit error rate (BER) performance.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.4 no.1
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• pp.227-232
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• 2000

This study applied asynchronous W-CDMA(3GPP) system that is suggested as an access method of IMT-2000, multimedia communication in next generation, and estimated fading channel by using pilot symbol different from traditional IS-95. And then, it applied PIC(Parallel Interference Cancellation) as multiple access interference cancellation and analyzed performance depending on the power rate between DPCCH(Control) and DPDCH(Data). As a result of simulation, it showed the best performance in C:D = 3:7 and 4:6, where set up as five users in case of hand design, and showed the best performance in C:D = 3:7, where did as ten users.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.10 no.3
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• pp.368-377
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• 1999

In this paper, the wide-band CDMA transmitter for 2 GHz band is designed and implemented. The CC-OQPSK implemented as ASIC has better spectral and power efficiency than the conventional QPSK system because it has constant envelope characteristics. Good harmonics rejection characteristics and gain of 20 dB are shown on the intermediate frequency stage using double-conversion scheme. The output power of two-stage RF amplifier is +2l.14 dBm in 1.9 GHz band. It is confirmed that the electrical characteristics of the transmitter satisfy with required the specification of the wide-band CDMA transmitter for 2 GHz band.

• Proceedings of the IEEK Conference
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• 2004.06a
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• pp.75-78
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• 2004

In this paper, we analyze the performance of transmitter and receiver of W-CDMA system using the channel coding and space time code in downlink over ITU-R realistic channel model. We can improve the data rate and the reliability of communications by a channel code, and we can get a diversity gain by using the space time code over fading channels. We also apply the RAKE receiver to improve a performance in multi-path fading channel environment.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 1999.11a
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• pp.135-138
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• 1999

본 논문에서는 차세대 멀티미디어 통신인 IMT-2000의 억세스방식으로 제안되고 있는 비동기 W-CDMA(3GPP) System을 적용, 기존의 IS-95와는 달리 Pilot symbol을 이용하여 페이딩채널을 추정하여, 이를 통한 다중사용자 간섭제거 방법으로 PIC(Parallel Interference Cancellation)을 적용하고 DPCCH(Contorl)과 DPDCH(Data)의 Power Ratio에 따른 성능을 분석하였다. 시뮬레이션 결과 Hard decision 인 경우 사용자5명의 설정에서 C:D : 3:7 과 4:6에서 가장 좋은 성능을 보였으며, 사용자를 10명으로 늘렸을 경우 C:D = 4:6 보다는 3:7의 비율에서 가장 나은 성능을 보였다.