• Journal of KIISE:Computer Systems and Theory
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• v.26 no.5
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• pp.584-594
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• 1999

이 논문에서는 CDMA(Code Division Multiple Access)셀룰러 시스템에서 우선순위 큐(Queue)에 기반을 둔 핸드오프채널할당기법의 모델을 제안하였다. 또한 제안한 모델의 성능을 컴퓨터 시뮬레이션을 통해 비우선순위기법 및 FIFO(First In First Out)큐기법과 비교하였다. 제안하는 모델의 핸드오프 채널할당 기법에서는 이동국의 진행방향에 있는 인접 셀(Neighbor Cell)의 파일롯 중에서 임계치가 T-ADD 이상인 파일롯이 있을 경우 기지국이 이 파일롯(Pilot)에 대한 파일롯 세기 측정메시지를 이동국으로부터 수신 한 지점에서 드롭타이머가 종료된후 현재의 셀에서 사용중인 파일롯에 대한 파일롯 세기 측정 메시지를 이동국으로부터 수신한 시점까지 핸드오프 처리가능 영역으로 정의하고 이를 우선순위 큐의 최대큐 대기시간으로 사용하였다. 제안된 기법의 성능을 분석하기 위한 성능평가 척도는 강조종료확률, 호 블록킹 확률, 전체 제공 트래픽에 대한 수행 트래픽 비율, 평균 규크기미치 핸드오프 시 평균 지연시간이다. 성능시뮬레이션결과, 제안된 기법이 전체 시스템 호처리 용량면에서 약간의 단점은 발생하지만 핸드오프 처리에 있어서 높은 성능을 유지함을 알수 있었다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.1B
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• pp.24-33
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• 2002

The cell search scheme for W-CDMA consists of the following three stages: slot synchronization(1st stage), group identification and frame boundary detection(2nd stage), and long code identification(3rd stage). The performance of the cell search when a mobile station is switched on, which is referred to as initial cell search, is decreased by the initial frequency and timing error. In this paper, we propose the pipeline structured initial cell search scheme using time trackers to compensate for the impact of the initial timing error in the stage 2 and stage 3. The simulation results show that the performance of the proposed scheme is maximal 1.5dB better than that of the conventional one when the initial timing error is near ${\pm}T_c$/2.

• Journal of Communications and Networks
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• v.7 no.2
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• pp.157-170
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• 2005

The combination of multiple antennas and multi-carrier code division multiple-access (MC-CDMA) is a strong candidate for the downlink of the next generation mobile communications. The study of such systems in scenarios that model real-life trans-missions is an additional step towards an optimized achievement. We consider a realistic MIMO channel with two or four transmit antennas and up to two receive antennas, and channel state information (CSI) mismatches. Depending on the mobile terminal (MT) class, its number of antennas or complexity allowed, different data-rates are proposed with turbo-coding and asymptotic spectral efficiencies from 1 to 4.5 bit/s/Hz, using three algorithms developed within the European IST-MATRICE project. These algorithms can be classified according to the degree of CSI at base-station (BS): i) Transmit space-frequency prefiltering based on constrained zero-forcing algorithm with complete CSI at BS; ii) transmit beamforming based on spatial correlation matrix estimation from partial CSI at BS; iii) orthogonal space-time block coding based on Alamouti scheme without CSI at BS. All presented schemes require a reasonable complexity at MT, and are compatible with a single-antenna receiver. A choice between these algorithms is proposed in order to significantly improve the performance of MC-CDMA and to cover the different environments considered for the next generation cellular systems. For beyond-3G, we propose prefiltering for indoor and pedestrian microcell environments, beamforming for suburban macrocells including high-speed train, and space-time coding for urban conditions with moderate to high speeds.

• The Journal of the Korea institute of electronic communication sciences
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• v.6 no.2
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• pp.163-170
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• 2011

This study proposed the composition of a new long-code MMSE detector using the pilot channel that demonstrated the most excellent performance under Rayleigh fading in the previous studies. It analyzed and explained how to maintain the stability of the weight vector(introduction to the course of radio waves) in the receiver. In the operation of the receiver system to remove radio interference, the signal vector distortion received in the channel where fading was present achieved good results by compensating for signal errors. When there was distortion, the response characteristics of the received signals were superior to the common matching filter according to the computer simulation. The long-code MMSE receiver proposed in the study was able to prolong the cycle by $16{\times}T_b$ in the fading environment to fulfill the satisfaction.

• Proceedings of the Korea Contents Association Conference
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• 2003.11a
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• pp.289-302
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• 2003

In this paper, the performance of a multicarrier CDMA system applying adaptive modulation and adaptive subchannel allocation scheme is analyzed in wireless environment. In case of the proposed system, total subchannels is 4 and data is transmitted over 2 subchannels with the biggest fading, Threshold of each channels is 5.2 ㏈, 9 ㏈, 13.2 ㏈ and 8.4 ㏈, 12.2 ㏈, 16.3 ㏈. The BER of 10-3 is 8.1 ㏈. This is increased 12.9 ㏈ in comparison with the existing system. The BPS according to average channel is needed average E$_{b}$ N$_{o}$ of about 15 ㏈ in 7 bit.t.

• Proceedings of the Korean Society of Computer Information Conference
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• 2010.07a
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• pp.173-179
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• 2010

Currently, the communication systems are progressing two ways as the wireless and multimedia and these need big transmission capacity then before. In these circumstance, communication services existed as two different service forms which have different rates and characteristics. For example Voice/Video Services accept some errors but transmit on realtime, but Date Services don't need to transmit on realtime but have to retransmit if these have only one bit error. In Voice/Date Integrated traffics, it has big throughput that realtime voice/video data which could have some errors if integrated traffic is increased rapidly have transmission priority, then Data traffics which delay is accepted is sent after that. In this paper, I introduce the calculation method for various traffic when voice/data mixed traffics is transmitted to asynchronous unslotted ALOHA CDMA system proposed and the result is presented. And We can easily theoretical analysis for the system traffic and changing traffic using proposed solution in this paper.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.1A
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• pp.17-24
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• 2003

Access network is one of the most critical components of telecommunication networks. Essentially it provides the final connection through to the subscriber and at the same it is usually the most expensive component in terms of capital investment and ongoing cost of maintenance and repair In recent, various access technologies with broadband have been developed and also are emerging newly Comparing fixed access networks, the concrete concept as well as the scope of mobile access networks or parts has not been defined yet although it is caused by peculiarities of mobile network with mobility-guarantee technology, use of RF resource, fixed-exchange and transport networks This article examines the characteristics and detailed functions of BTS, BSC, MSC and other components in CDMA mobile network under the IS-95 A/B and cdma 2000-1x standards comparing the ITU's access network functional model From the systematic and functional perspectives, futhermore, an alternative definition for access parts of mobile network is proposed.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 2003.05a
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• pp.283-286
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• 2003

Generally, the repeater in CDMA(Code Division Multiple Access) included HPA(HI-Power Amplifier) to amplifier communication signals. Also, HPA contained PD(Predistortor) to maintain the linearization of amplifier characteristics A configuration component of PD have been used electricity nonlinear devices such that diode. But this diode takes many influences at the circumstance temperature. Consequently, st can't maintain output linearization, and drop the communication Duality. The manufacturer set bias of the circuit to the manual at the first out of ware-house low. But the Q-point changes according to the change of the high temperature or low temperature. Therefore, we designed a system to maintain the Q-point by FDM(Fuzzy Decision Maker) in this paper.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.4A
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• pp.458-465
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• 2004

To reaffirm the use of a mainstream CMOS process for designing passive-like attenuator structures, a linearly controlled variable attenuator is realized with 0.35${\mu}{\textrm}{m}$ 2-poly 4-metal CMOS process. It uses the П configuration for large attenuation range and suitable matching property. Compared to conventional passive-like CMOS attenuators, it is demonstrated that this work advances the frequency band from MHz to ㎓ (DC- l㎓), and reduces the size to 700${\mu}{\textrm}{m}$${\times}$300${\mu}{\textrm}{m}$.. Both simulation results and test results are provided. They show the improved linear relation between attenuation and control voltage. It is very useful in CDMA or GSM band, which uses under 1㎓ frequency band. An alternative topology, Bridged-T configuration, is proposed to get over the limit of applications by elevating operation bandwidth. The proposed topology covers over DC-2㎓ frequency band, which means that the proposed architecture can cover the tripleband (800MHz CDMA/GSM, 1.5㎓ GPS, 1.9㎓z PCS system) in applications as well. The simulation results are provided.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.6B
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• pp.642-649
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• 2011

In this paper, we present the analysis of the characteristics of advanced mobile communication base station with multi-band about power loss, power efficiency and carbon reduction considering cable power loss. The advanced mobile base station system is installed on the outdoor for Antenna and RF part, and then the power loss is reduced because the fiber optic cable is used between RF part and baseband part. If the cable power loss is reduced by 5 dB replacing an entire the advanced base station systems, annual power consumption is reduced total 49,038 MWh in the CDMA 20W, WCDMA 30W, WiBro 10W systems. Furthermore the advanced base station system of annual $CO_2$ emission is 20,832 $tCO_2$ compare to 65,878 $tCO_2$. Therefore the advanced base system is confirmed considering green IT technology for the advanced mobile communication base station.