• Journal of Korea Multimedia Society
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• v.7 no.2
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• pp.204-210
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• 2004

This paper proposes a transmission probability control scheme and MAC protocol for packet data services in slotted CDMA system. In slotted CDMA system, multiple access interference is the major factor of unsuccessful packet transmissions. Therefore, in order to obtain the optimal system throughput, the number of simultaneously transmitted packets should be kept at a proper level. In the proposed protocol, the base station calculates the packet transmission probability of mobile stations according to the offered load and then broadcasts it. Mobile stations, which have a packet, attempt to transmit packet with the received probability. Numerical analysis and simulation results show that the proposed scheme can offer better system throughput than the conventional one, and guarantee a good fairness among all mobile stations regardless of the offered load.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.14 no.9
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• pp.912-918
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• 2003

In this paper, we designed and implemented the dual band monopole antenna for cellular CDMA(Code Division Multiple Access) and IMT-2000(International Mobile Telecommunication 2000) repeater. The antenna was designed by using 3D simulations program, HFSS(High Frequency Structure Simulator). Electrical characteristics were measured by using HP 8720C network analyzer and measured maximum S$\_$11/ was -10.9 dB for all frequency bands of interests in Cellular CDMA and IMT-2000. Simulation results for antenna gain at 859 MHz and 2027.5 MHz were 2.38 dBi and 4.02 dBi respectively with omni directional radiation pattern. The size of implemented antenna is compact and the antenna can be produced in low cost enough for commercialization.

• Proceedings of the IEEK Conference
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• 2001.09a
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• pp.327-330
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• 2001

CDMA2000 1x 기반의 무선 인터넷 서비스가 가능해짐에 따라 무선 멀티 미디어 서비스에 대한 수요가 점점 늘어나고 있다. 화상 전화나 VOD 서비스와 같은 실시간 멀티 미디어 서비스에 사용되는 UDP는 현재의 유선과 무선이 혼합된 망에서는 패킷 전송 주기와 패킷의 크기에 따라 매우 다른 성능을 보여준다. 무선 구간에서 전송 효율을 높이기 위해서는 대역폭과 패킷손실률 그리고 채널의 타임슬롯 시간을 고려해 야 한다. 본 논문에서는 CDMA2000 1x 망에서 망 측정을 통하여 실시간 멀티미디어 전송에 적합한 QoS 인자를 추출하여 이를 개선 향상을 위해서 하고 실시간 멀티 미디어 서비스를 위한 대안을 제시하였다.

• Korean Management Science Review
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• v.25 no.2
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• pp.25-42
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• 2008

CDMA/TOD with asymmetric capacity allocation between uplink and downlink is a highly attractive solution to support the next generation mobile systems. This is because flexible asymmetric allocation of capacity to uplink and downlink usually improves the utilization of the limited bandwidth. In this paper, we mathematically formulate an optimal timeslot and code allocation problem, which is to maximize the total utility considering the numbers of codes(channels) allocated to each data class and the forced terminations of previously allocated codes. We also suggest a real-time integrated timeslot and code allocation scheme using Lagrangean relaxation and subgradient optimization techniques. Experimental results show that the proposed scheme provides high-quality solutions in a fast time.

• Journal of KIISE:Information Networking
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• v.29 no.2
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• pp.141-155
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• 2002

A medium access control protocol is proposed for integrated voice and data services in the packet CDMA network with a small coverage. Uplink channels are composed of time slots and multiple spreading codes for each slot. This protocol gives higher access priority to the delay-sensitive voice traffic than to the data traffic. During a talkspurt, voice terminals reserve a spreading code to transmit multiple voice packets. On the other hand, whenever generating a data packet, data terminals transmit a packet based on the status information of spreading codes in the current slot, which is received from base station. In this protocol, voice packet does not come into collision with data packet. Therefore, this protocol can increase the maximum number of voice terminals.

• The KIPS Transactions:PartC
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• v.12C no.5 s.101
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• pp.717-724
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• 2005

In this paper, we Propose an efficient scheduler well suited for the next-generation wireless networks that can support multimedia traffic having various requirements. The scheduler is designed to provide each of multimedia classes with differentiated services. In particular, the scheduler is intended to maximize throughput and minimize packet loss ratio. To apply the scheduler, we suppose that the wireless network is based on TDD/CDMA system The scheduler assigns a packet in a dedicated uplink-slot to the user within a frame to operate scheduling of packets transmitted by the users belonging to the specific class in an efficient manner. Such a manner also enables the scheduler to meet different QoS requirements. The paper also includes performance comparison with other schemes and analysis of the proposed scheduling algorithm by using simulation. We also analyze the proposed scheme by using simulation. The simulation compares the proposed scheduling algerian with previously proposed schemes in terms of the performance.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.21 no.1
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• pp.161-174
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• 1996

Addressed in this paper is performance analysis of the maximum-likelihood code acquisition technique for slotted-mode preamble search in the CDMA reverse link. The probabilities of detection, miss, and false alarm are derived analytically for a multiple $H_{1}$ cell case in a frequency-selective Rayleigh fading channel, based on the statics of the CDMA noncoherent demodulator output. the probability density function of the decision variable consisting of successive demodulator outputs is also derived by considering the fading characteristics of the received signal for both single and dual antenna cases. The performance of the code acquisition technique is evaluated numerically with an emphasis on investigating the effects of post-detection integration, fading rate, and antenna diversity on the detection performance.

• Electronics and Telecommunications Trends
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• v.16 no.1 s.67
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• pp.10-17
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• 2001

21세기 정보화 사회에서는 언제, 어디서나, 누구나와 통화하고자 하는 개인의 욕구가 다양하게 표출될 것이며, 통신시스템은 이러한 통신욕구를 만족시키기 위한 저가격, 고품질의 다양한 부가서비스 제공을 목적으로 발전되어갈 것이다. 최근 통신시장을 주도하고 있는 것은 인터넷으로서 이 수요는 가히 폭발적이라고 할 수 있다. 이 인터넷 서비스의 특징은 상향 링크와 하향 링크의 데이터량이 비대칭성을 나타내고 있기 때문에 이러한 서비스를 효율적으로 제공하는 방식이 필요하며, 현재로서 가장 효율적인 방식은 IMT-2000용 TDD 방식이다. 이 방식은 하나의 주파수로 송신과 수신을 하는 TDD 방식을 기반으로 하여 하나의 프레임을 여러 개의 타임슬롯으로 나누고, 사용자는 각각 정해진 타임슬롯만을 사용하는 TDMA의 방식을 결합시키어, 하나의 타임슬롯 내에서도 복수 명의 사용자가 동시에 사용하게 하는 CDMA 방식을 활용한 무선접속 기술로서 비대칭 고속 데이터 서비스를 주어진 대역 내에서 효율적으로 사용할 수 있는 방법이다. 본 고에서는 이 방식의 연구개발 동향과 물리계층 및 주요 핵심기술과 TDD 방식이기 때문에 적용 가능한 성능 향상 기술에 대하여 정리 분석하였다.

• The Journal of the Korea institute of electronic communication sciences
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• v.5 no.4
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• pp.450-456
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• 2010

In the high-speed packet service, next generation mobile communication system has emerged as a major feature. If the fire of these high-speed kit services and non-continuous transmission of data due to the symmetrical nature of daeyiteo traffic for D-CDMA system has been actively studied. Small amounts of data moving in the uplink, but the real-time video downlink transmission, such as downloading large files to move data and services to those with asymmetric traffic characteristics, a system that can efficiently handle the data requirements be. Of 3GPP TDD(Time Division Duplex) scheme based on CDMA and TDMA in a way by introducing the concept through the proper allocation of time slots that can handle asymmetric traffic efficiently, has an advantage. TD-CDMA system by considering the characteristics of the frame configuration of transmission methods, such as physical channel structure and channel coding has been investigated. In addition, the HARQ scheme TD-CDMA system performance is analyzed by comparing them.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.2B
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• pp.146-153
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• 2006

It is required to have researches on efficient resource allocation schemes in an integrated voice and data CDMA system with the spreading of high-speed wireless internets. In this paper, we proposed a efficient resouce allocation scheme for providing a high speed data service in an integrated CDMA system. In an integrated voice/data CDMA system, resources for voice users are allocated with high priority and residual resources are allocated to the data service. In this case, it is necessary to use a resource allocation scheme for minimizing interference. In this paper, we first explain about a interference minimizing method and define QoS requirements. Based on the method, we proposed a efficient resource allocation scheme which satisfy the QoS requirements. The proposed scheme controls the transmission rate and delay of data users with a priority information such as the number of packets in a queue. From the simulation results, we show that the proposed scheme reduce the blocking probability and delay and improve the performance.