• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2001.10a
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• pp.117-120
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• 2001

In this paper, a contention-based reservation MAC protocol is proposed for non-real-time bursty traffic services in the wireless ATM networks. In order to reduce the collisions of the reservation request packets, the base station scheduler calculates the transmission probability using the number of RAS minislots and the estimated load of the reservation request packets. And it broadcasts the calculated transmission probability through the downlink control channel. Mobile terminals, which have a traffic burst, select randomly a RAS minislot and transmit the reservation request packet with the received transmission probability. The reservation request packet contains the number of packets in the buffer. The base station allocates slots based on the buffer status of the received reservation request packets.

• Journal of Communications and Networks
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• v.18 no.4
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• pp.567-579
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• 2016

Several energy saving techniques in cellular wireless networks such as active base station (BS) selection, transmit power budget adaptation and user association have been studied independently or only part of these aspects have been considered together in literature. In this paper, we jointly tackle these three problems and propose an integrated framework, called dynamic cell reconfiguration (DCR). It manages three techniques operating on different time scales for ultimate energy conservation while guaranteeing the quality of service (QoS) level of users. Extensive simulations under various configurations, including the real dataset of BS topology and utilization, demonstrate that the proposed DCR can achieve the performance close to an optimal exhaustive search. Compared to the conventional static scheme where all BSs are always turned on with their maximum transmit powers, DCR can significantly reduce energy consumption, e.g., more than 30% and 50% savings in uniform and non-uniform traffic distribution, respectively.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.8C
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• pp.605-612
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• 2008

This paper researches the estimating location using repeater effect adjustment method in CDMA based system. Repeaters are commonly used by commercial and amateur radio operators to extend signals in the radio frequency range from one receiver to another. The repeater signals are increasing arrival time from base station to mobile station. So if we calculates the mobile station using repeater signals, the estimating position error is increased. However nobody researched about adjusting repeater effects. This paper proposes repeater effect adjustment algorithm. For adjusting repeater effects, we make the triangle using mobile station, reference base station and neighbor base station, and then detect the repeater effects using the triangle characteristic. The proposed method system showed the improved performance in estimating parameters and locating positions by computer simulations.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.8 no.6
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• pp.1115-1120
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• 2004

In this paper, a CSSMA/AI MAC protocol for data services in packet CDMA network is presented. The main features of this protocol are the code status sensing and code reservation for reducing the packet collision. The base station broadcasts the code status on a frame-by-frame basis just before the beginning of each preamble transmission, and the mobile station transmits a preamble for reserving a randomly selected code based on the received code status. After having transmitted the preamble, the mobile station listens to the downlink of the selected code and waits for the base station reply. If this reply indicates that the code has been correctly acquired, it continues the packet transmission for the rest of the frame. If there are other packets waiting for transmission, the base station broadcasts the status of the code as reserved, and the mobile station transmits a packet on a reserved code for the successive frames.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.9B
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• pp.1542-1550
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• 2000

Fiber optic link systems based on SCM scheme are widely used as efficient and economic RF signal links between base station and a central station in mobile communication networks. However, its performance can be seriously limited depending on the operational conditions of not only the optical transmission system but also the wireless link in various environments. In this paper, we propose an analytic model for performance analyses of the SCM fiber optic link for CDMA RF signal transmission in various link environments. We present optimal operational conditions taking account of the nonlinear effects of the optical transmission system, and the multiple access interference produced at the wireless link. It has been shown through the BER analyses in this paper that the selection of optical modulation index of the SCM fiber optic links can be found optimally to minimize the fiber optic link noises and intermodulation distortion due to LD.

• Proceedings of the IEEK Conference
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• 2005.11a
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• pp.89-92
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• 2005

For the past years, wireless communications environment have developed with explosive demand of internet service and increase of subscriber. Anytime anywhere, we can access internet service and recently, we can access internet with portable terminal using wireless communications. So several schemes have been proposed for the efficient service. In this paper, we may improve performance of wibro system using adaptive antennas scheme at the base station (BS) and mobile station(MS),operating jointly. In wibro system, the joint use of transmit beamforming at BS and receive beamforming at MS is improved the SINR and increased the capacity compared to conventional system[1],[2].

• Annual Conference of KIPS
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• 2009.04a
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• pp.1230-1232
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• 2009

본 논문에서는 공용 주파수 대역에서 IEEE 802.11 WLAN과 IEEE 802.16 WMAN과의 효율적인 공존을 위한 MAC 프로토콜을 제안한다. 제안한 프로토콜은 IEEE 802.11 WLAN과 IEEE 802.16 WMAN이 주파수를 공유하며 지리적으로 공존하는 환경을 가정하였다. IEEE 802.16 WMAN의 BS(Base station)와 SS(Subscriber station)의 통신에서 DL(Down Link)구간에서는 SS가 자신의 DL-burst에서 IEEE 802.11의 CTS를 보내 주변의 IEEE 802.11 디바이스들의 통신을 지연시킴으로써 IEEE 802.11 WLAN 및 IEEE 802.16 WMAN이 공존하면서도 충돌을 방지해 전송 효율을 높일 수 있다. 본 논문에서 제안하는 MAC 프로토콜의 동작에 대해 설명하고 시뮬레이션을 통해 기존 방법보다 향상된 성능을 유지함을 보인다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.8C
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• pp.689-695
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• 2007

Wireline relay stations(RS's) are connected to cellular base stations(BS's) via radio-over-fiber(RoF) to enhance system capacity and to reduce shadow areas. Unlike wireless multi-hop systems, BS-to-RS signaling is transmitted out-of-band, thus reducing the effect of interference caused by frequency reuse. In this paper, antenna arrays used in addition to the wireline RS's are considered to evaluate the transmission capacity gain and performance variations according to the may structures. In particular, RS locations to maximize the gain, may distribution patterns for a given number of antenna elements, performance enhancement for a varying number of elements are experimentally determined to suggest a proper utilization of antenna ways in conjunction with wireline RS's.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2011.05a
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• pp.731-734
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• 2011

This paper proposed the Low power configuration of Single hop WSN(Wireless Sensor Network) system. When the RF communication is done each tag node during the WSN systems operating, power consumption is greatest. There for, if you configure the Network with the RF communication module turn on/off periodically, power consumption less then operating the module all the time without it toggles. However, some data omissions may occur in which transmission and receipt is done. So this paper proposed the algorithm for low power system without data omissions.

• Journal of information and communication convergence engineering
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• v.1 no.3
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• pp.115-118
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• 2003

This paper analyzes Bit Error Rate (BER) performance of a wireless communication system using BPSK modulation technique with a smart antenna at base station. The channels under consideration are Additive White Gaussian Noise (AWGN) channel or a slow, flat Rayleigh fading channel with AWGN. Under the assumptions that the MMSE beamformer is used and the time delays of all users are approximately equal, we first analytically derive closed-form expressions for the BER of the desired user. Then, computer simulation is carried out to verify the theoretical results.