• Journal of Digital Contents Society
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• v.6 no.2
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• pp.131-135
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• 2005

Nowadays, the demand for the wireless technology has gradually increased to support the services of high speed wired internet and also the interest of a mobile terminal convergence has increased. In the next generation, the mobile terminal could merge with the celluar phone, wireless LAN, portable internet, digital multimedia brodcasting, mobile game and sensor(smart-tag and biometrics) through the unified single user interface. Moreover, the system is supported to multi-mode at difference networks, which have variable functions and high performance for available service. Inthis paper, we investigate the minimum requirements and the core technologies of the next generation mobile terminals.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.42 no.5
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• pp.1102-1109
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• 2017

In Train Control Network(TCN), to support advanced services beyond control applications, it was revised to support high speed ethernet as IEC 61375-2-5(ETB) and IEC 61375-3-4(ECN). And Train Topology Discovery Protocol(TTDP) was included by which train-consist can be automatically configured. Meanwhile, to adopt wireless LAN as an next onboard network, TTDP need to be modified to reflect the characteristics of WLAN. This paper proposed a TTDP for WLAN using transmission power control and the number of HELLO-ACK handshake. And it determined whether the TTDP executed using the two WLAN interfaces having different bandwidths is correct or not. The proposed TTDP can allow to reduce interference from other nodes. For evaluation of performance of TTDP, NS-2 was used. The evaluation result shows the high reliability of the TTDP in wireless environment.

• Proceedings of the Korean Information Science Society Conference
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• 2004.04a
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• pp.682-684
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• 2004

최근 유비쿼터스 혁명으로 인해 장소 및 통신기기에 제약 없이 정보를 주고받는 환경으로의 요구가 증대되고 있다. 이러한 요구를 충족하고자 IP 계층에서 투명한 이동성을 제공하는 차세대 무선 프로토콜인 Mobile IPv6 기술이 필수적이다. 그러나 기존 Mobile IPv6는 제한된 컴퓨팅 능력을 가진 소형 이동 단말에는 탑재할 수 없다는 문제점이 있다. 이를 해결하기 위해서는 Mobile IPv6를 하드웨어 모듈로 구현하는 것이 필요하고, 이와 더불어 무선 환경을 지원하기 위해서 무선랜 MAC 기술의 하드웨어 구현이 요구된다. 이에 본 논문에서는 Mobile IPv6 모듈이 무선랜을 지원할 수 있도록 IEEE 802.11 MAC 모듈을 하드웨어로 설계 및 구현하였다.

• Journal of Advanced Navigation Technology
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• v.6 no.1
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• pp.44-51
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• 2002

This paper describes the performance evaluation and analysis of an Orthogonal Frequency-Division Multiplexing (OFDM) system having the least Inter Symbol Interference (ISI) in a multi-path fading channel environment. Wireless Local Area Network (W-LAN) in accordance with IEEE 802.11a and IEEE 802.11b provides high-speed transmission to universities, businesses and other various places. In addition, service providers can offer a public W-LAN service on restricted areas such as a subway. The proliferation of W-LAN has led to greater W-LAN service demands, but problems are also on the rise in offering a good W-LAN service. In particular, urban areas with high radio wave interference and many buildings are vulnerable to deteriorated QoS including disconnected data and errors. For example, when high-speed data is transmitted in such areas, the relatively high frequency generates ISI between Access Points (AP) and Mobile Terminals (such as a notebook computer), leading to a frequency selective fading channel environment. Consequently, it is difficult to expect a goodW-LAN service. The simulation proves that the OFDM system enables W-LAN to implement QoS in high-speed data transmission in a multi-path fading channel environment. The enhanced OFDM performance with 52 sub-carriers is verified via data modulation methods such as BPSK, QPSK and 16QAM based on IEEE 802.11a and punched convolutional codes with code rate of 1/2 and 3/4 and constraint length of 7. Especially, the simulation finds that the OFDM system has better performance and there is no data disconnection even in a mobile environment by applying a single tap equalizer and a decision feedback equalizer to a mobile channel environment with heavy fading influence. Given the above result, the OFDM system is an ideal solution to guarantee QoS of the W-LAN service in a high-speed mobile environment.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.2A
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• pp.202-213
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• 2004

In this paper, we propose a preamble structure and synchronization/channel estimation methods for OFDM-based multiple antenna WLAN systems that have 200Mbps transmit rate. With the proposed preamble structure, multiple antenna WLAN systems are backward-compatible with IEEE 802.11a systems which use the same 5㎓ band and synchronization performance is better than that of single antenna OFDM systems. For channel estimation, the preamble overhead is small and performance degradation by timing synchronization error that causes the critical problem of conventional comb-type multiple antenna channel estimation method also can be minimized by frequency domain phase recovery. Synchronizer and channel estimator for proposed preamble structure are implemented and verified using Verilog HDL. For the system with 4 transmit antennas and 4 receive antennas, about 150K gates are needed for synchronizer and 12K gates for channel estimator.

• Information and Communications Magazine
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• v.24 no.8
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• pp.40-52
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• 2007

본고에서는 비/저활용(57-66GHz) 대역에 대한 새로운 주파수 자원을 개척하여 HDTV급 신호를 케이블 및 위성방송 셋톱박스, 게임콘솔, DVD플레이어, 캠코더 및 이동식 멀티미디어 장비와 무선으로 연결시키는 전송 기술 개발을 위하여 Intel, Philips, Motorola, IBM, SiBeam, Panasonic, Sony등 세계적인 기업들이 국제 표준화(IEEE802.15, ETSI/BRAN, ECMA International) 공동 협력 및 기술 개발 경쟁을 벌이고 있는 상황이다. 본 표준기술은 국내 기업이 세계 시장을 장악하고 있는 LCD, PDP 및 차세대 DVD플레이어 등에 적용될 Wireless HD-SDI(High Definition Serial Data Interface)/ DVI(Digital Visual Interface)와, 외장 하드 디스크, 메모리 등 외부 기억 장치와의 자원 공유에 사용될 Muti-Gbps급 Wireless LAN, Wireless PAN, Wireless SAN(System Area Network) 등에 적용될 무선 전송 기술이다. 비/저활용 $59{\sim}66GHz$ 대역에 대한 국제 표준화로 IEEE802.15.3c를 중심으로 활발히 일어나고 있는 표준기술과 표준화 동향을 살펴본다.

• Information and Communications Magazine
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• v.32 no.3
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• pp.69-76
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• 2015

무선랜(Wireless LAN)으로도 불리는 Wi-Fi 기술은 1997년 IEEE 802.11 전송 규격(Legacy Standard)이 출간된 이후 지속적인 보완과 개정 작업을 통해 그 규격이 발전되어 가며 스마트폰, Tablet, Note-PC 등 개인 휴대 단말 기기를 위한 데이터 네트워크의 필수적인 구성 요소가 되었다. IEEE 표준과 별도로 표준 인증기관인 Wi-Fi Alliance를 통하여 제품 간 무선연결 호환성의 확보 뿐 아니라 Wi-Fi 기반 서비스 규격 제정에 이르기까지 Wi-Fi 표준 작업이 수행되고 있다. 본고에서는 나날이 발전해 온 Wi-Fi 기술 표준을 전송 속도 향상 측면과 주파수 대역 확장 측면에서 살펴보고, 차세대 Wi-Fi 기술인 IEEE 802.11ax, 즉 HEW(High Efficiency WLAN) 표준에 대하여 살펴보도록 한다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.3
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• pp.446-452
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• 2006

In this paper, I evaluated the throughput of various multimedia traffic by using computer simulation over wireless LAN environment based on 802.11e MAC protocol. The number of mobile terminals which generate various traffic and have different Internet QoS varies to improve the reliability of performance evaluation by simulation. Therefore, we investigate throughput of traffic that each mobile terminal generates. I expect that the result of study will be utilized as a fundamental data to control priorities of various types of traffic in case of formulating a scheduling policy supporting a variety of Internet QoS over wired and wireless networks.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.11A
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• pp.1124-1131
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• 2008

In this paper, we propose a timing synchronization scheme and its hardware architecture of the next generation IEEE 802.11n wireless LAN standard which is based on MIMO-OFDM technique. Proposed timing synchronization method takes two steps which consist of two modified auto-correlators. For coarse timing synchronization, a sliding window differentiator is used after a conventional auto-correlation in order to avoid plateau problem. The conjugate symmetry property of L-LTS is utilized for the simplification of fine timing synchronization. Since cross-correlation based methods are not required, the computational complexity and the number of multipliers can be reduced. In order to reduce the hardware complexity, we have used sign multipliers. Based on simulation results, the proposed method outperforms a conventional method. The proposed scheme can be applied to IEEE 802.11n systems and can easily be expanded to frequency synchronization scheme.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 1998.05a
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• pp.155-158
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• 1998

차세대 이동통신 서비스는 영상을 포함한 멀티미디어 서비스나 고속 데이터통신 서비스가 가능해야한다. 본 논문에서는 W-CDMA 방식을 이용한 IMT-2000 단말기의 주파수 합성기를 포함하는 송신부를 설계한다. 요구되는 성능은 채널간격 10MHz, 변ㆍ복조 방식은 QPSK, 데이터 전송속도는 4.096Mcps, 주파수 합성기는 19.2MHz의 기준 주파수로 2,200∼2,300MHz 및 140MHz/260MHz의 주파수를 만든다. 구현된 주파수 합성기 및 송신부가 IMT-2000단말기의 요구 성능을 만족함을 보이고, W-CDMA를 이용한 WLL, Wireless LAN등 다양한 무선장비에 이용될 것으로 기대된다.