• Title, Summary, Keyword: wireless local area network(WLAN)

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Channel Equalization Schemes using Midamble for WAVE Systems (WAVE 시스템에서 미드엠블을 이용한 채널 등화 방식)

  • Hong, Dae-Ki;Kang, Bub-Joo
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.14 no.10
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    • pp.2215-2222
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    • 2010
  • A Wireless Access for Vehicular Environment (WAVE) system based on Orthogonal Frequency Division Multiplexing (OFDM) is made for vehicle to vehicle wireless communications. The physical layer standard of the WAVE system is very similar to that of the IEEE802.11a wireless local area network (WLAN). Therefore, the performance of the WAVE system is degraded by continual channel variation in the WAVE multipath fading channels after starting initial channel estimation. In this paper, we research the performance improvement of equalization in 64 Quadrature Amplitude Modulation (QAM) transmission in WAVE environment. The proposed algorithms use the training sequence and the midamble sequence which is used for fast channel variation such as WAVE environments. Additionally, various interpolation methods are also used for the channel tracking.

A Location Technique Based On Calibrated Radio Frequency Propagation Model For Wireless Local Area Networks (교정된 전파전파 모델에 기반한 WLAN 측위 기법)

  • Kim, Hee-Sung;Shim, Ju-Young;Choi, Wan-Sik;Lee, Hyung-Keun
    • Journal of Institute of Control, Robotics and Systems
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    • v.14 no.8
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    • pp.760-766
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    • 2008
  • This paper proposes an efficient location technique to find an indoor location under the IEEE 802.11 wireless local area networks. The proposed method is based on the range measurements obtained from a simple radio frequency propagation model. Thus, unlike the radio frequency fingerprint correlation method, it does not suffer from the computational burden during the real-time location service period and can quickly reply the location requests of many users at the same time. To increase the location accuracy in spite of the frequent non-line-of-sight error occurrences, the proposed method calibrates the distortion of the non-line-of-sight error by a simple measurement surveying procedure that does not require the surveyor's manual interaction. Experimental results show the capability of the proposed method.

A Study on the Implementation of Wireless LAN MAC(medium access control) Layer for a Medical Information Transmission (의료 정보(심전도 데이터) 전송을 위한 무선 LAN MAC 계층 구현에 관한 연구)

  • 류점수;고성일;김영길
    • Journal of the Korean Institute of Telematics and Electronics S
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    • v.34S no.12
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    • pp.50-59
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    • 1997
  • A wireless LAN medical information transmission system is useful for patients who need mobility in a local area environment. This paper proposes a method using WLAN(wireless local area network) and implements a stand-alone system with MAC(meidum access control) layer protocol referenced IEEE 802.11 draft standard. The system consists of a 8bit-microprocessor which handles media access control protocol and a WL100(GEC Plessey) chip which takes care of phsical layer specific routines and uses a RF module DE6003(GEC Plessey). The major features of the implemented system are the CSMA/CA protocol used a consecutive DATA-ACK trasmission method which yields more effective bandwidth allocation for asyncronous traffic transmission and the modified PCF protocol for time-bounded traffic transmission, which operates in ad-hoc network topology apart from IEEE 802.11 draft standard confirm PCF mode operate in infrastruture topology.

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Technical and Patent Information Analysis of Wireless LAN (무선 LAN 기술 및 특허동향 분석)

  • Kim, Jae-Woo;Yeo, Woon-Dong;Sung, Kyung-Mo
    • Proceedings of the IEEK Conference
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    • pp.277-280
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    • 2004
  • A wireless LAN(WLAN) is a local area network without wires. WLANs have been around for more than a decade, but are just beginning to gain momentum because of falling costs and improved standards. This paper presents the state of the arts and analyses the patent information of wireless local area network technology.

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Channel Estimation for WLAN System Employing CCK Modulation in Multipath Fading Channels

  • Cho, Jin-Woong;Kang, Cheol-Ho
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.11 no.8
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    • pp.1437-1443
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    • 2000
  • This paper considers a channel estimation technique in a wireless local area network (WLAN) system with complementary code keying (CCK) signaling over multipath fading channels. This scheme uses the maximum correlator output of RAKE receiver for the extraction of the channel parameters. The performance of the proposed detection technique is compared with that of a noncoherent detection technique, and a significant improvement of performance is observed in terms of the bit error probability.

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Design of VCO for WLAN using Phase Shift (Phase Shift를 이용한 WLAN용 VCO의 설계)

  • 박영호;강태영;추성중;박정호
    • Proceedings of the IEEK Conference
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    • pp.617-620
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    • 2003
  • In this paper, a monolithic VCO has been designed for Wireless Local Area Network(WLAN) applications. The differential form VCO is constructed using positive feedback with capacitor and phase shift for low phase noise performance. The VCO shows the phase noise of -92.725 dBc/Hz at an offset frequency of 10KHz and the tunning range of 5.822~6.154GHz.

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A Handover Scheme in MAP based B3G Networks (MAP 기반 B3G 이동 망에서 핸드오버 지원 방안)

  • Park Sangjoon;Lee Jongchan;Kim Hyungjong
    • Journal of the Korea Society for Simulation
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    • v.13 no.3
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    • pp.31-41
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    • 2004
  • In this paper, we consider the strategy of Universal Mobile Telecommunication System (UMTS) and Wireless Local Area Network (WLAN) internetworking that provide the seamless vertical handover for mobile nodes. We propose Mobility Anchor Points (MAP) based UMTS/WLAN internetworking architecture to support the vertical handover. Also, on integrated UMTS/WLAN networks, we propose a vertical handover scheme that avoids the call blocking caused by the network resource shortage. We provide the numerical analysis to investigate the performance evaluation to the proposed scheme and compare the proposed scheme with the existing scheme.

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Study of the Direct Digital Frequency Synthesizer for FHSS in Wireless LAN Systems (무선 LAN 시스템에서 FHSS을 위한 직접형 디지틀 주파수 합성기에 대한 연구)

  • 임세홍;장용수;이완범;김환용
    • Proceedings of the IEEK Conference
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    • pp.45-48
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    • 1999
  • The demands of WLAN(Wireless Local Area Network) systems increase rapidly in whole society and this phenonenon has been expected that WLAN wi11 substitute for wired-LAN. The FHSS(Frequency Hopped Spread Spectrum) method using the WLAN is changed to the performance of Frequency synthesizer. In this paper, we proposed pipeline-accumulator using ring-counter method instead of constant accumulator that has demerits of size and power consumption. Designed DDFS generated operating frequency of 167MHz and maximum output frequency of 83.5MHz.

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Synchronization Algorithm for Wireless LAM Using OFDM Transmission Technique (OFDM 전송기술을 이용하는 무선 LAN용 동기 알고리즘)

  • 김장욱;유기희;오창헌;조성준
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.29 no.2A
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    • pp.157-165
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    • 2004
  • The synchronization algorithm of IEEE 802.11a WLAN(Wireless Local Area Network) has three consecutive processes, which use a short code training symbol, a long code training symbol and a pilot symbol respectively. But in using this synchronization processes, the actual embodiment has two problems. First, the synchronization process has the complex structure using a long code training symbol and a pilot symbol. Second, since the long training symbol is only compensated with the offset correction coefficient, it can not be trusted perfectly. If the equalizer coefficient is obtained in this unstable period, the system performance is degraded. In particular, the system performance becomes worst in case of the 54 Mbps transmission system using the maximum length of data. In this paper, the new algorithm is proposed which can resolve the embodiment complexity of synchronization processes and structural defect, and also it is confirmed by simulation.

A Study on Improvement of a Performance by Preventing the Ping-pong Effect when IP Handover (IP Handover 시 Ping-pong효과 방지에 따른 성능개선방안 연구)

  • Kim, Tae-Wan;Cho, Il-Kwon
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.34 no.8B
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    • pp.760-767
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    • 2009
  • While network evolution toward all IP based wired and wireless converged network is on the move, services are being progressed into converged and complex services from simply coupled services, and telecommunication operators are developing new technologies which enable users to move between heterogeneous networks without discontinuity of a current service. In this paper, we propose a IP handover mechanism which reduces ping-pong effect during IP handover between WLAN and CDMA2000 1x EV-DO Rev.A neworks. We present stability and enhanced latency of the proposed IP handover mechanism by experimentation. The mechanism was developed under the 3rd phase of BcN project.