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

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Analytical Modeling of TCP Dynamics in Infrastructure-Based IEEE 802.11 WLANs

  • Yu, Jeong-Gyun;Choi, Sung-Hyun;Qiao, Daji
    • Journal of Communications and Networks
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    • v.11 no.5
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    • pp.518-528
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    • 2009
  • IEEE 802.11 wireless local area network (WLAN) has become the prevailing solution for wireless Internet access while transport control protocol (TCP) is the dominant transport-layer protocol in the Internet. It is known that, in an infrastructure-based WLAN with multiple stations carrying long-lived TCP flows, the number of TCP stations that are actively contending to access the wireless channel remains very small. Hence, the aggregate TCP throughput is basically independent of the total number of TCP stations. This phenomenon is due to the closed-loop nature of TCP flow control and the bottleneck downlink (i.e., access point-to-station) transmissions in infrastructure-based WLANs. In this paper, we develop a comprehensive analytical model to study TCP dynamics in infrastructure-based 802.11 WLANs. We calculate the average number of active TCP stations and the aggregate TCP throughput using our model for given total number of TCP stations and the maximum TCP receive window size. We find out that the default minimum contention window sizes specified in the standards (i.e., 31 and 15 for 802.11b and 802.11a, respectively) are not optimal in terms of TCP throughput maximization. Via ns-2 simulation, we verify the correctness of our analytical model and study the effects of some of the simplifying assumptions employed in the model. Simulation results show that our model is reasonably accurate, particularly when the wireline delay is small and/or the packet loss rate is low.

Quad-Band RF CMOS Power Amplifier for Wireless Communications (무선 통신을 위한 Quad-band RF CMOS 전력증폭기)

  • Lee, Milim;Yang, Junhyuk;Park, Changkun
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.23 no.7
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    • pp.807-815
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    • 2019
  • In this paper, we design a power amplifier to support quad-band in wireless communication devices using RF CMOS 180-nm process. The proposed power amplifier consists of low-band 0.9, 1.8, and 2.4 GHz and high-band 5 GHz. We proposed a structure that can support each input matching network without using a switch. For maximum linear output power, the output matching network was designed for impedance conversion to the power matching point. The fabricated quad-band power amplifier was verified using modulation signals. The long-term evolution(LTE) 10 MHz modulated signal was used for 0.9 and 1.8 GHz, and the measured output power is 23.55 and 24.23 dBm, respectively. The LTE 20 MHz modulated signal was used for 1.8 GHz, and the measured output power is 22.24 dBm. The wireless local area network(WLAN) 802.11n modulated signal was used for 2.4 GHz and 5.0 GHz. We obtain maximum linear output power of 20.58 dBm at 2.4 GHz and 17.7 dBm at 5.0 GHz.

Idle Mode for Deep Power Save in IEEE 802.11 WLANs

  • Jin, Sung-Geun;Han, Kwang-Hun;Choi, Sung-Hyun
    • Journal of Communications and Networks
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    • v.12 no.5
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    • pp.480-491
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    • 2010
  • Along with the wide acceptance of IEEE 802.11 wireless local area network (WLAN), new applications such as Internet protocol (IP) telephony over WLAN are fast emerging today. For battery-powered IP phone devices, the life time extension is a key concern for the market acceptance while today's 802.11 is not optimized for snch an operation. In this paper, we propose a novel idle mode operation, which comprises paging, idle handoff, and delayed handoff. Under the idle mode operation, a mobile host(MH) without any active session does not need to perform handoff within a predefined paging area (PA). Only when it enters a new PA, an idle handoff is performed. The proposed idle mode allows an MH without traffic to extend its life time. We develop a new analytical model in order to comparatively evaluate our proposed scheme. The numerical resnlts demonstrate that the proposed scheme outperforms the existing schemes with respect to power consumption.

A Handover Mechanism in Internetworking with UMTS/WLAN based on HMIPv6 (HMIPv6 기반의 UMTS/WLAN 연동 네트워크에서의 핸드오버 방안)

  • Jeong Eunjoo;Park Sangjun;Lee Hyewon K.;Kim Jaeha;Kim Byunggi
    • Journal of KIISE:Information Networking
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    • v.32 no.4
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    • pp.508-514
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    • 2005
  • The research in internetworking between UMTS and WLAN, which is completed with merits and demerits, Is actively progressed to establish global roaming environments. This internetworking is classified into two groups: loosely-coupled and tightly-coupled. h tightly-coupled mechanism demands lots of investment and considerable amountof time to construct, which is directly connoted between UNTS and WLAN via IWU. On the other hand, a tersely-coupled mechanism is more scalable and easier to implement than a tightly-coupled one while it has critical drawbacks of packet loss and blocking of services due to handover delay. To alleviate these drawbacks. this work proposes a handover scheme between UMTS and WLAN, which is based on HMIPv6. The performance of the proposed scheme is evaluated by the simaulation. The proposed internetworking scheme based on HMIPv6 shows hotter performance than those based on MIPv6.

Wireless LAN with Medical-Grade QoS for E-Healthcare

  • Lee, Hyung-Ho;Park, Kyung-Joon;Ko, Young-Bae;Choi, Chong-Ho
    • Journal of Communications and Networks
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    • v.13 no.2
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    • pp.149-159
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    • 2011
  • In this paper, we study the problem of how to design a medical-grade wireless local area network (WLAN) for healthcare facilities. First, unlike the IEEE 802.11e MAC, which categorizes traffic primarily by their delay constraints, we prioritize medical applications according to their medical urgency. Second, we propose a mechanism that can guarantee absolute priority to each traffic category, which is critical for medical-grade quality of service (QoS), while the conventional 802.11e MAC only provides relative priority to each traffic category. Based on absolute priority, we focus on the performance of real-time patient monitoring applications, and derive the optimal contention window size that can significantly improve the throughput performance. Finally, for proper performance evaluation from a medical viewpoint, we introduce the weighted diagnostic distortion (WDD) as a medical QoS metric to effectively measure the medical diagnosability by extracting the main diagnostic features of medical signal. Our simulation result shows that the proposed mechanism, together with medical categorization using absolute priority, can significantly improve the medical-grade QoS performance over the conventional IEEE 802.11e MAC.

Optimal RTS-CTS Threshold to Maximize the Capacity of IEEE 802.11 WLAN (IEEE 802.11 무선 LAN의 최대 용량을 위한 최적의 RTS-CTS Threshold)

  • Choi, Woo-Yong
    • IE interfaces
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    • v.16 no.2
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    • pp.195-200
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    • 2003
  • In this paper, the selective use of RTS and CTS frames is considered to analyze the capacity of IEEE 802.11 WLAN (Wireless Local Area Network). The RTS and CTS frames are used to transmit the data frames longer than dot11RTSThreshold according to IEEE 802.11 specification. The analysis of the optimal RTS-CTS threshold is derived to maximize the capacity of IEEE 802.11 WLAN. And, numerical examples are also presented for IEEE 802.11 a and b WLANs.

Design and Implementation of Wideband Patch Antenna with Folded and Shorted Structure for 5 GHz WLAN (폴디드 구조와 단락 구조를 이용한 5 GHz 무선 랜용 광대역 패치 안테나 설계 및 구현)

  • Kim Yong-Hee;Han Jun-Hee;Lee Won-Kew;Yang Woon-Geun
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.17 no.8
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    • pp.760-766
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    • 2006
  • In this paper, we present a wideband patch antenna with folded and shorted structure for 5 GHz WLAN(Wireless Local Area Network). The proposed antenna used folded and shorted structure in the rectangular patch for miniaturization and wide frequency bandwidth. The antenna was designed by using 3D simulation program, HFSS(High Frequency Structure Simulator) software of the Ansoft company and the implemented antenna was measured by using HP 8720c network analyzer and far field measurement chamber. Simulation result on the return loss shows fairly good characteristic of at least 13.41dB in whole frequency range of interests, and the 10dB bandwidth is 1,523MHz which shows wide bandwidth characteristic. And the simulated maximum gain of the proposed antenna is 6.57 dBi at 5.825GHz. Measured result for the 10dB bandwidth of the implemented folded and shorted structure antenna is 1,377 MHz. Measured maximum gain of the implemented antenna is 6.87dBi at 5.775GHz. Measured results for the implemented antenna showed applicable performances for the 5 GHz WLAN.

Design and Implementation of Dual Band Modified Biconical Antenna for Wireless LAN

  • Oh Jong Dae;Son Ji Myoung;Yang Woon Geun
    • Proceedings of the IEEK Conference
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    • pp.181-184
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    • 2004
  • In this paper, we propose the dual band(2.4GHz and 5GHz) antenna for access point of WLAN(Wireless Local Area Network) which has similar radiation patterns for each band. Simulation results by using HFSS(High Frequency Structure Simulator) for the proposed antenna are presented. The electrical characteristics of the proposed antenna are measured with HP 8510C network analyzer and included. And radiation patterns are measured with rectangular anechoic far field antenna chamber. Measured results show that $S_{11}$ is less than - 14dB and VSWR(Voltage Standing Wave Ratio) is less than 1.5 for all frequency bands of interest. The measured maximum gain for elevation pattern at 2.40GHz is about 2.46dBi at $theta=-78^{\circ}$ and maximum gain for 5.825GHz is about 2.70dBi at $theta=-80^{\circ}.$ And the implemented antenna has good radiation pattern characteristic, therefore, we expect that the implemented dual band antenna is applicable for access point of WLAN.

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Development of a WLAN Based Monitoring System for Group Activity Measurement in Real-Time

  • Tsunoda, Hiroshi;Nakayama, Hidehisa;Ohta, Kohei;Suzuki, Akihiro;Nishiyama, Hiroki;Nagatomi, Ryoichi;Hashimoto, Kazuo;Waizumi, Yuji;Keeni, Glenn Mansfield;Nemoto, Yoshiaki
    • Journal of Communications and Networks
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    • v.13 no.2
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    • pp.86-94
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    • 2011
  • In recent years, there has been a rise in epidemiological evidence suggesting the health benefits of a physically active lifestyle. However, it is not always easy for individuals to personally recognize the optimal conditions for exercise and physical activity. Wearable acceleration-based pedometers have become widely used in estimating the amount of physical activity, and to a limited extent, providing information regarding exercise intensity, but they have never been used to assess adaptation to exercise. In order to realize simultaneous activity monitoring for multiple users exercising outdoors, we developed a prototype wireless local area network (WLAN) based system. In our system, a WLAN is deployed outside, and a user wearing a smart phone and monitoring device exercises freely within the coverage area of the wireless network. By doing so, the developed system is able to monitor the activity of each user andmeasures various parameters including those related to exercise adaptation. In a demonstration experiment, the developed system was evaluated and used to monitor users enjoying a Nordic walk, after which users were immediately able to receive their exercise report. In this paper, we discuss the requirements and issues in developing an activity monitoring system and report the findings we obtained through the demonstration experiment.

Design and Implementation of Dual Wideband Dipole Type Antenna for the Reception of S-DMB and 2.4/5 GHz WLAN Signals (S-DMB와 2.4/5 GHz WLAN 신호 수신을 위한 이중 광대역 다이폴형 안테나의 설계 및 구현)

  • Kim, Sung-Min;Yang, Woon-Geun
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.17 no.11
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    • pp.1021-1029
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    • 2006
  • In this paper, we designed and implemented a dual wideband dipole type antenna for the reception of S-DMB (Satellite Digital Multimedia Broadcasting) and 2.4/5 GHz WLAN(Wireless Local Area Network) signals. The proposed antenna based on conventional monopole type dual band antenna was implemented as planar wideband dipole type antenna with the volume of $8{\times}33.8{\times}1.68mm^3$. The proposed antenna is printed type on FR4 substrate of 1.6 mm thick and composed of a dipole type antenna for low frequency band and two symmetric structured resonance elements for high frequency band. We confirmed antenna area with dense surface current for each frequency band with simulation. By varying the length of the antenna area with dense surface current, we could vary resonance frequency of each frequency band separately. Impedance bandwidths$(VSWR{\leq}2)$ are 362 MHz(14.23 %) for 2 GHz band and 1188 MHz(22.13, %) for 5 GHz band which show wideband characteristic. Measured maximum gains were 4.33 dBi for 2 GHz band and 5.48 dBi for 5 GHz band which showed improved performance. And the implemented antenna has a good omni-directional radiation pattern characteristic.