• Proceedings of the IEEK Conference
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• 2007.07a
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• pp.129-130
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• 2007

I/Q demodulator is designed using RC-CR quadrature divider with two balanced mixer for WLAN applications. The I/Q demodulator has low power dissipation, good I/Q mismatch, a good isolation and conversion loss. The measured results shows close agreement with the predicted performance.

• Journal of Communications and Networks
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• v.16 no.3
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• pp.305-310
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• 2014

Optimal position of access point (AP) is important for multi-gigabit wireless transmission in terahertz (THz) wireless local area network (WLAN)-type applications, where there exist the THz characteristic multiple clusters in channel propagation. By considering the multiple clusters in THz indoor communications, this paper investigates the optimal AP position when two APs are issued for increasing the system capacity. Numerical results reveal that the central position of each AP within each half service region, which offers the shortest cumulated path length for line-of-sight paths, is optimal to achieve the maximal system capacity.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.7 no.4
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• pp.71-75
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• 2008

A folded monopole antenna is proposed for mobile communication applications. The proposed antenna covers CDMA and GSM at low frequency band, and it has a wide bandwidth (6.85 GHz) at high frequency band to cover GPS, DCS, USPCS, UHfS, WLAN (2.4, 5.2, 5.8 GHz), and the future application of IEEE 802.16e mobile WiMAX.

• The Journal of the Korea institute of electronic communication sciences
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• v.15 no.1
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• pp.31-38
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• 2020

In this paper, we propose a quadruple band antenna for GPS/WLAN/WiMAX application. The proposed antenna has quadruple band characteristics by considering the interconnection of four strip lines and DGS on the ground place. The total substrate size is 20.0 mm (W1) ⨯27.0 mm (L1), thickness (h) 1.0 mm, and the dielectric constant is 4.4, which is made of 20.0 mm (W2)⨯ 27.0 mm (L8 + L6+ L10) antenna size on the FR-4 substrate. From the fabrication and measurement results, bandwidths of 60 MHz (1.525 to 1.585 GHz) bandwidth for GPS band, 825 MHz (3.31 to 4.135 GHz) bandwidth for WiMAX band and 480 MHz (2.395 to 2.975 GHz) and 385 MHz (5.10 to 5.485 GHz) bandwidth for WLAN band were obtained on the basis of -10 dB. Also, gain and radiation pattern characteristics are measured and shown in the frequency of triple band as required.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.43 no.8 s.350
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• pp.84-90
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• 2006

With the widespread of the wireless Internet and wireless LAN, different wireless technologies such as 3G cellular networks and WLAN will cooperate to support more users and applications with higher data rate over wider areas. When a mobile node moves around in the hybrid networks, it needs to perform seamless vertical handoffs between different wireless networks to provide high performance data transmission. When an application with TCP connection in a mobile node performs a vertical handoff, TCP performance is degraded due to packet losses even though it maintains the previous TCP state information during handoff, because 3G and WLAN have different available bandwidth. In this paper, we propose a new congestion control algorithm for vertical handoff to improve the TCP performance by measuring the rough end-to-end available bandwidth and calculating the slow-start threshold. By ns-2 simulation, we show that the proposed algorithm enhances the TCP performance during vertical handoffs compared to the previous algorithms.

• The Journal of the Korea institute of electronic communication sciences
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• v.13 no.1
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• pp.15-22
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• 2018

In this paper, a microstrip-fed triple-band monopole antenna for WLAN/WiMAX applications was proposed. The proposed antenna is consist of two arc-shaped and one strip line structure, then get the three current path and then designed in order to get triple resonant characteristics. We carried out simulation about parameters. Taking account of coupling effect, Adjusted the length of the two arc-shaped and one strip line, we get the optimized parameters. The proposed antenna is fabricated on an FR-4 substrate, the dielectric constant is 4.4, and total size is $23.5mm(W1){\times}32.0mm(L1){\times}1.0mm(t)$, and its proposed antenna size is $21.0mm(W6){\times}31.0mm(L7)$. From the measured results, return loss of the proposed antenna satisfied return loss 927 MHz (1.844~2.771 GHz), 926 MHz (3.33~4.256 GHz), and 1,415 MHz (5.13~6.545 GHz). And measured results of gain and radiation patterns displayed for operating bands.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.23 no.6
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• pp.740-747
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• 2019

In this paper, an antenna applicable to WLAN and WiMAX frequency bands is designed, fabricated, and measured. The proposed antenna is designed to have two branch strip line in the patch plane and a rectangular slit in the ground plane based on microstrip feeding for triple band characteristics and added a vertical strip in the ground plane to enhance impedance bandwidth characteristics. The proposed antenna is designed on a substrate with a relative permittivity of 4.4, a thickness of 1.0 mm, and has a size of $18.0mm(W1){\times}37.3mm$ (L4+L5+L7). From the fabricated and measured results, impedance bandwidths of 480 MHz (2.32 to 2.80 GHz) for 2.4/2.5 GHz band, 810 MHz (3.22 to 4.03 GHz) for 3.5 GHz band, and 1,820 MHz (5.05 to 6.87 GHz) for 5.0 GHz band were obtained based on the impedance bandwidth. Measured 3D pattern and gains are displayed.

• The Journal of the Korea institute of electronic communication sciences
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• v.14 no.1
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• pp.119-126
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• 2019

In this paper, a monopole antenna applicable to WLAN standardization is designed, fabricated, and tested. The proposed antenna is designed to have three microstrip lines based on microstrip feeding method and inserted one stub to enhance impedance characteristics. Then, it obtained triple band characteristics of the proposed antenna. We adjusted and optimized the lengths and width of the three microstrip lines and one inserted stub to obtain the required impedance bandwidth for this paper. The proposed antenna has $23.0mm(W){\times}53.1mm(L1)$ on a dielectric substrate of $24.0mm(W1){\times}60.0mm(L){\times}1.0mm$ size. From the fabrication and measurement results, bandwidths of 158 MHz (841 to 1000 MHz) for 900 MHz band, 630 MHz (2.32 to 2.95 GHz) for 2400 MHz band, and 1,040 MHz (4.95 to 5.99 GHz) for 5000 MHz band were obtained based on the impedance bandwidth. The fabricated antenna also obtained the measured gain and radiation pattern characteristics in the required triple band of the proposed antenna.

• The Journal of the Korea institute of electronic communication sciences
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• v.14 no.3
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• pp.475-482
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• 2019

In this paper, we propose a triple band antenna for GPS / DCS / WLAN system. The proposed antenna has the characteristics required by considering the interconnection of two strip lines and various slits on the ground place. The total substrate size is $31mm(W1){\times}50mm(L1)$, thickness (h) 1.6 mm, and the dielectric constant is 4.4, which is made of $22mm(W7+W12+W8){\times}43mm(L4+L3)$ antenna size on the FR-4 substrate. From the fabrication and measurement results, bandwidths of 340 MHz (1.465 to 1.805 GHz), 480 MHz (2.155 to 2.635 GHz) and 1950 MHz (4.975 to 6.925 GHz) were obtained on the basis of -10 dB. Also, gain and radiation pattern characteristics are measured and shown in the frequency triple band as required.

• Journal of information and communication convergence engineering
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• v.6 no.2
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• pp.233-237
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• 2008

This paper presents proposal for an application (only for Windows-based Mobile) that can synchronize the Third Generation Windows-based mobile with the prescribed server. This application can be used by mobile users to send information directly to the WAS server wirelessly. In this paper a comparison between Third Generation technology and WLAN ( both are parallel technologies first one embodied by IMT-2000 standards and the second one by ITU Standards) has been made and also a comparison between Wi-Fi and Bluetooth has been made.