• Proceedings of the Korean Information Science Society Conference
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• 2002.10e
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• pp.289-291
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• 2002

100Mbps의 전송속도를 만족하는 TDMA 방식의 전송 방식의 MAC을 연구중이다. 현재까지 진행된 MAC에 대한 간단한 소개와 또 MAC 프레임의 구조를 설명하고 이를 개발하기 위하여 11Mbps급의 IEEE 802 11b 모뎀을 활용한 방법에 대하여 설명한다.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.48 no.2
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• pp.79-84
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• 2011

In this paper we design MIMO antenna with high isolation between antennas by using an isolation aid for WLAN. Two dual-band PIFAs which operates IEEE 802.11n are arranged symmetrically along the central axis of antenna frame and ground plane. By inserting an isolation aid between two PIFAs the isolation is improved maximum 5dB and 7dB for 2.4GHz band and 5GHz band respectively. Total efficiency is above 60%. ECC is below 0.1.

• JSTS:Journal of Semiconductor Technology and Science
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• v.7 no.2
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• pp.98-101
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• 2007

A fully integrated 5-GHz CMOS power amplifier for IEEE 802.11a WLAN applications is implemented using $0.18-{\mu}m$ CMOS technology. An on-chip transmission-line transformer is used for output matching network and voltage combining. Input balun, inter-stage matching components, output transmission line transformer and RF chokes are fully integrated in the designed amplifier so that no external components are required. The power amplifier occupies a total area of $1.7mm{\times}1.2mm$. At a 3.3-V supply voltage, the amplifier exhibits a 22.6-dBm output 1-dB compression point, 23.8-dBm saturated output power, 25-dB power gain. The measured power added efficiency (PAE) is 20.1 % at max. peak, 18.8% at P1dB. When 54 Mbps/64 QAM OFDM signal is applied, the PA delivers 12dBm of average power at the EVM of -25dB.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2008.05a
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• pp.133-136
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• 2008

In this paper, the parallel coupled line(PCL) band-pass filter satisfying IEEE 802.11a (a:$5.15{\sim}5.25$, b:$5.25{\sim}5.35$, c:$5.725{\sim}5.875$ [GHz]) has been designed for 5[GHz]band W-Lan RX-System applications. The designed PCL Band-Pass filter is of advantage to make a design formula that is small, light and approximate accuracy. It choose a microstrip plane figure because it is possible that a multiplicity of resonator was designed. It was shown that bandwidth was 14% from 5.15GHz to 5.92GHz at the -3dB designed filter. As a result, it is enough to use the designed filter at W-LAN RX-system of the 5GHz band.

• Journal of Advanced Navigation Technology
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• v.13 no.6
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• pp.846-853
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• 2009

This paper presents the design of a high efficiency frequency multiplier with load-pull simulation and analyses the nonlinear distortion of the frequency multiplier. The frequency multiplier shows serious distortion of multiplying signal bandwidth because of nonlinearity when modulated signal is applied, so a digital predistortion with look up table (LUT) is applied to compensate for the distortion of the frequency multiplier. The frequency multiplier is designed to produce 5.8GHz output by doubling the input frequency to be operating at IEEE 802.11a standard wireless LAN. The output spectrum shows 12dB ACPR improvement both at +11MHz, +20MHz offset from center frequency after linearization.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.41 no.6 s.324
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• pp.33-39
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• 2004

Design of efficient Medium Access Control (MAC) protocols with both high throughput performances is a major focus in distributed contention based MAC protocol research. In this paper, we propose an efficient contention based MAC protocol for wireless Local Area Networks, namely, the Developed Collision Resolution (DCR) algorithm. This algorithm is developed based on the following innovative ideas: to speed up the collision resolution, we actively redistribute the backoff timers for all active nodes; to reduce the average number of idle slots, we use smaller contention window sizes for nodes with successful packet transmissions and reduce the backoff timers exponentially fast when a fixed number of consecutive idle slots are detected. We show that the proposed DCR algorithm provides high throughput performance and low latency in wireless LANs.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.3B
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• pp.165-173
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• 2012

In this paper, we propose a random backoff scheme for Emergency Warning Messages (EWMs) in the vehicle-to-vehicle environment. The EWMs are disseminated from a vehicle that detects an emergency situation to other vehicles in a multi-hop fashion. Since the vehicle-to-vehicle communication based on IEEE 802.11 adapts CSMA/CA, the density of vehicles increase the probability of collisions between transmissions. Moreover, in the presence of background traffic, the EWM should have a higher priority than that of other messages in neighboring vehicles. To that end, we propose the Distant-Dependent Adaptive Backoff (DDAB) scheme, which set a different contention window for random backoff depending on the distance from the sender to the receiver. In the case when a vehicle is expected to located in the outskirts of the communication boundary, the proposed scheme makes the contention window size small in order to compete the background traffic transmission. Otherwise the contention window is set to a large number to reduce the collision possibility among the EWM transmissions. Via simulations, we show that the proposed scheme performs better than the previous schemes for EWM.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39A no.4
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• pp.180-187
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• 2014

In this paper, a extension of a fixed-complexity sphere decoder (FSD) to perform interference signal detection and cancelling is proposed for downlink multiuser multiple input-multiple output (MIMO) communication system. It is based on the application of channel matrix expansion on generalized sphere decoder (GSD), and modification of the channel matrix ordering scheme to a FSD algorithm for interference detection. A Monte Carlo simulation shows that the proposed algorithm improves the receiver performance by 3 dB as compared to maximum likelihood detection without interference cancelling at 10% packet error rate in configuration of 702 Mbit/s datarate for four users respectively on IEEE802.11ac.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.23 no.10
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• pp.90-99
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• 2009

In this paper, we proposed the new class-E frequency multiplier design that include the highest efficient characteristics. The proposed frequency multiplier is designed for 5.8[GHz] output using the frequency multiplier about 2.9[GHz] input signal. And studying in this paper is for the design and the implementation of the class E frequency multiplier. For the result, the maximum highest efficient characteristics 32[%] which is with output power 24.5[dBm] and 8.5[dB], is shown with frequency multiplier for the 2.9/5.8[GHz] class E. And we applied the linear method to the implemented class E frequency multiplier. As a result, the output spectrum for the linear is upgrade to 12[dB], 12[dB], 13[dB] of the ACPR characteristics on the +11[MHz], +20[MHz], +30[MHz] offset frequency in the center frequency. The result is satisfied with the 3.83[%] of the lineared EVM for the 64-QAM modulated method with the 54[Mbps] transmission velocity. In this paper, we show that the good compensation result of the linearity and the efficiency through the digital pre-linear method of the distortion with the frequency multiplier. Therefore, we suggested the frequency multiplier method are applying to WLAN, cellular, PCS, WCDMA, and etc.

• ETRI Journal
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• v.33 no.4
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• pp.558-568
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• 2011

In this paper, we propose an efficient macrodiversity handover (MDHO) technique for time-division-based interference-limited IEEE 802.16j multihop wireless relay networks. In the proposed MDHO, when the diversity set members of the mobile station (MS) are a base station (BS) and relay station (RS), the MS receives the signal transmitted by the BS in the first phase. During the second phase, it also receives the simultaneous transmissions of the BS and RS. Furthermore, when the diversity set members are two RSs or two BSs, the MS receives only the simultaneous transmissions of the diversity set members. The superiority of the proposed MDHO is validated using analytical and simulation results. The performance analysis metrics are the average downlink (DL) carrier to interference and noise ratio (CINR), the average DL spectral efficiency, and the average service outage probability. Evaluation results show that the proposed MDHO significantly outperforms the conventional MDHO. The CINR gain achieved using the proposed MDHO is 4.71 dB compared to the conventional MDHO.