• Journal of Satellite, Information and Communications
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• v.9 no.4
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• pp.82-86
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• 2014

In this paper, we propose a novel modulation scheme specialized in real time broadcast system using a multicopter. Since multicopters have many advantages in aerial photography, they have been widely used in broadcasting technologies. However, because of restrictions on flight time, it is difficult to utilize multicopters in real time broadcasting systems. Therefore, video transmission using multicopter is necessary for low power communication techniques in air channel environment. Performance results of the hybrid modulation in this paper are compared to that of conventional modulations with Bit Error Rate (BER) and Signal to Noise Ratio (SNR) simulations. The results also showed that proposed system is suitable for aerial photography. Experiments demonstrated the superiority of the proposed modulation scheme by showing received symbols through an USRP equipment.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2019.05a
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• pp.243-246
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• 2019

In cognitive radio networks, secondary transmitters should cease its transmission immediately under the detection of primary transmission in the spectrum they are using. Then they need to exploit another idle spectrums and resynchronize to the newly found idle spectrums. Most of related work presume the existence of separate control channel used by secondary users commonly for exchanging the information of idle spectrums. However, this presumption is not feasible in real world cognitive radio scenario. Therefore we address a proactive spectrum synchronization scheme with no need of separate control channel. Our scheme lets secondary users exchange the spectrum information periodically during normal communication process and determine the next spectrum band in advance of detecting primary transmission. We evaluate our scheme in a real world cognitive radio environments set up with USRPs.

• Information and Communications Magazine
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• v.27 no.8
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• pp.37-42
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• 2010

최근 학계에서 많이 연구되고 있는 무선인지기술(CR : Cognitive Radio)을 실제 하드웨어로 구현하는 경향이 두드러지고 있다[1,2]. 또한 IEEE 802.22의 표준화가 완료되고 미국의 DTV전환과 함께 무선인지기술이 본격적으로 적용되면서 연구된 결과를 실제 시스템에서 구현하여 입증할 필요성이 증가하고 있다. 본 고에서는 대표적인 오픈소스 하드웨어 플랫폼인 GNU Radio에 대해 설명하고 무선인지기술을 적용한 시스템을 소개한다.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.27 no.2
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• pp.216-219
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• 2016

In this paper, the SIW(Substrate Integrated Waveguide)-based feeding antenna for the application of SDR(Software Defined Radar) is designed and manufactured. It is usually well-known that SIWs are easily integrated on PCB and have low transmission loss toward high powered input signal. Also, it is recommended that SIWs are strongly immunized to Electromagnetic Interferences(EMI). In particular, the manufactured antennas are loaded on the USRP(Universal Software Radio Peripheral) platform and employed to detect target RCS as an experiment in this paper. The operating frequency of the proposed antenna is in ISM(Industrial, Scientific and Medical) band(2.4~2.48 GHz) and the measured gain is over 8 dBi at 2.44 GHz.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.10
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• pp.1190-1196
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• 2016

In this paper, a cross-layer interworking scheme for different protocols is proposed to provide an efficient internet services in very small aperture terminal (VSAT) based satellite communication systems. In addition, we implement the proposed interworking model and prove the feasibility of the proposed system. VSAT based satellite communication systems commonly use digital video broadcasting (DVB)-S2 standard. Unfortunately, DVB-S2 has inefficient parts to support IP based internet services because it has originally been designed to support broadcasting services. Generic stream encapsulation (GSE) protocol, which is a layer 2 protocol, has been proposed to mitigate this inefficiency. We propose a cross-layer interworking scheme to cooperate efficiently between IP and GSE protocols and between GSE protocol and DVB-S2, respectively. In addtion, we implement the proposed interworking schemes via computer softwares and prove the feasibility using NI-USRP and commercial DVB receiver.

• Journal of Korea Society of Digital Industry and Information Management
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• v.8 no.4
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• pp.91-98
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• 2012

This paper implements 2X2 MIMO Long Term Evolution (LTE) base station using Software defined radio (SDR) technology. The implemented base station system processes baseband signals on a Graphics Processor Unit(GPU). GPU is a high-speed parallel processor which provides very important advantage of using a very powerful C-based programming environment that is Compute Unified Device Architecture (CUDA). The implemented software-based base station system processes baseband signals through GPU. It utilizes USRP2 as its RF transceiver. In order to guarantee a real-time processing of LTE baseband signals, we have adopted well-known signal processing algorithms such as frame synchronization algorithms, ML detection, etc. using GPU operating in parallel processing.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.12
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• pp.2145-2152
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• 2016

Internet generalization has led to increased demands for Internet banking. Various security programs to protect authentication information are being developed; however, these programs cannot protect the wireless communication sections of wireless keyboards. In particular, vulnerabilities have been reported in the radio communication sections of 27 MHz wireless keyboards. In this paper, we explain how to analyze M's 27 MHz wireless keyboard. We also experimentally show that an attacker can acquire authentication information during domestic Internet banking using a 27 MHz wireless keyboard. To do this, we set up an experimental encironment to analyze the electromagnetic signal of a 27 MHz wireless keyboard.

• Information and Communications Magazine
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• v.30 no.2
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• pp.11-17
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• 2013

5세대 이동통신 시스템은 100Gbps급의 용량 증대를 목표로 하고 있으며, 이를 지원하기 위해서 무선 백홀에서 10GHz 이상 대역을 활용하는 연구가 시도되고 있다. 또한, 사용자를 지원하기 위한 무선 접속망에서는 고용량의 용량 증대 달성을 위해서 massive MIMO 등의 기술들이 활용될 수 있다. 하지만 5GHz 이하의 대역에서 많은 안테나를 활용하기 위해서는 공간상의 제약이 발생하기 때문에 이를 극복하기 위해서 집적화된 안테나에 대한 연구가 필요하다. 집적화된 안테나의 방사패턴에 따른 채널 특성은 기존 채널 특성과는 많은 차이가 있으며 이론적인 연구에는 한계가 발생할 수밖에 없어서 실제 검증 시스템의 구현을 통해서 측정을 통한 분석 연구가 필요하다. 이에 따라 본 논문에서는 집적화된 안테나를 기반으로 하는 무선 접속망의 설계를 위해서 SDR 기술인 GNURadio와 USRP 보드를 활용한 시스템을 설계하고 성능 분석한 결과를 제시한다. 본 연구를 통해서 집적화된 안테나 기반의 용량에 대한 성능이 동일한 수신 SNR 관점에서는 기존 MIMO의 성능과 비교해서 큰 차이가 없음을 보인다.

• Proceedings of the Korea Information Processing Society Conference
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• 2015.10a
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• pp.319-321
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• 2015

인지무선네트워크 (Cognitive Radio Networks) 환경에서 스펙트럼의 원소유주인 1차사용자가 전송을 개시하는 경우, 같은 채널을 사용하는 2차사용자의 TCP (Transmission Control Protocol) 는 전송 불능 상태가 되어 심각한 성능저하가 발생한다. 이러한 성능저하는 1차사용자의 등장으로 인해 채널이 사용 불가능 해지는 상태를 패킷 손실로 판단하여 재전송 타임아웃이 발생하기 때문에 발생된다. 우리는 이 문제를 링크 또는 물리 계층 (하위계층) 과 TCP간의 크로스레이어링을 통하여 해결하고자 한다. 하위 계층은 1차사용자의 전송이 감지되면, 이를 TCP에게 시그널링하고, TCP는 이를 통해 재전송 타이머와 혼잡 윈도우를 고정시키고, 패킷 전송을 중단하도록 한다. 또, 하위계층이 가용 채널을 감지하게 되면, 재차 TCP에게 시그널링을 함으로써, 전송이 신속하게 재개되도록 한다. 제안하는 방법은 실제 USRP(Universal Software Radio Peripheral)에 구현하여 성능의 향상을 검증한다.

• International Journal of Computer Science & Network Security
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• v.23 no.2
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• pp.140-146
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• 2023

With the rapid growth of new users and massive need for very high data rate in 5G communications system, different technologies have been developed and applied to enhance communication efficiency. One of those technologies is the MISO, MISO and MIMO which transmits and receives information with more reliability by using multiple antennas on transmitter or/and receiver side. This paper presents the latest trends in 5G telecommunications system based on software defined radio, A novel low-cost SIMO, MISO and MIMO using flexibility between USRP and Simulink is implemented tested and validated.