• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• v.9 no.1
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• pp.539-542
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• 2005

In this paper, we propose a wireless data access system, which used direct sequence spread spectrum method and the ISM band with 900MHz radio frequency. By applying bi-directional transmission between wireless transmitter and receiver, it can be effectively connected with any kinds of RF-ID with 900MHz ISM band. Therefore it could economically be used as peripheral equipments for RF-ID system.

• The Journal of the Acoustical Society of Korea
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• v.41 no.1
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• pp.16-29
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• 2022

This paper presents a Doppler shift estimation method and signal processing schemes for Direct Sequence Spread Spectrum (DSSS) transmission to overcome the Doppler shift due to the moving of the underwater communication unit. The proposed method estimates a Doppler shift via 2 step procedures using the preamble with the two 64-length Frank sequences which has a good self-correlation characteristic and is insensitive to the Doppler shift. Furthermore, a packet of DSSS underwater mobile communication and a RAKE receiver are designed using the proposed Doppler shift estimation method. Due to the modulation scheme of the designed DSSS underwater mobile communication using Differential-Quadrature Phase Shift Keying (DQPSK) for the data symbol transmission, the RAKE receiver dose not need a phase tracking and easily makes coherent signals among the combining RAKE branches. The designed RAKE receiving scheme including the proposed Doppler shift estimation method successfully decides information data using the DSSS signal transmitted from the pseudo-moving transmitter with velocity upto about 17.5 m/s.

• The Magazine of the IEIE
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• v.18 no.2
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• pp.18-25
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• 1991

• The Journal of Korean Institute of Communications and Information Sciences
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• v.23 no.9A
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• pp.2141-2152
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• 1998

In this paper, we design and implement an indoor wireless modem using small signal of ISM band regulation, which can tranceive reliable data streams. We use direct sequence spead spectrum (DS-SS) signaling with synchronous BPSK and QPSK modulation, convolutional coding with viterbi decoding. The radio frequency module uses frequency devision duplexing in 900 MHz band, and the digital module is implemented with FPGAs for the purpose fo ASIC design. The perfomrance of our own acquistion and tracking circuit consisting digital matched filter and decision logic is proved by experiments, and the possibility of file transfer at indoor environment with the entrie system that the modem is connected the PC through RS-232C port is verified.

• Electronics and Telecommunications Trends
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• v.12 no.6 s.48
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• pp.1-14
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• 1997

본 글에서는 일반적인 무선 LAN 기술과 사용 주파수 대역에 대해서 간략히 기술하였고, 특히, 스펙트럼 확산방식을 사용하는 무선 LAN의 규제항목을 DS방식과 FH방식으로 구분하여 IEEE 802.11 표준(안)을 중심으로 두 방식을 비교하였다. 그리고 무선 LAN과 관련된 제외국 표준(안) 및 관련 법규(ETS 300 328 표준(안), IEEE 802.11 표준(안), FCC Part 15.247, 일본 RCR-33A 등)를 국내 무선 LAN 기술기준과 비교하여 새로운 기술기준 항목을 도출하였다.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.46 no.8
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• pp.1-9
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• 2009

In this paper, we describe DSSS transceiver development robust to jamming signals as an investigation of ECCM transceiver for UAV uplink. The jamming margin is 15dB or greater with the development target of transceiver because the jamming margin is more important than the transmission rate of data and the spreading code can be changeable. The rake receiver is applied to combine multipath components and turbo code which the coding gain is 7.2dB as a FEC. In this paper, the whole structure, design method and functional test result about the designed modem are described and a conclusion is made.

• Information and Communications Magazine
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• v.30 no.12
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• pp.17-24
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• 2013

본고에서는 세계전파통신회의(WRC: World Radio Conference)에서 IMT로 지정된 주파수 현황과 국내 이동통신 주파수 현황 및 계획을 알아본다. 또한 현재 시점에서 데이터 트래픽 증가 추세에 비추어 2020년 Beyond4G(5G)시대를 대비한 ITU(국제전기통신연합) 해당 표준화그룹의 소요량 예측 및 통신방식별 분담 율을 분석하였다. 주파수 수요예측에 따라 WRC-15에서 IMT 추가 주파수 지정 목적으로 진행하고 있는 위성, 방송, 과학 및 고정 등 기존업무와의 공유 연구 진행현황을 주파수 대역별로 살펴본다. 또한 도시 밀집 지역에서 대용량 데이터 전송을 위한 서비스 기술이 중요해진 시점에서 Beyond4G(5G) 시대를 위해 우리나라가 주도하고 있는 6GHz 이상 대역을 IMT로 활용하기 위한 활동을 소개한다. 마지막으로 WRC가 주파수를 분배 할당하는 방식인 '주파수 대역에 서비스 방식 지정'과 달리 '서비스 방식에 의한 주파수 대역 점유(예: LTE 기술표준(PS-LTE)을 PPDR대역에서 활용) 가능성'등 LTE 기술표준의 확산 추세에 대응하기 위해 5G시대에 준비할 사항에 대한 시사점을 언급하였다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38C no.8
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• pp.713-718
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• 2013

In this paper, additional data transmission scheme was proposed based on SSB-OFDM Communication system which was know as efficient technique for bandwidth, because it used only single side band instead of double side band. When sending additional data which should be well spreaded for low power characteristics and error robustness. Gold code was selected for spreading code because it has excellent low-cross correlation characteristics. Through computer simulation, the validity was proved that proposed system is well worked with SSB-OFDM system.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.2C
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• pp.175-183
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• 2006

This letter proposes a Direct Sequence Spread Spectrum (DS-SS)-based Flight Termination System(FTS) and show the simulation results and implements the system using FRGAs. The DS-SS FTS has immunity interference signals and the influence of jamming signal. Moreover, a DS-SS FTS can provides effects on an authentication and encryption with spread codes. And the system uses more less power than an analog FM system. We used Reed-Solomon (32, 28) code and triple Data Encryption Standard(3DES) for error correction and data encryption. Also we used counter algorithm for unauthenticated device's attack The spread codes of In-phase channel and Quadrature channel were generated by Gold sequence generators. The system was implemented in Altera APEX20K100E FPGA for the ground system and EPF10K100ARC240-3 for the airborne system.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.18 no.2
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• pp.218-230
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• 1993

A power line modem(PLM) which transfers data safely through power lines in houses or small offices is considered. When a power line is used for communications, transmitted signals could be affected by the channel characteristics such as frequency-selective fading, interference, and time-varying attenuation. In order to overcome these impairments, a direct sequence(DS) technique which is well known as an effective instrument against a variety of interferences and hostile channel properties is employed. Using a DS technique, however, requires more circuits such as PN code generator circuits, code modification circuits, and complicated synchronization circuits, and it also results in substantial acquisition delay. In this paper, some of these circuits are implemented via software programmed in the system controller, and the complicated synchronization circuits are replaced by simple circuits utilizing a 60 Hz power signal for synchronization. The synchronization ciruits used in this paper virtually eliminate the substantial acquisition delay, and is also designed to free influence of 60 Hz zero crossing jitters which reside in a power signal. As a result, a PLM using a DS technique is realized in the form of wall-socket plug, and the PLM hardware would be very much simplified.