• Title/Summary/Keyword: Co-Channel Interference

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Development of DSSS Uplink System for Missile Remote Control (유도탄 원격통제를 위한 대역확산 상향링크 시스템 개발)

  • Lee, Sangbum;Choi, Seoungduck;Kim, Whanwoo
    • Journal of the Institute of Electronics and Information Engineers
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    • v.50 no.8
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    • pp.110-118
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    • 2013
  • This paper describes the development of DSSS wireless communication uplink system for missile remote control. In consideration of low probability of intercept, low probability of exploitation, anti-jam, low latency, and doppler frequency offset, we used DSSS partially DBPSK. Also we used the selective diversity with two receiving antennas to mitigate multipath interference which is the dominant channel impairment and the turbo product code(TPC) for forward error correction(FEC) to improve bit error rate performance.

Performance of Block Error Probabilities of FS MC-CDMA System using BCH Coding Scheme in Slow Multipath Fading Channels (슬로우 다중경로 페이딩 채널환경에서 BCH 부호화기법을 이용한 FS MC-CDMA 시스템의 블록에러확률의 성능 개선)

  • Jin, Ze-Guang;Kang, Heau-Jo
    • Journal of Advanced Navigation Technology
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    • v.12 no.2
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    • pp.115-121
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    • 2008
  • In this paper, we analysis the error performance improvement of the FS MC-CDMA, whose information data are spread spectrum with direct sequences(DS), and each subband signal is transmitted using a subcarrier frequency, combining BCH code in Mobile communication channels which is characterized by Nakagami fading. The effect of co-channel interference on the block error performance is also studied in this paper. As a results of study, the coding techniques provides more efficient improvement than non-coding, but the coding techniques are required more band as many coding rate. Our study demonstrates that the system is combined coding techniques, the amount of improvement is capable of efficiently exploiting over the Nakagami fading.

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Aeronautical Telemetry Link Development for High Speed Data Transmission (고속 자료전송을 위한 비행체용 원격측정링크 개발)

  • Lee, Sangbum;Choi, Seoungduck;Kim, Whanwoo
    • Journal of the Institute of Electronics and Information Engineers
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    • v.50 no.7
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    • pp.43-51
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    • 2013
  • This paper describes the development of the telemetry link system for the high data rate transmission in high speed rocket application. In consideration of bandwidth efficiency, frequency selective fading and doppler frequency offset, we used DQPSK instead of PCM/FM which has been the primary modulation format in aeronautical telemetry. Also we used the spatial diversity with multiple receiving antennas to mitigate multipath interference which is the dominant channel impairment and the Turbo Product Code for Forward Error Correction to improve bit error rate performance.

Study on Tidal Current Simulation and its Application to Speed Trial around Straits of Korea (대한해협에서의 선박의 속력 시운전시 조류 예측에 관한 연구)

  • Lee, Hee-Su;Choi, Dai-Hyun;Park, Jong-Chun;Jeong, Se-Min;Kim, Young-Hun
    • Journal of Ocean Engineering and Technology
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    • v.24 no.6
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    • pp.23-29
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    • 2010
  • Korean shipbuilding companies have sometimes carried out sea trials to measure a vessel's speed performance around the western channel of the Straits of Korea, where the flow fields are very complicated because of the effect of various flows such as sea, tidal, geostrophic, and wind-driven currents. Because these flows seem to present significant interference to a ship, the numerical reproduction of the flow-fields in the vicinity of the target sites could provide a better understanding of the sea environments while performing sea trials. In this study, we used the MEC ocean model to simulate the tidal currents around Tsushima Island and compared the simulated tidal amplitudes and currents with the measurements of Teague et al. (2001). The tidal amplitudes of the present simulation results agreed well with the observations. Based on the numerical simulation, the optimal direction and proper sites for a speed trial are described.

An Adaptive Hot-Spot Operating Scheme for OFDMA Downlink Systems in Vertically Overlaid Cellular Architecture

  • Kim, Nak-Myeong;Choi, Hye-Sun;Chung, Hee-Jeong
    • ETRI Journal
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    • v.28 no.3
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    • pp.282-290
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    • 2006
  • In vertically overlaid cellular systems, a temporary traffic concentration can occur in a hot-spot area, and this adversely affects overall system capacity. In this paper, we develop an adaptive hot-spot operating scheme (AHOS) to mitigate the negative effects from the nonuniform distribution of user location and the variation in the mixture of QoS requirements in orthogonal frequency division multiple access downlink systems. Here, the base station in a macrocell can control the operation of picocells within the cell, and turns them on or off according to the system overload estimation function. In order to determine whether the set of picocells is turned on or off, we define an AHOS gain index that describes the number of subcarriers saved to the macrocell by turning a specific picocell on. For initiating the picocell OFF procedure, we utilize the changes in traffic concentration and co-channel interference to the neighboring cells. According to computer simulation, the AHOS has been proved to have maximize system throughput while maintaining a very low QoS outage probability under various system scenarios in both a single-cell and multi-cell environments.

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A study of synchronization scheme for DVB-S2x receivers based on burst super-frame transmission (버스트 슈퍼프레임 전송 기반의 DVB-S2x 수신기를 위한 동기부 설계에 관한 연구)

  • Oh, Jonggyu;Oh, Dukgil
    • Proceedings of the Korean Society of Broadcast Engineers Conference
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    • 2016.11a
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    • pp.63-65
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    • 2016
  • DVB (Digital Video Broadcasting)-S2 (Satellite - Second Generation) 표준은 현재 위성방송 시스템으로 가장 많이 사용되고 있는 표준이나, 추가적인 성능향상과 보다 다양한 응용분야에 적용하기 위해 DVB-S2 기술을 확장한 DVB-S2x (Satellite - Second Generation Extension) 시스템이 제정되었다. 그 중에서도 612,540 심볼 길이의 수퍼프레임 (Super-frame) 구조를 선택적으로 도입하여 긴 데이터 길이에 대해 스크렘블링 (Scrambling)을 적용하는 방법과 PLS (Physical Layer Signaling) 코드와 같은 참조 데이터 필드를 반복적으로 사용하는 방법 등을 사용할 수 있도록 하였다. 이를 통해 동일채널 간섭 (co-channel interference)에 대한 강인성을 증가시키고, 매우 낮은 SNR (Signal to Noise Ratio) 환경에서의 수신기 성능 향상 효과를 제공하게 된다 본 논문에서는 버스트 슈퍼프레임 전송 기반의 DVB-S2x 수신기를 위한 동기부를 설계하고 구조를 제안한다. 슈퍼프레임의 포맷은 DVB-S2x Annex E 의 규격 중 2 번 포맷을 이용하였으며, 2 번 슈퍼프레임 포맷은 버스트 (burst) 기반의 전송 방식에 용이한 측면이 있다. 동기부는 크게 버스트 검출부, 주파수 복구부, 신호 이득 조절부 그리고 심벌 타이밍 복구부로 구성된다.

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A Study on the Design and Implementation of a DSSS-based MODEM for a Right Termination System(FTS) (대역확산방식 비행종단시스템의 모뎀설계와 구현에 관한 연구)

  • Lim Keumsang;Kim Jaehwan;Cho Hyangduck;Kim Wooshik
    • 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.

A Study on an Efficient VDES Gain Control Method Conforming to the International Standard (국제 표준 규격에 부합하는 효율적인 VDES 이득제어 방안 연구)

  • Yong-Duk Kim;Min-Young Hwang;Won-Yong Kim;Jeong-Hyun Kim;Jin-Ho Yoo
    • Proceedings of the Korean Institute of Navigation and Port Research Conference
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    • 2022.06a
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    • pp.339-343
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    • 2022
  • In this study, a method for simplifying the structure of the VDES RF receiver, and the gain control method of the receiver to comply with the international standard in this structure was described. The input level of the wanted signal and unwanted signal to the receiver was defined, and when the two signals were input, the saturation state at the ADC was checked at the receiver output. As a result of the simulation by the circuit simulator, it was satisfied that the output power of the receiver was in the SFDR region of ADC with respect to the adjacent channel interference ratio, intermodulation, and blocking level. Through this study, it was found that the structure of th proposed RF receiver conforms to the international standard.

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Design and Implementation of Interference-Immune Architecture for Digital Transponder of Military Satellite (군통신위성 디지털 중계기의 간섭 회피 처리 구조 설계 및 구현)

  • Sirl, Young-Wook;Yoo, Jae-Sun;Jeong, Gun-Jin;Lee, Dae-Il;Lim, Cheol-Min
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.42 no.7
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    • pp.594-600
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    • 2014
  • In modern warfare, securing communication channel by combatting opponents' electromagnetic attack is a crucial factor to win the war. Military satellite digital transponder is a communication payload of the next generation military satellite that maintains warfare networks operational in the presence of interfering signals by securely relaying signals between ground terminals. The transponder in this paper is classified as a partial processing transponder which performs cost effective secure relaying in satellite communication links. The control functions of transmission security achieve immunity to hostile interferences which may cause malicious effects on the link. In this paper, we present an efficient architecture for implementing the control mechanism. Two major ideas of pipelined processing in per-group control and software processing of blocked band information dramatically reduce the complexity of the hardware. A control code sequence showing its randomness with uniform distribution is exemplified and qualification test results are briefly presented.

Study on Acquisition Method for GAS-CP-CDMA (Cyclic-Prefix Code Division Multiple Access using Good-Autocorrelation-Sequence) (GAS-CP-CDMA 동기 포착 방법 연구)

  • Lee, Seong-Min;Kim, Young-Je;Kim, Whan-Woo
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.33 no.11A
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    • pp.1087-1094
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    • 2008
  • In this paper, we propose the acquisition method of the Cyclic-Prefix CDMA using Good-Autocorrelation-Sequence (GAS-CP-CDMA) system. The sequences for GAS-CP-CDMA are m-sequence and constant amplitude zero autocorrelation code (CAZAC) with good autocorrelation property. The GAS-CP-CDMA system is proposed for interference cancellation in multi-user and -path environment in co-cell. However, the reliable initial acquisition in multi-path fading channel and multi-user system environment is crucial. In this paper, non-coherent power detector and threshold value are used for discriminating signal acquisition. The sequence used for computer simulation is CAZAC. The simulation results show proper threshold value depends on the number of users. Through the computer simulation, we draw setting up method of the optimum threshold value for the GAS-CP-CDMA system.