• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2005년도 추계종합학술대회
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• pp.1037-1040
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• 2005

본 논문에서는 다중 안테나 방식인 시공간 블록코드를 HDR-WPAN 시스템에 적용하여 페이딩 채널 환경에서 그 성능을 분석하였다. 다중 안테나 방식은 안테나마다 다른 페이딩을 겪은 신호를 다수의 송/수신 안테나에 의해 결합함으로써 경로 간의 채널 골을 서로 보완시켜 수신 성능을 향상시키는 기술이다. 시공간 블록코드는 최대 공간 다이버시티 이득을 얻을 수 있고 간단한 선형 처리만으로도 최대 근사화(ML) 수신기 구현이 가능한 시공간 다이버시티 기법이다. HDR-WPAN 시스템에 시공간 블록코드를 적용하였을 경우 페이딩 채널 환경에서 기존 시스템보다 10$^{-4}$ 의 BER(bit error rate) 기준에서 최대 14dB의 다이버시티 이득을 가졌다. 시뮬레이션 결과를 통해 HDR-WPAN 시스템에 시공간 블록코드를 적용하였을 경우 적은 전력으로도 신뢰성 있는 통신을 할 수 있음을 확인하였다.

• 한국인터넷방송통신학회논문지
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• 제9권2호
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• pp.117-122
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• 2009

본 논문에서는 다중 안테나 (Multiple-Antenna)를 적용한 초광대역 무선통신 (UWB: Ultra Wide-Band) 시스템에서 이중 이진 터보 부호의 성능을 보인다. 본 논문에서는 PPM-TH (Pulse Position Modulation-Time Hopping) 방식과 PAM-DS (Pulse Amplitude Modulation-Direct Sequence) 방식의 UWB 시스템을 모두 고려하였으며, 다중 안테나 기술로 시공간 블록 부호 (STBC : Space Time Block Code) 송신 다이버시티와 수신 다이버시티 기술을 적용하였다. 그리고 이진 터보 부호에 비해서 부호어 사이의 최소 거리 (Minimum Distance)가 길어서 복호 성능이 좋으며 처리량 (Throughput)이 높아서 복호 처리 시간이 짧은 장점을 가지고 있는 이진 이중 터보 부호를 적용하였다. 본 논문의 결과는 UWB 시스템을 구현하는데 적용될 수 있다.

• Journal of Positioning, Navigation, and Timing
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• 제11권3호
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• pp.181-189
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• 2022

The public open signals from Global Navigation Satellite System (GNSS) including Global positioning system (GPS) are used widely by many peoples in the world except for the public regulated restriction signals which are encrypted. Nowadays there are growing concerns about GNSS signal spoofing which can deceive the GNSS receivers by abusing these open services. To counter these spoofing threats, many researches have been studied including array antenna techniques which can detect the direction of arrival by means of Multiple Signal Classification (MUSIC) algorithm. Originally the array antenna techniques were developed to countermeasure the jamming signal in electronic warfare by using the nulling or beamforming algorithm toward a certain direction. In this paper, we study the anti-spoofing techniques using array antenna to overcome the jamming and spoofing issues simultaneously. First, we will present the theoretical analysis results of spoofing signal response of Minimum Variance Distortionless Response (MVDR) algorithm in array antenna. Then the eigenvector algorithm of covariance matrix is suggested and verified to work with the existing anti-jamming method. The modeling and simulation are used to verify the effectiveness of the anti-spoofing algorithm. Also, the field test results show that the array antenna system with the proposed algorithms can perform the anti-spoofing function. This anti-spoofing method using array antenna is very effective in the view point of solving both the jamming and spoofing problems using the same array antenna hardware.

• 한국통신학회논문지
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• 제28권10A호
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• pp.788-795
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• 2003

We analyze the performance of a truncated power controlled CDMA(code division multiple access) cellular systems with base station antenna arrays. Erlang capacity and the channel capacity which is a maximum date rate to maintain almost error free communication are analytically derived. The numerical results show there can be a substantial increase in Erlang capacity and in channel capacity by antenna arrays incorporating with the truncated power control scheme.

• 한국통신학회논문지
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• 제37권1A호
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• pp.8-16
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• 2012

최근에 인지무선시스템에서 부사용자의 성능을 향상시키기 위해서 다중 안테나 기술을 사용하는 연구가 많이 진행되고 있다. 이런 다중 안테나 시스템에서는 안테나 수가 증가할수록 복잡성이나 시스템 가격 등의 문제가 발생한다. 이러한 문제들을 해결하기 위해 이용 가능한 안테나의 부분집합을 찾아 일부 안테나만 사용하는 안테나 선택기법이 사용된다. 본 논문에서는 IEEE 802.11n을 기반으로 시스템을 구축하였으며 인지무선 시스템의 상관채널에서의 안테나 선택기법을 제안한다. 수신 안테나보다 송신안테나가 많은 다중안테나 시스템을 고려하여 송신 안테나를 수신안테나와 같은 수로 선택하여 준다. 안테나 선택에서 모든 안테나 조합을 고려하는 것은 비현실적이다. 따라서 채널 상관 행렬의 벡터 사영 값을 이용한 크기 값을 안테나 선택 기준으로 해준다. 이 알고리즘은 우선사용자에게 미치는 간섭은 줄여주면서 부사용자의 통신 성능은 향상시켜준다.

• Journal of Positioning, Navigation, and Timing
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• 제11권2호
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• pp.91-98
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• 2022

In the next generation wireless communication system, the beamforming technique based on a massive antenna is one of core technologies for transmitting and receiving huge amounts of data, efficiently and accurately. For highly performed and highly reliable beamforming, it is required to accurately estimate the Angle of Arrival (AOA) for the desired signal incident to an antenna. Employing the massive antenna with a large number of elements, although the accuracy of the AOA estimation is enhanced, its computational complexity is dramatically increased so much that real-time communication is difficult. In order to improve this problem, AOA estimation algorithms based on the massive antenna with the low computational complexity have been actively studied. In this paper, we compute and analyze the computational complexity of the cascade AOA estimation algorithm based on the Flexible Massive Concentric Circular Array (FMCCA). In addition, its computational complexity is compared to conventional AOA estimation techniques such as the Multiple Signal Classification (MUSIC) algorithm with the high resolution and the Only Beamspace MUSIC (OBM) algorithm.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제9권11호
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• pp.4387-4404
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• 2015

The energy-efficient design of sensing-based spectrum sharing of a multi-input and multi-output (MIMO) cognitive radio (CR) system with imperfect multiple antenna spectrum sensing is investigated in this study. Optimal resource allocation strategies, including sensing time and power allocation schemes, are studied to maximize the energy efficiency (EE) of the secondary base station under the transmit power and interference power constraints. EE problem is formulated as a nonlinear stochastic fractional programming of a nonconvex optimal problem. The EE problem is transformed into its equivalent nonlinear parametric programming and solved by one-dimension search algorithm. To reduce searching complexity, the search range was founded by demonstration. Furthermore, simulation results confirms that an optimal sensing time exists to maximize EE, and shows that EE is affected by the spectrum detection factors and corresponding constraints.

• Journal of electromagnetic engineering and science
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• 제15권4호
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• pp.219-223
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• 2015

In this paper, a miniaturized radio frequency choke (RFC) using modified stubs is proposed to improve isolation characteristics in a multiple-input-multiple-output (MIMO) antenna system. The proposed RFC, based on the LC resonance, is designed to suppress the leakage current that leads to the degradation of antenna diversity performances in the MIMO antenna configuration. The proposed RFC is composed of two open stubs that are implemented on the top of the ground plane and miniaturized by adding a slit structure on the ground plane. The MIMO antennas are also designed to verify isolation performance in the LTE 2300 band (2,300-2,400 MHz). The MIMO antennas perform well with low reflection coefficient characteristics and high isolation characteristics in the whole LTE 2300 band. To evaluate the isolation in the MIMO system, the envelope correlation coefficient (ECC) is calculated, and the value is less than 0.08. The achieved ECC is regarded as a reasonable result for improving isolation performance in the frequency range of 2,300-2,400 MHz; also, radiation patterns of antenna elements are maintained regardless of the presence of RFC.

• Journal of Positioning, Navigation, and Timing
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• 제5권1호
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• pp.37-45
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• 2016

In this paper, design and implementation issues for a network-oriented RF emitter localization system with array antenna are discussed. For hardware, the problem of array mismatch and RF/IF channel mismatch are introduced and the calibration schemes for solving those problems are also provided. For software, it is explained how to overcome the drawback of conventional MUltiple Signal Identification and Classification (MUSIC) algorithm in a point of identifying the number of received signals and problems such as Data Association Problem and Ghost Node Problem in regard to multiple emitter localization are presented with some approaches for getting around those problems. Finally, for implementation, a criterion for arranging each of sensors and a requirement for alignment of array antenna' orientation are also given.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2000년도 추계종합학술대회 논문집(1)
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• pp.149-152
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• 2000

In this paper, the reverse link performance of an imperfect power controlled DS/CDMA cellular system that uses a base station array antenna which can effectively remove the multiple access interference is analyzed considering both beam forming algorithm and power control error in shadowing. The blocking probability of the DS/CDMA cellular system based on array parameters, Eb/No and statistics of interference is derived, and then the system capacity corresponding to a certain blocking probability is calculated. On the assumption that the blocking probability is set 1 ％, the system capacity using MCGM algorithm with 12 antenna arrays is increased about 59 % than that using 8 antenna arrays when power control error is 2.5 ㏈.