• Proceedings of the IEEK Conference
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• 2000.09a
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• pp.83-86
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• 2000

DS/CDMA 이동통신 환경에서 채널의 용량을 제한하는 가장 큰 요인은 다중 사용자 간섭 신호의 영향이다. 본 논문에서는 어레이 안테나와 적응 혼합 다중 사용자 검파기 구조 (MUD: Multi-User Detection)를 이용하여 이러한 문제를 제거한다. 어레이 안테나의 각각의 빔 형성기는 MUD에서 궤환되는 기준 신호를 이용하여 원하는 사용자의 방향으로 빔을 형성하고 간섭 신호 방향으로는 널을 형성하여 제거하게 된다. 수신 신호의 전력이 제어되지 못하여 원근 문제(near-far problem)가 발생할 경우, 제안한 MUD는 적응적으로 지배적인 상관 값에 대해서는 직렬형, 비슷한 크기의 신호들은 병렬형 간섭 제거기를 통하여 제거함으로써 기존의 고정형 간섭 제거기보다 우수한 성능을 나타내었다.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.37 no.7
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• pp.1-8
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• 2000

In this paper, we introduce a modified interference cancellation scheme for multiuser detection in CDMA(Code Division Multiple Access). This detector uses SIC(Successive Interference Canceller) scheme and divides the received signals to reduce the delay time. In this proposed structure, the active users are divided into a number of groups. Within each group, parallel detection is performed to estimate the output signal of that group. The estimated output signal due to that group is then subtracted from the received signal and the resulting residual signal is used for the parallel detection of the next group. This parallel and serial cancellation process is repeated until the last group in the stage is completed. The estimated output signals due to all groups except -th group are MAI for the user signals in -th group. Therefore, the estimated output signals due to all groups except th group are subtracted from the received signal, and then the obtained signal becomes the input signal of -th SIC. The proposed RDSIC (Reduced Delay time of Successive Interference Canceller) has performance and complexity close to the SIC, but with much less detection delay.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2003.10a
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• pp.686-690
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• 2003

직접 확산 부호 분할 다원 접속 (Direct Sequence Code Division Multiple Access : DS-CDMA) 시스템과 시분할 다원 접속 (Time Division Multiple Access : TDMA) 시스템을 동일 주파수 대역에서 중첩되어 전송할 때 DS-CDMA 신호에서의 TDMA 신호의 협대역 간섭이 문제된다. 본 논문에서는 DS-CDMA 신호의 협대역 간섭(narrowband interference : NI)를 제거하는 방법으로서 노치필터를 이용해서 협대역 간섭파 제거법을 제안하고, 간섭제거기(CCI canceller)를 이용해서 다중접속간섭을 제거하여 DS-CDMA 신호의 성능을 개선한다. 본 논문은 잡음, 다중접속 간섭 및 협대역 간섭환경에서 DS-CDMA 신호와 TDMA 신호의 주파수 공용 시스템에 적용할 때의 성능을 분석하였다.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1995.04b
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• pp.153-156
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• 1995

본 논문은 gouging이 있는 free-formed parametric surface 모델로부터 간섭영역을 찾아 공구간섭을 검사하고 이를 제거하여 실시간으로 3축 NC가공을 할 수 있는 방법을 제안한다. 제안되는 방법은 parametri surface로부터 cartesian 경로를 따라 offset surface를 구하고 정의된 가공평면과의 교차곡선을 구하는 것에서 부터 시작한다. 교차곡선으로부터간섭 loop의 형성 여부를 검사함으로써 간섭영역을 찾을 수 있고 간섭을 제거하기 위해 간섭영역내의 모든 CC점이 공구 중심으로 부터 최소한 공구를 벗어나 위치하도록 공구를 공구의 측방향으로 이동시켰다. 이 논문은 free-formed surface의 gouging 부위에서 발생하는 공구간섭을 신속히 제거하고 CL data를 생성하여 실시간으로 3축 NC 가공을 하기 위한 하나의 접근이다.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.42 no.1
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• pp.59-64
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• 2005

To achieve a goal of minimum output power, the beamformer tends to cancel the desired signal if there exists correlated interference sources such as multipaths of the desired signal. In this paper, we propose a new method which overcomes the signal cancellation problem for correlated interferences. Instead of decorrelating the correlated interferences, the proposed bramformer regards them as replicas of the desired signal and coherently combines them with desired signal. This method uses an eigenvector constraint that suppresses a noise and uncorrelated interferences but keeps the desired signal and correlated interferences. Indisputably, the beamformer does not require any preliminary information on correlated interferences. Simulation results show that the proposed beamformer overcomes the signal cancellation problem and improves signal-to-noise ratio (SNR) of the array output when the correlated interferences exist.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.12 no.3
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• pp.360-369
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• 2001

This paper proposes the groupwise serial cross interference cancellation(GSCIC) algorithm for coherent detection and analyzes the groupwise serial block interference cancellation(GSBIC) and GSCIC algorithm for an asynchronous wideband DS-CDMA system in a single cell over multipath fading channels. In general, the GSIC algorithm can be grouped into two classes: i.e., GSBIC and GSCIC algorithm. In this paper, the proposed GSCIC algorithm is to improve the performance of the GSBIC algorithm. We compare the performance of the GSCIC and existing GSBIC algorithm in a multipath fading channel to that of the existing SIC algorithm. As a result, the performance of GSCIC algorithm is somewhat better compared with the GSBIC algorithm according to reduction factor $R_{f}$ and is similar to that of the SIC algorithm. And also, the GSBIC and GSCIC algorithms have the advantage that it can be analyzed system performance easily, changing the number of users within a user group according to system capacity.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38A no.9
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• pp.810-816
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• 2013

In this paper, we propose a SSD (simultaneous single-band duplex) system using Digital Cancellation. Also, we propose a method for Digital Cancellation when RF Cancellation is effectively performed. The proposed system has estimation frame for effective self-interference channel estimation in time-domain. The proposed system calculates signal power for selection of optimal coefficient after digital cancellation. Then, the proposed system selects coefficient of minimum signal power. Further, the proposed system uses LDPC code to minimize the effects of remaining self-interference signal. The proposed system shows BER performance of at 20dB by cancelling self-interference and iterating LDPC code. That is, the proposed system shows that the SSD communication is possible in static self-interference channel.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2010.11a
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• pp.59-62
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• 2010

디지털 기술의 발달로 인해 세계 각국에서 지상파 DTV 방송망을 핵심인프라로 활용하기 위한 노력이 지속되고 있다. 하지만 국내 지상파 DTV 표준인 ATSC방식은 주파수 이용관점에서 효율적이지 못한 단점을 가지고 있다. 이러한 단점을 해결하기 위해 그 동안 동일채널 중계기술이 많이 연구되어 왔다. 그러나 동일채널간섭으로 인한 신호품질 저하, 긴 처리시간, 송출전력 제한 등의 제약조건으로 인해 실제 방송망에서는 동일채널 중계기술이 활용되지 못하고 있는 실정이다. 이에 본 논문에서는 DAB용 간섭제거 기반 동일채널 중계기를 ATSC 시스템에 적용하였다. 제안하는 동일채널 중계기는 타이밍 옵셋 보상을 위한 위상 전 왜곡기법, 파일럿 성분 추정 및 제거를 위한 직류 제거기, 송/수신신호 간의 상관도를 기반으로 궤환신호의 지연시간을 추정하는 기법이 적용되었으며, 전산 모의실험을 통해 그 성능을 확인하였다. 전산 모의실험을 통해 주 송신신호보다 간섭신호가 큰 환경에서 제안한 동일채널 중계기의 간섭제거 능력을 확인하였고, 이에 따라 동일채널 중계기의 송출능력을 개선하는 동시에 짧은 처리 지연시간 및 양호한 신호품질을 얻을 수 있었다.

• Journal of the Institute of Convergence Signal Processing
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• v.14 no.2
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• pp.110-116
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• 2013

The amplification rate of a RF repeater is limited by the feedbacked signals from the same repeater. And an ICS (Interference Cancellation System) repeater has been developed to remove the feedbacked signals. The ICS repeater estimates the amplitudes and the phases of the feedbacked signals and removes the estimated feedback signals from the received input signal of the repeater. However, it requires lots of hardware complexity and this leads to the increase the cost of the repeater. Moreover, the ICS repeater can not solve the pilot pollution problems. To solve these problems, we have studied the implementation and adaptation of smart antenna system for RF repeaters. We have designed a smart antenna system with a switching beam structure in order to reduce the hardware and computational complexity. After analyzing the proposed smart antenna system, we found out that the amplification rate of the proposed repeater increases 23dB compare to the amplification rate of ICS repeater and the output SINR increases 6dB compare to the ICS repeater.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.22 no.12
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• pp.2653-2663
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• 1997

The successive and parallel interference cancellation schemes are two well-known types of multi-stage interference cancellation schemes using the conventional correlator receivers as a basic building block, which has been known to significantly improve the performance of DS/CDMA system in the multiple access communication. Performance comparison between these two schemes is made strictly based on the analytical and it has been shown that the successive interference cancellation (SIC) scheme is more resistant to fading than the parallel interference cancellation (PIC) scheme. We further investigate the performance of the successive IC scheme subject to the delay constraint, which may be imposed typically on most of service applications with a real-time transmission requirement, including speech and video applications. Our analysis demonstrates that the performance may be significantly improved by the groupwise successive interference cancellation (GSIC) scheme, which can be properly optimized to meet the given delay constraint.