• The Journal of the Acoustical Society of Korea
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• 제23권2E호
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• pp.56-67
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• 2004

Despite abundant research outcomes of blind source separation (BSS) in many types of simulated environments, their performances are still not satisfactory to be applied to the real environments. The major obstacle may seem the finite filter length of the assumed mixing model and the nonlinear sensor noises. This paper presents a two-step speech enhancement method with multiple microphone inputs. The first step performs a frequency-domain BSS algorithm to produce multiple outputs without any prior knowledge of the mixed source signals. The second step further removes the remaining cross-channel interference by a spectral cancellation approach using a probabilistic source absence/presence detection technique. The desired primary source is detected every frame of the signal, and the secondary source is estimated in the power spectral domain using the other BSS output as a reference interfering source. Then the estimated secondary source is subtracted to reduce the cross-channel interference. Our experimental results show good separation enhancement performances on the real recordings of speech and music signals compared to the conventional BSS methods.

• 한국통신학회논문지
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• 제18권4호
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• pp.519-529
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• 1993

Compact-SQAM이라 명명된 전력 및 대역폭 효율적인 변조기법을 제시하였다. 부가백색잡음, 심볼간의 상호간섭방해 및 timing jitter가 존재하는 선형 및 비선형의 단일 방송파 전송환경하에서, 또한 각종 인접채널방해 - 즉, 목적 및 인접방해채널간의 간격 및 목적채널상의 페이딩정도가 다른 다수 반송파전송환경하에서 본 변조기법의 성능을 Computer simulation을 통해 실험적으로 분석하였다. 분석결과, Compact-SQAM은 기존의 QPSK, OQPSK, MSK, 1JF-OQPSK(또는 SQORC) 및 SQAM과 비교하여 대역폭 효율상의 장점이 있으며, 구현이 매우 간단한 복조기 사용시에도 그 오류확률특성이 우수함을 보였다. 특히, 가용-주파수대역이 극히 제한되는 비선형 다중 반송파 전송채널에서 타 변복조방식보다 주파수 이용 효율 및 오류확률 특성이 우수함을 보였다.

• International Journal of Internet, Broadcasting and Communication
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• 제13권3호
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• pp.17-24
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• 2021

Recently, a lossless non-orthogonal multiple access (NOMA) implementation without successive interference cancellation (SIC) has been proposed in the literature of NOMA. This lossless non-SIC NOMA was achieved via correlated superposition coding (CSC), in contrast to conventional independent superposition coding (ISC). However, only the achievable data rates for CSC NOMA were investigated. Thus, this paper proposes a practical CSC NOMA scheme under Rayleigh fading channel environments. First, we design the practical CSC NOMA scheme, namely quadrature correlated superposition modulation (CSM) NOMA, without channel coding, i.e., uncoded systems. In addition, we calculate the symbol error rates (SERs) for this quadrature CSM NOMA scheme. Then, simulations demonstrate that for the weak channel gain's user, the SER performance of the proposed quadrature CSM NOMA is shown to be improved greatly, compared to that of the conventional quadrature amplitude modulation (QAM) NOMA, whereas for the strong channel gain's user, the SER performance of the proposed quadrature CSM NOMA degrades a little, compared to that of the conventional QAM NOMA. As a result, the proposed quadrature CSM NOMA scheme could be considered as a practical NOMA scheme for CSC NOMA schemes toward the fifth-generation (5G) and next generation communications.

• 한국소음진동공학회논문집
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• 제13권11호
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• pp.831-837
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• 2003

This paper investigates the insertion loss of nosie barrier with a interference device, The efficiency of the conventional interference-type noise barrier depends on specific frequency, Thus this study is performed to improve the efficiency of the nosie barrierin the range of broadband frequency. by changing the shape of interference device and adding the channel with various depths, The boundary element method (BEM) is used to predict the insertion loss of noise barrier. Two-dimensional boundary element model is created to simulate the performance of long barrier with a line source.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 추계학술대회논문집
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• pp.749-754
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• 2002

This paper investigates the insertion loss of nosie barrier with a interference device. The efficiency of the conventional interference-type noise barrier depends on specific frequency. Thus this study is performed to improve the efficiency of the nosie barrier in the range of broadband frequency, by changing the shape of interference device and adding the channel with various depths. The boundary element method (BEM) is used to predict the insertion loss of noise barrier. Two-dimensional boundary element model is created to simulate the performance of long barrier with a line source.

• ETRI Journal
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• 제39권2호
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• pp.255-263
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• 2017

This paper proposes a graph-theatrical approach to optimize spatial reuse by adopting a technique that quantizes the channel information into single bit sub-messages. First, we introduce an interference graph to model the network topology. Based on the interference graph, the computational requirements of the algorithm that computes the optimal spatial reuse factor of each user are reduced to quasilinear time complexity, ideal for practical implementation. We perform a resource allocation procedure that can maximize the efficiency of spatial reuse. The proposed spatial reuse scheme provides advantages in beamforming systems, where in the interference with neighbor nodes can be mitigated by using directional beams. Based on results of system level measurements performed to illustrate the physical interference from practical millimeter wave wireless links, we conclude that the potential of the proposed algorithm is both feasible and promising.

• 디지털콘텐츠학회 논문지
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• 제5권3호
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• pp.187-191
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• 2004

모바일 통신 채널의 빠른 변화는 다중 반송파 변조의 성능에 많은 영향을 준다. 본 논문에서는 다중 반송파 CDMA 네트워크의 BER 성능을 분석하였고 등가 신호 대 전체 잡음 전력비를 라이시안 페이딩, 부분대역간섭 다중접속 사용자 간섭채널에서 유도하였다. MC-CDMA 시스템의 역방향 링크 등가 SNIR을 사용하여 MC-CDMA/BPSK 신호의 성능을 부분대역간섭의 점유율과 간섭 전력에 따라서 평가하였다. 그리고 다중반송파 멀티미디어 시스템의 QoS를 향상하기 위한 부분대역간섭의 영향을 종합적으로 연구하였다.

• ETRI Journal
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• 제33권3호
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• pp.320-325
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• 2011

This paper considers the effects of simultaneous correlated multipath fading and shadowing on the performances of a signal-to-interference ratio (SIR)-based dual-branch selection combining (SC) diversity receiver. This analysis includes the presence of cochannel interference. A generalized fading/shadowing channel model in an interference-limited correlated fading environment is modeled by generalized-K distribution. Closed-form expressions are obtained for probability density function and cumulative distribution function of the SC output SIR, as well as for the outage probability. Based on this, the influence of various fading and shadowing parameter values and the correlation level on the outage probability is examined.

• 전자공학회논문지S
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• 제34S권8호
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• pp.10-19
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• 1997

In this paper, perfodrmance of matched-filter (MF) acquisition scheme is analyzed for a direct-sequence/code-division-multiple-access (DS/CDMA) system in a microcellular environment. Mean acquistion time is used as a performance measure. It is demonstrated that acquisition performance is enhanced using interference suppression filter in a Rician fading channel. To apply for multiuser environments, multiple access interference is considered in the performance analysis. From the numerical results, it is shown that mean acquistion time decreases with the increasing SNR/chip, and acquisition performance is improved as the number of taps of interference suppression filter. It is also shown that mean acquisition time increases with the number of users in the system, and acquistion performance is degraded as the icrease of narrowband interference bandwidth. The analysis in this paper can be applied to a DS/CDMA overlay environment.

• 대한전자공학회논문지TC
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• 제41권1호
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• pp.13-22
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• 2004

논문은 W-CDMA 고속 다운링크 패킷접속(HSDPA: high-speed downlink packet access) 시스템에서 다중경로 간섭성분에 대해 직렬간섭제거(SIC successive interference cancellation) 알고리즘을 적용하여 오류율 성능을 유도하고 수치해석으로 성능을 분석한 것이다. 성능분석 결과에 의하면, 다중경로수가 증가함에 따라 오류율 성능이 급격하게 포화됨을 알 수 있었고, 확산이득(PG)이 증가할수록 성능향상이 매우 커짐을 확인하였다. 두개의 다중경로와 평균 오류율 $1.0{\times}10^{-3}$에서 확산이득 PG=64와 128의 경우 기존 검출방식에 비해 직렬간섭제거 성능이 각각 7dB와 1.4dB이상 우수함을 보였다. 파일럿 채널과 데이터 채널들에 할당하는 가중치가 '1'에 가까울수록 오류율 성능이 포화됨을 알 수 있었다. 그리고 다중코드수(K)가 증가할수록 다중경로수에 비례한 간섭전력 증가로 인해 성능저하가 커졌다. 또한 상대적으로 뒤에 도달한 다중경로의 페이딩 채널이득이 적을수록 성능이 향상됨을 알 수 있었다 이상과 같은 성능분석 결과에 따르면 고속전송을 위한 다중코드, 낮은 처리이득 및 채널 페이딩 등의 환경에서 성능향상을 위해서는 다중경로 간섭제거가 필수적임을 알 수 있었다.