• The Journal of the Acoustical Society of Korea
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• v.20 no.4
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• pp.17-21
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• 2001

There are some methods to enhance the ‘sweet spot’in loudspeaker-based 3D audio systems. Most of them can be only applied to narrow frequency band inherently. In this paper, we introduce the more robust 3D sound reproduction system which has far wider robust bandwidth. The system applies a sum and difference filter to the conventional three loudspeaker-based one.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.18 no.12
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• pp.1994-2000
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• 1993

A new lattice structure using decision feedback and augmented prediction for estimating and suppressing the narrowband interference is presented. The performance of the proposed interference canceller is compared to the conventional interference cancellation filter. The reference signal of the interference canceller is formed by using the chip decisions, which is correlated with the narrowband interference components of the received signal. The decision feedback technique reduce the distortion of the desired signal which is introduced by the interference canceller through the use of feedback chip decisions. And by linear prediction of the error signal, the residual interference component of can be eliminated, Using this unconteminated error signal to update the adaptive filter coefficients, the performance of the rejection can be improved. In the simulation, it is assumed that the processing gains are 7 and 15, signal to interference ratio is -10[dB], and 5% interference band. The results show that the BER performance of the proposed filter structure is improved by 1~3dB.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.13 no.7
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• pp.693-701
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• 2002

In this paper, we analyze the coverage of asynchronous IMT(International Mobile Telecommunication)-2000 reverse link with a MUD(Multi-User Detector) system. The MUD system is utilized to increase the coverage of reverse link. Also we have considered a propagation loss model and an interference effect. Because it is very difficult that we have calculated the interference accurately, so a fractional cell loading factor(F) is used in this paper. We make use of a MUD efficiency($\beta$) to analyze the performance; this efficiency is presented the MAI of reduction. A simulation utilizes Hata's model, we calculated the coverage according to voice and data services. In this paper, we have assumed that the frequency of carrier has 800 MHz or 1.9 GHz, and a bandwidth is decided 3.84 MHz. We have predicted the performance of actual system by the analysis of capacity and coverage.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.5 no.4
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• pp.639-644
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• 2001

Sequence Code Division Multiple Access) and TDMA(Time Division Multiple Access) system. In this system, the narrowband TDMA signals can cause intolerant interferences to CDMA signals. In this paper, DS-CDMA/TDMA frequency sharing system have been analyzed in AWGN(Additive white Gaussian Noise), MAI (Multi Access Interference) and NI(Narrowband Interference) environment. Also, performance improvement has been obtained by adopting an adaptive notch filtering scheme using complex filter bank and CCI canceller.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.38 no.3
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• pp.1-8
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• 2001

In the DS/CDMA mobile communication systems, the parallel interference canceller is used in order to reduce the multiple access interference and the multipath fading. It is needed the accurate interference estimate in the multistage parallel cancellation. In this paper, the adaptive cancellation method and the new tentative decision device arc proposed and the performance is analyzed. The adaptive cancellation method uses the normalized least mean square(NLMS) algorithm to calculate the weight adaptively, and new tentative decision device uses the hyperbolic tangent decision with null zone. Computer simulation shows that the proposed scheme has the improved performance and the number of user is increased 48% compared with the conventional receiver.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.7B
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• pp.686-694
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• 2002

In this paper, we introduce an improved sorting method of the IGIC(Improved initial stage Grouping Interference Canceller) system for advanced BER(Bit Error Rate) performance in DS-CDMA. Among non liner Interference Cancellers, the PIC(Parallel IC) with advanced initial stage by sorting method has the name of the IGIC(Improved initial stage Grouping Interference Canceller) system. In this system, All group are shared with the same number of users. But, if each group are divided the same users, so that difference of the signals strength appeared greatly in the same group. Up to this time, the weak signals have more effect of the MAI (Multiple Access Interference) from the strong signals in the same group. The proposed IC (Interference Canceller) to solve those problems has a better performance by using improved sorting method from IGIC system. A new sorting method is the technique that the strength of signals would be liked in the same group. So, the MAI is reduced as difference of signal strength minimize. Analysis of performance assayed to make comparison with other non liner interference canceller when power controlled and not one.

• 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.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.3B
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• pp.179-187
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• 2002

This paper proposes and analyzes the iterative groupwise equal-delay interference cancellation(IGEIC) algorithm for coherent detection of an asynchronous wideband DS-CDMA system in a single cell over multipath fading channels. The IGEIC algorithm divide users in a system into several groups, and subtract out interference signal from the received signal as many as the number of users within a user group, iteratively. The IGEIC algorithm is also classified into the iterative groupwise equal-delay serial interference cancellation(IGESIC) algorithm and the iterative groupwise equal-delay parallel interference cancellation(IGEPIC) algorithm. In the case of perfect correlation for spreading codes, it shows that the performance of IGESIC and IGEPIC algorithm is the same after interference cancellation of as many as the number of users within a user group, but the performance of IGEPIC algorithm is superior to the IGESIC algorithm just before fecal cancellation within a user group. The results show that (he performance of the two proposed algorithms are also superior to the SIC algorithm by 3dB.

• 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.