• Journal of the Institute of Electronics Engineers of Korea TC
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• v.40 no.2
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• pp.56-63
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• 2003

We investigate some implementation factors that affect the performance of multi-rate parallel interference cancellers (PICs) for the international mobile telecommunications-2000 (IMT-2000) 3rd-generation partnership project (3GPP) system. We consider the simple multi-rate PIC [1,2] that can remove effectively multiple access interference (MAI) through block-based detection and sample-based cancellation in asynchronous user environments. The PIC structure has significantly lower complexity as compared with that of the existing scheme, especially as the number of users increases. We analyze the effects of timing error, oversampling rate, unsynchronized users and/or outer-cell interference, and the number of Quantization bits on the PIE performance through extensive computer simulations. The models for such factors and the optimum parameters are drawn. Finally, we evaluate the receiver complexities of the PIC receivers employing using the advanced removal scheme.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.1C
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• pp.102-108
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• 2006

In this paper, we propose an interference cancellation(IC) scheme using a partial Rake(PRAKE) combining in ultra-wideband(UWB) multipath fading channels. In this IC scheme, differently from the conventional transmitter model, which employs a guard interval between each frame, the guard interval is employed between each slot for estimating the multiple access interference(MAI). The UWB systems using the proposed IC scheme have little performance degradation without regard to the number of user, while the conventional UWB systems have a significant performance degradation according to the number of user. In order to reduce the receiver complexity, the PRAKE combining of post-canceled signal and the partial user IC scheme are also proposed.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 1999.11a
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• pp.130-134
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• 1999

In this paper, we introduce a modified interference cancellation scheme for multiuser detection in CDMA. This detector uses successive interference canceller(SIC) and the divided received signal concepts. The active users are splits into two groups large signal power group and small signal power group- throughout ranking, matched filter, decision, regeneration. And each group is subtracted from the received signal respectively to obtain good BER performance. Each of the resulting signal is become respectively SICs input signal The computer simulation and analysis of structure demonstrate that the proposed SIC keeps the SICs BER performance, complexity and reduces SICs delay time.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.2C
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• pp.112-118
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• 2011

In this paper, we conduct an objective performance analysis of the crosstalk cancellation scheme studied in [11]. While the conventional scheme is only applicable to a listener on the optimal listenable region (sweetspot), the space skew/crosstalk cancellation (SS/CC) scheme in [11] can mitigate crosstalk regardless of the listener's position by using listener position tracking (LPT) system. The SS/CC scheme is composed of two parts: LPT-based SS and CC parts. In this paper, the SS/CC scheme is evaluated by some criteria such as follows: condition number, and the balance characteristic, its root mean square error, and running average.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.2 no.4
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• pp.519-529
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• 1998

In this paper, we analyze the effects of interference canceller on the performance of multitone DS/CDMA system. Although there are various kinds of interference cancellers suggested by different researchers, we adopt a canceller used by Yoon et at.［9］. We consider three kinds of inteferences, that is, multiPath interference(MPI), interchannel interference(ICI) and multiple access interference(MPI). The equations for variances ate derived for the inteferences and thermal noise used for signal to noise ratio calculation. We also consider RAKE reception over multipath channel and three stage interference canceller used for performance improvement. We draw some conclusions that interference canceller is effective in multitone DS/CDMA system and the performance is further improved with the higer order of diversity and larger number of PN chips.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.12 no.1
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• pp.1-10
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• 2001

In this paper, a multistage parallel interference canceller (MPIC) and a partial multistage parallel interference canceller (PMPIC) are employed as a technique for improving the performance of the asynchronous DS-CDMA systems. The degree of the effect of the timing errors and phase errors on the interference cancellation capability of two types of cancellers is theoretically analyzed and the computer simulation is performed to confirm the analytical results. From the results, the large performance improvement is obtained by employing MPIC and PMPIC with perfect synchronization over the conventional matched filter, and the performance improvement obtained by MPIC and PMPIC is very close to each other as the number of the stage of MPIC and PMPIC increases. When the timing errors and phase errors are considered (in the case of imperfect synchronization), the performance improvement reduces as the performance degradation at the first stage (no cancellation) has a bad effect on the decision statistics at each stage. However MPIC and PMPIC have the strong interference cancellation capability in spite of imperfect synchronization as the number of the stage increases. An interference canceller, which has the strong interference cancellation capability as well as lower complexity for the implementation, is needed for practical systems with timing errors and phase errors because the perfect synchronization is impossible. Therefore, the excellent tradeoff between complexity and performance offered by PMPIC makes it an attractive approach for practical systems.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.7
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• pp.2623-2631
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• 2010

In this paper, we propose a new interference cancellation(IC) receiver for multirate Multicarrier DS/CDMA(MC DS/CDMA) system based on orthogonal variable spreading factor(OVSF) code. The users are assigned different lengths of OVSF codes as a spreading code according to their data rates and the active users having same representative code split into a group for effective cancellation. The code grouping interference cancellation(IC) receiver performs cancellation between the groups first and cancellation within group. This proposed IC receiver can cancel the interferences using desired user's code information and then desired signals are detected. The results show that the large improvement in performance can be attained by group-wise IC scheme and we can make the effective systems compare to conventional ones. The bit error rate of the system is analytically derived in frequency selective Rayleigh fading channel and we also compare the system performance with that of multirate DS/CDMA system. We also analyze the performance of the proposed system with same bandwidth and processing gain. The results show the large improvement in performance that can be attained by cancellation scheme.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2010.07a
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• pp.174-176
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• 2010

이 논문에서는 직교 주파수 분할 다중 접속방식(orthogonal frequency division multiple access : OFDMA)을 이용한 상향 링크 시스템에서 수신된 신호에 주파수 옵셋이 존재할 때 나타나는 영향을 보상하는 방법을 제안한다. OFDMA에서 각 사용자가 전송한 신호에서 발생하는 주파수 옵셋은 다중 접속 간섭(multi-user interference : MUI)을 발생시킨다. 이러한 다중접속 간섭은 OFDMA 시스템의 성능을 저하시키는 주요한 원인 중에 하나이다. 이 논문에서는 시간영역에서 특정 사용자의 신호에 대한 주파수 옵셋의 보상을 한 뒤, 주파수 영역에서 일반적인 채널간간섭 제거 방법을 적용하여 다중 접속 간섭에 의한 영향을 효과적으로 제거하는 방법을 제안한다. 또한 부반송파에 위치에 따라 달리 나타나는 다중 접속 간섭의 크기에 따라 간섭 제거 방법을 달리하여 보다 적은 계산량으로 간섭을 제거하는 방법을 제안한다.

• 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 Communications and Information Sciences
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• v.27 no.4A
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• pp.330-335
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• 2002

In the direct sequence code division multiple access system, the problem of multiple access interference due to multiple access is generated. A interference cancelling receiver is used to solve this problem. The conventional interference cancelling receiver is structure of successive interference canceller using antenna array. In this structure, the difference of between method I and method II depends on updating weight vector. In this paper, the adaptive blind CMA array interference cancelling receiver using cost function of constant modulus algorithms is proposed to update weight vector at conventional structure. The simulation compared the proposed interference cancelling receiver with two conventional interference cancelling receivers by signal to interference ratio and bit error rate curve under additive white Gaussian noise environment. The simulation results show that the proposed receiver has about the gain of SIR of 1.5[dB] more than method I which is conventional receiver at SIR curve, and about the gain of SIR of 0.5(dB) more than method II. In BER curve, the proposed IC receiver about the gain of SNR of 2[dB] more than method I and about the gain of SNR of 0.5[dB] more than method If, Thus, the proposed interference cancelling receiver has the higher performance than conventional interference cancelling receivers.