• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.1
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• pp.23-31
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• 2015

In this paper, we design a SSD(simultaneous single band duplex) system using RF cancellation and digital cancellation. And then, we analyze performance of the SSD system using pre-distorter with HPA non-linearity. Also, we analyze digital cancellation performance of the SSD system using pre-distorter with HPA non-linearity. Additionally, digital cancellation cancels residual self-interference. In linear conditions, digital cancellation can cancel self-interference of 40dB. Therefore, the SSD system has good BER performance because most of self-interference is canceled. But, in HPA non-linearity conditions, digital cancellation cancels residual self-interference of 25dB. In this conditions, self-interference is greater than desired signal. Therefore, bit informations of distant station can not be received. But, we confirm that if the proposed system uses pre-distorter then bit information of distant station can be received by HPA non-linearity compensation. Also, we confirm that even though the proposed system uses pre-distorter, if HPA non-linearity increases then digital cancellation performance is degraded by imperfect compensation of HPA non-linerity.

• Journal of Advanced Navigation Technology
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• v.6 no.1
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• pp.17-26
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• 2002

In this paper, we have analyzed the BER (Bit Error Rate) performance of multi-user detectors employing SIC(Successive Interference Cancellation) and PIC (Parallel Interference Cancellation) which are the representative schemes in the subtractive interference cancellation. We have considered the MUD structure employing HIC (Hybrid Interference Cancellation) which combines SIC with PIC scheme, and then analyzed the BER performance. We have evaluated the BER performance of SIC and HIC schemes which execute the soft decision to generate the tentative data bit for the purpose of the interference cancellation in MAI and noise environments. Through the numerical analysis and computer simulation, it is shown that HIC can remove the effect of MAI more efficiently than the others, that improve the BER performance and increase the capacity of DS-CDMA systems regardless of the power control conditions. The reason is that the SIC scheme in front of HIC can solve the near-far problem caused by the imperfect power control and PIC scheme in the rear of it can improve the performance much more.

• ETRI Journal
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• v.28 no.2
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• pp.231-234
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• 2006

The cancellation performance of a linearization loop is limited by the degree of an amplitude imbalance and a phase imbalance. A delay mismatch causes a phase variation as a function of frequency. Therefore, the cancellation performance and linearization bandwidth are limited by a delay mismatch. The expression for the effects of an amplitude imbalance, a phase imbalance, and a delay mismatch on the characteristics of a linearization loop is derived and analyzed. The simulation results are compared with the results obtained by means of using a commercial simulation tool and the exact agreement is reported. The derived equation could be used in designing a linearization loop and predicting the cancellation performance of the linearization loop usefully. Some useful characteristics, known from the simulation results obtained by using the derived equation, of a linearization loop for designing and implementing feedforward amplifiers are described in detail.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.22 no.11
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• pp.2388-2400
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• 1997

In this paper, we analyzed the serial interference cancellation scheme and proposed the new serial interference cancellation scheme suppressing multiple access interference. Compensating for the near-far effect and the multiple access interference is critical for the stable performance of DS/CDMA system, and the serial multiple access interference cancellation has been proposed as one of the compensation methods. But this serial interference cancellation scheme has a linear variation in the number of cancellation operation each users. Becaure of this variation, it is difficult to show a stable performance. Hence, we suggested a new serial interference applying window technique to overcome this fault and made a performance estiamation.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39A no.2
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• pp.100-108
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• 2014

In this paper, we design SSD(simultaneous single band duplex) system using RF(radio frequency) cancellation and digital cancellation. we analyze characteristic of residual self-interference after RF Cancellation signal when error of phase shifter occur in RF cancellation. When phase shifter error of $0^{\circ}$, $0.5^{\circ}$, $1^{\circ}$ and $2^{\circ}$ occur in RF cancellation, residual self-interference signal power after RF cancellation is bigger than desired signal power of distant station. So, it is impossible to receive transmit data of distant station. but we confirm that it is possible to receive transmit data of distant station by digital cancellation with frame structure. Also, in digital cancellation with frame structure, if residual self-interference signal after RF cancellation is too large then LMS algorithm requires more time to estimate self-interference channel. That is, performance degradation occurs because self-interference channel estimation has not completed in estimation frame.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.12 no.8
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• pp.3704-3724
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• 2018

This paper proposes an advanced turbo receiver with joint inter-carrier interference (ICI) self cancellation and channel equalization for multiple-input multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) systems over rapidly time-varying channel environment. The ICI caused by impairment of local oscillators and carrier frequency offset (CFO) is the major problem for MIMO-OFDM communication systems. The existing schemes (conjugate cancellation (CC) and phase rotated conjugate cancellation (PRCC)) that deal with the ICI cancellation and channel equalization can't provide satisfactory performance over time-varying channels. In term of error rate performance and low computational complexity, ICI self cancellation is the best choice. So, this paper proposes a turbo receiver to deal with the problem of joint ICI self cancellation and channel equalization. We employ the adaptive phase rotations in the receiver to effectively track the CFO variations without feeding back the CFO estimate to the transmitter as required in traditional existing scheme. We also give some simulations to verify the proposed scheme. The proposed schene outperforms the existing schemes.

• The Journal of Information Systems
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• v.30 no.2
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• pp.105-126
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• 2021

Purpose The purpose of this study is to implement a optimal machine learning model about the cancellation prediction performance in car sales business. It is to apply the data set of accumulated contract, cancellation, and sales information in sales support system(SFA) which is commonly used for sales, customers and inventory management by imported car dealers, to several machine learning models and predict performance of cancellation. Design/methodology/approach This study extracts 29,073 contracts, cancellations, and sales data from 2015 to 2020 accumulated in the sales support system(SFA) for imported car dealers and uses the analysis program Python Jupiter notebook in order to perform data pre-processing, verification, and modeling that is applying and learning to Machine learning model after then the final result was predicted using new data. Findings This study confirmed that cancellation prediction is possible by applying car purchase contract information to machine learning models. It proved the possibility of developing and utilizing a generalized predictive model by using data of imported car sales system with machine learning technology. It can reduce and prevent the sales failure as caring the potential lost customer intensively and it lead to increase sales revenue by predicting the cancellation possibility of individual customers.

• 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.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.9C
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• pp.896-905
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• 2009

In this paper, we propose an enhanced iterative ICI (Inter Carrier Interference) cancellation method for cooperative STBC-OFDM (Space Time Block Coded-Orthogonal Frequency Division Multiplexing) system. In cooperative STBC-OFDM system, ICI cancellation is necessary because ICI due to the independent local oscillators always exits. The conventional iterative ICI cancellation method has severe performance degradation due to the initial estimation error. Also the performance degradation increases as CFOs (Carrier Frequency Offsets) and modulation order increases. Therefore, in this paper, we propose an enhanced iterative ICI cancellation method which can reduce the initial estimation error by giving a priority to initial estimation and cancellation process. Through the complexity and performance comparisons, we verwey that the proposed method has better performance with approximately same complexity compared with the conventional method.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.3
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• pp.629-631
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• 2007

In hands-free full-duplex communication systems, acoustic signals picked up by the microphones can be mixed with echo signals as well as noises, which may result in poor performance of the corresponding communication system. Also, the system performance may decrease further if the reverberation occurs since it is harder to estimate the impulse response of the demixing system. For blind source separation (BSS) in such cases, a time-frequency masking approach can be employed to separate undesired echo signals and noises, but, permutation ambiguities also should be solved for the echo cancellation. In this paper, we propose a new acoustic echo cancellation (AEC) approach utilizing the time-frequency masking and higher-order statistics, whereby a desired signal selection, based on coherence and third-order statistics (i.e., kurtosis), is introduced along with output signal normalization. Simulation results demonstrate that the proposed approach yields better echo and noise cancellation performances than the conventional AEC approaches.