• Proceedings of the IEEK Conference
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• 1999.06a
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• pp.849-852
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• 1999

In this paper, the performance of DS/CDMA receiver is analyzed, which employs a cascaded interference canceller using a soft detection. The channels considered is characterized by the multipath fading which is one of the factors for the performance degradation in mobile communication systems. The idea behind the cancellation is that the co-channel interference can be regenerated at the receiver and is subtracted from the received signal. The numerical results show the improvement of BER can be obtained by the proposed cancellation scheme.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.10 no.7
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• pp.1010-1021
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• 1999

In this paper, error performance of DS/CDMA GMSK system has been analyzed in a radio channel which is characterized by multi-user interference(MUI) and Nakagami fading. The DS/CDMA GMSK system adopts Maximum Ratio Combining(MRC) diversity and co-channel interference (CCI) to enhance system performance. Using the derived error probability equation, the error performance of DS/CDMA GMSK system has been evaluated and shown in figures to discuss as a function of PN code length(N), number of multi-user(K), number of diversity branch(L), and bit energy per noise power ratio ($E_b/N_0$), fading index(m). The results show that there is a substantial enhancement in performance by employing an MRC diversity or a CCI canceller. Additional improvement can be obtained when the MRC diversity and the CCI canceller are adopted in cascade form. Consequently, we expected that proposed system structure is reliable to the voice communication system in Nakagami fading, multi-user interferences and multipath channel.

• Journal of Broadcast Engineering
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• v.15 no.6
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• pp.830-844
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• 2010

In this paper, we propose an equalization digital on-channel repeater (EDOCR) with a feedback interference canceller (FIC) for single frequency network of the ATSC terrestrial DTV system. The proposed EDOCR with FIC does not have only high output power by cancelling feedback signals caused by insufficient antenna isolation through the FIC, but also shows better quality of output signals than the conventional on-channel repeaters (OCRs) by removing multipath signals existing between the main transmitter and the OCR, and residual feedback signals through an equalizer. In addition, computer simulations are provided to figure out the superior performance of the proposed EDOCR with FIC.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.10 no.4
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• pp.506-519
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• 1999

An adaptive array antennal and a CCI canceller have been considered as techniques for cancelling Multi-User Interference(MUI) in Direct Sequence Code Division Multiple Access(DS-CDMA) system. These techniques have different problems respectively in the process of cancelling MUI as the number of users increases. For that reason, the scheme which can cancel MUI effectively by compensating for the problems of each of the techniques has been required. For the scheme, the technique to connect an adaptive array antenna and a CoChannel Interference(CCI) canceller in cascade form has been studied. In the existing study about the cascade connection method, the effect of cancelling MUI about two interference signals is analyzed, but the analysis for the quantitative BER(Bit Error Rate) improvement according to the number of users is not considered. Therefore, in this paper, we have analyzed the degree of BER performance improvement quantitatively according to the number of users by introducing the receiving system, which connects an adaptive array antenna and a CCI canceller to a DS-CDMA system in cascade form. For the method of analyzing the performance, we have performed the theoretical analysis and the simulation, considering the case of adopting only an adaptive array antenna and of cascade connection respectively, and having compared and analyzed the results. From the results, it is confirmed that in the case of adopting only an adaptive array antenna, the problems occur in the process of cancelling MUI according to the number of users and the receiving direction of interference signals, and can be compensated by the cascade connection method. In conclusion, we have known that MUI is cancelled effectively by using the cascade connection method, and the much better BER performance improvement is obtained.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38A no.11
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• pp.955-966
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• 2013

We propose two feedback interference cancellers(FICs) to improve the performance of the equalization digital on-channel repeater(EDOCR) with the FIC for the ATSC DTV broadcasting system. The FIC estimates the feedback channel between Tx. and Rx. antennas of the repeater by cross-correlating the reference signal and the feedback signal. Since there is a DC pilot which ruins the white property of the ATSC DTV signals, the FIC cannot estimate the feedback channel accurately. To solve the problem, the structural method which uses an additional DC pilot free reference for feedback channel estimation and the algorithmic method based on the digital signal processing which whitens the ATSC DTV signals and performs the feedback cancellation in the whitened signal domain. Simulation results show that the proposed two FICs show better feedback cancellation performance than the conventional FIC.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.33A no.4
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• pp.37-46
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• 1996

In this paper, we analyzed the performance improvement of the DS-CDMA/dPSK cellular mobile communication system with CCI canceller and RAKE receiver techniques in mobile radio channel which is characterized by AWGN, Multi-user interference (mUI) and frequency-selective rayleigh fading. System capacity i.e., number of user per cell has been derived and the evaluated results are shown in figuraes as a function of PN code sequence length, number of RAKE receiver tap, BER and E$_{b}$/N$_{o}$. The voice activity factor is assumed to be 3/8 the number of sectors in a cell 3 and MUI is modeled as gaussian process. From the results, the capacity of the DS-CDMA/DPSK cellular mobile communication system is improved by adopting CCI canceller. When we adopt the RAKE receiver to mitigate the multipath fading, the error performance is improved and the amount of improvement is proportional ot the number of taps L in the case that each tap contains a signal component and the better of improvement can be obtained, the smaller of the SNR difference in each tap. The system capacity is more increased when the CCI canceller and the RAKE receiver is used in cascade.

• Proceedings of the Korean Institute of Communication Sciences Conference
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• 2004.07a
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• pp.382-382
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• 2004

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.8B
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• pp.1371-1382
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• 2000

IMT-2000 system is the third generation mobile communication system which aims at mobile multimedia services with global roaming. Like 2nd generation system, the IMT-2000 system is also under strong influence of interferences among active subscribers in the multiple access environment. That is, in multiple access environment, signals from one subscriber could interfere with others in the same cell or in the neighboring cells. The interference control in the IMT-2000 systems is much more difficult then the interference control in the 2ndgeneration CDMA cellular systems, since the transmitted power of a subcriber might be different that of others in the IMT-2000 system. In this paper, a parallel interference cancellation with traffic discrimination is proposed which can effectively cancel interferences by grouping the subscribers into several equi-power classes. As a conclusion, simulation results show that the proposed method outperforms the conventional partial PIC scheme in several aspects.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.11 no.3
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• pp.484-491
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• 2000

It is necessary to apply SSB modulation method with high bandwidth efficiency to the DS-CDMA mobile communication systems in order to accommodate the increasing number of voice users as well as the broad band and high data rate service in the future. Even though the bandwidth efficiency increases if SSB modulation is applied to BPSK-DS/CDMA, its performance gets degraded because of the increased multiple access interference. Therefore for eliminating the increased multiple access interference, the SSB/BPSK-DS/CDMA with successive interference canceller(SIC) is proposed and its performance and capacity are analyzed. With the limited system bandwidth, it is shown that the SSB/BPSK-DS/CDMA with SIC can accommodate more capacity than the conventional BPSK-DS/CDMA with SIC.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.4
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• pp.830-837
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• 2009

In this thesis, Multi-code/Multi-carrier CDMA(MC/MC CDMA) system which is combination of Multi-code CDMA and Multi-carrier CDMA is analyzed. This system is suitable fur multi-rate services that use multi-codes and high data rate transmission that employ multi-carriers. In addition, the MC/MC CDMA system is robust against frequency selective fading, is good for narrowband interference rejection, and has higher spectral efficiency. In this paper, The users are assigned OVSF codes as a spreading code according to their data rates and divides the active users having different representative code split into a number of groups for effective cancellation. At the receiver, The code grouping interference canceller performs cancellation between the groups. The proposed receiver does not require any information about interference users, such as code, data and amplitude, and has relatively low complexity. The results show the large improvement in performance that can be attained by cancellation scheme.