• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.9 no.4
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• pp.439-449
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• 1998

In this paper, error performance of DS-CDMA communication system has been analyzed in a radio channel which is characterized by multi-user interference (MUI). Also, performance improvement has been obtained by both numerical analysis and simulation techniques when 3-element array antenna and co-channel interference (CCI) canceller are employed as a means for overcoming an MUI effect. The MUI was modelled as a gaussian random process. In array antenna scheme we only considered a directivity of antennal. The results show that there is a substantial enhancement in performance by employing an array antenna or a CCI canceller. CCI canceller gives better improvement in performance than the array antenna with D=2.67. Additional improvement can be obtained when the array antenna and the CCI canceller are adopted in cascade form. In this case the error performance approaches that of AWGN environment.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.8 no.3
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• pp.221-231
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• 1997

This paper presents an analysis of a hybrid direct-sequence/slow frequency hopped code division multiple access(DS/SFH-CDMA) system employing noncoherent M-ary frequency shift keying(MFSK) modulation in a multiple m-distribution fading environment. Multipath interfer- ence(MPI) and multiuser interference(MUI) is taken into accout and the spectral efficiency is calculated for uncoded as well as simple channel coding systems. The predetection multipath CCI canceller in conjunction with convolution coding is employed for improving the bit error rate(BER) performance. The BER of noncoherent hybrid system is obtained using a Gaussian interference approximation. From the results, we know that the error performance more deteriorates as the depth of fading becomes deeper. The DS part of the modulation combats the multipath interference, whereas the FH part is a predetection against large multiuser interference. It is shown that, for the con- sidered types of a channel coding, the use of a predetection coding is still essential for obtained a satisfactory bit error performance. The results show that the capacity of the DS/SFG-CDMA MFSK communication system increases in proportion to the length of PN code sequence in the presence of AWGN and MUI. In m-distribution fading environment the capacity increases in proportion to the fading index. The capacity is increased and error performance is improved when the CCI Canceller and Convolution code technique are adopted, respectively. From the results, it is known that the error performance of $4\times10^{-2}$ by adopting Canceller technique. Also convolutional coding technique is the improvement of error performance attains about $10^{-5}$ in code rate 1/2.

• Journal of Advanced Navigation Technology
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• v.14 no.5
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• pp.745-751
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• 2010

In this paper, the proposed a narrowband interference cancellation techniques for the frequence sharing of Ultra wideband Impulse Radio communication system and narrowband communication system. In this system, the narrowband communication signals can cause intolerant interferences to Impulse Radio signals. In this paper, Ultra wideband Impulse Radio system have been analyzed in AWGN, MAI 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. The results show that there is a substantial enhancement in performance by employing the adaptive notch filtering and/or CCI canceller.

• ETRI Journal
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• v.33 no.5
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• pp.670-678
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• 2011

This paper investigates the design and performance of a digital on-channel repeater (DOCR) for use in Advanced Television Systems Committee (ATSC) digital television (DTV) broadcasting. The main drawback of a DOCR is the echo interference caused by coupling between transmitter and receiver antennas, which induces system instability and performance degradation. In order to overcome this problem, an echo canceller based on the adaptive echo channel estimation (ECE) technique has been researched and applied for a DOCR. However, in the case of ATSC, the pilot signal, which is used for carrier synchronization, may cause a DC offset error and reduce the isolation performance of the echo canceller for a DOCR in an ATSC network. Moreover, since the multipath fading effect of a radio channel usually occurs in a real environment, it should be minimized to improve the overall performance of a DOCR. Therefore, due to the limited isolation performance of echo canceller and the multipath fading effect, an interference cancellation system (ICS) is proposed for a DOCR in an ATSC network. The performance of the proposed DOCR with an ICS is evaluated by software simulation and hardware test results.

• ETRI Journal
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• v.31 no.4
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• pp.357-364
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• 2009

In this paper, we propose a novel equalization on-channel repeater (OCR) with a feedback interference canceller (FIC) to relay terrestrial digital multimedia broadcasting signals in single frequency networks. The proposed OCR not only has high output power by cancelling the feedback signals caused by insufficient antenna isolation through the FIC, but also shows better output signal quality than the conventional OCR by removing multipath signals existing between the main transmitter and the OCR through an equalizer. In addition, computer simulations and laboratory test results demonstrate that the proposed OCR successfully cancels feedback signals and compensates channel distortions and provides a higher quality transmitting signal with higher output power than conventional OCRs.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.7
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• pp.1321-1327
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• 2009

In this paper, as the mobile communication service is widely used and the demand for wireless repeaters is rapidly increasing because of the easiness of extending service areas. But a wireless repeater has a problem the oscillation due to feedback signal. We proposed a new hybrid interference canceller using the adaptive filter with CMA(Constant Modulus Algorithm)-Grouped LMS(Least Mean Square) algorithm in the adaptive interference canceller. The proposed interference canceller has better channel adaptive performance and a lower MSE(Mean Square Error) than conventional structure because it uses the cancellation method of Grouped LMS algorithm. The proposed detector uses the LMS algorithms with two different step size to reduce mean square error and to obtain fast convergence. This structure reduces the number of iterations for the same MSE performance and hardware complexity compared to conventional nonlinear interference canceller.

• Journal of the Korean Institute of Telematics and Electronics
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• v.26 no.1
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• pp.129-139
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• 1989

During a signal is being transmitted, an interference signal can be introduced through an unknown channel. In these cases, an adaptive system, so called adaptive noise canceller, can restore the original signal from the corrupted signal by first identifying the unknown interference channel on the minimum mean square error criteron, and then by cancelling the interference signal using the identified interference channel. Whereas this method is quite effective when the a priori knowledges about the characteristics of the interference signal and of the intrference channel are unknown or time-varyng, but has a drawback that the presence of the original signal has a severe effect on the optimum value of the interference channel to be identified on the miniumum mean square eror criterion In this paper an adaptive noise canceller and its algorithms are introduced that can restore the original signal more accurately especially when the correlatedness between the original signal and the interference signal is small.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.5 no.6
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• pp.1056-1061
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• 2001

In this paper we have evaluated the degree of performance improvement in Multi-Carrier CDMA system adopting CCI canceller against MUI under mobile channel coexisting MU which is a major interference degrading the performance of Multi-carrier CDMA system. As a result of analysis, BER performance was improved by adopting CCI canceller and it was found that the amount of performance improvement was largely increased as Eb/No became higher. As an example, in case that data service BER = 10$^{-5}$ must be achieved with $E_{b/}$ $N_{o}$ = 12 ㏈, 4 users could be supported without CCI canceller while 30 users could be supported with CCI canceller, Also, we found that performance improving effect of 5$\times$10$^{-3}$ in a point of view BER could be achieved by adopting CCI canceller with fixed $E_{b/}$ $N_{o}$. o/. o/.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.9 no.2
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• pp.105-110
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• 2009

The techniques of intelligent interference cancellation are used for achieving the improvement of deterioration, which is arisen to the interoperable terminal(GSM and DVB-H). In this paper, we propose a novel system that improve the DVB-H received performance by using the method of an adaptive interference canceller for GSM900 and DVB-H terminal. The interference for the collocated GSM900 and DVB-H receiver is cancelled by using the adaptive canceller with the low-noise ADC(Analog to Digital Converter) in the RF stage.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.9
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• pp.1058-1064
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• 2008

In this paper, we proposed a new hybrid interference canceller using the adaptive filter with Grouped CMA(Constant Modulus Algorithm)-LMS(Least Mean Square) algorithm in the RF(Radio Frequency) repeater. The feedback signal generated from transmitter antenna to receiver antenna reduces the performance of the receiver system. The proposed interference canceller has better channel adaptive performance and a lower MSE(Mean Square Error) than conventional structure because it uses the cancellation method of Grouped CMA algorithm. This structure reduces the number of iterations fur the same MSE performance and hardware complexity compared to conventional nonlinear interference canceller. Namely, MSE values of the proposed algorithm were lower than those of LMS algorithm by 2.5 dB and 4 dB according to step sizes. And the proposed algorithm showed fast speed of convergence and similar MSE performance compared to VSS(Variable Step Size)-LMS algorithm.