• Journal of the Korea Institute of Information and Communication Engineering
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• v.9 no.4
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• pp.693-697
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• 2005

In this paper, it was estimated the BER performance of the individual system type by applying the SFH type and the FFH type to the FH MC-DS CDMA system that combined the strong points of MC DS/CDMA and that of Frequency Mewing under the Nakagami fading channel with Multi-tone Jamming. An increase in the number of hoppings means that it can improve theBER performance by reducing the receiving burden of the FH MC DS/CDMA by achieving a frequency diversity effect. Therefore, I verified that the performances of the FH MC DS/CBMA system could be impoved by increasing the number of hoppings.

• Proceedings of the IEEK Conference
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• 1999.11a
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• pp.5-8
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• 1999

In this paper, we present narrowband interference (NBI) cancelling algorithm applied to wideband spread spectrum system. We introduce multi-carrier transmission technique to overcome hardware inplementation difficulty of wideband spreading above 40MHz and to enhance NBI performance. A direct-sequence spread spectrum receiver using both decision-feedback and two sided LMS filters for combating narrowband interference is applied. We show that performance of this receiver outperforms conventional NBI rejection systems in tone jamming, partial band jamming, and impulsive channel through the bit error ratio evaluation. In addition, we propose a new technique to improve the performance of time domain NBI rejection algorithm sensitive to impulsive channel.

• Journal of Communications and Networks
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• v.7 no.1
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• pp.13-20
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• 2005

In this paper, a new multi carrier, direct sequence code division multiple access (MC-DS-CDMA) system is proposed. Our new signal construction is based on convolutional encoding of the transmitted data, serial-to-parallel (S/P) conversion of the encoded data, Walsh-Hadamard-transformation (WHT), a second S/P conversion of the WHT outputs, spread spectrum (SS) modulation with a common pseudo-noise (PN) sequence, and then multicarrier transmission. The system bit error rate (BER) performance in frequency selective fading channel in the presence of additive white Gaussian noise (AWGN) and a jamming tone is analyzed and simulated. The numerical results are compared with those from an orthogonal MC-DS-CDMA system of Sourour and Nakagawa [7]. It is shown that the two systems have almost the same BER performance, but the proposed scheme has better anti-jamming ability.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• v.9 no.1
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• pp.543-546
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• 2005

In this paper, it was estimated the BER performance of the individual system type by applying the SFH type and the FFH type to the FH MC-DS CDMA system that combined the strong points of MC DS/CDMA and that of Frequency Hopping under the Nakagami fading channel with Multi-tone Jamming. An increase in the number of hoppings means that it can improve the BER performance by reducing the receiving burden of the FH MC DS/CDMA by achieving a frequency diversity effect. Therefore, I verified that the performances of the FH MC DS/CDMA system could be improved by increasing the number of hoppings.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.37 no.8
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• pp.1-10
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• 2000

Performance analyses of hybrid DS-SFH spread-spectrum systems using coherent MSK and QPSK modulation techniques are considered over Rayleigh fading channel in the presence of multi-tone jamming. The BER equations for MSK and QPSK systems with non-diversity reception in the receiver are derived as the concept of average signal-to-noise power ratio E$\_$b//N$\_$0/ and jamming-to-signal power ratio JSR, and the performances is evaluated for various system parameters. The evaluation of performance is done between fading and nonfading system, and between MSK and QPSK system. Results show that the performances of two systems are similar in low JSR. However, MSK system outperforms QPSK system as JSR increases. Overall performances of two systems are a little improved as the DS spreading gain increases for the total spread-spectrum bandwidth fixed. The performance difference between fading system and nonfading system is similar in low E$\_$b//N$\_$0/, however, it becomes very largewith increase of E$\_$b//N$\_$0/..

• Proceedings of the Korea Information Processing Society Conference
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• 2003.05b
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• pp.1497-1500
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• 2003

본 논문에서는 나카가미 페이딩 채널하에서 MC DS/CDMA 방식에 FH 방식을 적용한 FH MC/DS CDMA 시스템의 성능을 분석하였다. 나카가미 페이딩 지수 m과 MRC 다이버시티의 브랜치 수 L이 증가할 때 호핑 횟수 1과 4에 대한 분석결과 약 2.8dB의 성능차이를 보이고 있음을 앞 수 있었다. 호핑 횟수의 증가는 주파수 다이버시티 효과를 가져옴으로써 FH MC DS/CDMA 시스템에서 수신측의 부담을 줄이면서 BER 성능을 향상시킬 수 있음을 의미하며 따라서 호핑 횟수를 증가시킴으로써 부담 MC/DS CDMA 시스템의 성능을 개선할 수 있음을 입증하였다.

• 제어로봇시스템학회:학술대회논문집
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• 2005.06a
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• pp.1234-1238
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• 2005

As the low power GPS signal is susceptible to interference, interference can seriously degrade the performance of GPS receiver. This paper designs a ANIEF(Adaptive Narrowband Interference Excision in Frequency domain) filter that removes narrow band interferences with low signal loss. This filter uses the pre-correlation technique and attempts to filter out the interference in the frequency domain. The interference excision performance of the designed filter is evaluated for various interferences using the ANIEF filter inserted GPS software receiver and the interference generator. Interferences considered in this paper are single-tone CWI(Continuous Wave Interference), multi-tones CWI, pulsed CWI, and swept CWI. The narrowband interference excision filter in frequency domain is very effective against various interferences and the strong interference with a simple structure. However, the signal power loss is unavoidable while transforming. In this paper, the hamming window and overlap technique are adopted to reduce the signal power loss. Finally, the interference excision performance and the reduced signal power loss of the ANIEF filter are shown.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.13 no.5
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• pp.492-499
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• 2002

Performance analysis and comparison of the hybrid DS-SFH spread-spectrum (SS) system using coherent MSK and QPSK modulation techniques over Rayleigh fading channel are considered in the presence of MTJ(multi-tone jamming). To analyze the BER performance of the hybrid systems with or without the Rake receiver, signal-to-noise plus interference ratio is derived as a function of the average signal-to-noise ratio, the jammer-to-signal ratio and other system parameters. Numerical results show that the performance difference between the two modulation schemes, MSK and QPSK, is negligible for low JSR, while it becomes significant with the increase of JSR. In multi-path Rayleigh fading channel without Rake receiver, the performances of the two modulation schemes are slightly improved as the DS spreading gain is increased when the total SS bandwidth is fixed. In particular, there is an optimum DS spreading gain for large JSR, in which a minimum BER is achieved, while only DS spreading gives the best performance for small JSR. For hybrid systems with Rake receiver, it is shown that the hybrid system of the MSK modulation scheme provides better anti-jamming performance and larger performance improvement with the increase of multi-path resolution capability of Rake receiver than that of QPSK modulation for all conditions.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• v.2
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• pp.359-364
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• 2006

Interference can seriously degrade the performance of GPS receiver because GPS signal has extremely low power at earth surface. This paper presents a Narrowband Interference Excision Filter (NIEF) in frequency domain that removes narrowband interferences with small signal loss. A NIEF transforms the received GPS signals with interferences into the frequency domain with FFT and then compute statistics such as mean and standard deviation to determine an excision threshold. All spectrums exceeding the threshold are removed and the remaining spectrums are restored by IFFT. A NIEF effectively can remove various and strong interferences with a simple structure. However, the signal power loss is unavoidable during FFT and IFFT. Besides the hamming window and overlap technique, a threshold-whitening technique and an adaptive detection threshold are adopted to effectively reduce the signal power loss. The performance of implemented NIEF is evaluated using real signals obtained by 12 bit GPS signal acquisition board. The output of NIEF is fed into the Software Defined Receiver to evaluate the acquisition and tracking performance. Experimental results shows that many types of interference such as single-tone CWI, AM, FM, swept CWI and multi-tones CWI are effectively mitigated with small signal power loss.