• Journal of applied mathematics & informatics
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• v.31 no.5_6
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• pp.869-876
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• 2013

The design of large family size with the optimal cross-correlation property is important in spread spectrum and code division multiple access communication systems. In this paper we present the sequences with the decimation $d=2{\cdot}2^m-1$, calculate the cross-correlation spectrum for $0{\leq}t{\leq}2^n-2$ and count the number of the value $2^m-1$ occurring for $0{\leq}{\tau}2^n-2$. The sequences have the optimal cross-correlation property. The work on this paper can make it easier to count the number of the whole value occurring for $0{\leq}{\tau}2^n-2$.

• The Journal of the Korea institute of electronic communication sciences
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• v.8 no.6
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• pp.891-897
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• 2013

The spectrum and the number of the values of the cross-correlation function between the maximal period binary sequences have been extensively studied because of their importance in communications applications. In this paper, we propose the new family of the sequences using the decimation $d=2^{m-1}(3{\cdot}2^{m}-1)$. And we find the spectrum of the cross-correlation function of the sequences and analyze the number of times each value occurs for $0{\leq}{\tau}{\leq}2^{n}-2$.

• Journal of the Optical Society of Korea
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• v.14 no.4
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• pp.357-362
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• 2010

The joint transform correlator (JTC) has been the best known technique for pattern recognition and identification. This paper proposes a new technique of fringe adjustment by adopting a sinusoidal amplitude-modulated iterative filter convolved with an interference fringe pattern in the joint power spectrum (JPS) domain. The comparison of our new technique and other techniques is presented to show that the newly proposed technique can successfully improve both the correlation peaks and the peak signal-to-noise ratio (PSNR). Simulated results of enhanced interference fringes are also presented.

• Journal of Communications and Networks
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• v.15 no.3
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• pp.276-282
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• 2013

Self-encoded spread spectrum (SESS) is a novel modulation technique that acquires its spreading code from a random information source, rather than using the traditional pseudo-random noise (PN) codes. In this paper, we present our study of the SESS system performance under pulsed-noise jamming and show that iterative detection can significantly improve the bit error rate (BER) performance. The jamming performance of the SESS with correlation detection is verified to be similar to that of the conventional direct sequence spread spectrum (DSSS) system. On the other hand, the time diversity detection of the SESS can completely mitigate the effect of jamming by exploiting the inherent temporal diversity of the SESS system. Furthermore, iterative detection with multiple iterations can not only eliminate the jamming completely but also achieve a gain of approximately 1 dB at $10^{-3}$ BER as compared with the binary phase shift keying (BPSK) system under additive white gaussian noise (AWGN) by effectively combining the correlation and time diversity detections.

• The Journal of the Korea institute of electronic communication sciences
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• v.7 no.2
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• pp.263-269
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• 2012

Code-Division Multiple-Access(CDMA) allows several users simultaneous access to a common channel by assigning a distinct pseudonoise sequence called spectrum code to each user. Each user in a CDMA system uses a assigned spectrum code to modulate their signal. Choosing the codes used to modulate the signal is very important in the performance of CDMA systems. The best performance will occur when there is good separation between the signal of a desired user and the signals of other users. The receiver synchronizes the code to recover the data. The use of an independent code allows multiple users to access the same frequency band at the same time. In this paper we propose a generalized model of non-linear binary sequence using trace function and analyze cross-correlation of these sequences. These sequences with low correlation, large linear span and large family size, in a direct-sequence spread spectrum communication system, help to minimize multiple access interference, increase security degree of system and enlarge user number.

• Broadcasting and Media Magazine
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• v.11 no.1
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• pp.68-77
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• 2006

The Cognitive Radio (CR) technology is a promising solution for exploiting the limited spectrum resources and providing flexibility of spectrum usage. Future interactive broadcasting service can be realized by utilizing CR concept, since the up-link return channel can be found by the spectrum sensing method, which is core functional block of the CR system. In this paper, the spectrum sensing technologies of CR system is presented. First the system architecture of the CR with spectrum sensing block is presented. The suggested spectrum sensing technique consists of the coarse and the fine spectrum sensing. The coarse spectrum sensing technique adopted the wavelet transform to provide the multi-resolution sensing feature - Multi-Resolution Spectrum Sensing (MRSS). The fine spectrum sensing technique uses the beneficial properties of the autocorrelation function Analog Auto-Correlation (AAC). The simulation results for the proposed sensing technologies are presented for various incumbent signals.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.11
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• pp.1420-1422
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• 2016

In order to guarantee the multiuser transmission performance of a chirp spread spectrum system, the cross-correlation coefficient (CCC) among multiple users should be carefully considered. In this paper, we propose a chirp rate allocation scheme for reducing the multiple access interference based on the cross-correlation coefficient. The simulation results show that the proposed scheme can improve the multiple access interference performance.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.11
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• pp.1417-1419
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• 2016

In order to improve the transmission performance of a chirp signal-based chirp spread spectrum system, the cross-correlation coefficient (CCC) should be carefully considered. In this paper, we derive the CCC for analyzing the transmission performance and propose the optimal chirp rate based on the analysis. The simulation results verify the mathematical derivations and show that the considered scheme can improve the performance by considering the CCC.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.10 no.3
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• pp.12-18
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• 2001

Frequency domain has been used to detect chatter vibration and to decide commencing point of chatter for the milling processes. For this, power spectrum of accelerations signal is analyzed in the frequency domain. Also, the power spectrum and surface roughness are measured, compared, and evaluated according to the depth of cut by experimental works. As a results, it is known that the commencing point of chatter can be decided the behavior of the maximum amplitude of the power spectrum of acceleration signal and there is a correlation between the power spectrum of acceleration signal and the surface roughness. In conclusion, the power spectrum of acceleration signal can be used as a useful information for detec-tion and estimation of chatter vibration in machining.

• Journal of Satellite, Information and Communications
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• v.8 no.3
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• pp.6-9
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• 2013

Cognitive Radio is an intelligent interference avoidance idle spectrum communication system for your environment and actively determine the frequency bandwidth recycling by sharing the spectrum in a way that maximizes the efficiency of radio resource technology. At this time, this does not cause interference to the PU spectrum sensing technology is important. If you can choose, depending on the state of the channel spectrum sensing algorithm will be more efficient sensing. Matched filter detection system model that reflects the individual sensing through a fuzzy controller in this paper, energy detection and self-correlation detection are proposed and analyzed.