• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2012.05a
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• pp.237-240
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• 2012

Binary sequences of period $N=2^k-1$ are widely used in many areas of engineering and sciences. Some well-known applications include code-division multiple-access (CDMA) communications and stream cipher systems. In this paper, we analyze the equation $(x+1)^d=x^d+1$ over finite fields. The $d$ of the equation is used to analyze cross-correlation of binary sequences.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.4
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• pp.730-736
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• 2012

PN(Pseudo Noise) sequences play an important role in wireless communications, such as in a CDMA(code division multiple access) communication system. If there is a crash when multiple users simultaneously connected to a system, then PN sequences with low correlation help to minimize multiple access interference in such communication system. In this paper we propose a family of non-linear extended binary sequences with low cross-correlations and the family include $m$-sequence, GMW sequence, Kasami sequence and No sequence with optimal cross-correlation in terms of Welch bound. And we analyze cross-correlation of these sequences.

• The Magazine of the IEIE
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• v.34 no.2
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• pp.48-61
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• 2007

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.8B
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• pp.802-808
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• 2002

In this paper, a new signal constellation design method is proposed for Multi-Phase(MP)/CDMA and its performance is compared with that of conventional method. In general MPSK modulation, the neighbor phases are allocated to the symbols that have only one different bit. However, the neighbor phases are allocated to the signal levels that have small differences in amplitude after clipping process since the transmitting signals in MP/CDMA are not binary symbols but the signal levels. The analysis shows that the performance of proposed scheme is much better than that of conventional method and it is better to increase the number of clipping levels than decrease the number of clipping levels and increase the region of guard phase.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.19 no.5
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• pp.971-980
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• 1994

The need increased capacity in the cellular system has resulted in the adoption of digital technology with CDMA as the channel access method. It has been recognized that the distinction of the base station is important for its performance in CDMA, since the same spreading sequences are used by the all base stations. Time offset of the pseudo-random noise binary code are used to distinguish signals received at a mobile station from different base station. But the start of the zero offset PN sequence is chosen arbitrary without the background of the systematic and mathematical elaboration. This paper proposes a mothed that define the start of the zero offset PN sequence mathematically. This paper also discusses a method that can easily calculate the time offset of the received spreading sequence with respect to the zero offset PN sequence.

• Proceedings of the IEEK Conference
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• 2002.07c
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• pp.1705-1708
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• 2002

Spreading codes with ZCD(zero-correlation duration) property have the MAI(multiple access interference) rejection ability in the CDMA systems. A class of multi-level spreading codes, i.e., Zero padded ternary ZCD codes are introduced in this paper. By the selected zero-padding method to the binary ZCD codes, ternary ZCD codes are generated and they have enhanced ZCD property and family size than the binary ZCD codes.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.45 no.11
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• pp.15-22
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• 2008

The cdma2000 1xEV-DO system controls the data rates of mobile terminals based on a binary overload indicator from the base station and a simple probabilistic model. However, this control scheme has difficulty in predicting the future behavior of mobile terminals due to a probabilistic uncertainty and has no reliable means of suppressing the traffic overload, which may result in performance degradation of CDMA systems that have interference-limited capacity. This Paper proposes a new traffic control scheme that controls the data rates of mobile terminals effectively by predicting the future traffic load and adjusting the forward-link control channel. The proposed scheme is analyzed by modeling it as a multi-dimensional Markov process and compared with conventional schemes. The numerical results show that the maximum cell throughput of the proposed scheme is much higher than those of the conventional schemes.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.9C
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• pp.817-824
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• 2006

The crest factor properties of 16-QAM modulated one- and two-code assisted multi-carrier code-division multiple-access (MC-CDMA) signals employing complementary pair as spreading sequences are characterized. It is shown that a set of relationship between the two 16-QAM symbols entirely characterize the power envelope waveforms of the signals. There exists 60 different sets of relationship, which results in 16 different crest factors as a result of various equivalent transforms on the corresponding message symbols. It is also shown that the individual crest factor corresponding to each message combination is always bounded by 3dB.

• Journal of Institute of Control, Robotics and Systems
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• v.19 no.7
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• pp.614-619
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• 2013

In multi-robot systems, ultrasonic sensors are widely used for localization and/or obstacle detection. However, conventional ultrasonic sensors have a drawback, that is, the interference problem among ultrasonic transmitters. There are some previous studies to avoid interferences, such as TDMA (Time Division Multiple Access) and CDMA (Code Division Multiple Access). In multiple autonomous mobile robots systems, the Doppler-effect has to be considered because ultrasonic transceivers are attached to the moving robots. To overcome this problem, we find out the ASK (Amplitude Shift Keying)-CDMA technique is more robust to the Doppler-effect than the BPSK (Binary Phase Shift Keying)-CDMA technique. In this paper, we propose a new code-expression method and a Monte-Carlo based algorithm that optimizes the ultrasonic code combination in the ASK-CDMA ultrasonic system. The experimental results show that the proposed algorithm improves the performance of the ultrasonic multiple accessing capacity in the ASK-CDMA ultrasonic system.

• Journal of Communications and Networks
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• v.12 no.4
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• pp.330-333
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• 2010

In this paper, using binary (N, M, L, $\epsilon$) low correlation zone (LCZ) sequence sets, we construct new quaternary LCZ sequence sets with parameters (2N, 2M, L, $2{\epsilon}$). Binary LCZ sequences for the construction should have period $N\;{\equiv}\;3$ mod 4, L|N, and the balance property. The proposed method corresponds to a quaternary extension of the extended construction of binary LCZ sequence sets proposed by Kim, Jang, No, and Chung [1].