• Journal of the Institute of Electronics Engineers of Korea TC
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• v.46 no.3
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• pp.15-18
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• 2009

In this paper, we propose ST-MWSK (space-time M-ary orthogonal Walsh sequence keying) employing MWSK which does not require channel estimation at the receiver. The computational complexity for the noncoherent ML (maximum-likelihood) detector of ST-MWSK is significantly reduced compared to that of ST-FSK (ST frequency-shift keying). Also, the performance of ST-MWSK is virtually identical to that of ST-FSK.

• Journal of Satellite, Information and Communications
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• v.5 no.1
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• pp.22-26
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• 2010

In this paper, we propose an effective method for detecting signals among multi-user in cooperative communication system. Spread sequence is inserted to NULL space of synchronization channel to synchronize between each user among frame formats of the cooperative communication and then transmitted. In the receiver, the wanted signal is detected by using correlation among the inserted spread sequences. As simulation results, correlations among the signals using Kasami/Walsh sequence in AWGN, Rician, and Rayleigh channel are shown. Using the simulation results in this paper, we expect a reliable cooperative communication.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.3C
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• pp.331-337
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• 2007

In this paper, we propose a novel Walsh coded training signal design and Walsh decoding method to estimate the channel response in MIMO-OFDM systems. The Walsh coded training signals are designed to have orthogonal property in time domain. Using the orthogonal property, the Walsh decoding process makes it possible to separate the desired training signal from the received signal and to estimate the channel response. The computer simulation results show that the proposed method exhibits almost the same performance as Li's original method using the optimal training sequence, even though the proposed method has much lower complexity.

• Proceedings of the KIEE Conference
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• 1998.11a
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• pp.159-162
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• 1998

In this paper, an algorithm of the automatic commissioning for vector controlled induction motor using controller characteristics is proposed. The automation of commissioning sequence is carried out using Walsh function analysis. In the proposed method, the distortion of the controller output waveform is easily detected and can be automatically tuned by using Walsh function analysis. This tuning algorithm has the advantage such as less sensitivity to the variation of other parameters and high sensitivity to parameter error. Hence, the easy tuning of high performance drive system of the induction motor is possible. Some experiments are carried out to prove the validity of the proposed automatic commissioning algorithm.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.2A
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• pp.116-123
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• 2002

The jacket matrix is based on the Walsh-Hadamard matrix and an extension of it. While elements of the Walsh-Hadamard matrix are +1, or -1, those of the Jacket matrix are ${\pm}$1 and ${\pm}$$\omega$, which is $\omega$, which is ${\pm}$j and ${\pm}$2$\sub$n/. This matrix has weights in the center part of the matrix and its size is 1/4 of Hadamard matrix, and it has also two parts, sigh and weight. In this paper, instead of the conventional Jacket matrix where the weight is imposed by force, a simple Jacket sequence generation method is proposed. The Jacket sequence is generated by AND and Exclusive-OR operations between the binary indices bits of row and those of column. The weight is imposed on the element by when the product of each Exclusive-OR operations of significant upper two binary index bits of a row and column is 1. Each part of the Jacket matrix can be represented by jacket sequence using row and column binary index bits. Using Distributed Arithmetic (DA), we present a VLSI architecture of the Fast Jacket transform is presented. The Jacket matrix is able to be applied to cryptography, the information theory and complex spreading jacket QPSK modulation for WCDMA.

• ETRI Journal
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• v.34 no.2
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• pp.168-174
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• 2012

In Advanced Television Systems Committee (ATSC) terrestrial digital television (DTV) systems, additional very low-rate data can be transmitted by modulating the amplitude and polarity of the transmitter identification (TxID) signal. Although the additional data transmission scheme offers reliable transmission and has a very large coverage area, it has a limitation on the data rate. In this paper, we propose a novel additional data transmission scheme based on the TxID sequences of the ATSC DTV system and Walsh modulation. The proposed scheme not only increases the data rate significantly, but also offers a virtually identical coverage area compared to a conventional scheme.

• Journal of Communications and Networks
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• v.14 no.2
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• pp.206-212
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• 2012

In this paper, in order to effectively apply unitary space-time modulation to the direct-sequence spread-spectrum multiple-access (DSSS-MA) networks, we propose a low-rate, noncoherent, unitary, and space-time modulated DSSS system supporting any number of transmit antennas based on Walsh matrices. The proposed scheme simultaneously performs bandwidth spreading and space-time coding and outperforms those using high-rate, conventional unitary space-time constellations. Furthermore, the proposed scheme allows for a simple detector structure based on fast Walsh transforms.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.16 no.7 s.98
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• pp.697-708
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• 2005

The forward link of the 3G CDMA system may become limited under the increasing of the number of users. The conventional channelization code, Walsh code, has not enough sizes f3r much possible users, therefore, the quasi orthogonal function(QOF), which process optimal crosscorrelation with Walsh code, is considered. In this paper, we investigate quasi orthogonal function on Jacket matrices, which can lead lower correlations values and better performance in 3G CDMA system. Moreover, to simplify the detector and improve the BER performance, a novel detection for QOF CDMA system is proposed. Finally, the simple recursive generation of the bent sequences for QOF mask function is discussed.

• Proceedings of the KIEE Conference
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• 1987.07b
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• pp.1622-1624
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• 1987

In general, pseudo noise generator(PNG) used for PLR System consists of linear feedback shift register. Based on a W.F. representation of shift registers, a method for analyzing operational characters & sequence of PNG are studied. PNG is characterized by the time-recursive equation & PNG sequence is analyzed by the output state variable equation. Methods studied in this paper are illustrated by appropriate example.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.16 no.11 s.102
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• pp.1147-1154
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• 2005

In this paper, we propose some PAPR(Peak to Average Power Ratio) reduction methods using WHT(Walsh Hadamard Transform) to reduce high PAPR generated in OFDM system because of multi carrier modulation. These proposed methods are the methods which has additional PAPR reduction performance without a loss of bandwidth efficiency and a large increment of calculation complexity than common PAPR reduction methods by combining the WHT with some common methods. In this paper, we propose two PAPR reduction methods made by combining a SLM(Selective Mapping) and DSI(Dummy Sequence Insertion) with a WHT. From simulation result, we can find that the PAPR reduction methods using a WHT can get about 1 dB additional PAPR reduction performance than common PAPR reduction methods; they are SLM and DSI. And, because our proposed methods have not only PAPR reduction effect, but also frequency diversity effect, more stabile data transmission is possible in nonlinear HPA and multipath fading channel.