• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.10B
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• pp.1714-1721
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• 2000

In the mobile communication using DS-CDMA systems the problem of multiple user interference which reduce the performance is generated by multiple user access. In this paper to solve this problem we proposed the direct decision blind adaptive receiver with knowledge of only the desired user's spreading sequence. Simulation result present that the total user's power has equal gain The gain of signal to interference ratio for the proposed blind DD-LMS receiver has about 6[dB] than conventional receiver at additive white Gaussian noise and large gain at multipath channels. And when interference user's power has more large gain than desired user's power the gain of SIR for the proposed receiver has large value. And simulation result of bit error rate present that DD-LMS receiver has higher performance than LCCMA receiver. Thus the proposed blind DD-LMS receiver has robustness against interference of high power user and multipath channels.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.19 no.11
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• pp.2067-2080
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• 1994

Recently, joint blind equalization and carrier recovery for digital mobile transmission system is of growing interest. In this paper, we describe new receiver structure of joint godard blind equalizer and various recovery loop for QAM modulated signal. After a brief review of Godard blind equalizer and MAP estimation Costas loop, Generalized Costas loop, Leclert loop, Angular form loop, we present two kinds of receiver structures for joint blind equalization and carrier recovery. Using a Monto Carlo simulation technique, we can confirm that two kinds of receiver structures operate very well in the steady state.

• Journal of Communications and Networks
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• v.6 no.1
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• pp.26-34
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• 2004

A blind interference canceller in the presence of subchipspaced multipath channels for direct-sequence code division multiple access (DS-CDMA) down-link system is considered. This technique is based on combining the existing blind interference canceller with a technique that involves assigning subchip-tap spacing to the Rake receiver. The proposed receiver minimizes the receiver’s output energy subject to a constraint in order to mitigate the multiple access interference (MAI) along each multipath component, and then suboptimally combining all the multipath components. Moreover, it is able to mitigate the mismatch problem when subchip-spaced multipath components arrive at the blind interference canceller. It is known that optimal combining techniques perform a decorrelation operation before combining, which requires both knowledge and computational complexity. In the following, we have adopted a simpler but suboptimum approach in the combining of the suppressed signals at the output of our proposed receiver. Computer simulation results verify the effectiveness of the proposed receiver to handle subchip-spaced multipath components and still suppresses MAI significantly.

• Proceedings of the Korean Information Science Society Conference
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• 2003.04a
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• pp.257-259
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• 2003

본 논문에서는 전자화폐 시스템의 인출 프로토콜의 안전성에 관해서 고찰한다. 익명성을 제공하는 인출 프로토콜에서는 사용자 인증과 더불어 은닉 서명을 동시에 사용한다. 먼저 은닉 서명을 분류하고, 이들 은닉서명 프로토콜과 사용자 인증 프로토콜의 결합 방식 중에서 인증후 은닉서명 방식(Identification-then-Blind Signature)에 대한 공격을 설명한다. 그리고 인증과 은닉서명을 동시에 하는 방식(Identification-and-Blind Signature)을 이용해서 명시적 수신자 은닉 서명(Blind Signature Scheme with Explicit Identified Receiver)을 제안하며, 그것들의 안전성에 대해서 분석한다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.42 no.4
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• pp.739-746
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• 2017

Orthogonal frequency division multiplexing(OFDM) systems have many advantages. However, OFDM systems are much affected by a nonlinear distortion because those systems have a high peak to average power ratio(PAPR) value. A selected mapping technology was suggested to reduce a PAPR value. The technology does not have data loss but receivers need side information to know modified phase sequence. Therefore, side information causes decreased a transmission efficiency. In this paper, we suggest a blind SLM receiver using a cross correlation technology. This receiver does not require side information. The proposed blind SLM receiver calculates sums of cross-correlation between transmitted pilot signals multiplied by each phase sequence and received pilot signals. So, this receiver detects side information which has a maximum sum cross-correlation value. We compared our proposed SLM receiver to a conventional blind SLM receiver through bit error rate(BER) and side information error rate(SIER) performances. Simulation results show that the proposed SLM receiver has improved BER and SIER performances than the conventional SLM receiver.

• Proceedings of the KIEE Conference
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• 2002.11c
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• pp.411-413
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• 2002

In this paper we researched about the ultrasonic cane which aids the blind to walk. We used ultrasonic in recognizing the object and implemented pulse counting method in measuring the distance. The distance measuring system consists of transmitter unit, receiver unit and micro-processor. We used broadband ultrasonic sensors in transmitter unit and receiver unit. The blind is able to recognize the distance between obstacles and himself as it used a vibration system.

• Proceedings of the IEEK Conference
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• 2000.09a
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• pp.25-28
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• 2000

In this paper, we choice multicarrier direct-sequence code division multiple access using bandwidth effectively in communication system. Because this system is based on DS-CDMA the same problem is raised. That is, the degradation of the performance is due to multiple access interference. To solve this problem, we proposed the blind adaptive receiver for MC DS-CDMA system. Simulation results show that the proposed blind receiver has more about 0.5(dB) value of SNR than conventional receiver.

• Proceedings of the KIEE Conference
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• 1998.11b
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• pp.624-626
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• 1998

Adaptive channel equalization accomplished without resorting to a training sequence is known as blind equalization. In this paper, we present a auto-switching blind, equalization for 8-VSB HDTV receiver. The scheme operate in two mode : blind equalization mode and decision-directed equalization mode. This proposed scheme changes from the blind equalization mode at high error levels to the decision-directed equalization mode at lower error levels smoothly and automatically. Manual switch from the blind equalization mode to the decision-directed mode is not necessary.

• ETRI Journal
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• v.45 no.2
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• pp.226-239
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• 2023

Challenges in cognitive radio and tactical communications include recognizing anonymously received signals and estimating parameters in a blind or semi-blind manner. In this paper, we examine this issue for orthogonal frequency division multiplexing (OFDM) signaling. There are several parameters in OFDM signaling, and the blind receiver must extract and consider the synchronization issue. We assume that the blind receiver is aware of modulation type, OFDM, and not aware of chip duration and the length of cyclic prefix. First, we present new criteria based on kurtosis to estimate these parameters and compare their performance at different levels of additive white Gaussian noise with methods based on correlation, kurtosis, maximum likelihood, and matched filter. Then, we perform synchronization and estimate the start time based on these criteria and several new criteria in two steps: fine and coarse synchronization. Finally, in a more practical setup, we present the idea of jointly estimating the mentioned parameters and the signal start time as coarse synchronization. We compare different criteria and show that one of the proposed criteria has the highest efficiency.

• ETRI Journal
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• v.42 no.1
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• pp.26-35
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• 2020

Herein, we consider uplink multiuser massive multiple-input multiple-output systems when multiple users transmit information symbols to a base station (BS) by applying simple space-time block coding (STBC). At the BS receiver, two detection filters for each user are used to detect the STBC information symbols. One of these filters is for odd-indexed symbols and the other for even-indexed symbols. Using constrained output variance metric minimization, we first derive a special relation between the closed-form optimal solutions for the two detection filters. Then, using the derived special relation, we propose a new blind adaptive algorithm for implementing the minimum output variance-based optimal filters. In the proposed adaptive algorithm, filter weight vectors are updated only in the region satisfying the special relation. Through a theoretical analysis of the convergence speed and a computer simulation, we demonstrate that the proposed scheme exhibits faster convergence speed and lower steady-state bit error rate than the conventional scheme.