• The Journal of the Institute of Internet, Broadcasting and Communication
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• 제9권6호
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• pp.9-14
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• 2009

In this paper, we proposed spreading code slicing technique for efficient transmitter detection in AT-DMB system with single frequency network. At the transmitter, the spreading code for transmitter identification inserted using slicing technique on forehead of null symbol and then transmitted. In this point, it requires high correlation characteristic spreading code. At the receiver, peak to peak value calculated by correlation process before signal demodulation. The transmitter information by proposed technique is employed to implement the single frequency network (SFN) which is proposed for solving a frequency inefficiency problem of the MFN. The results of the paper can be applied to wireless multimedia digital broadcasting system.

• International Journal of Computer Science & Network Security
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• 제24권9호
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• pp.41-49
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• 2024

This paper proposes dual symbol superposition block carrier transmission with frequency domain equalization (DSS-FDE) system. This system is based upon χ-transform matrix, which is obtained by concatenation of discrete Hartley transform (DHT) matrix and discrete Fourier transform (DFT) matrices into single matrix that is remarkably sparse, so that, as it will be shown in this paper, it only has non-zero entries on its principal diagonal and one below the principle anti-diagonal, giving it shape of Latin alphabet χ. When multiplied with constellation mapped complex transmit vector, each entry of resultant vector is weighted superposition of only two entries of original vector, as opposed to all entries in conventional DFT based OFDM. Such a transmitter is close to single carrier block transmission with frequency domain equalization (SC-FDE), which is known to have no superposition. The DSS-FDE offers remarkable simplicity in transmitter design and yields great benefits in reduced complexity and low PAPR. At receiver-end, it offers the ability to harvest full diversity from multipath fading channel, full coding gain, with significant bit error rate (BER) improvement. These results will be demonstrated using both analytical expressions, as well as simulation results. As will be seen, this paper is Part III of three-paper series on alternative transforms for multicarrier communication (MC) systems.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제5권4호
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• pp.684-702
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• 2011

This paper proposes a TDMA-based multichannel medium access control (MAC) protocol for QoS provisioning in mobile ad hoc networks (MANETs) that enables nodes to transmit their packets in distributed channels. The IEEE 802.11 standard supports multichannel operation at the physical (PHY) layer but its MAC protocol is designed only for a single channel. The single channel MAC protocol does not work well in multichannel environment because of the multichannel hidden terminal problem. Our proposed protocol enables nodes to utilize multiple channels by switching channels dynamically, thus increasing network throughput. Although each node of this protocol is equipped with only a single transceiver but it solves the multichannel hidden terminal problem using temporal synchronization. The proposed energy efficient multichannel MAC (EM-MAC) protocol takes the advantage of both multiple channels and TDMA, and achieves aggressive power savings by allowing nodes that are not involved in communications to go into power saving "sleep mode". We consider the problem of providing QoS guarantee to nodes as well as to maintain the most efficient use of scarce bandwidth resources. Our scheme improves network throughput and lifetime significantly, especially when the network is highly congested. The simulation results show that our proposed scheme successfully exploits multiple channels and significantly improves network performance by providing QoS guarantee in MANETs.

• JSTS:Journal of Semiconductor Technology and Science
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• 제17권1호
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• pp.48-55
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• 2017

This paper proposes a new link structure that transmits power, clock, and data through a single optical fiber for a future automotive network. A pulse-position modulation (PPM) technique is adopted to guarantee a DC-balanced signal for robust power transmission regardless of transmitted data pattern. Further, circuit implementations and theoretical analyses for the proposed PPM transceiver are described in this paper. A prototype transceiver fabricated in 65-nm CMOS technology, is used to verify the PPM signaling part of the proposed system. The prototype achieves a $10^{-13}$ bit-error rate and 0.188-UI high frequency jitter tolerance while consuming 14 mW at 800 Mb/s.

• The Journal of Korean Institute of Communications and Information Sciences
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• 제25권6A호
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• pp.885-892
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• 2000

A multi-used detector(MUD) using a radial basis function(RBF) network is proposed in a multicarrier-code division multiple access (MC-CDMA) system. In the proposed scheme, a RBF network is connected to the frequency domain in order to effectively utilize the frequency diversity. Simulations have been performed over the frequency selective and multipath fading channel. From these simulations, the proposed receiver is verified to be used for making the performance improvement in combating near-far effects and increasing the number of active users. The system capacity is increaed about 1.8 times at a BER of $10^{-3}$ under a single cell when the proposed scheme is compared with MUD using a parallel interference canceller(PIC).

• Journal of Positioning, Navigation, and Timing
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• 제10권3호
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• pp.159-168
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• 2021

Precise Point Positioning-Real Time Kinematic (PPP-RTK) is an improved PPP method that provides the user receiver with satellite code and phase bias correction information in addition to the satellite orbit and clock, thus enabling single-receiver ambiguity resolution. Single station PPP-RTK concept is special case of PPP-RTK in that corrections are computed, instead of a network, by only one single GNSS receiver. This study is performed to experimentally verify the positioning accuracy performance of single baseline RTK level by a user who utilizes correction for a single station PPP-RTK using dual frequencies. As an experimental result, the horizontal and vertical 95% accuracy was 2.2 cm, 4.4 cm, respectively, which verify the same performance as the single baseline RTK.

• The Transactions of The Korean Institute of Electrical Engineers
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• 제64권9호
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• pp.1398-1405
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• 2015

Domestic railway communication in Korea has been introduced for mutual communications among control center, operation staffs, and maintenance staffs. It has been mainly used as railway disaster and safety functions from VHF and UHF from 1980’s and TRS-Astro and TRS-Tetra from the 2000’s. Recently for urban railways communications, 18GHz and 2.4GHz ranges have been utilized for image transmissions and control command communications, respectively. This paper analyzes technical development of LTE-R, LTE communication for Railways, that has been designed as a single integrated railway wireless network in order to merge the current various communication systems. In this paper, we present the details of the examination of the LTE-R test-bed using 2.6GHz test frequency in Daebul test line through CW test and optimization test.

• Human Ecology Research
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• 제62권2호
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• pp.217-231
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• 2024

The aims of this study were to identify (a) the social network contact frequency of the elderly with children, relatives, and friends; (b) the impact of contact frequency (face-to-face/non-face-to-face) on life satisfaction of the elderly; and (c) the moderating effect of digital capabilities of the elderly on the relationship between social contact frequency and life satisfaction. Data were obtained from the National Survey of Older Koreans 2020. The sample comprised 6,119 adults aged 65+ who were in single or couple households. The principal findings were as follows. First, couple households, higher levels of education, and better health status increased life satisfaction of the elderly. Second, the higher the frequency of face-to-face contact with children and the higher the frequency of non-face-to-face contact with friends, the more positive the effect on life satisfaction of the elderly. Third, the interaction effect of the digital capabilities of the elderly differed according to children, relatives and friends. There was a significant and positive moderating effect on the relationship between life satisfaction and the frequency of face-to-face/non-face-to-face contact with children and the frequency of face-to-face contact with relatives. Conversely, there was a significant negative effect on the relationship between life satisfaction and the frequency of face-to-face/non-face-to-face contact with friends. By examining the impact of non-face-to-face contact on life satisfaction of the elderly in the era of digital transformation, the findings have significance in that they provide basic data to support policies and education programs aimed at improving the digital capabilities of the elderly.

• Journal of Communications and Networks
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• 제15권5호
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• pp.496-503
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• 2013

In an orthogonal frequency division multiplexing system, conventional interpolation techniques cannot correctly balance performance and overhead when estimating dynamic long-delay channels in single frequency networks (SFNs). In this study, classical filter analysis and design methods are employed to derive a complex interpolator for maximizing the resistible echo delay in a channel estimator on the basis of the correlation between frequency domain interpolating and time domain windowing. The coefficient computation of the complex interpolator requires a key parameter, i.e., channel length, which is obtained in the frequency domain with a tentative estimation scheme having low implementation complexity. The proposed complex adaptive interpolator is verified in a simulated digital video broadcasting for terrestrial/handheld receiver. The simulation results indicate that the designed channel estimator can not only handle SFN echoes with more than $200{\mu}s$ delay but also achieve a bit-error rate performance close to the optimum minimum mean square error method, which significantly outperforms conventional channel estimation methods, while preserving a low implementation cost in a short-delay channel.

• Korean Journal of Fisheries and Aquatic Sciences
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• 제54권5호
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• pp.798-807
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• 2021

The directivity characteristics of acoustic transducers for conventional single-beam echo sounders considerably limit the detection of fish-size information in acoustic field surveys. To overcome this limitation, using the split-aperture technique to estimate the direction of arrival of single-echo signals from individual fish distributed within the sound beam represents the most reliable method for fish-size classification. For this purpose, we design and develop a split-beam data acquisition and processing system to obtain fish-size information in conjunction with a 50-kHz single-beam echo sounder. This split-beam data acquisition and processing system consists of a notebook PC, a field-programmable gate array board, an external single-transmitter module with a matching network, and four-channel receiver modules operating at a frequency of 50-kHz. The functionality of the developed split-beam data processor is tested and evaluated. Acoustic measurements in an experimental water tank showed that the developed data acquisition and processing system can be used as a fish-sizing echo sounder to estimate the size distribution of individual fish, although an external single-transmitter module with a matching network is required.