• ETRI Journal
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• v.29 no.3
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• pp.363-370
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• 2007

In this paper, we propose a flexible turbo decoding algorithm for a high order modulation scheme that uses a standard half-rate turbo decoder designed for binary quadrature phase-shift keying (B/QPSK) modulation. A transformation applied to the incoming I-channel and Q-channel symbols allows the use of an off-the-shelf B/QPSK turbo decoder without any modifications. Iterative codes such as turbo codes process the received symbols recursively to improve performance. As the number of iterations increases, the execution time and power consumption also increase. The proposed algorithm reduces the latency and power consumption by combination of the radix-4, dual-path processing, parallel decoding, and early-stop algorithms. We implement the proposed scheme on a field-programmable gate array and compare its decoding speed with that of a conventional decoder. The results show that the proposed flexible decoding algorithm is 6.4 times faster than the conventional scheme.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.18 no.3
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• pp.61-69
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• 2018

In this paper, we propose a method for recognizing ground target using dual polarization channels in millimeter waveband air-to-surface radar. First, the Push-Broom target detection method is described and the received signal is modeled considering flight-path scenario of air-to-surface radar. The scattering centers were extracted using the RELAX algorithm, which is a time domain spectral estimation technique, and the feature vector of the target was generated. Based on this, a DB for 4 targets is constructed. As a result of the proposed method, it is confirmed that the target classification rates is improved by more than 15% than the single channel using the data of the dual polarization channel.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.12
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• pp.2317-2323
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• 2015

In this paper, we analyze the performance of dual-hop amplify-and-forward (AF) relaying in cooperative networks with partial relay selection. An AF relay gain considered in this paper includes channel-noise-assisted relay gain. Leveraging a received signal-to-noise ratio (SNR) model, we derive exact closed-form expressions for the probability density function (pdf) and cumulative distribution function (cdf) of the end-to-end SNR. Moreover, an exact closed-form expression of the ergodic capacity for dual-hop AF relaying with channel-noise-assisted relay gain and partial relay selection is investigated. The analytical results shown in this paper are confirmed by Monte-Carlo simulations.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2007.02a
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• pp.101-104
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• 2007

Ad hoc 네트워크는 기반구조가 없는 무선네트워크이다. Ad hoc 네트워크는 재난지역, 군사지역, 홈 네트워킹 서비스, 텔레매틱스 서비스 같은 곳에서 응용될 수 있다. 최근Ad hoc 네트워크의 처리량을 향상시키기 위해 방향성 안테나를 사용하거나 이중채널을 사용하는MAC프로토콜이 제안되고 있다. DUBMAC프로토콜은 이중채널에 방향성 안테나를 사용하여 처리량 성능을 향상시킨 프로토콜이다. 본 논문에서는 DUDMAC프로토콜에 전력 제어 기법을 적용하여 네트워크의 처리량을 향상시키는 MAC 프로토콜을 제안한다. 제안하는 MAC 프로토콜은 새로운 블로킹 알고리즘을 사용하여 공간 재사용을 향상시킨다. 제안하는 블로킹 알고리즘은 RTS 또는 CTS 수신 시 블로킹 테이블에 저장된 수신세기를 사용하여 기존의 DUDMAC의 블로킹 영역을 FULL_BLOCKING 영역과 SEMI_BLOCKING 영역으로 구분하여 성능을 개선한다. 제안하는 MAC 프로토콜의 처리량 성능은 퀄넷 시뮬레이터 버전 3.8을 사용하여 확인하였다.

• Smart Media Journal
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• v.1 no.4
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• pp.8-17
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• 2012

In this paper, we introduce the appoaches that aim to improve user experience in mobile device by the use of multiple vibration signal feedback, conducted by Haptics and Virtual Reality laboratory at POSTECH. We introduce current progresses of our 'Vibrotactile flow using multiple vibration actuators' and 'Real-time dual-channel haptic music player.' The 'Vibrotactile flow using multiple vibration actuators' produces vibrotactile flow sensations by using multiple actuators and that improves the information transfer on mobile devices. The 'Real-time dual-channel haptic music player' generates vibrotactile sensation by transforming auditory signal, which improves the user experience of mobile devices. These approaches can be good examples to fulfill the demands of better information transfer capability and user experience on mobile devices.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.21 no.7
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• pp.1820-1832
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• 1996

The performance of a carrier recovery is severely degraded because of amplitude fluctuations and random phases of the received signai caused by multipath fading in mobile radio channel. In this paper, we present two kinds of carrier recovery technique using pilot tone such as TCT(Tone Calibration Technique) and DTCT(Dual Tone Calibration Technique) and analyze these performance both in Rayleigh and Rician fadings. we also evaluate the BER performance of two carrier recovery systems in terms of design parameters such as pilot-to-singnal power ratio, and detection filter-to-pilot filter bandwidth ratio.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38B no.3
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• pp.216-221
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• 2013

In this paper, wireless channel characteristics of massive MIMO system is analyzed by comparing angular spread, cross polarization discrimination(XPD) and delay spread of dual polarized 4 and 128 transmit array antenna systems, by using 3D rat-tracing simulator, Wireless Insite in microcell environments. The analysis shows that increasing the number of transmit antennas results in the smaller angular spread and delay spread, and the higher value of XPD.

• Journal of Sensor Science and Technology
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• v.14 no.5
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• pp.350-356
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• 2005

We have developed a dual-channel type automatic measurement system to evaluate AC-DC current transfer difference of the thermal current converter(TCC) which is primary standard of AC current. The output drift effect of the TCC is minimized by measuring simultaneously the output voltages of two TCCs using voltmeter. Furthermore, the offset voltage of the voltmeter is cancelled nearly out by taking the average values of two outputs of TCCs measured with the forward-reverse directions using dual channel scanner. The uncertainties of the automatic system were 7 to $86{\mu}A/A$ for 3 mA to 10 A at 40 Hz to 20 kHz, which were evaluated by the comparisons between adjacent range of TCCs and inter-comparison with national measurement institute of Germany(PTB). The capability for ac-dc transfer difference measurement was improved by one order compared with that for the manual ac-dc measurement system.

• Journal of Satellite, Information and Communications
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• v.12 no.2
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• pp.51-55
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• 2017

This paper aims to maximize the energy harvesting rate and channel capacity in RF-energy harvesting networks (RF-EHNs) under the constraints of maximum transmit power and minimum quality of service (QoS) in terms of rate capacity for each user. We study a multi-user RF-EHN with frequency division multiple access (FDMA) in a Rayleigh channel. An access point (AP) simultaneously transmitting wireless information and power in the RF-EHN serves a subset of active users which have a power-splitting antenna. To gauge the network performance, we define energy efficiency (EE) and propose an optimization solution for maximizing EE with Lagrangian dual decomposition theory. In simulation results, we confirm that the EE is effectively maximized by the proposed solution with satisfying the given constraints.

• The KIPS Transactions:PartA
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• v.9A no.1
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• pp.93-98
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• 2002

This paper introduces the design of high-speed analog-to-digital converter (ADC) for hard disk drive (HDD) read channel applications. This circuit is bated on fast regenerative autozero comparator for high speed and low-error rate comparison operation, and Double Speed Dual ADC (DSDA) architecture for efficiently increasing the overall conversion speed of ADC. A new type of thermometer-to-binary decoder appropriate for the autozero architecture is employed for no glitch decoding, simplifying the conventional structure significantly. This ADC is designed for 6-bit resolution, 800 Msample/s maximum conversion rate, 390 mW power dissipation, one clock cycle latency in 0.65 m CMOS technology.