• Journal of the Optical Society of Korea
• /
• v.12 no.4
• /
• pp.337-345
• /
• 2008

This article presents the RSOA-based re-modulation schemes for practical application to the WDM-PON link. Emphasis is put on the three methods for reducing the residual downstream signal in the upstream transmission; the simplest one is to use the RSOA gain-saturation property, the second uses selective filtering of the adiabatic-chirped DFB-LD output spectrum, and the last uses a dynamic RSOA gain control by varying its driving current according to the incident binary signal. The reflection sensitivity in the proposed re-modulation link is also qualitatively presented in the cases of using two different types of seed light: coherent light from DFB-LD array and spectrum-sliced incoherent ASE light. We show experimental results of an error-free bidirectional gigabit transmission over 20 km at -30 dB reflection with the spectrum-sliced ASE seed light.

• Journal of Communications and Networks
• /
• v.1 no.2
• /
• pp.86-88
• /
• 1999

The Discrete Fourier Transform (DFT) and the Inverse Discrete Fourier Transform (IDFT) are commonly used in signal processing applications, in particular in digital communication sys-tems using the multi-carrier modulation principle. In such systems an IDFT is computed at the transmitter end, and a DFT at the re-ceiver end. This paper examines a technique of computations, for which only negligible differences appear between the DFT and the IDFT calculations while the number of arithmetic operations re-quired is substantially reduced. This offers significant advantages for the design of an IDFT/DFT processor for Discrete Multitone(DMT) systems.

• Proceedings of the IEEK Conference
• /
• 2003.07e
• /
• pp.2427-2430
• /
• 2003

A uniformly sampled digital pulse-width modulation adopting a pre-compensation filter scheme for applications in high-resolution digital-to-analog data conversion is described. It is shown that linearization of the intrinsic distortion resulting in uniformly sampled pulse-width modulation can be achieved by using a non-integer delay digital filter embedded within a noise shaping re-quantizer.

• Journal of the Korea Society of Computer and Information
• /
• v.17 no.8
• /
• pp.51-60
• /
• 2012

I propose the 5Gbps/1.25Gbps WDM/TDM hybrid Passive Optical Network(PON) with inverse RZ(Return to Zero) code coded downstream and NRZ(Non Return to Zero) upstream re-modulation and analyze its performance by performing simulation with MATLAB. The results have shown that an optical line termination (OLT) can be connected to 8, 16 optical network unit (ONU)s with the Bit Error Rate(BER) of $10^{-9}$ when the distance between OLT and ONU is 10Km and transmitted optical powers are more than -3.8, -0.9dBm, respectively. The proposed WDM/TDM hybrid PON system can solve the problem of data rate limit in upstream which happened in the conventional TDM PON because the upstream data rate is proportional to ONU and does not require a light source in ONU and its control circuits in OLT, thus can be a useful technology for asymmetric optical subscriber networks.

• Proceedings of the Korean Society of Broadcast Engineers Conference
• /
• 2000.11b
• /
• pp.9-13
• /
• 2000

This paper represents analysis of field test results of terrestrial DTV on channel repeaters over Taejon city area. Two kind of on channel repeaters were tested. Non-regenerative repeater performs filtering, amplifying and re-transmit received main DTV signal. Regenerative repeater performs demodulation, modulation and amplifying and re-transmit received main DTV signal. The non-regenerative repeater threshold D/U ratio is about 10dB better than regenerative repeater's one.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2013.11a
• /
• pp.17-18
• /
• 2013

To minimize construction of nuclear facility, it is required to reduce reinforcing bar amount and solve reinforcing bar concentration and for this, it is necessary to develop appication design technology and modular of high strength reinforcing bar. Hence, KHNP reduces excessive reinforcing bar amount which can cause possibility of poor construction of concrete through design standard development and modular of nuclear facility structure using high strength reinforcing bar to raise economics and has its purpose to maintain high-level safety and durability as they are. This study is to introduce application method for the Rebar Modulation of High-Strength Reinforcing Bars to the Nuclear Power Plant Structures.

• Journal of the Optical Society of Korea
• /
• v.13 no.3
• /
• pp.361-366
• /
• 2009

We propose the performance enhancing method optimization of an asynchronous 2.5 Gbps/1.25 Gbps optical subscriber network with inverse RZ (Return to Zero) coded downstream and NRZ (Non Return to Zero) upstream re-modulation by adjusting threshold level control of a receiver. We theoretically analyze the BER (Bit Error Rate) performance by modeling the occurrence of BER by simulation with MATLAB according to the types of downstream data. The results have shown that the normalized threshold level in an optical receiver could be saturated at 1/3 as the SNR (Signal to Noise Ratio) increases. The needed SNR for obtaining the BER $10^{-9}$ can be reduced by $\sim$5 dB by optimizing the normalized threshold level at 1/3 instead of by using the conventional receiver with threshold level of 0.5. The proposed system can be a useful technology for asynchronous optical access networks with asymmetric upstream and downstream data rates, because the improved minimum receiving power could replace a light source with a source with lower power and lower cost in an OLT (Optical Line Termination).

• Journal of the Korea Institute of Information Security & Cryptology
• /
• v.31 no.6
• /
• pp.1279-1290
• /
• 2021

As vehicle technology has grown, autonomous driving that does not require driver intervention has developed. Accordingly, CAN security, an network of in-vehicles, has also become important. CAN shows vulnerabilities in hacking attacks, and machine learning-based IDS is introduced to detect these attacks. However, despite its high accuracy, machine learning showed vulnerability against adversarial examples. In this paper, we propose a adversarial CAN frame generation method to avoid IDS by adding noise to feature and proceeding with feature selection and re-packet for physical attack of the vehicle. We check how well the adversarial CAN frame avoids IDS through experiments for each case that adversarial CAN frame generated by all feature modulation, modulation after feature selection, preprocessing after re-packet.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.39 no.7
• /
• pp.665-671
• /
• 2015

The performance of fault diagnostics for a planetary gearbox depends on vibration modulation characteristics, which can vary with manufacturing & assembly tolerance, and load condition. In this paper, a fault diagnostics technique that considers vibration modulation characteristics is proposed for the effective fault detection of planetary gearboxes in wind turbines. For identifying the vibration modulation characteristics in practice, re-sampled vibration signals are processed with narrow band-pass filters. Thereafter, the optimal position of the vibration extraction window is identified for effective detection of faulty signals under the varying vibration modulation characteristics. The proposed diagnostics technique makes it possible to perform robust diagnostics of the planetary gearbox with regard to the changeable vibration modulation effect. For demonstrating the proposed fault diagnostics technique, a 2-kW WT testbed is designed with two DC motors and gearboxes. A faulty gear with partial tooth breakage is machined and assembled into the gearbox.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2013.10a
• /
• pp.399-401
• /
• 2013

In this paper, we present the method to impove the performance by using iterative decoding in LDPC codes with 8-PSK modulation. Iterative decoding is the technique that improve the performance after the input signals of receiver are re-calculated by using the soft decision output of decoder. DVB-S2 system with 8-PSK modulation based on iterative decoding had a better performance than DVB-S2 with 8-PSK modulation over Gaussian channels.