• KIPS Transactions on Computer and Communication Systems
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• v.4 no.1
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• pp.5-10
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• 2015

D2D (Device-to-Device) communication underlaying LTE-advanced networks is a promising technology to improve the system capacity and spectral efficiency. By sharing the same radio resources with cellular user equipments, D2D communications can significantly enhance the overall spectral efficiency. However, it may cause interference between D2D link and cellular link. Careful resource allocation and interference coordination between cellular and D2D communications are very important and need to be properly handled. This paper proposes a radio resource allocation scheme based on FFFR (Flexible Fractional Frequency Reuse) for D2D communication underlaying cellular networks. The base station selects randomly resource blocks assigned to cellular users, and reuses them for a D2D pair. Through simulations, we have confirmed that the proposed scheme improves the system throughput, reduces the computational complexity, and mitigates the interference of D2D link and cellular link.

• Journal of Power Electronics
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• v.10 no.4
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• pp.342-350
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• 2010

Randomizing the switching frequency (RSF) to reduce the electromagnetic interference (EMI) of switching power converters is a well-known technique that has been previously discussed. The randomized pulse position (RPP) technique, in which the switching frequency is kept fixed while the pulse position (the delay from the starting of the switching cycle to the turn-on instant within the cycle) is randomized, has been previously addressed in the literature for the same purpose. This paper presents a double-hybrid technique (DHB) for EMI reduction in dc-dc switching regulators. The proposed technique employed both the RSF and the RPP techniques. To effectively spread the conducted-noise frequency spectrum and at the same time attain a satisfactory output voltage quality, two parameters (switching frequency and pulse position) were randomized, and a third parameter (the duty ratio) was controlled by a digital compensator. Implementation was achieved using field programmable gate array (FPGA) technology, which is increasingly being adopted in industrial electronic applications. To evaluate the contribution of the proposed DHB technique, investigations were carried out for each basic PWM, RPP, RSF, and DHB technique. Then a comparison was made of the performances achieved. The experimentally investigated features include the effect of each technique on the common-mode, differential-mode, and total conducted-noise characteristics, and their influence on the converter’s output ripple voltage.

• Journal of the Korean Institute of Gas
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• v.14 no.4
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• pp.18-23
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• 2010

After conducting QRA(quantitative risk assessment) for the high pressure urban gas pipelines planned to be installed, RMMs(risk mitigation measures) when the societal risk is outside the acceptable region have been derived in this paper. Also risk reduction rates are calculated for each RMM. As a result of QRA, we find out that damaged distance caused by radiational heat is largely dependent upon the wind velocity and the atmospheric stability. The measure that has the highest risk reduction effect is No. 10 which includes pipeline corrosion monitoring, MOV(motor operated valve) installation and the method to protect pipeline damage caused by third-party mechanical interference, and which shows 75 % of risk reduction effect.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.8C
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• pp.742-749
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• 2009

In this paper, we propose mitigation techniques using time-domain shortening filter (TSF) and frequency-domain shortening filter (FSF) to overcome inter-block interference (IBn and inter-carrier interference (ICn due to the time difference of arrival (TDoA) and carrier frequency offset (CFO) between downlink and uplink signals from access point (AP) and subscriber station (SS) in synchronous digital duplexing (SDD)/orthogonal frequency division multiple access (OFDMA) systems for indoor wireless communication. The proposed TSF and FSF maximize SIR for shortening in time (SIRST) and SINR for shortening in frequency (SINRSF), respectively, by using channel impulse responses and timing information among stations, obtained from mutual ranging procedure. It is verified by computer simulation that the proposed TSF and FSF reduce effectively the effects of IBI and ICI in the SDD/OFDMA systems.

• Journal of Electrical Engineering and Technology
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• v.11 no.2
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• pp.480-489
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• 2016

Hidden station problem can occur in power-line communication (PLC) networks. A simple solution to the problem has been proposed to use request-to-send (RTS)/clear-to-send (CTS) exchange, but this approach cannot solve the hidden station problem perfectly. This paper revisits the problem for PLC networks and designs a protocol to solve it. We first analyze the throughput performance degradation when the hidden station problem occurs in PLC networks. Then, we propose an interferer aware multiple access (IAMA) protocol to enhance throughput and fairness performances, which uses unique characteristics of PLC networks. Using the RTS/CTS exchange adaptively, the IAMA protocol protects receiving stations from being interfered with neighboring networks. Through extensive simulations, we show that our proposed protocol outperforms conventional random access protocols in terms of throughput and fairness.

• Journal of electromagnetic engineering and science
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• v.16 no.2
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• pp.74-79
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• 2016

This paper proposes an optimum array configuration to improve null steering time for mobile controlled reception pattern antenna (CRPA) systems. The proposed array consists of a single reference element at the center and nine auxiliary elements arranged in a circular array. The array radius and the vertical positions of the center element are optimized using a genetic algorithm in conjunction with a constrained least-mean-square algorithm. The results demonstrate that the proposed array is suitable for mobile CRPA systems without significant side nulls in satellite directions.

• Journal of Advanced Navigation Technology
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• v.14 no.6
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• pp.808-816
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• 2010

Spectrum sharing between wireless systems becomes a critical issue due to emerging new technologies and spectrum shortage. Since WRC-07 allocated 3400-3600MHz band for the coming fourth generation (4G) or IMT-Advanced on a co-primary basis along with existing Fixed Wireless Access (FWA), it requires spectrum sharing studies to solve the interference problems between two systems. In this paper, I propose the separation distance between service coverages as a sharing fundamental criterion based on the interference to noise power ratio (I/N) received in a FWA base station from several IMT-Advanced base stations on the cellular systems. Especially, some results imply that I/N values compared to the worst case can be greatly reduced with MIMO SDMA interference mitigation technique of IMT-Advanced base stations so that these two systems can co-exist in the same frequency with appropriate separation distance.

• Nuclear Engineering and Technology
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• v.53 no.12
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• pp.3966-3978
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• 2021

ISFRA (Integrated SFR Analysis Program for PSA) computer program has been developed for simulating the response of the PGSFR pool design with metal fuel during a severe accident. This paper describes validation of the ISFRA aerosol model against the Aerosol Behavior Code Validation and Evaluation (ABCOVE) experiments undertaken in 1980s for radionuclide transport within a SFR containment. ABCOVE AB5, AB6, and AB7 tests are simulated using the ISFRA aerosol model and the results are compared against the measured data as well as with the simulation results of the MELCOR severe accident code. It is revealed that the ISFRA prediction of single-component aerosols inside a vessel (AB5) is in good agreement with the experimental data as well as with the results of the aerosol model in MELCOR. Moreover, the ISFRA aerosol model can predict the "washout" phenomenon due to the interaction between two aerosol species (AB6) and two-component aerosols without strong mutual interference (AB7). Based on the theory review of the aerosol correlation technique, it is concluded that the ISFRA aerosol model can provide fast, stable calculations with reasonable accuracy for most of the cases unless the aerosol size distribution is strongly deformed from log-normal distribution.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.15 no.4
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• pp.230-236
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• 2022

In this paper, we propose an efficient concatenated code for both random and ISI errors on diffusion-based molecular communication channels. The proposed concatenated code was constructed by combining the ISI-mitigating code designed for ISI mitigation and the ISI-Hamming code strong against random errors, and the BER(bit error rate) performance was analyzed through simulation. In the case of the above M=1,200 channel environment, it was found that the error rate performance of the concatenated code follows the error rate performance of the ISI-mitigating code, which is strong against ISI, and follows the error rate performance of the ISI-Hamming code, which is strong against random errors, in the channel environment below M=600. In M=600~1,200, the concatenated code shows the best error rate performance among those of three codes, which is analyzed because it can correct both random errors and errors caused by ISI. In the following cases of below M=800, it can be seen that the error rate of the concatenated code and the ISI-mitigating code shows an error rate difference of about 1.0×10^-1 on average.

• Journal of Internet Computing and Services
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• v.16 no.3
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• pp.1-11
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• 2015

WBAN(Wireless Body Area Network) operating around the human body aims at medical and non-medical service at the same time. and it is the short-range communication technology requiring low-power, various data rate and high reliability. Various studies is performing for IEEE 802.15.4, because IEEE 802.15.4 can provide high compatibility for operate WBAN among communication standard satisfiable these requirements. Meanwhile, in the case of coexisting many IEEE 802.15.4-based WBAN, signal interference and collision are the main cause that is decreasing data reliability. but IEEE 802.15.4 Standard does not consider about coexistence of many networks. so it needs improvement. In this paper, To solve about this problem, identify coexistence problem of IEEE 802.15.4-based WBAN by preliminary experiments. and propose a scheme to mitigate the reliability decrease at multiple coexistence WBAN. The proposed scheme can be classified in two steps. The first step is avoidance to collision on the CFP through improving data transmission. The second step is mitigation collision through converting channel access method. Proposed scheme is verified the performance by performing comparison experiment with Standard-based WBAN.