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Performance analysis of APSK modulation for DVB-S2 transmission over nonlinear channels
Sung, Wonjin,Kang, Seokheon,Kim, Pansoo,Chang, Dae-Ig,Shin, Dong-Joon John Wiley Sons, Ltd. 2009 International journal of satellite communications Vol.27 No.6
<P>For increased bandwidth efficiency and receiver performance, standards for satellite broadcasting systems are evolving by utilizing efficient transmission techniques. The second-generation digital video broadcasting for satellites (DVB-S2) adopts the amplitude phase shift keying (APSK) modulation for enhanced performance over nonlinear channels. In this paper, we derive error rate bounds for APSK modulated symbols and generalize the bounds to the case of distorted constellation, which occurs when the maximum transmission amplitude is saturated by the soft-limiter type channel. The derived bound is shown to significantly improve the previously known result, to accurately predict both the symbol error rate and bit error rate in the entire signal-to-noise ratio (SNR) region of interest. Using the derived formula, the optimal input power level for the soft-limiter channel is determined, and the corresponding minimal error rates for 16- and 32-APSK are quantified. The result is also interpreted in terms of optimal input back-off (IBO) for nonlinear power amplifiers by evaluating the performance degradation as a function of IBO. Copyright © 2009 John Wiley & Sons, Ltd.</P>
Interference Effects of Low-Power Devices on the UE Throughput of a CR-Based LTE System
Wonjin Sung,Soyeon Kim 한국전자파학회JEES 2014 Journal of Electromagnetic Engineering and Science Vol.14 No.4
Recently, the use of mobile devices has increased, and mobile traffic is growing rapidly. In order to deal with such massive traffic, cognitive radio (CR) is applied to efficiently use limited-spectrum resources. However, there can be multiple communication systems trying to access the white space (unused spectrum), and inevitable interference may occur to cause mutual performance degradation. Therefore, understanding the effects of interference in CR-based systems is crucial to meaningful operations of these systems. In this paper, we consider a long-term evolution (LTE) system using additional spectra by accessing the TV white space, where low-power devices (LPDs) are licensed primary users, in addition to TV broadcasting service providers. We model such a heterogeneous system to analyze the co-existence problem and evaluate the interference effects of LPDs on LTE user equipment (UE) throughput. We then present methods to mitigate the interference effects of LPDs by ‘de-selecting’ some of the UEs to effectively increase the overall sector throughput of the CR-based LTE system.
3차원 주파수 재사용 패턴의 성능 및 반송파 결합을 사용하는 시스템으로의 적용 방안
성지훈(Jihoon Sung),성원진(Wonjin Sung) 한국전자파학회 2012 한국전자파학회논문지 Vol.23 No.11
셀룰러 이동통신의 주요 성능 열화 요인으로 작용하는 셀 간 간섭을 제어하기 위하여, 인접한 셀 간에 주파수 자원을 선택적으로 할당하는 주파수 재사용 기법을 활용할 수 있다. 기존의 주파수 재사용 패턴에 대한 연구는 주로 2차원 공간에 제한되어 있었기 때문에, 도심 지역의 사무용 빌딩과 같이 사용자가 밀집된 지역에 설치된 펨토셀에 적용하기 위해서는 3차원 공간에서의 주파수 재사용 방식에 대한 연구가 필요하다. 본 논문에서는 3차원 공간에서 사용 가능한 주파수 패턴들을 제안하고, 각 패턴별 성능을 채널 용량 측면에서 분석한다. 특히, LTEAdvanced 시스템의 요소 반송파 결합 기술을 고려시 제안 방식의 적용을 통해 보다 유연한 3차원 주파수 재사용 패턴을 생성할 수 있음을 보이고, 시뮬레이션을 통해 제안 방식의 성능을 평가한다. Assigning different frequency resources among adjacent cells, namely the frequency reuse technique can be utilized to mitigate intercell interference, which is a major cause of performance degradation in cellular systems. Since most of conventional frequency reuse patterns are limited to the two-dimensional environment, the research for the three-dimensional frequency reuse would be beneficial especially for the implementation of femto cells in downtown office buildings. We propose frequency reuse patterns in three-dimensional space and evaluate their performance of each pattern in terms of channel capacity. In particular, we show that the proposed three-dimensional frequency reuse patterns can be applied for carrier-aggregated transmission of LTE-Advanced systems. The performance of the proposed patterns is evaluated using computer simulation.
Na, Wonjin,Lee, Geunsung,Sung, Minchang,Han, Heung Nam,Yu, Woong-Ryeol ELSEVIER (APPLIED SCIENCE) 2017 COMPOSITE STRUCTURES -BARKING THEN OXFORD- Vol.168 No.-
<P><B>Abstract</B></P> <P>The tensile strength of unidirectional (UD) carbon fiber composites was predicted considering the interfacial shear strength (IFSS). First, the effect of the IFSS on the load transfer to the surrounding fibers when a fiber was broken was analyzed using finite element method and then the stress concentration factor (SCF) of each surrounding fiber was determined. The multiple fracture number was calculated using the SCF and a statistical approach that can calculate the probability of fiber breakage propagation due to the stress concentration when the broken fibers exist in neighbor. Finally, the tensile strength of UD carbon fiber composites was predicted using the multiple fracture number and was compared with experimental results, demonstrating the validity of the current method. An optimal IFSS that can ensure the maximum tensile strength of UD carbon fiber composites is discussed based on the calculation results.</P>
전원진 ( Wonjin Jeon ),김영두 ( Young-doo Kim ),박성열 ( Sung-youl Park ),이경환 ( Kyong-hwan Lee ) 한국폐기물자원순환학회(구 한국폐기물학회) 2020 한국폐기물자원순환학회 춘계학술발표논문집 Vol.2020 No.-
반응물 형태가 폐비닐 열분해 반응에 미치는 영향을 알아보고자, 반회분식 반응시스템을 이용하여 폐비닐 열분해 반응을 수행하였다. 포장용 폐비닐을 묶음 형태와 분쇄 입자 형태로 가공하여, 400℃의 반응온도에서 90분 간 질소의 주입 유량을 변화시키며 실험을 진행하였다. 반응조건에 따라 얻어진 오일의 수율은 67.7-76.1% 였으며, 디젤 연료에 해당하는 성분(C11-C22)이 주요 생성물로 나타났다. 열분해 오일의 주요 성분은 n-파라핀 및 n-올레핀으로 나타났으며, 입자 형태의 반응물을 사용한 경우에 n-파라핀의 농도가 상대적으로 높게 나타났고 질소 유량이 증가함에 따라 그 농도가 증가함이 관찰되었다. 또한, 입자 형태의 반응물을 사용한 결과, 주요생성물인 디젤 분의 고위발열량(higher heating value, HHV)이 상대적으로 높게 나타났다. 이를 통해, 반응물의 형태 및 질소의 흐름에 따라 생성되는 열분해 오일의 조성이 제어될 수 있다는 것을 확인하였다. 또한, 입자형태의 폐비닐 원료는 연속식 반응물 공급 시스템에 적합한 원료의 형태이므로, 연속식 열분해 반응기 설계에도 유용한 정보를 제공한다고 할 수 있다.
Analysis of Time-Spreading OCDMA Systems With Partially Coherent Sources
Park, Sang-Gyu,Sung, Wonjin IEEE 2009 Photonics Technology Letters Vol.21 No.12
<P>The effect of partial coherence of optical sources on the performance of time-spreading optical code-division multiple access (TS-OCDMA) systems is investigated. We develop a simple analytic model for the evaluation of bit-error-rate performance, and verify the validity of the model using Monte Carlo simulations. We present performance comparisons with fully coherent sources as well as statistically multiplexed sources, to indicate a desirable operation strategy of TS-OCDMA systems.</P>
Jonghyun Park,Wonjin Sung,Duman, Tolga M IEEE 2010 IEEE communications letters Vol.14 No.11
<P>In this letter, multiuser multiple-input multiple-output (MIMO) precoding which achieves the Gaussian broadcast channel (GBC) capacity under the per-antenna power constraint (PAPC) is investigated. In particular, closed-form expressions for both the MIMO precoder and the corresponding sum capacity are presented for the two-user case. We show that the result can also be utilized to provide the two-user capacity expression under the total power constraint (TPC) of transmit antennas.</P>
Group-Based Multibit Cooperative Spectrum Sensing for Cognitive Radio Networks
So, Jaewoo,Sung, Wonjin IEEE 2016 IEEE Transactions on Vehicular Technology VT Vol.65 No.12
<P>In cooperative spectrum sensing (CSS), a multibit combination rule shows better sensing performance than one-bit hard combination rules at the sacrifice of the reporting overhead. To overcome the tradeoff between the sensing performance and the reporting overhead, we propose a novel group-based multibit CSS scheme with a limited reporting overhead. The proposed scheme adopts contention-based reporting to restrain the reporting overhead while achieving multiuser diversity with an increased number of secondary users (SUs). Moreover, SUs report one-bit sensing results to a fusion center instead of sending multibit quantization information, and the rest of the information is embedded in the time slot. The simulation results demonstrate that, as the number of SUs increases, the proposed scheme improves the sensing performance and the average throughput of SUs, whereas the conventional one-bit or multibit combination schemes show a tradeoff between the sensing performance and the throughput of SUs.</P>