http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
Performance of an OFDMA Based Multichannel Slotted ALOHA for Cognitive Radios
CHOE, Sangho,PARK, Sung-Kwon The Institute of Electronics, Information and Comm 2010 IEICE TRANSACTIONS ON COMMUNICATIONS - Vol.93 No.12
<P>We present an orthogonal frequency division multiple access (OFDMA) based multichannel slotted ALOHA for cognitive radio networks (OMSA-CR). The performance of an infinite population based OMSA-CR system is analyzed in terms of channel capacity, throughput, delay, and packet capture effect. We investigate the channel capacity for OMSA-CR with perfect or imperfect spectrum sensing. We introduce the proposed CR MAC based on two channel selection schemes: non-agile channel selection (NCS) and agile channel selection (ACS). Comparing them, we show the tradeoff between complexity and system performance. We verify the proposed CR system model using numerical analysis. In particular, using simulation with a finite populated linear feedback model, we observe the OMSA-CR MAC tradeoff between throughput and minimum delay whose results matched those of the analytical framework. Numerical results for the proposed system throughput are also compared to conventional MACs, including pure ALOHA based CR MAC.</P>
An Adaptive MIMO-OFDM with an LS predictor for Cellular Systems
Sangho Choe,Hyundong Kim 대한전자공학회 2007 ITC-CSCC :International Technical Conference on Ci Vol.2007 No.7
This paper presents a robust multiple input multiple output orthogonal frequency division multiplexing (MIMO-OFDM) system with a low rate least square (LS) predictor that properly compensates delay. Via computer simulation in mobile fading channels, we verify that the data capacity of proposed MIMO-OFDM is 20% greater than that of conventional MIMO-OFDM.
실시간 산불 모니터링을 위한 이벤트 처리 기반 저전력 저비용 무선 센서 네트워크
최상호(Sangho Choe),유정화(Jeong-Hwa Yoo),폰수게수라니(Ponsuge Surani Shalika Tissera),강조인(Jo-In Kang),양희경(Hee-Kyung Yang) 대한전기학회 2020 전기학회논문지 Vol.69 No.5
In this paper, we propose an event-driven low-power low-cost wireless sensor network (WSN) for real time wildfire monitoring. The proposed system will be mainly deployed and operated in a fire alert (or monitoring) area that could be divided into several sectors, each sector consisting of a controller (AP: access point) and its controlled nodes. For the evaluation of the proposed system, we implement a test bed (TB) using Arduino Uno board that has a smoke detector and a ZigBee module. The presented sensor nodes that are operated in power saving mode (PSM) during most of idle period have a longer battery life. Once a node detects smoke sample (which is termed as sensData) that is larger than a given threshold, it will generate a transmission message, called msgSensInfo (msgSensInfo1 for node fusion or msgSensInfo2 for AP fusion), and transmit that message to the AP and then the remote server. When a sensing event or a wake-up message event occurs, the presented node system is woken up from PSM, and gives a prompt (real-time) response including sensing message msgSensInfo generation and its transmission to AP. The proposed system has a data fusion algorithm collecting and synthesizing either multiple spatial samples (in case of AP fusion) or multiple time samples (in case of node fusion) that improves the fire detection performance further. Therefore, compared to existing low-cost WSN schemes, the proposed low-cost WSN scheme would be better at the perspective of real time performance, cost-effectiveness, and life-cycle such that it would be a good candidate for wildfire prevention as well as initial fire fighting.
Predictive Closed-Loop Power Control for Delay-Prone Burst Transmission Systems in Rayleigh Fading
The Institute of Electronics, Information and Comm 2010 IEICE TRANSACTIONS ON COMMUNICATIONS - Vol.93 No.5
<P>We present a predictive closed-loop power control scheme for delay-prone burst transmission systems. The scheme has a sample-by-sample predictor compensating burst delay and a built-in channel encoder reducing power control command bit error.</P>
DWT-based Denoising and Power Quality Disturbance Detection
Ramzan, Muhammad,Choe, Sangho The Institute of Electronics and Information Engin 2015 IEIE Transactions on Smart Processing & Computing Vol.4 No.5
Power quality (PQ) problems are becoming a big issue, since delicate complex electronic devices are widely used. We present a new denoising technique using discrete wavelet transform (DWT), where a modified correlation thresholding is used in order to reliably detect the PQ disturbances. We consider various PQ disturbances on the basis of IEEE-1159 standard over noisy environments, including voltage swell, voltage sag, transient, harmonics, interrupt, and their combinations. These event signals are decomposed using DWT for the detection of disturbances. We then evaluate the PQ disturbance detection ratio of the proposed denoising scheme over Gaussian noise channels. Simulation results also show that the proposed scheme has an improved signal-to-noise ratio (SNR) over existing scheme.
Denoising and Detection of Power Quality Events Using Wavelet Transform
Muhammad Ramzan,Sangho Choe 대한전자공학회 2015 ITC-CSCC :International Technical Conference on Ci Vol.2015 No.6
We present a new denoising technique using discrete wavelet transform (DWT), where correlation thresholding is used such that the PQ events are efficiently and reliably detected. We evaluate the PQ event detection rate of the proposed denoising scheme over Gaussian noise channels. Simulation results show that the proposed scheme has an improved signal-to-noise ratio (SNR) over existing wavelet based scheme, even it is relatively simple.