• Journal of Internet Computing and Services
• /
• v.17 no.6
• /
• pp.9-15
• /
• 2016

In this paper, we propose a smart HLS(HTTP Live Stream) platform with dynamic single buffering for the best transmission of adaptive video bit-rates. This smart HLS can optimizes the channel transition zapping-time with the monitoring of bandwidth between HLS server and OTT(Over The Top) client. This platform is designed through the control of video stream due to proper multi-bitrates and bandwidths. This proposed OTT can decode the live and VOD(Video On Demand) videos with the buffering of optimumal bitrate. And, the HLS can be cooperated with a smart OTT, and segmented for the m3u8 files of H.265 MPEG-2 TS(Transport Stream) videos. As a resullt, this single buffer based smart OTT can transmit optimal videos with the maximum data buffering according to the adaptive bit-rate depending on the network bandwidth efficiency and the decoded VOD video, too.

• Journal of Ocean Engineering and Technology
• /
• v.22 no.2
• /
• pp.65-71
• /
• 2008

Recently, many researches in relation to data transmission with faster speed and greater volume, many researches have been carried out on sonar systems for underwater communication. According to these researches, an acoustic transducer for underwater communication requires wide bandwidth properties. In domestic researches for underwater communication sonar, an operating frequency in the range of $20{\sim}40\;kHz$ is used. In this paper, we propose anon-resonance type acoustic transducer for underwater communication. The TVR (transmitting voltage response) characteristics increased linearly as the frequency increased, and the RVS (receiving voltage sensitivity) characteristics were constant as the frequency increased. Traditional techniques for wide bandwidth transducershave a limit and a transmission loss difference at lower and higher frequency operating ranges. In this paper, the new transducer proposed decreased the transmission loss under some conditions. It was optimized with the FE analysis tool (ATILA) and evaluated using the TVR and the RVS characteristics in the range of $10{\sim}90\;kHz$. The value of TVR was 138 dB at 20 kHz and 148 dB at 40 kHz, and the differences was 12 dB. The value of RVS was $195{\pm}2\;dB$ and nearly constant. From theseresults, it is certain that the developed transducers can be used for an underwater communication network in the 1.3 km range with both a 20 kHz bandwidth and 30 kHz center frequency.

• Korean Journal of Agricultural and Forest Meteorology
• /
• v.23 no.4
• /
• pp.366-373
• /
• 2021

This study attempted to establish a field data-based write analysis standard by analyzing field observation data, which is non-linear data of southern garlic. Five regions, including Goheung, Namhae, Sinan, Changnyeong, and Haenam, were selected for analysis. Observation values for each observation station were extracted from the temperature data of farmland in the region through inverse distance weighted. Southern-type garlic production and temperature data were collected for 10 years, from 2010 to 2019. Local regression analysis (Kernel) of the obtained data was performed, and growth temperatures were analyzed, such as 0.8 (18.781℃), 0.9 (18.930℃), 1.0 (19.542℃), 1.1 (20.165℃), and 1.2 (21.042℃) depending on the bandwidth. The analyzed optimum temperature and the grown temperature (4℃/25℃) were applied to extract the growth temperature for each temperature by using the temperature response model analysis. Regression analysis and correlation analysis were performed between the analyzed growth temperature and production data. The coefficient of determination(R²) was analyzed as 0.325 to 0.438, and in the correlation analysis, the correlation coefficient of 0.57 to 0.66 was analyzed at the significance probability 0.001 level. Overall, as the bandwidth increased, the coefficient of determination was higher. However, in all analyses except bandwidth 1.0, it was analyzed that all variables were not used due to bias. The purpose of this study is to accommodate all data through non-linear data. It was analyzed that bandwidth 1.0 with a high coefficient of determination while accepting modeling as a whole is the most suitable.

• Journal of Positioning, Navigation, and Timing
• /
• v.11 no.4
• /
• pp.341-349
• /
• 2022

When designing a new RNSS signal, the performance analysis for the legacy signal providing the same service, is required to determine the performance requirements. However, there are few studies on the secured service (SS) signal performance analysis, and the waveform is the only published information on the signal design component of the SS signal. Therefore, in this paper, we introduce several figures-of-merit (FoMs) that can be used for performance analysis in terms of the waveform. And then, we calculate the FoMs, such as autocorrelation main peak to secondary peak ratio (AMSR), spectral efficiency, Gabor bandwidth, multipath error, and jamming resistance quality factor, for the existing SS signals and discuss the analysis results. Finally, we conclude that the superior waveform for each FoM is different, and that the consideration of the trade-off relationship between the FoMs is required for waveform design.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.13 no.5
• /
• pp.23-29
• /
• 2009

On December 13, 1996, an earthquake with local magnitude (M$_L$) 4.5 occurred in the Yeongwol area of South Korea. The epicenter was 37.2545$^{\circ}$N and 128.7277$^{\circ}$E, which is located inside the Okcheon Fold Belt. The waveform inversion analysis was carried out to estimate source parameters of the event according to the filtering bandwidth of seismic data. Using 0.02$\sim$0.2 Hz filtering bandwidth, focal depth and seismic moment were estimated to be 6 km and 1.3$\times$10$^{16}$ N$\cdot$m, respectively. This seismic moment corresponds to the moment magnitude (M$_W$) 4.7. The focal mechanism by the waveform inversion and P wave first motion polarity analysis is a strike slip faulting including a small thrust component, and the direction of P-axis is ENE-WSW. The moment magnitude estimated by spectral analysis was 4.8, which is similar to that estimated by waveform inversion. Average stress drop was estimated to be 14.3 MPa.

• Journal of KIISE:Information Networking
• /
• v.31 no.2
• /
• pp.188-195
• /
• 2004

We have analyzed the performance of TCP in the CDMA mobile communications systems with the adaptive modulation and coding(AMC). The wireless channel using AMC is characterized with not high error rate but highly varying bandwidth. Due to time-varying bandwidth, timeout events of TCP occurs more frequently, which leads to the throughput degradation. The analysis model is composed of the two parts. In the first part, we divide TCP packet stream into ‘packet groups’and derive the probability distribution of the wireless transmission time of each Packet group that reflects the time varying characteristics of AMC. In the second part, we formulate embedded Markov chain by making use of the results of the first part to model TCP timer mechanism and wireless transmission. Since our system model is characterized by the forward link high speed data transmission using AMC, the results reported in this paper can be used as a guideline for the design and operation of HSDPA, 1xEV-DO, and 1xEV-DV.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.17 no.3 s.106
• /
• pp.287-294
• /
• 2006

In the paper, characterization and analysis of UWB(Ultra Wide Band) antennas in time domain are described. The impulse propagation channel including UWB antennas is proposed for the analysis in time domain. Using the proposed propagation channel, the technique of obtaining impulse response of UWB antenna is proposed. Also, ringing, peak value of the impulse response, and the width of the impulse response are introduced as parameters for characterizing a UWB antenna in time domain. A modified UWB conical monopole antenna, a UWB TEM horn antenna, and a UWB stepped fat monopole antenna were fabricated. From the measurement of reflection coefficients, three antennas had bandwidth more than 3 GHz. The impulse responses of the antennas were measured in an anechoic chamber. The results showed that the TEM horn with highest gain has the highest peak amplitude and the stepped fat monopole antenna with narrowest bandwidth for reflection coeffcient had the widest width of the impulse response. Also, ringing in the stepped fat monopole antennas and the UWB conical monopole antenna were observed.

• The Journal of the Acoustical Society of Korea
• /
• v.38 no.5
• /
• pp.494-510
• /
• 2019

Underwater acoustic communication channel parameters consist of impulse response, delay spreading, scattering function, coherence bandwidth, frequency selective fading, coherence time and time variant magnitude fading statistics on which communication system modem and channel coding are designed. These parameters are influenced by sound velocity profile, platform motion and sea surface roughness in given acoustical oceanography condition. In this paper, channel model based on phasor, channel simulator, measurement and analysis method of channel parameters are given in a fixed source-to-receiver system and the parameters are analyzed using shallow water experimental data. For two different source-to-receiver ranges of 300 m and 600 m, the parameters are characterized by three multipaths such as a direct, a surface reflection path with time variant scattering and a bottom reflection path. The results present a channel modelling method of a fixed source source-to-receiver system, channel parameters measurement and analysis methods and a system design and performance assessment method in shallow water.

• Journal of Digital Convergence
• /
• v.20 no.4
• /
• pp.459-468
• /
• 2022

In medical area, very high resolution images, which is loss sensitive data, are used. Therefore, the use of optical internet with high bandwidth and the transmission of high realiability is required. However, according to the nature of the Internet, various data use the same bandwidth and a new scheme is needed to differentiate effectively these data. In order to achieve the differentiation, optical delay line buffers are used. However, these buffers is constructed based on some optimal values such as the average offered load, measured data burst length, and basic delay unit. Once the buffers are installed, they are impossible to reinstall new buffers. So, the scheme changing burst length dynamically was considered. However, this method is highly unstable. Therefore, in this article, in order to guarantee the stable operation of the scheme, the analysis of operation conditions is performed. With the analysis together with the scheme, high resolution medical data with the higher class can transmit stably without loss.

• Journal of electromagnetic engineering and science
• /
• v.11 no.2
• /
• pp.122-127
• /
• 2011

A general analysis of an aperture-coupled vertically mounted strip antenna is presented to examine its circuit characteristics. Based on the present analysis, an equivalent circuit model is developed, and an analytic or semi-analytic evaluation of the related circuit element values is described. The effects of structure parameters on the antenna characteristics were studied with the developed equivalent circuit, and the design curves were obtained. To check the validity of the proposed analysis and design theory, two C-band antennas (5.0 GHz and 4.5 GHz) were designed and fabricated. Their computed characteristics, derived from the proposed network analysis, were compared with the measurement and simulation results. The error of the current model in predicting the operating center frequency was less than 0.50 %. In addition, the observed bandwidth was found to be comparable to the conventional microstrip antennas. All the results fully validated the efficiency and accuracy of the proposed analysis and network model.