• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.38A no.1
• /
• pp.96-107
• /
• 2013

In this study, we examine the effect of spreading sequence matched filtering on the power parameters of ultrawideband (UWB) multiuser interference (MUI) under different multiple access (MA) scenarios. More specifically, we investigate the manner in which the length of the sequence MF affects the average power, peak power, and the peak-to-average ratio (PAR) of the matched filtered version of an MUI signal. The results of the analysis performed for a simplified scenario are supported by the simulation results obtained for a realistic multipath environment.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.33 no.6C
• /
• pp.444-449
• /
• 2008

Selected mapping is well-known scheme for peak to average power ratio(PAPR) reduction in orthogonal frequency multiplexing(OFDM) systems. In this paper, we proposed a new scheme for generating a set of candidate transmission sequences. In conventional SLM, candidate sequences were generated by rotating the phases of the frequency domain OFDM M-ary symbols but in proposed scheme, candidate sequences are generated by multiplying the m-sequences with data in bit format of OFDM signals. Computer simulation results show that, as compared to the conventional SLM scheme, the proposed approach has better PAPR reduction performance and especially in case of OFDM systems which has small number of subcarriers has better performance than large ones.

• Journal of Internet Computing and Services
• /
• v.13 no.2
• /
• pp.13-20
• /
• 2012

SLM (Selected Mapping) is an efficient PAPR (Peak-to-Average Power Ratio) reduction scheme without transmitted signal distortion in OFDM (Orthogonal Frequency Division Multiplexing) systems. However, enormous IFFTs (Inverse Fast Fourier Transforms) are needed to generate sufficient candidate OFDM signals, which cause the SLM to become quite complex. In this paper, we propose a new SLM scheme that replaces the IFFT operations with a conversion of the first candidate OFDM signal. The proposed scheme significantly reduces computational complexity, while it shows almost the same PAPR performance as the conventional SLM scheme.

• Korean Journal of Materials Research
• /
• v.21 no.7
• /
• pp.396-402
• /
• 2011

In this study, by using tin chloride solution as a raw material, a nano-sized tin oxide powder with an average particle size below 50 nm is generated by a spray pyrolysis process. The properties of the generated tin oxide powder depending on the inflow speed of the raw material solution are examined. When the inflow speed of the raw material solution is 2 ml/min, the majority of generated particles appear in the shape of independent polygons with average size above 80-100 nm, while droplet-shaped particles show an average size of approximately 30 nm. When the inflow speed is increased to 5 ml/min, the ratio of independent particles decreases, and the average particle size is approximately 80-100 nm. When the inflow speed is increased to 20 ml/min, the ratio of droplet-shaped particles increases, whereas the ratio of independent particles with average size of 80-100 nm decreases. When the inflow speed is increased to 100 ml/min, the average size of the generated particles is around 30-40 nm, and most of them maintain a droplet shape. With a rise of inflow speed from 2 ml/min to 5 ml/min, a slight increase of the XRD peak intensity and a minor decrease of specific surface area are observed. When the inflow speed is increased to 20 ml/min, the XRD peak intensity falls dramatically, although a significant rise of specific surface area is observed. When the inflow speed is increased to 100 ml/min, the XRD peak intensity further decreases, while the specific surface area increases.

• ETRI Journal
• /
• v.35 no.4
• /
• pp.714-717
• /
• 2013

Peak power reduction techniques in orthogonal frequency division multiplexing (OFDM) has been an important subject for many researchers for over 20 years. In this letter, we propose a side-information-free technique that is based on the concept of random variable (RV) transformation. The suggested method transforms RVs into other RVs, aiming to reshape the constellation that will consequently produce OFDM symbols with a reduced peak-to-average power ratio. The proposed method has no limitation on the mapping type or the mapping order and has no significant effect on the bit error rate performance compared to other methods presented in the literature. Additionally, the computational complexity does not increase.

• Journal of Korean Society of Water and Wastewater
• /
• v.19 no.5
• /
• pp.619-624
• /
• 2005

This work is for examining a simplified equation based on the rational formula, which can easily decide storm-water detention volume in small urban catchments. The storm-water detention volume is determined by the inflow hydrograph flowing to detention basin and the outflow hydrograph discharged from the detention basin. The ratio of average outflow over the period of rainfall duration against allowable discharge was 0.5 in former simplified equation. But this research has found that the average outflow ratio depends on the storage methodology. In the case of the on-line storage method, the average outflow ratio is a function of the time of concentration of the catchments and rainfall duration, which ranged from 0.5~1.0. In the case of the off-line storage method, the average ratio is a function of peak discharge and allowable discharge except above time of concentration and rainfall duration, where its function value ranged from 1.0~2.0. When applying this equation to small catchment in Mokpo city, South Korea, we could easily calculate the relation curve between the storm-water detention volume and allowable discharge.

• The Transactions of the Korean Institute of Electrical Engineers C
• /
• v.50 no.7
• /
• pp.329-333
• /
• 2001

The pulsed poser system has been widely used to many applications, such as E/P(Electrostatic Precipitator), DeNox/DeSOx power system, ozon generator, etc. A pulse energy efficiency for load depends on the rising time, peak value, pulse duration and impedance matching, etc. The pulse generator generally required for short pusle duration and high peak value was forced to consider its volume and economy. In this study, developing a compact pulse generator that applied for cascading method to be made of two pulse transformers, we compared cascading voltage with non cascading one by applying the pulse energy to load. Adopting cascading technique to pulse transformer, we found that average cascading voltage was about 60[%] of theoretical value. Maximum cascading ratio was calculated at 60 times compared with non cascading voltage.

• Journal of Korean Society of Water and Wastewater
• /
• v.18 no.1
• /
• pp.49-58
• /
• 2004

This study is to analyze the affecting factors to the peak factor in the drinking water supply Facilities. The peak factor is a very important element to determine the capacity of the water supply facllities. Several factors such as Population served, average day water demand, ratio of domestic water use, ratio of affairs & business water use and water use per capital per day were selected as the affecting factors in this study. In this study, peak factor characteristics for Korean facilities were compared with those for Japanese ones. As a result, non-exceedance probability was suggested as the designing method for the peak factor. Also, the 50% non-exceedance probability values and the 90% values based on the 1998-1999 data were suggested in this study.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.9 no.12
• /
• pp.4872-4891
• /
• 2015

Orthogonal frequency division multiplexing (OFDM) signals suffer from the problem of high peak-to-average power ratio (PAPR), which complicates the design of analog front-end of the system. Companding is a well-known PAPR reduction technique that involves transforming signal amplitudes using a deterministic function. OFDM signal amplitude, on average, is Rayleigh distributed but the distribution can vary significantly from symbol to symbol, especially when constellation size increases. In this paper, a new adaptive companding scheme is proposed along with its design methodology aiming at optimizing the compander performance by accommodating this variation in its design. This is achieved by designing compander parameters separately for statistically dissimilar symbols in OFDM waveform and making the compander select from these parameters, during run-time, according to the features of input symbols.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.27 no.1
• /
• pp.131-134
• /
• 2023

The age of information (AoI) was proposed to quantify the freshness of information about the status of a remote source system, which is defined as the amount of time that has elapsed since a packet was created at its source. This paper analyzes the age of information of a discrete time Geo/D/1/1 status update system. For this purpose, the system is modeled as a discrete-time two-state Markov chain. The stationary probability distributions for peak AoI and AoI are obtained. The average peak AoI, the average AoI, and the freshness ratio of information are also derived. Some numerical results of the analysis are presented.