• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.12 no.3
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• pp.378-390
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• 2001

In this paper, it is analyzed that the error performance of a Multi-Carrier DS-CDMA system in a single cell with multipath Rician fading and multiple access interference (MAI) and the error performance of the system is compared with that of a Sing1e-Carrier DS-CDMA system. Moreover, the convolutional coding techniques with code rate of 1/2, 1/3, and 1/4 are adopted in order to improve the error performance degraded by the multipath fading and MAI and performance improvement through the coding techniques is analyzed. As a result, it is shown that the number of users in each system can be determined by the number of branches of the rake receiver in a Single-Carrier DS-CDMA system and the number of carriers in a Multi-Carrier DS-CDMA system. Furthermore, the convolutional coding should be chosen with considering the trade-off between coding gain and a power limitation in a Multi-Carrier DS-CDMA system. In case of increasing the number of carriers, the processing gain is decreased but the error performance is improved through the effect of frequency diversity and the system can be possibility implemented due to the low chip rate.

• Nutrition Research and Practice
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• v.2 no.1
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• pp.35-40
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• 2008

A cross-sectional study involving 400 mothers was conducted in the Manya Krobo district of Ghana with the objective of studying household dietary practices, quality of diets and family nutritional status of rural Ghana, A combination of methods, including structured interviews using questionnaire, dietary assessments and anthropometry was used to collect data for the study. The data obtained was analyzed using Statistical Package for Social Sciences (SPSS) Version 10 in Windows. Means and standard deviations were generated for continuous variables and frequency distribution for categorical variables. Most women consumed meals three times a day but only a few (12.5%) cooked all three meals at home. Breakfast and lunch were the two main meals purchased from food vendors. The most frequently consumed food items on daily basis were the starchy staples, maize, fish, pepper, onion, tomato and palm fruits. The nutritional qualities of diets were poor in terms of calcium and the B-vitamins. A significant proportion of the women were nutritionally at risk of being either underweight (12%), overweight (17%) or obese (5%). For adequate nutrition in this population, nutrition education intervention programs aimed at improving nutrient intake through improved diet diversity and increased use of local foods rich in calcium and the B-vitamins needs to be undertaken. There is also the need to intensify education on excessive weight gain and its attendant health problems in the area.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.10
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• pp.4738-4758
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• 2017

Resource allocation plays a crucial role in multiuser multiple input multiple output orthogonal frequency division multiplexing (MIMO-OFDM) systems to improve overall system performance. While previously proposed resource allocation algorithms are mainly designed from the point of view of the information-theoretic, we formulate the resource allocation problem as an average bit error rate (BER) minimization problem subject to a total power constraint when considering employing realistic MIMO detection techniques. Subsequently, we derive the optimal subcarrier and power allocation algorithms for three types of well-known MIMO detectors, including the maximum likelihood (ML) detector, linear detectors, and successive interference cancellation (SIC) detectors. To reduce the complexity, we also propose a two-step suboptimal algorithm that separates subcarrier and power allocation for each detector. We also analyze the diversity gain of the proposed suboptimal algorithms for various MIMO detectors. Simulation results confirm that the proposed suboptimal algorithm for each detector can achieve a comparable performance with the optimal allocation with a much lower complexity. Moreover, it is shown that the suboptimal algorithms perform better than the conventional algorithms that are known in the literature.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.15 no.7
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• pp.635-643
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• 2004

In this paper, dual-polarized 2${\times}$2 array antenna is designed and fabricated for the polarization diversity applications in wireless LAN system. For the improved bandwidth and isolation characteristics, the aperture coupled feeding and the L-shaped probe feeding are employed for each polarization. The measured bandwidths of the fabricated antenna are 210MHz for aperture coupled feeding and 280MHz for L-shaped probe feeding. The isolation for two ports is -40dB and the antenna gain is measured as 14.3${\pm}$0.2dBi in the operating frequency band of wireless LAN.

• Journal of Korea Multimedia Society
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• v.10 no.12
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• pp.1632-1644
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• 2007

Wireless Mesh Networks aim to attain large connectivity with minimum performance degradation, as network size is increase. As such, scalability is one of the main characteristics of Wireless Mesh Networks that differentiates it from other wireless networks. This characteristic creates the need for bandwidth efficiency strategies to ensure that network performance does not degrade as the size of the network increase. Several researches have been done to realize mesh networks. However, the researches conducted were mostly focused on a per TCP/IP layer basis. Also, the studies on bandwidth efficiency and bandwidth improvement are usually dealt with as separate issues. This paper aims to simultaneously study bandwidth efficiency and improvement. Aside from optimizing the bandwidth given a fixed capacity, the capacity is also increased using results of physical layer studies. In this paper, the capacity is improved by using the concept of non-overlapping channels for wireless communication. A channel allocation scheme is conceptualized to choose the transmission channel that would optimize the network performance parameters with consideration of chosen Quality of Service (QoS) parameters. Network utility maximization is used to optimize the bandwidth after channel selection. Furthermore, a routing scheme is proposed using the results of the network utilization method and the channel allocation scheme to find the optimal path that would maximize the network gain.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.48 no.4
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• pp.77-83
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• 2011

In this paper, we study the throughput-delay tradeoff of OFDMA systems in context of 2-dimensional resource allocation, and analyze the effect of frequency diversity and user-multiplexing in time domain that has on delay QoS performance. Based on the analysis results, we investigate the impacts of delay QoS on spectral efficiency. In high SNR regime, the optimal DoM (degree of multiplexing) maximizing the spectral efficiency is identified. The results of the high SNR analysis can give us an intuition on an efficient resource allocation policy. Finally, through the simulation results, we verify that our approach with its optimal DoM yields substantial capacity gain.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.5C
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• pp.338-343
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• 2005

MIMO(Multiple Input Multiple Output) systems are considered as one of the most promising systems for next generation mobile communication systems which require efficient frequency resource utilization as well as high data rate transmissions. BLAST-STTC is the MIMO system which transmits information from many of STTC encoder groups with two transmit antennas and cancels the interference from other groups in receiver. In this paper we propose a reverse-ordered iterative decoding scheme for BLAST-STTC systems which achieve full diversity gain for all groups and improve the performance of interference cancellation, and compare the error performance of the proposed scheme with general schemes.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.42 no.8 s.338
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• pp.33-40
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• 2005

This paper presents a structure of the searcher using a diversity in array antenna systems operating in the cdma2000 1x signal environments. The new technique exploits the fact that the In-phase and quadrature components of interferers can respectively be viewed as an independent gaussian noise at each antnna element in most practical cdma signal environments. The proposed PN acquisition scheme is a singles-dwell PN acquisition system consisting of two stages, that is, the searching stage and the verification stage. The searching stage independently correlates the receiver multiple signals with PN generator of each antenna element for obtaining the synchronous energy at the entire region. Then, the searching results of each antenna element are non-coherently combinind. The verification stage compares the searching energy with the optimal threshold, which is predesigned in the lock detector, and decides whether the acquisition is successful or fail. In this paper, we analyzed the effect of tile diversity order to determine the mean acquisition time. In general, it is known that the mean acquisition time significantly decrease as the number of antenna elements increases. But, as the diversity order goes up, the enhancement of the performance is saturated. Therefore, to decrease the mean acquisition time of the searcher, we must design the optimal array antenna systems by considering the operating SNR range of the receiver, the probability of detection $P_D$ and that of false alarm $P_{FA}$ . The Performance of the proposed PN acquisition scheme is analyzed in frequency selective Rayleigh fading channels. In this paper, the effect of the number of antenna elements on PN acquisition scheme is shown according to the probability of detection $P_D$ and that of false alarm $P_{FA}$.

• The Journal of Industrial Distribution & Business
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• v.10 no.3
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• pp.35-44
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• 2019

Purpose - The purpose of this study is to empirically investigate the effect of choice of cause on the purchase intention by dividing it into the situation selected by the consumer and the company. This study also examines the moderating effect of cause options diversity and company-cause fit on the relationship between choice of cause and purchase intention. This will provide the theoretical information necessary to gain an in-depth understanding of the consumer's intention to purchase the cause-related marketing campaign, and in practice, it is expected that companies will be able to obtain useful information for effective planning and execution of the cause-related marketing campaign. Research design, date, and methodology - This study's survey was carried out on the college students of university located in Shandong, China. It was from November 4-11, 2018, and a total of 440 questionnaires were distributed, with 424 collected. Of them, effective questionnaires used in the final study were a total of 400 except 24 that couldn't be used. In this study, empirical analysis was done with frequency analysis, reliability analysis, analysis of variance and simple effect analysis by using Statistics Package SPSS 20.0. Results - The results are reported below: first of all, in the cause-related campaign consumers are more willing to buy the products when they are allowed to choice the focal cause of charity than when the company selects the cause of charity. Furthermore, the positive effect of allowing consumers to choice the cause of charity (vs. company choice) on purchase intentions is greater for high cause diversity to select. Finally, the positive effect of allowing consumers to choice the cause of charity (vs. company choice) on purchase intentions is greater when perceived fit between the company and the cause charity is low. Conclusions - This study extends the scope of the consumer perspective from consumer purchase intention research to the choice of cause in the cause-related marketing. When consumers select the cause, it would be better to provide the cause charity in diversifying selection and provide options for low fit between company and cause charity.

• Journal of Advanced Navigation Technology
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• v.14 no.1
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• pp.33-40
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• 2010

In this paper, the bit-error-ratio (BER) performances of Digital Radio Mondiale Plus (DRM+) system which stand for the European standard to bring analogue FM radio to digital radio in Band-II(30-170 MHz) are evaluated under multipath fading channel models used in Band-II and the adjacent channel interference (ACI) caused by FM signal. From the simulation results, the DRM+ system shows robust performances under time-varying channel environments even though the speed of a vehicle is equal to 300km/h. And it is shown that the frequency diversity, determined by delay spread of multipath fading channel, increases the coding gain of the DRM+ system with an increase of delay spread. In addition, to guarantee the BER performance of 10-4 for DRM+ system with ACI due to FM signal, the simulation results show that the desired signal-to-ACI power ratio must be more than -30 dB when the carrier frequency distance is 150 kHz.