• Journal of Korean Institute of Industrial Engineers
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• v.25 no.4
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• pp.500-509
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• 1999

In this paper, we consider an optimal routing problem when point-to-point and point-to-multipoint connection traffics are offered in an ATM network. We propose a mathematical model for cost-minimizing configuration of a logical network for a given ATM-based BISDN. Our model is essentially identical to the previous one proposed by Kim(Kim, 1996) which finds a virtual-path configuration where the relevant gains obtainable from the ATM technology such as the statistical multiplexing gain and the switching/control cost-saving gain are optimally traded-off. Unlike the Kim's model, however, ours explicitly considers the VP's QoS(Quality of Service) for more efficient utilization of bandwidth. The problem is a large-scale, nonlinear, and mixed-integer problem. The proposed algorithm is based on the local linearization of equivalent-capacity functions and the relaxation of link capacity constraints. As a result, the problem can be decomposed into moderate-sized shortest path problems, Steiner arborescence problems, and LPs. This fact renders our algorithm a lot faster than the previous nonlinear programming algorithm while the solution quality is maintained, hence application to large-scale network problems.

• IE interfaces
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• v.20 no.2
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• pp.216-226
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• 2007

In code-division multiple-access (CDMA) systems with soft handoff, mobile station (MS) within soft handoff region can use multiple radio channels and receive their signals from multiple base stations (BSs) simultaneously. In this paper, the effects of soft handoff region ratio (SHRR) on reverse link of a CDMA cellular system are analytically investigated. In order to analyze the network performance and quality of service (QoS) perceived by users more realistically, both the soft capacity increasing factor and the traffic load variation affected by SHRR are jointly considered and a two-dimensional continuous time Markov chain (CTMC) model is built. In the numerical example, it is observed that the optimal guard channel exists according the variations of the traffic load and propagation conditions when the proper value of SHRR is determined.

• Phonetics and Speech Sciences
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• v.13 no.3
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• pp.21-29
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• 2021

The present study investigated how one's cognitive resources are related to speech perception by examining Korean speakers' executive function (EF) capacity and its association with voice onset time (VOT) and f0 sensitivity in identifying Korean stop laryngeal categories (/t'/ vs. /t/ vs. /t^h/). Previously, Kong et al. (under revision) reported that Korean listeners (N = 154) in Seoul and Changwon (Gyeongsang) showed differential group patterns in dialect-specific cue weightings across educational institutions (college, high school, and elementary school). We follow up this study by further relating their EF control (working memory, mental flexibility, and inhibition) to their speech perception patterns to examine whether better cognitive ability would control attention to multiple acoustic dimensions. Partial correlation analyses revealed that better EFs in Korean listeners were associated with greater sensitivity to available acoustic details and with greater suppression of irrelevant acoustic information across subgroups, although only a small set of EF components turned out to be relevant. Unlike Seoul participants, Gyeongsang listeners' f0 use was not correlated with any EF task scores, reflecting dialect-specific cue primacy using f0 as a secondary cue. The findings confirm the link between speech perception and general cognitive ability, providing experimental evidence from Korean listeners.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.13 no.6
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• pp.2949-2963
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• 2019

A novel distributed compress-and-forward (CF) system based on multi-relay network is presented. In this system, as the direct link between the source and destination is invalid due to some reasons, such as the limited power, special working environment, or even economic factors, relays are employed to receive analog signals and carry on distributed compressed encoding. Subsequently, the digital signals are transmitted to the destination via wireless channel. Moreover, a theoretical analysis for the system is provided by utilizing the Chief Executive Officer (CEO) theory and Shannon channel capacity theory, and the rate-distortion function as well as the connection between the transmission rate and the channel capacity are constructed. In addition, an optimal signal-to-noise ratio (SNR) -based power allocation method is proposed to maximize the quantization SNR under the limited total power. Simulation result shows that the proposed CF system outperforms the amplify-and-forward (AF) system versus the SNR performance.

• Electronics and Telecommunications Trends
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• v.39 no.1
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• pp.62-73
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• 2024

Artificial intelligence relies on data-driven analysis, and the data processing performance strongly depends on factors such as memory capacity, bandwidth, and latency. Fast and large-capacity memory can be achieved by composing numerous high-performance memory units connected via high-performance interconnects, such as Compute Express Link (CXL). CXL is designed to enable efficient communication between central processing units, memory, accelerators, storage, and other computing resources. By adopting CXL, a composable computing architecture can be implemented, enabling flexible server resource configuration using a pool of computing resources. Thus, manufacturers are actively developing hardware and software solutions to support CXL. We present a survey of the latest software for CXL memory utilization and the most recent CXL memory emulation software. The former supports efficient use of CXL memory, and the latter offers a development environment that allows developers to optimize their software for the hardware architecture before commercial release of CXL memory devices. Furthermore, we review key technologies for improving the performance of both the CXL memory pool and CXL-based composable computing architecture along with various use cases.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.6A
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• pp.555-567
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• 2010

Unlike single-hop systems, multi-hop systems that use relay nodes assign a part of the overall resources to relay communications. If efficient resource allocation schemes are not adopted, this leads to a loss of resources. Moreover, because we may not be able to guarantee high-link performance due to the adjacent-cell interference in relay-based cellular systems, resource efficiency can be severely decreased. In this paper, we propose efficient resource allocation schemes for downlink relay-based networks in 3GPP (3rd Generation Partnership Project) LTE (Long Term Evolution)-Advanced systems. Unlike conventional schemes that have static resource regions for each data link, the proposed schemes dynamically allocate the resources of each link to resource blocks, by considering the channel state and the capacity of each link. We also propose resource overlapping schemes in which two different links overlap at the same resource region, so as to improve cell or user throughput performance. The proposed resource overlapping schemes do not require additional processes such as interference cancellation in users, thank to considering additional interference from resource overlapping in advance.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.37 no.6
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• pp.1025-1032
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• 2017

In this paper, the level of service (LOS) is defined for high-speed railway links and rolling stocks. Based on this LOS, how to manage high-speed railway facility is also suggested. The LOS is divided into 6 levels from A to F. The measurement of effectiveness (MOE) for railway links is derived from the relationship between a total delay time and a railway link utilization ratio. Another MOE, volume over capacity (V/C), is also proposed. On the other hand, the LOS for high-speed railway rolling stocks is based on the density of people in a rolling stock. Above all, LOS D is defined to the total number of seats. Then, LOS A is 50% of the LOS D, LOS B is 70% of the LOS D, LOS C is 90% of the LOS D and LOS D~F is defined as the maximum seats and standing people at the level of each. Finally, a method to manage high-speed railway links and rolling stocks is proposed in order to keep the level of service at the target by the government.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.22 no.10
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• pp.2171-2180
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• 1997

In this paper, we proposed a MAC protocol called P/S-DCA that using dynamci channel allocation scheme for supports the multimedia traffic in wireless ATM, and analysis theoretically the throughput and delay of up/down link according to varying the down traffic load. To evaluate and the dynamic channel allocation scheme, simulations are executed with varying down traffic load. The results are proved that system capacity is improved better than PRMA and C-PRAM. The system capacity, denoting by $M_{0.01}$, is defined as the maximum number of conversations which can be supported under constraint of packet dropping probability no more than 1%. It is shown that the values of $M_{0.01}$ for ${\lambda}_{d}=0.5,\;{\lambda}_{d}=0.2\;{\lambda}_{d}=0.1\;{\lambda}_{d}=0.001$ are about 43, 69, 77 and 83, respectively. This indicates that P/S-DCA protocol achieves a significant improvement in system capacity relative to PRMA and C-PRMA protocol.

• Journal of Communications and Networks
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• v.14 no.4
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• pp.434-442
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• 2012

Several gateway selection schemes have been proposed that select gateway nodes based on a single Quality of Service (QoS) path parameter, for instance path availability period, link capacity or end-to-end delay, etc. or on multiple non-QoS parameters, for instance the combination of gateway node speed, residual energy, and number of hops, for Mobile Ad hoc NETworks (MANETs). Each scheme just focuses on the ment of improve only a single network performance, i.e., network throughput, packet delivery ratio, end-to-end delay, or packet drop ratio. However, none of these schemes improves the overall network performance because they focus on a single QoS path parameter or on set of non-QoS parameters. To improve the overall network performance, it is necessary to select a gateway with stable path, a path with themaximum residual load capacity and the minimum latency. In this paper, we propose a gateway selection scheme that considers multiple QoS path parameters such as path availability period, available capacity and latency, to select a potential gateway node. We improve the path availability computation accuracy, we introduce a feedback system to updated path dynamics to the traffic source node and we propose an efficient method to propagate QoS parameters in our scheme. Computer simulations show that our gateway selection scheme improves throughput and packet delivery ratio with less per node energy consumption. It also improves the end-to-end delay compared to single QoS path parameter gateway selection schemes. In addition, we simulate the proposed scheme by considering weighting factors to gateway selection parameters and results show that the weighting factors improve the throughput and end-to-end delay compared to the conventional schemes.

• Journal of the Earthquake Engineering Society of Korea
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• v.11 no.2 s.54
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• pp.11-17
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• 2007

In current seismic design practice, the response modification factor (R-factor) is used as a factor to reduce the elastic base shear demand to the design force level. As is well-known, the R-factor is a committee-consensus factor and, as such, highly qualitative and empirical. The relationship between the R-factor and the connection rotation capacity available in a particular structural system has remained a missing link. In this paper, a rational procedure to evaluate the R-factor is proposed. To this end, the relationship between the available connection rotation capacity and the R-factor is defined and quantified using nonlinear pushover analysis. An RRS steel frame designed according to IBC 2000 was used to illustrate and verify the proposed procedure. Nonlinear time history analysis results indicated that the R-factor definition proposed in this study is generally conservative from design perspective.