• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.12C
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• pp.1208-1215
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• 2009

In OFDM systems, mobile channel degrades the system performance seriously. Therefore, channel estimation technique is required to compensate for the degradation from the channel effects. However, conventional channel estimations in frequency domain induce ICI which is induced from Doppler frequency. In addition, a linear interpolation method causes inaccurate channel estimation. In order to minimize the effect of the interference and interpolation error, the proposed method combines LS method and Kalman filtering algorithm. Channel impulse response is adaptively tracked by Kalman filtering based on the information from LS estimator. Simulation results are presented to verify the performance of the proposed channel estimation over mobile channel environment. Simulation results show that the proposed method can effectively compensate for channel degradation.

• Journal of the Korea Society of Computer and Information
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• v.23 no.8
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• pp.51-57
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• 2018

In this paper, we investigate the impact of channel estimation error on the D2D power control algorithm. In the previous work, D2D power control algorithm has been proposed under the assumption that the channel between the transmitter and the corresponding receiver is perfectly estimated. In reality, the channel estimation error is more often the case. The first question is that the power control algorithm designed for perfect channel estimation is still valid under the channel estimation error environment ? The second question is, if it is not valid, what could be the possible remedy for the channel estimation error ? In this paper, to answer the first question, we investigate the impact of the channel estimation error on the power control algorithm. We first review the D2D power control algorithm designed for perfect channel estimation. Then, we model the channel estimation error. Finally, we summarize the main results observed from the analysis of the simulation.

• Journal of the Korean earth science society
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• v.27 no.7
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• pp.757-767
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• 2006

Alluvial-plain deposits in the southeastern part of the Eumsung Basin (Cretaceous) are characterized by coarse-grained channel fills encased in purple siltstone beds. It represents distinct channel geometry, infill organization, and variations in facies distribution. The directions of paleocurrent, sedimentary facies changes, and channel-fill geometry can be used to reconstruct a channel network in the alluvial system developed along the southeastern margin of the basin. The channel-fill facies represent downstream changes: 1) down-sizing and well-sorting in clast and martix of channel fills and 2) internal organization of scour fill or gravel lag and overlying cross-stratified, planar-stratified beds. These findings suggest multiple stages of channel-filling processes according to flooding and subsequent stream flows. In the small-scale pull-apart Eumsung Basin (${\sim}7{\times}33km^2$ in area), vertical-stacked alluvial architecture of the coarse-grained channel fills encased in purple siltstone is expected to result from episodic channel shifting under a rapidly subsiding setting.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.6
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• pp.1080-1082
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• 2016

In a multi-hop CR (Cognitive Radio) network, each node find a path to destination node through several links. If links have the same frequency channel, there can be a serious interference among the links and it can reduce the network capacity. In multi-channel CR networks, each channel has different capacity according to the inter-link interference, and each channel has different traffic properties of primary users. In this paper, we propose channel scheduling scheme to minimize channel interferences and collision with primary users. Simulation results show the improvement of channel capacity and collision rate with primary users.

• Journal of IKEEE
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• v.23 no.1
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• pp.302-305
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• 2019

Non-orthogonal multiple access (NOMA) has been considered for the fifth generation (5G) mobile networks to provide high system capacity and low latency. We calculate the channel capacity for the weak channel user in NOMA and the channel capacity region for NOMA. In this paper, Gaussian mixture channel is compared to the additive white Gaussian noise (AWGN) channel. Gaussian mixture channel is modeled when we assume the practical signal modulation for the inter user interference, such as the binary phase shift keying (BPSK) modulation. It is shown that the channel capacity with BPSK inter user interference is better than that with Gaussian inter user interference. We also show that the channel capacity region with BPSK inter user interference is larger than that with Gaussian inter user interference. As a result, NOMA could perform better in the practical environments.

• Proceedings of the Korea Information Processing Society Conference
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• 2009.04a
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• pp.842-845
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• 2009

Wireless ad hoc networks often suffer from rapidly degrading performance with the number of user increases in the network. One of the major reasons for this rapid degradation of performance is the fact that users are sharing a single channel. Obviously, the problem of using single shared channel schemes is that the probability of collision increases with the number of nodes. Fortunately, it is possible to solve this problem with multi-channel approaches. Due to the especial properties of multiple channels, using the multiple channels is more efficient than single channel because it enhances the capacity of the channel and reduces the error rate during data transmission. Some multi-channel schemes us one dedicated channel for control packets and one separate channel for data transmissions. On the other hand, another protocols use more than two channels for data transmissions. This paper summarizes six multiple channel protocols based on these two kinds of schemes. Then we compare them and discuss the research challenge of multiple channel protocols.

• Journal of the Korean Operations Research and Management Science Society
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• v.34 no.3
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• pp.165-177
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• 2009

The purpose of this study is to investigate the impact of the Internet channel introduction on the channel composed of a monopoly manufacturer and an independent physical retailer. This study also examines what would be the best strategy for the Independent physical retailer to respond to the new internet channel entry. The game theoretic model consists of a monopolist manufacturer selling its product through a channel system including one independent physical store before the entry of an internet store. The audition of the internet store to this channel system results in a mixed channel comprised of two different types of channels. The new internet store is launched by the manufacturer. The results show that an Internet channel entry has the following impacts on the existing channel members. First, the manufacturer's internet channel introduction mitigates the double marginalization problem of the traditional channel. Second, the manufacturer could enhance Its channel power by introducing its own internet channel while it diminishes that of the incumbent independent physical retailer. Third, manufacturer's adding a new internet store leads to a higher demand. Finally, with its own internet direct channel, the manufacturer has an opportunity to practice price discrimination. The manufacture leaves only those with a strong preference for the physical store to be served by the Independent physical store. The results suggest that the independent physical store's best strategy to the entry of the manufacturer's Internet channel is to focus on the consumers who are highly loyal to the physical store while maintaining a high retail price.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.18 no.8
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• pp.1136-1145
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• 1993

The channel capacities of various lading channels are calculated and compared with that of Gaussian noise channel to find out the decrements of channel capacity according to each fading environment. As a result, it is confirmed that the channel capacities in Rician and m-distribution fading channels approach to that of Gaussian noise channel as direct-to-indirect power ratio in Rician fading channel and fading index m in m-distribution fading channel increases respectively. And the difference between two channel capacities of Gaussian noise channel and each fading channel which is dependent on carrier-to-noise power ratio (CNR) is found. Also the improvement of channel capacity of Rayleigh fading channel by introducing two-branch diversities is obtained. For diversity reception, predetection maximal-ratio and postdetection selective combining techniques are adopted. The results show that the improvement of channel capacity by predetection maximal-ratio combining diversity is superior to the postdetection selective combining diversitiy regardless of correlation coefficient between two diversity branches in Raylelgh fading channel. The best improvement is achieved when two branches are noncorrelative in both two diversify techniques and as correlation coefficient of two diversity branches is smaller, the improvement of channel capacity is greater.

• JSTS:Journal of Semiconductor Technology and Science
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• v.13 no.3
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• pp.213-223
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• 2013

A unified channel thermal noise model valid in all operation regions is presented for short channel MOS transistors. It is based on smooth interpolation between weak and strong inversion models and consistent physical model including velocity saturation, channel length modulation, and carrier heating. From testing for noise benchmark and comparing with published noise data, it is shown that the proposed noise model could be useful in simulating the MOSFET channel thermal noise in all operation regions.

• IE interfaces
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• v.16 no.3
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• pp.311-321
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• 2003

We propose the improved channel assignment and management methods for an efficient use of traffic channel resource for supporting 12.2 Kbps, 64 Kbps, and 384 Kbps traffic with the different quality of service(QoS) in the radio network controller(RNC) in asynchronous IMT-2000 system. We consider two types of traffic channel block assignments for utilizing the traffic channel efficiently; the Completely Shared(CS) channel assignment and the Partially Dedicated and Partially Shared(PDPS) channel assignment. The former is that all traffic channel blocks are completely shared with all traffic types. The latter is that some traffic channel block is independently assigned to each traffic type and the other blocks are completely shared with some traffic type. We also propose the traffic channel management method which consists of the block and task management step, for efficiently assigning, releasing, and managing the channel resource. Finally, we evaluate the performance through various numerical examples when applying our proposed channel block assignment and resource management methods.