• 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.

• ETRI Journal
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• v.35 no.5
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• pp.919-922
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• 2013

A MIMO multi-way relay channel with full data exchange in which K users exchange messages with each other via the help of a single relay is considered. For the case in which each link is quasi-static Rayleigh fading and the relay is full-duplex, the fundamental diversity-multiplexing tradeoff (DMT) is investigated, and we show that a compress-and-forward relay protocol can achieve the optimal DMT.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 1993.10a
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• pp.1053-1062
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• 1993

The effect of loading speed on soil failure was studied by using a high speed triaxial compression test. Tests were conducted at 0.35-6.2m/s loading speed to compress soil specimens of sandy loam at different moisture contents. The axial stress at fracture increased with increase in loading speed up to certain critical speeds, however they decreased as the speed up to certain critical speeds, however they decreased as the speed increased further. Experiments were also conducted in the field of sandy loam soil with the vibrating tillage tool. Tests were done at 0.33-0.85m/s tractor speed oscillating frequency 13.7hz and oscillating amplitude 59mm. The maximum oscillating velocity of tillage tool was 2.5m/s. It was observed that for the oscillating operation, initially draft slightly increased with increase in forward speed and then it decreased .For the non-oscillating operation, draft increased continuously with increase in forward speed. Approach of studying soil failure in the laboratory test can be related to the field experiments.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39A no.7
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• pp.404-412
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• 2014

Exploiting multiple antennas at mobile devices is difficult due to limited size and power. In this paper, a distributed MIMO protocol achieving the capacity of conventinal MIMO systems is proposed and analyzed. For exploiting distributed MIMO features, Quantize-Map-and-Forward (QMF) scheme shows improved performance than Amplify-and-Forward (AF) scheme. Also, the protocol based on multiple access channel (MAC) is proposed to improve the multiplexing gain. We showed that sufficient condition of the number of slave nodes to achieve the gain of a MAC based protocol. Because the base station can support multiple clusters operating in distributed MIMO, the total cellular capacity can be extremely enhanced in proportional to the number of clusters.

• Journal of Communications and Networks
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• v.11 no.5
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• pp.433-444
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• 2009

The bi-directional relay channel is the natural extension of a three-terminal relay channel where node a transmits to node b with the help of a relay r to allow for two-way communication between nodes a and b. That is, in a bi-directional relay channel, a and b wish to exchange independent messages over a shared channel with the help of a relay r. The rates at which this communication may reliably take place depend on the assumptions made on the relay processing abilities. We overview information theoretic limits of the bi-directional relay channel under a variety of conditions, before focusing on half-duplex nodes in which communication takes place in a number of temporal phases (resulting in protocols), and nodes may forward messages in four manners. The relay-forwarding considered are: Amplify and forward (AF), decode and forward (DF), compress and forward (CF), and mixed forward. The last scheme is a combination of CF in one direction and DF in the other. We derive inner and outer bounds to the capacity region of the bi-directional relay channel for three temporal protocols under these four relaying schemes. The first protocol is a two phase protocol where a and b simultaneously transmit during the first phase and the relay r alone transmits during the second. The second protocol considers sequential transmissions from a and b followed by a transmission from the relay while the third protocol is a hybrid of the first two protocols and has four phases. We provide a comprehensive treatment of protocols in Gaussian noise, obtaining their respective achievable rate regions, outer bounds, and their relative performance under different SNR and relay geometries.

• The Bulletin of The Korean Astronomical Society
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• v.46 no.2
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• pp.45.3-46
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• 2021

Supernovae classes have been defined phenomenologically, based on spectral features and time series data, since the specific details of the physics of the different explosions remain unrevealed. However, the number of these classes is increasing as objects with new features are observed, and the next generation of large-surveys will only bring more variety to our attention. We apply the machine learning technique of multi-label classification to the spectra of supernovae. By measuring the probabilities of specific features or 'tags' in the supernova spectra, we can compress the information from a specific object down to that suitable for a human or database scan, without the need to directly assign to a reductive 'class'. We use logistic regression to assign tag probabilities, and then a feed-forward neural network to filter the objects into the standard set of classes, based solely on the tag probabilities. We present STag, a software package that can compute these tag probabilities and make spectral classifications.

• Clinics in Shoulder and Elbow
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• v.2 no.2
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• pp.143-150
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• 1999

Purpose: The purpose of this study is to describe the characteristic clinical findings and treatment of suprascapular nerve entrapment by ganglion and to evaluate its results. Materials and Methods: Seven paitents with suprascapular nerve entrapment were evaluated on an average 13 months(range, six months to three years two months) after surgical excision and decompression. There were six males and one female. The mean age at operation was 31 years(range, 23 to 40 years), Suprascapular nerve entrapment were caused by compression of ganglion cyst in suprascapular notch or spinoglenoid notch in all cases. All patients complained of pain located over posterolateral area of the shoulder. Two patients had atrophy of both the supraspinatus and infraspinatus muscles, In four patients, only the infraspinatus muscle was involved. Muscle strength on both forward flexion and external rotation was decreased in two patients. In four patients, only external rotation was decreased. All patients underwent open excision of ganglion cyst and decompression. Results: The most dramatic effect of operation was prompt disappearance of pain in all patients. The average visual analog scale had improved from 7.2 to 0.6 point at the latest follow-up evaluation. An atrophy of the supraspinatus or infraspinatus muscle partially disappeared in four of six patients and muscle strength of forward flexion or abduction improved in all of six patients. The overall result was excellent for five patients and good for two. Conclusion: Surpascapular nerve entrapment by ganglionic cyst had clinically unique symptoms and signs on physical examination. Surgical excision is effective for symptomatic and functional outcomes. We believe that early intervention can be one of treatment modality before an irreversible damage occurs if the ganglion is large enough to compress suprascapular nerve, and to develop severe pain and muscular atrophy.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.13 no.8
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• pp.3821-3841
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• 2019

Cloud radio access networks (C-RANs) have been regarded in recent times as a promising concept in future 5G technologies where all DSP processors are moved into a central base band unit (BBU) pool in the cloud, and distributed remote radio heads (RRHs) compress and forward received radio signals from mobile users to the BBUs through radio links. In such dynamic environment, automatic decision-making approaches, such as artificial intelligence based deep reinforcement learning (DRL), become imperative in designing new solutions. In this paper, we propose a generic framework of autonomous cell activation and customized physical resource allocation schemes for energy consumption and QoS optimization in wireless networks. We formulate the problem as fractional power control with bandwidth adaptation and full power control and bandwidth allocation models and set up a Q-learning model to satisfy the QoS requirements of users and to achieve low energy consumption with the minimum number of active RRHs under varying traffic demand and network densities. Extensive simulations are conducted to show the effectiveness of our proposed solution compared to existing schemes.