• Journal of KIISE:Information Networking
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• v.37 no.3
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• pp.249-253
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• 2010

Resource of wireless frequency bandwidth is gradually going to be deficient due to explosive increase of traffic and saturated non-licensed frequency band such as ISM. In the contrary, many licensed frequency bands are revealed to be low in utilization by several measurement based researches. To alleviate this inefficiency, a concept of cognitive radio is suggested. Cognitive radio lets non-licensed user exploit the licensed frequency band as long as non-licensed user does not interfere licensed user and as a result, it is possible to harness wireless frequency more efficiently. IEEE 802.22 is the first standard network with cognitive radio technology and it employs Two-Stage channel sensing mechanism to accomplish both enough licensed user protection and efficient channel utilization. In this paper, we analyze the overhead of Two-Stage channel sensing mechanism and identify the influence of channel sensing time to the overhead.

• Journal of the Korea Society of Computer and Information
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• v.13 no.4
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• pp.11-18
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• 2008

Document clustering is an important method for document analysis and is used in many different information retrieval applications. This paper proposes a new document clustering model using the re-weighted term based NMF(non-negative matrix factorization) to cluster documents relevant to a user's requirement. The proposed model uses the re-weighted term by using user feedback to reduce the gap between the user's requirement for document classification and the document clusters by means of machine. The Proposed method can improve the quality of document clustering because the re-weighted terms. the semantic feature matrix and the semantic variable matrix, which is used in document clustering, can represent an inherent structure of document set more well. The experimental results demonstrate appling the proposed method to document clustering methods achieves better performance than documents clustering methods.

• Journal of the Ergonomics Society of Korea
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• v.18 no.3
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• pp.73-86
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• 1999

Nowadays, VCR(Video Cassette Recorder) has various functions, but users use to fail operating these function because of the complexity of operation. The process of operating VCR contains user's cognitive characteristics. It is necessary for designing it that we must identify a user's mental process in the behind of operational behaviors. This effort, as well as considering physical dimensions and layout, can make VCR easy to use. In this research, VCR remote controller are analyzed by the cognitive method and experiments. Three types of VCR remote controllers, cognitive VCR models and two non-cognitive(typical) VCR models, are adopted as experimental objects to test the validation of the suggested user's cognitive mode of VCR. As results, when VCR was operated by the cognitive prototype of remote controller, task completion time was reduced to 80.5%, and the number of errors was reduced to 96.8%.

• Journal of the Ergonomics Society of Korea
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• v.19 no.3
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• pp.51-60
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• 2000

Non-verbal sound feedback, called earcon, has been used for portable digital electronic products to give appropriate information for the selected function. This study evaluated usability based on user cognition time, error rate, and subjective satisfaction using 20 male and female subjects. The study compared five major user functions from a portable digital electronic product with currently available earcons and the same functions from the product with the new earcons (suggested by this study) which considered user cognitive characteristics, such as loudness, pitch, melody, and length. For subjective evaluation, the study assessed various earcons by subjective impression of sounds using the seven-point rating scales. Major statistical results indicated that the new earcons significantly reduced user error rates and generally improved user performance functions, such as 'play, off, stop, fast forward, and rewind.'

• Electronics and Telecommunications Trends
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• v.36 no.4
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• pp.135-144
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• 2021

The field of user authentication in Korea has experienced new dimensions since December 2020. Accredited certificate, which had been in use for 21 years since 1999, has been abolished. Accredited certificates have provided a trust foundation for various ICT-based industrial developments; however, new changes in the authentication sector are also required due to changes in the service and policy environment. Changes in the service environment occur rapidly because of the emergence of new technologies such as AI, IoT, Bio, Blockchain, and the daily use of non-face-to-face environments caused by COVID-19. Even with changes in the service environment, user authentication remains an essential foundation for providing services. This paper summarizes the current status of user authentication techniques, analyzes major changes in the service environment (such as Metaverse) associated with user authentication, and presents the direction of authentication techniques (Decentralized, Invisible, Privacy-preserving) through the derived implications.

• Journal of the Korean Society for Library and Information Science
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• v.28
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• pp.247-266
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• 1995

The purpose of information retrieval is to help users solve their problems. To fulfill the purpose the user's problem needs to be focused on. The purpose of this study is to identify components and the structure of the user's problem in an academic research environment. From this study it was found that the scientific problem dealt within an academic environment is complicate and the problem is composed of 8 topical and 4 non-topical components. And they could be organized into a stucture. This study has three implications for user-oriented information retrieval. (1) The components and the structure of the problem need to be the framework for the effective information retrieval process and for the evaluation of information retrieval. (2) The research methodology used in this study can be applied to other information service situations and this will result in greater practical implication of a study for more effective information retrieval. And (3) for more effective user-oriented information retrieval, the user needs to be observed and studied in the actual' situation. This study showed that the complicate problem of the actual user can be studied in a systematic way and this resulted in important implications for information retrieval.

• ETRI Journal
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• v.38 no.4
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• pp.622-633
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• 2016

A discontinuous reception (DRX) operation is included in the Long Term Evolution (LTE) system to achieve power saving and prolonged battery life of the user equipment. An improvement in DRX power saving usually leads to a potential increase in the packet delay. An optimum DRX configuration depends on the current traffic, which is not easy to estimate accurately, particularly for non-real-time applications. In this paper, we propose a novel way to vary the DRX cycle length, avoiding a continuous estimation of the data traffic when only non-real-time applications are running with no active real-time applications. Because a small delay in non-real-time traffic does not essentially impact the user's experience adversely, we deliberately allow a limited amount of delay in our proposal to attain a significant improvement in power saving. Our proposal also improves the delay in service resumption after a long period of inactivity. We use a stochastic analysis assuming an M/G/1 queue to validate this improvement.

• Journal of the Korean Society of Costume
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• v.66 no.2
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• pp.61-75
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• 2016

The purpose of this study was to develop interactive smart clothing based on visual and tactile sensitivities to promote non-verbal communication between people with hearing impairments. The study analyzed various cases of interactive smart clothing, different non-verbal communication tools, as well as results of user demand survey to extract essential factors. Then these factors were categorized into technology or design concept. The technological aspect of the development considered the following factors: the usability, detachability, purposiveness, and economic feasibility. The design aspect considered the following factors: the usability, detachability, formativeness and wearability. A prototype was designed considering the user's requirements. The developed prototype had sensors, Bluetooth technology, and gave access to wireless communication in order to enable non-verbal communication between people with hearing impairments.

• Korean Journal of Artificial Intelligence
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• v.11 no.1
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• pp.9-15
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• 2023

As mobile devices such as smartphones, tablets, and kiosks become increasingly prevalent, there is growing interest in developing alternative input systems in addition to traditional tools such as keyboards and mouses. Many people use their own bodies as a pointer to enter simple information on a mobile device. However, methods using the body have limitations due to psychological factors that make the contact method unstable, especially during a pandemic, and the risk of shoulder surfing attacks. To overcome these limitations, we propose a simple information input system that utilizes gaze-tracking technology to input passwords and control web surfing using only non-contact gaze. Our proposed system is designed to recognize information input when the user stares at a specific location on the screen in real-time, using intelligent gaze-tracking technology. We present an analysis of the relationship between the gaze input box, gaze time, and average input time, and report experimental results on the effects of varying the size of the gaze input box and gaze time required to achieve 100% accuracy in inputting information. Through this paper, we demonstrate the effectiveness of our system in mitigating the challenges of contact-based input methods, and providing a non-contact alternative that is both secure and convenient.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38A no.9
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• pp.798-809
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• 2013

In this paper, we propose robust relay and destination filter design methods for the multi-user peer-to-peer amplify-and-forward relaying systems while taking imperfect channel knowledge into consideration. Specifically, the relay and destination filter sets are developed to minimize the sum mean-squared-error (MSE). We first present a robust joint optimum relay and destination filter calculation method with an iterative algorithm. Motivated by the need to reduce computational complexity of the iterative scheme, we then formulate a simplified sum MSE minimization problem using the relay filter decomposability, which lead to two robust sub-optimum non-iterative design methods. Finally, we propose robust modified destination filter design methods which require only local channel state information between relay node and a specific destination node. The analysis and simulation results verify that, compared with the optimum iterative method, the proposed non-iterative schemes suffer a marginal loss in performance while enjoying significantly improved implementation efficiencies. Also it is confirmed that the proposed robust filter design methods provide desired robustness in the presence of channel uncertainty.