• 대한인간공학회지
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• 제24권1호
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• pp.19-26
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• 2005

Mobile internet access using such devices as PDAs and cellular phones becomes popular as mobile technologies grow. However, the characteristics of small screen devices such as small screen size and pen-based input cause many usability problems. In this study, a human factors experiment was conducted to identify the factors affecting the usability of information search on a PDA. Factors manipulated in the experiment included use of wheel equipment, scroll dimension, and screen orientation. Task completion time, error frequency, and subjective satisfaction level were measured. In addition, various users' behavioral patterns such as scanning routes and mainly used scrolling methods were analyzed. Scroll dimension has a significant effect on task completion time. Scroll equipment and screen orientation affect subjective satisfaction level. The results could be applied to designing information structure of web sites for mobile use by providing vertical scroll and using external scroll equipments.

• 한국정보기술학회 영문논문지
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• 제10권1호
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• pp.57-69
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• 2020

In general, many IoT devices, including smart phones, use LTE, Wi-Fi, and Bluetooth, and these communication modules generate a lot of energy consumption during periodic data transmission. This paper proposes a method of the data transmission mode change for improving energy efficiency in various communication environments that mobile devices may encounter. We propose an algorithm for setting the mode considering energy efficiency, data transmission performance and cost when the mobile device transmits data, and transmitting the data in an optimized manner according to the state of the mobile device. The proposed algorithm is implemented through experiments on energy efficiency for each communication module, and the scenario is used to verify how efficiently the proposed algorithm uses energy.

• 스마트미디어저널
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• 제12권3호
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• pp.68-76
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• 2023

Emerging mobile edge computing (MEC) can be used in battery-constrained Internet of things (IoT). The execution latency of IoT applications can be improved by offloading computation-intensive tasks to an MEC server. Recently, the popularity of unmanned aerial vehicles (UAVs) has increased rapidly, and UAV-based MEC systems are receiving considerable attention. In this paper, we propose a dynamic computation offloading paradigm for UAV-based MEC systems, in which a UAV flies over an urban environment and provides edge services to IoT devices on the ground. Since most IoT devices are energy-constrained, we formulate our problem as a Markov decision process considering the energy level of the battery of each IoT device. We also use model-free Q-learning for time-critical tasks to maximize the system utility. According to our performance study, the proposed scheme can achieve desirable convergence properties and make intelligent offloading decisions.

• 한국인터넷방송통신학회논문지
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• 제12권1호
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• pp.257-264
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• 2012

모바일 디바이스의 발전으로 인해 사람들에 대한 정보와 자원의 교환 및 공유를 보다 손쉽게 하였으며, 컴퓨팅 기술과의 결합으로 모바일 컴퓨팅을 이용한 서비스에 대한 관심이 증가되고 있다. 또한 이에 관한 많은 연구들이 진행 중에 있으며 특히 사용자 개개인의 성향과 상황에 맞는 추천 서비스의 필요성은 더욱 더 필요한 실정이다. 본 논문에서는 개개인의 성향과 적절한 추천 서비스를 제공하기 위해서 사용자의 현재 상황을 인식한 뒤 각각의 사용자에 따른 능동적 추천 서비스를 위해 각 개인의 프로파일을 분석하여 추론 및 분석을 통해 서비스를 도출할 수 있는 상황인식 프로토타입을 제안하였다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제15권8호
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• pp.2827-2848
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• 2021

Mobile Crowdsourcing (MCS) has become an emerging paradigm evolved from crowdsourcing by employing advanced features of mobile devices such as smartphones to perform more complicated, especially spatial tasks. One of the key procedures in MCS is to collect answers from mobile users (workers), which may face several security issues. First, authentication is required to ensure that answers are from authorized workers. In addition, MCS tasks are usually location-dependent, so the collected answers could disclose workers' location privacy, which may discourage workers to participate in the tasks. Finally, the overhead occurred by authentication and privacy protection should be minimized since mobile devices are resource-constrained. Considering all the above concerns, in this paper, we propose a lightweight and privacy-preserving answer collection scheme for MCS. In the proposed scheme, we achieve anonymous authentication based on traceable ring signature, which provides authentication, anonymity, as well as traceability by enabling malicious workers tracing. In order to balance user location privacy and data availability, we propose a new concept named current location privacy, which means the location of the worker cannot be disclosed to anyone until a specified time. Since the leakage of current location will seriously threaten workers' personal safety, causing such as absence or presence disclosure attacks, it is necessary to pay attention to the current location privacy of workers in MCS. We encrypt the collected answers based on timed-release encryption, ensuring the secure transmission and high availability of data, as well as preserving the current location privacy of workers. Finally, we analyze the security and performance of the proposed scheme. The experimental results show that the computation costs of a worker depend on the number of ring signature members, which indicates the flexibility for a worker to choose an appropriate size of the group under considerations of privacy and efficiency.

• 한국인터넷방송통신학회논문지
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• 제24권1호
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• pp.31-36
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• 2024

최근 AI 기술을 활용하는 모바일 앱이 늘고 있다. 개인용 모바일 환경에서는 메모리 용량의 제약으로 인해 대용량 데이터로 구성된 워크로드의 학습 시 극심한 성능 저하가 발생할 수 있다. 본 논문에서는 이러한 현상을 규명하기 위해 AI 워크로드의 메모리 참조 트레이스를 추출하고 그 특성을 분석하였다. 그 결과 AI 워크로드는 메모리 쓰기 연산시 약한 시간지역성과 불규칙한 인기편향성 등으로 인해 잦은 스토리지 접근을 발생시켜 모바일 기기의 성능을 저하시킬 수 있음을 확인하였다. 이러한 분석을 토대로 본 논문에서는 AI 워크로드의 메모리 쓰기 연산을 영속 메모리 기반의 스왑 장치를 이용해서 효율적으로 관리할 수 있는 방안에 대해 논의하였다. 시뮬레이션을 통해 본 연구에서 제안한 구조가 기존의 모바일 시스템 대비 80% 이상 입출력 시간을 개선할 수 있음을 보였다.

• 정보화연구
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• 제10권2호
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• pp.251-261
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• 2013

다양한 휴대 인터넷 환경의 출현은 기존 모바일 기기의 네트워크 접근을 보다 쉽게 해주고 있다. 또한 무선 환경을 사용하는 모바일 기기 사용자는 혼자 사용하는 특징을 가지고 있으며 유선 환경보다 사용자 프로파일 정보를 쉽게 구할 수 있다. 이러한 모바일 기기의 특징은 개인화 서비스를 적용하기에 최적의 시스템이다. 본 논문에서는 모바일 기기 사용자를 위한 개인화된 모바일 음악 콘텐츠 추천 서비스를 제공한다. 이 서비스는 사용자의 액세스 히스토리(access history) 정보를 활용하여 시간에 가중치 부여를 이용한 협업 필터링 방법을 제안한다. 액세스 히스토리 정보는 사용자의 관심정보를 알아낼 수 있다. 이 정보를 이용하여 음악 장르의 선호도를 고려하고 시간에 따라 가중치를 부여하여 음악을 추천해준다. 이 방법은 기존의 음악 추천 시스템의 문제점인 사용자가 선호하는 음악장르가 시간이 지남에 따라 변화한다는 사실을 고려하지 못하는 문제점을 해결한다.

• International Journal of Internet, Broadcasting and Communication
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• 제12권3호
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• pp.56-63
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• 2020

The Avengers film produced by Marvel Comics shows visual effects that were impossible to produce in the past. Companies that produce film special effects were initially equipped with large personnel and equipment, but technology is gradually evolving to be feasible for smaller companies that do not have high-priced equipment and a large workforce. The development of hardware and software is becoming increasingly available to the general public as well as to experts. Equipment and software which were difficult for individuals to purchase before quickly popularized high-performance computers as the game industry developed. The development of the cloud has been the driving force behind software costs. As augmented reality (AR) performance of mobile devices improves, advanced technologies such as motion tracking and face recognition technology are no longer implemented by expensive equipment. Under these circumstances, after implementing mobile-based facial capture technology in animation projects, we have identified the pros and the cons and suggest better solutions to improve the problem.

• International Journal of Internet, Broadcasting and Communication
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• 제15권4호
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• pp.84-89
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• 2023

Recently, the sixth generation (6G) networks have become tremendous research topics. Intelligent reflecting surface (IRS) technologies have been envisioned, to increase spectrum and energy efficiency for the fifth generation (5G) mobile networks, towards the sixth generation (6G) communications. In this paper, especially for the strongest channel gain user, we investigate the bit-error rate (BER) of non-orthogonal multiple access (NOMA) systems with intelligent reflecting surface (IRS). First, we derive a BER expression in a closed-form of Q functions. Second, we investigate the BER performance improvement of IRS NOMA systems over NOMA systems versus the power allocation. Moreover, we analyze the BER performance improvement of IRS NOMA systems over NOMA systems versus the number of IRS devices. In results, NOMA equipped with IRS technologies could play an important role in the paradigm shift from 5G mobile networks to 6G mobile networks.

• International Journal of Internet, Broadcasting and Communication
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• 제9권4호
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• pp.25-30
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• 2017

Market of smart toys is showing rapid growth globally. Recently, new types of toys which can be synced with smart phones, so called smart toys, are being released continuously. As a result, products from RC cars with camera attached that can be driven and monitored using a connected smart phone to toys that would call kid's name once it has been entered through a mobile app. It has been confirmed that there are various way to connect those toys with mobile devices. In this paper, functions of smart toys are classified, and research on different synchronization methods of the toys sold in market as of July, 2017 are explained.