• KSII Transactions on Internet and Information Systems (TIIS)
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• 제11권12호
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• pp.5835-5854
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• 2017

The implementation of IEEE 802.15.6 in Wireless Body Area Network (WBAN) is contention based. Meanwhile, IEEE 802.15.4 MAC provides limited 16 channels in the Superframe structure, making it unfit for N heterogeneous nature of patient's data. Also, the Beacon-enabled Carrier-Sense Multiple Access/Collision-Avoidance (CSMA/CA) scheduling access scheme in WBAN, allocates Contention-free Period (CAP) channels to emergency and non-emergency Biomedical Sensors (BMSs) using contention mechanism, increasing repetition in rounds. This reduces performance of the MAC protocol causing higher data collisions and delay, low data reliability, BMSs packet retransmissions and increased energy consumption. Moreover, it has no traffic differentiation method. This paper proposes a Low-delay Traffic-Aware Medium Access Control (LTA-MAC) protocol to provide sufficient channels with a higher bandwidth, and allocates them individually to non-emergency and emergency data. Also, a Contention Differentiated Adaptive Slot Allocation CSMA-CA (CDASA-CSMA/CA) for scheduling access scheme is proposed to reduce repetition in rounds, and assists in channels allocation to BMSs. Furthermore, an On-demand (OD) slot in the LTA-MAC to resolve the patient's data drops in the CSMA/CA scheme due to exceeding of threshold values in contentions is introduced. Simulation results demonstrate advantages of the proposed schemes over the IEEE 802.15.4 MAC and CSMA/CA scheme in terms of success rate, packet delivery delay, and energy consumption.

• 한국통신학회논문지
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• 제31권4A호
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• pp.402-411
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• 2006

OFDMA 방식은 다중 사용자가 서로 다른 부반송파를 통해 동시에 신호를 전송하는 방식으로서, 주파수 효율이 높고, 간단한 단일 탭 등화기로 고속 전송 시 급격히 증가하는 인접 서브캐리어 간 간섭의 보상이 가능하며, FFT를 사용하여 고속으로 구현할 수 있기 때문에 최근 고속 데이터 무선 통신을 위한 전송방식으로 사용되고 있다. 하지만 이러한 OFDMA 시스템의 장점은 부반송파간의 직교성이 유지되는 경우에만 가능하며, 직교성이 깨지는 경우에는 인접 채널 간섭이 발생되어, 시스템 성능을 저하시키게 된다. 따라서 OFDM 시스템에서는 주파수 및 시간 동기의 중요성이 크게 강조된다. 본 논문에서는 효율적인 동기 성능을 위하여 802.16d/e 및 WiBro 시스템에서 사용되는 프리앰블을 분석하여 기존에 사용되던 방식에 비해 정확도가 높은 Timing Metric 을 유도함으로써 보다 확실한 시간 동기 알고리즘을 제안하고, 시간영역에서 소수배 주파수 옵셋 추정만이 가능한 문제점을 해결하기 위해 정수배 주파수 옵셋 추정이 가능한 주파수 동기화 구조를 제안한다. 제안된 시간 및 주파수 동기 알고리즘을 적용한 시스템의 모의실험을 통하여 OFDMA 시스템에서의 인접 채널 간 간섭에 의한 성능 열화가 저하됨을 알 수 있다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 하계학술대회 논문집 G
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• pp.2373-2376
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• 1998

This paper describes the development of the SCADA(Supervisory Control and Data Acquisition) system which can be controlled via the Internet. In this paper, the SCADA system is composed of a number of microprocessor-based RTU(Remote Terminal Unit)s, a MMI(Man Machine Interface) host, a SCADA server, and SCADA clients. There are two protocols used in the system. Each RTU and the MMI host are connected by a RS-485 line and CSMA/CD(Carrier Sense Multiple Access / Collision Detection) protocol is used to communicate with each other. TCP/IP(Transmission Control Protocol/Internet Protocol) is used among the MMI host, the SCADA server, and SCADA clients. The equipments installed in the field are controlled by a number of RTUs. The function of the MMI host is to acquire real-time data from RTUs and control them. The SCADA server supports data transfer between the networked MMI host and the SCADA client on the web-server through TCP/lP. Data transfer is possible regardless of the type of network only if there are TCP/lP Winsock-compatible stack driver. The SCADA client is implemented as the shape of web-page by means of JAVA language. Therefore, it runs on a web-browser such as Netscape and Explorer, and allows a number of users to access this SCADA system.

• 복식
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• 제63권5호
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• pp.35-50
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• 2013

This thesis is based on the study of formativeness and versatility of Sarong. For the aim of the research, Sarongs were classified into two types: rectangular and tube, using its original form as the basis. These two types of Sarongs were divided into more detailed groups depending on the purposes of attire, such as skirts, dresses, and capes. To look into the formativeness and versatility of Sarong, the usage of wear and expression methods were observed based on these categories. The following results were found regarding the versatility of Sarong: First, Sarong has a wide degree of versatility in terms of usage. It can be worn as a skirt, a head scarf, a dress, a cape, or used as a carrier or even a sleeping bag, based on one's intention. The change of usage is often accompanied with the change of forms, as can be shown by the longyi of Myanmar, the tube type Sarong, which is used as briefs. Second, Sarong has a wide degree of versatility in terms of function. Variations of instrumental and expressive function of Sarong are observed simultaneously. The physical function sometimes coincides with the changes of usage as mentioned above. The way that Sarong's are expressed in different social situations changes depending on the wearer's social status, religion, or origin. So by looking at the way a Sarong is worn, others can tell if a person is going to social events such as festivals and weddings. Third, Sarong has a wide degree of versatility in terms of design. However, even if same usage and function is pursued, the design can be different based on an individual. This is because the external change of Sarong is affected by individuality or aesthetic sense of the wearer.

• 복식문화연구
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• 제19권1호
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• pp.230-243
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• 2011

In this modern digital era, there are very vigorous arguments about digital and media aesthetics throughout culture and art on the basis of new transferring of recognition about the art-media's characteristics. Therefore, this paper tries to discover the art-media's characteristics and aesthetic value that are included in contemporary digital fashion through studying the fusion between digital and fashion. The purpose of this research is to offer positive and evolutive opportunity of artistic thinking to make the meeting between fashion and media suggest the future generation, adaptation and recognition in the media - developmental environment that will be deeper and more fueling. In the area of research method, this paper takes the method of theoretical research by referring national and foreign literatures and preceding research-papers, and carries out investigation and analysis about digital fashion for the last 10 years. The results of this study; The art-media's characteristics of modern digital fashion are virtuality, immateriality and characteristics of multimedia. The aesthetic values can be classified with four kinds of properties. First is hybridity initiated from multi-media that creates works; the second is infinite reproductivity initiated from the characteristics of the multi media and the digital carrier. Thirdly, there is also interactivity appeared all over the area of production, adaptation and perception caused by non-linearity and immateriality. Finally there is synesthesia that can extend the capability of sense through digital media.

• 한국통신학회논문지
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• 제34권5B호
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• pp.463-468
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• 2009

차량 간 통신에서는 무선 랜을 기반으로 한 연구가 활발히 진행되고 있으며, IEEE 802.11p WAVE(Wireless Access in the Vehicular Environment)에서도 802.11a를 기반으로 한 방식을 채택하고 있다. 하지만 무선 랜 방식은 하나의 채널을 경쟁 모드로 사용하기 때문에 빠른 접속을 요구하는 차량 환경에서 경쟁을 회피하기 위해 CSMA/CA(Carrier Sense multiple Access/Collision Avoidance) 알고리즘을 사용하는 것은 찾은 충돌로 인한 통신 지연을 유발 할 수 있다. 본 논문에서는 차량 간 통신에서 이러한 문제점을 해결하고 신뢰성 있는 데이터 전송을 지원하기 위하여 차량 환경에 적합한 클러스터링 기반의 멀티채널 매체접속제어 프로토콜을 설계하고 설계된 프로토콜을 바탕으로 차량 간 통신에 적합한 채널 조건을 확인하였다 클러스터 헤드를 통해 각 채널을 관리하고 채널을 할당함으로써 기존 경쟁 기반의 싱글 채널을 사용함에 따라 생기는 패킷 충돌 및 통신 지연을 60%이상 줄이는 것을 시뮬레이션을 통해 확인 하였다.

• 한국통신학회논문지
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• 제38B권7호
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• pp.543-552
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• 2013

차량통신간 자동차의 정보를 포함하는 메시지인 비콘을 주변의 자동차들에게 주기적으로 전송함으로 차량간의 안전을 보장해야 할 필요가 있다. 그러나 IEEE 802.11p/WAVE 환경에서는 혼잡상황에서 비콘 전송을 경쟁윈도우(Contention window)를 기반으로 한 MAC (Medium Access Control)에서 해결하도록 하였기 때문에 비콘 전송 과정에 충돌이 발생한다. 본 논문에서는 차량 혼잡 상황에서 비콘의 충돌을 막기 위해서 MAC 구조를 슬롯 p-persistent CSMA (Carrier Sense Multiple Access)라 가정하여 전송 확률에 대한 보수행렬(payoff)을 이용한 비 협조적 베이지안 게임이론을 적용하여 베이지안 내쉬 균형점(BNE)을 도출하였다. 본 논문에서는 도출된 BNE를 가지고 포화 상태에서 비콘 전송률을 높일 수 있는 혼잡 제어 알고리즘을 제안했다. 제안된 알고리즘으로 경쟁윈도우크기와 주변 자동차 수에 관련된 함수를 통해 전송 확률을 계산하였다. 시뮬레이션 결과를 통해서 제안된 알고리즘이 안정적으로 동작함을 보였다.

• Journal of Communications and Networks
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• 제15권1호
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• pp.77-86
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• 2013

Cognitive radio (CR) has emerged as one of effective methods to enhance the utilization of existing radio spectrum. Main principle of CR is that secondary users (SUs) are allowed to use the spectrum unused by primary users (PUs) without interfering PU's transmissions. In this paper, PUs operate on a slot-by-slot basis and SUs try to exploit the slots unused by PUs. We propose OSA protocols in the single channel and we propose an opportunistic spectrum access (OSA) protocols in the multi-channel cognitive radio networks with one control channel and several licensed channels where a slot is divided into contention phase and transmission phase. A slot is divided into reporting phase, contention phase and transmission phase. The reporting phase plays a role of finding idle channels unused by PUs and the contention phase plays a role of selecting a SU who will send packets in the data transmission phase. One SU is selected by carrier sense multiple access / collision avoidance (CSMA/CA) with request to send / clear to send (RTS/CTS) mechanism on control channel and the SU is allowed to occupy all remaining part of all idle channels during the current slot. For mathematical analysis, first we deal with the single-channel case and we model the proposed OSA media access control (MAC) protocol by three-dimensional discrete time Markov chain (DTMC) whose one-step transition probability matrix has a special structure so as to apply the censored Markov chain method to obtain the steady state distribution.We obtain the throughput and the distribution of access delay. Next we deal with the multi-channel case and obtain the throughput and the distribution of access delay by using results of single-channel case. In numerical results, our mathematical analysis is verified by simulations and we give numerical results on throughput and access delay of the proposed MAC protocol. Finally, we find the maximum allowable number of SUs satisfying the requirements on throughput and access delay.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제5권9호
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• pp.1492-1512
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• 2011

Due to multiple hops, mobility and time-varying channel, supporting delay sensitive real-time traffic in wireless local area network-based (WLAN) mesh networks is a challenging task. In particular for real-time traffic subject to medium access control (MAC) layer control overhead, such as preamble, carrier sense waiting time and the random backoff period, the performance of real-time flows will be degraded greatly. In order to support real-time traffic, an efficient adaptive packet scheduling (APS) scheme is proposed, which aims to improve the system performance by guaranteeing inter-class, intra-class service differentiation and adaptively adjusting the packet length. APS classifies incoming packets by the IEEE 802.11e access class and then queued into a suitable buffer queue. APS employs strict priority service discipline for resource allocation among different service classes to achieve inter-class fairness. By estimating the received signal to interference plus noise ratio (SINR) per bit and current link condition, APS is able to calculate the optimized packet length with bi-dimensional markov MAC model to improve system performance. To achieve the fairness of intra-class, APS also takes maximum tolerable packet delay, transmission requests, and average allocation transmission into consideration to allocate transmission opportunity to the corresponding traffic. Detailed simulation results and comparison with IEEE 802.11e enhanced distributed channel access (EDCA) scheme show that the proposed APS scheme is able to effectively provide inter-class and intra-class differentiate services and improve QoS for real-time traffic in terms of throughput, end-to-end delay, packet loss rate and fairness.

• 한국멀티미디어학회논문지
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• 제25권8호
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• pp.1167-1174
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• 2022

With the sustainable development and transformation of the city, public art as a business card of the famous city of culture has become a hot topic of research. The intervention of public art in public space not only brings users a sense of space experience, but also becomes a unique carrier of urban and rural image making. Although there is much research on the classification, aesthetics and function of public art, there is few quantitative research on user satisfaction. This paper takes the basic features of airport public art as a research object and the basic features of airport public art as the theoretical basis to study the impact of the basic characteristics of airport public art on user satisfaction. Research methods were based on questionnaire data of 247 people, in which models and hypotheses were tested using SPSS 21.0 software, based on the induction and extraction of nine influential factors in the basic characteristics of public art. The study found that public interpretation, media patterns, color perception, modeling form, place perception, city image and memory have significant positive effects on user satisfaction. The sharedness of public art, cognition and communication in public culture and spatial relations do not affect satisfaction. Conclusion, inspiration and prospect provide suggestions for designers and reference data and theoretical support for public art evaluation.