• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2014년도 추계학술대회
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• pp.595-598
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• 2014

IEEE 802.11 Wireless LAN 네트워크 상에서 동작하는 단말(Mobile Station)의 끊김 없는(Seamless) 이동성을 제공해 주기 위해서는 현재까지 연구된 핸드오버 기능 및 구조에 대한 연구와 함께 보다 다양해진 네트워크 환경과 다양한 단말들의 특성 등을 고려한 종합적인 핸드오버 기능에 대한 연구가 필요하다. 특히 새로운 AP를 찾기 위한 채널 스캐닝 과정이 핸드오버 지연시간의 대부분을 차지하고, 이는 WLAN 환경에서 Real-time Multimedia 서비스를 위한 끊김 없는 핸드오버를 하기에 가장 큰 장애요인으로 꼽힌다. 본 논문에서는 IEEE 802.11 WLAN 네트워크에서 단말의 끊김 없는 핸드오버를 제공해 주기 위하여 필요한 기능들을 도출하고, 다양한 네트워크 환경에서 채널 스캐닝 지연시간을 줄이기 위해서 핸드오버가 필요한 단말들이 선택적 채널 스캐닝을 할 수 있는 새로운 스캐닝 기법을 제안한다. 단말은 스캐닝 기법에 따라 이웃 AP들에 대해 사전 채널 스캐닝을 수행하여 각각의 AP가 현재 사용하고 있는 채널 정보를 인지하고, 이후 단말이 핸드오버가 임박했을 때 미리 정해진 스캐닝 그룹과 순서에 따라 선택된 채널에 대해서만 스캐닝을 수행하여, 불필요한 전체 채널 스캐닝을 최소화 함으로서 최적의 AP를 빠른 시간 내에 찾을 수 있도록 제안한다. 또한 단말의 이동에 따라 핸드오버가 필요한 상황이지만 RSSI 값이 Scan Trigger Value 보다 커서 핸드오버를 못하는 현상을 방지하고자, 단말에서 Scan Trigger Value와 Handover Threshold Value를 입력할 수 있는 방법을 제안하고자한다.

• 대한임베디드공학회논문지
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• 제8권6호
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• pp.311-318
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• 2013

In this paper, we consider a new packet scheduling algorithm for real-time traffic in the HSDPA system that has been introduced for the WCDMA system, in order to provide high transmission rates. The objective of the design is to meet the maximum tolerable delay and consider channel assignment based on the received SIR for real-time traffic users. The proposed scheduling algorithm shows that the users are ranked by the ratios of the bits in the buffer to the residual time for transmission as priority order; then the ranked users are assigned certain number of channels based on the SIR value table. The simulation results show that the proposed algorithm can provide a lower packet drop rate, and satisfy real time quality of service (QoS) requirements.

• 전자공학회논문지A
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• 제31A권4호
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• pp.1-10
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• 1994

In the real-time delivery of multimedia data streams over networks, the interruption of continuity in a single media stream and the mismatching of the data within the same time interval in multimedia data streams transfered in paralled on different channels are considered as the most serious synchronization problems. There are several mechanisms proposed to handle these problems. In this paper, these mechanisms are analyzed and compared in various point of view by the computer simulation. According to the simulation results, it has been shown that the method which uses the segmentation and the method which uses the seperate synchronization channel are superior to the method which uses the synchronization marks in view of the real-time transmission and quality of sevice. On the other hand, it can be seen that the method which uses the segmentation is superior to the method which uses the seperate synchronization channel from a channel utilization's point of view.

• 센서학회지
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• 제22권1호
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• pp.18-27
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• 2013

Real-time monitoring is one of the prime necessities in a weapon flight test that is required for the efficient and timely collection of large amounts of high-rate sampled data acquired by an event-trigger. The wireless sensor network is a good candidate to resolve this requirement, especially considering the inhospitable environment of a weapon flight test. In this paper, we propose a priority based multi-channel MAC protocol with CSMA/CA over a single radio for a real-time monitoring of a weapon flight test. Multi-channel transmissions of nodes can improve the network performance in wireless sensor networks. Our proposed MAC protocol has two operation modes: Normal mode and Priority Mode. In the normal mode, the node exploits the normal CSMA/CA mechanism. In the priority mode, the node has one of three grades - Class A, B, and C. The node uses a different CSMA/CA mechanism according to its grade that is determined by a signal level. High grade nodes can exploit more channels and lower backoff exponents than low ones, which allow high grade nodes to obtain more transmission opportunities. In addition, it can guarantee successful transmission of important data generated by high grade nodes. Simulation results show that the proposed MAC exhibits excellent performance in an event-triggered real-time application.

• 한국입자에어로졸학회지
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• 제14권4호
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• pp.107-119
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• 2018

In this study, we have developed a real-time monitoring device for measuring PM10 and PM2.5 of ambient aerosol particles. The real-time PM monitor (SENTRY Dust Monitor) uses the optical scattering method and has 16 channels in particle size. The laboratory and field tests were carried out to evaluate the developed SENTRY Dust Monitor. Arizona Test Dust particles were used as test particles in the laboratory test and the field test was carried out at the Jongno-gu Observatory in Seoul. The measurements of PM10 and PM2.5 concentrations obtained by SENTTRY Dust Monitor were compared with Grimm Dust Monitor (Model 1.108) and a beta ray gauge. It was shown that the PM10 and PM2.5 concentrations obtained by SENTRY Dust Monitor agree well with that of the reference devices. Based on the results obtained in this study, it could be concluded that the SENTRY Dust Monitor can be used as a PM monitoring device for real-time monitoring of the ambient aerosols.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2002년도 하계종합학술대회 논문집(4)
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• pp.351-354
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• 2002

DVR(Digital Video Recorder), a recently popular visual monitoring system, is required to support multi camera channel display(upto 16 channels) with various display modes in real-time. For such a multichannel display system, it is well known that tearing artifacts become more serious. Thus, one needs to design a display system for DVR so that it does not show tearing artifacts as much as possible, but keeps real-time display speed. In this paper, we present our efforts in designing and implementing a display system which rarely ever shows tearing artifacts, but without degradation of required real-time display speed, and which displays character information stably without blinking.

• 한국입자에어로졸학회지
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• 제10권1호
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• pp.1-8
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• 2014

In this study, we have developed a real-time monitoring device for measuring $PM_{10/2.5/1}$ of ambient aerosol particles. The real-time PM (Particulate Matter) monitor was based on the light scattering method and had 16 channels in particle size. The laboratory and field tests were carried out to evaluate the performance of the PM monitor developed. Arizona Road Dust particles ranging from diameter of 0.1 to $20{\mu}m$ were generated as test particles in the laboratory test. The field test was carried out at the Seoul Meteorological Observatory. We can obtain the particle size and number concentration (particle size distribution) only from the real-time PM monitor developed. Therefore, the average density of aerosol particles was used to obtain the PM data from the particle size distribution. The $PM_{10/2.5/1}$ results of the PM monitor were compared with the data of the Grimm Dust Monitor (Model 1.108) and a beta ray gauge (Thermo Fisher Scientific). As a result, it was shown that the $PM_{10/2.5/1}$ results obtained by the real-time PM monitor agreed well with the data of the reference devices, and overall, the real-time PM monitor could be used as a PM monitoring device for real-time monitoring of the ambient particles.

• 정보처리학회논문지C
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• 제13C권6호
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• pp.669-676
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• 2006

본 논문에서는 실시간 객체모델인 Time-triggered Message-triggered Object (TMO)를 사용하여 분산 실시간 멀티미디어 스트리밍 서비스를 효과적으로 개발 할 수 있는 새로운 소프트웨어 프레임워크와 스트림 동기화 메커니즘을 소개한다. 본 프레임워크의 목적은 개발자로 하여금 복잡한 실시간 멀티미디어 스트리밍 서비스를 쉽게 설계하고 적시 스트리밍 기능들을 제공하는데 있다. 이를 위해서 본 프레임워크는 Multimedia Streaming TMO, MMStream TMO Support Library 그리고 TMO Support Middleware로 구성된다. 특히, MMStream TMO와 동기화 기법이 제공하는 time-trigger번 특성은 QoS 보장이 어려운 통신 채널과 시스템 환경에서 불규칙한 미디어 데이터 전달 및 처리하는 역할을 실시간으로 수행한다. 결론적으로 본 논문에서 제시한 프레임워크의 적시 서비스 능력은 향후 실시간 멀티미디어 스트리밍 서비스 개발에 기여할 것으로 기대된다.

• International Journal of Advanced Culture Technology
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• 제7권4호
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• pp.96-103
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• 2019

In this paper, we propose two-stage multichannel architecture for oyster product management system, called cloud stage and agent stage. There are two communication channels at each stage. In cloud stage, the embedded system in the smart scale communicates with the server through two channels, Ethernet or 3G/LTE mobile communication. In agent stage, PCs and smart phones called agents communicate with the server also through Internet and 3G/LTE mobile communication. Compared with previous system in which the amount of the oyster produced in oyster workplaces could be monitored only at the console of only one oyster main server, developed system makes it possible to monitor the amount of produced oyster at several PCs (or smart phones). In addition to the amount of oysters produced at all oyster workplaces the environment of oyster workplaces such as temperature and humidity can be monitored on agents to judge the freshness. Two-stage architecture with multiple channels makes it possible to monitor the amount of oyster product and environment of the oyster workplace at any place in real time.

• 한국전기전자재료학회논문지
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• 제35권4호
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• pp.342-347
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• 2022

In-situ analyzation and detection of real-time chemical reactions can be a significant part in interpreting the underlying mechanism in very reactive chemical reactions. To do this, first we have designed a microfluidic device (MFD) pattern for observation of synthesis of hierarchical nanostructures based on graphene oxide (GO), conjugating the well-known coupling reaction by which the solution of 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC)-mediated coupling is enhanced in the presence of n-hydroxysuccinimide (NHS) to make amide bonding, hereafter called as the EDC coupling. Then, we have manufactured microfluidic devices with multiple tens of micrometer-sized channels that can circulate those nanomaterials to be chemically reacted in the channels. These microfluidic devices were made by negative photo lithography and soft lithography. We showed the possibility of using Raman spectroscopy to reveal the basic mechanism of the energy storage applications.