• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.2
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• pp.452-458
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• 2014

In Wireless Sensor Networks the Medium access control (MAC) protocol has many challenges to solve such as reducing energy consumption, supporting QoS(quality of service) fairness, and reducing delivery delay. This paper proposed a low-delay supporting MAC protocol in multi-hop Wireless Sensor Networks. The proposed protocol uses the RB(rapid beacon) frame for reducing delivery delay. The RB frame is a modified IEEE 802.15.4 beacon frame. For sender adaptive-wakeup, the RB frame includes a seed number for determining of a receiver wakeup time. And for next hop receiver adaptive-wakeup, the RB frame includes the length of remaining data packet information. Results showed that our LD-MAC protocol outperformed other protocol in terms of data packet delivery delay.

• Annual Conference of KIPS
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• 2006.05a
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• pp.493-496
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• 2006

유비쿼터스 프로파일은 유비쿼터스 환경에서 콘텐츠 적응화를 위해 CC/PP를 확장한 프로파일로서, 프로파일을 구성하는 정보들은 네트워크에 분산되어 존재하며, 생성 시 게이트웨이의 프로파일 관리 저장소에서 통합되게 된다. 이와 같이 프로파일들이 네트워크에 분산되어 존재하기 때문에 통합 및 관리에 어려움을 가지고 있다. 본 논문에서는 효율적인 유비쿼터스 프로파일들을 통합 운영할 수 있는 프레임워크를 설계한다. 제안한 프레임워크는 프로파일 운영 아키텍쳐와 프로파일 처리 기능을 중심으로 설계하였으며, 통합 및 관리를 할 수 있는 기능을 포함하고 있다. 프레임워크는 운영되는 장소에 따라 클라이언트 프레임워크(CF), 유비쿼터스 프레임워크(UF), 저장소 프레임워크(RF)로 구분되며, 특성에 맞는 기능을 가지고 있다. 제안된 프레임워크는 프로파일 생성, 전송, 통합 관리 기능을 가지고 있어, 유비쿼터스 프로파일 운용 시스템 구축에 효율적이다.

• The KIPS Transactions:PartC
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• v.14C no.3 s.113
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• pp.285-292
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• 2007

In the adaptable bandwidth allocation technique, a transmission plan for variable rate video data is made by the CBA algorithm and the data is transmitted by considering network traffic. But the CBA algorithm produces a transmission plan where the size of the increasing interval of transmission rate is generally larger than the size of the decreasing interval. And the transmission rate in CBA algorithm is changed in overflow curve during the increasing interval of transmission rate. This ぉy cause many frames to be discarded when available transmission rate is small. In this paper, a smoothing algorithm is proposed, where transmission rate is changed in the middle of underflow curve and overflow curve, but the transmission rate increases at the minimum. In order to show the performance, the proposed algorithm and a CBA algorithm were applied to a transmission plan in the adaptable bandwidth allocation technique, and the minimum frame rates, the average frame rates, the variation of frame rates, and the numbers of discarded frames were compared in both algorithms.

• Proceedings of the Korea Institutes of Information Security and Cryptology Conference
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• 2006.06a
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• pp.295-298
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• 2006

인터넷의 발달로 네트워크를 통한 멀티미디어 데이터 서비스가 늘어나면서 유료 콘텐츠에 대한 저작권 관리와 보호 및 다양한 이기종의 단말 장치에 적합한 콘텐츠 적응(adaptation) 서비스에 대한 필요성이 높아지고 있다. 이를 위하여 현재까지 DRM, Scalable Coding, Progressive Encryption, ISMA, ARMS, Metadata Adaptation 등 다양한 연구가 진행되어 왔지만 요구사항을 포괄적으로 만족하는 멀티미디어 전송 프레임워크는 부재한 상태이다. 이에, 본 논문에서는 기존 기법을 분석하고 기능을 통합하여 안전하고 보다 여러 종류의 단말 장치에 서비스가 가능하며 다양한 서비스 형태를 가질 수 있는 프레임워크를 설계하였다. 이를 통해 멀티미디어 서비스가 보다 광범위하게 활용되고 확산 될 수 있으리라 기대된다.

• Annual Conference of KIPS
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• 2009.11a
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• pp.445-446
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• 2009

IEEE 802.11 환경은 RTS/CTS(Request To Send/Clear To Send)을 지원한다. TS/CTS의 사용하면 Hidden Node Problem을 해결할 수 있지만 같은 셀안에 다른 노드를 대기상태로 만드는 False Node Problem이 발생하여 전송률을 감소시킨다. 따라서 본 논문에서는 체크포인트 방식을 사용하여 매체점유시간을 줄이는 제어프레임을 설계하고자 한다. 설계한 제어프레임의 OPNET을 사용하여 시뮬레이션하며, 기존의 제어프레임과 제안하는 제어프레임의 Delay를 비교함으로써 무선네트워크 환경에서 전송 효율을 비교 분석한다.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.18 no.6
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• pp.157-162
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• 2018

This study uses sensors and Raspberry Pi to measure the values of current and voltage and transmits the measured sampled values to a network, carrying them in the frame of IEC 61850-9-2. A laboratory model was composed to send the sampled values, using the frame of IEC 61850-9-2. This study conducted a protocol analysis, using Wireshark for the accurate verification of the occurrence of the frame of IEC 61850-9-2. A visual analysis was conducted by displaying the received sampled values of current and voltage on the monitor in graphs. In addition, this study tested if the sampled values of IEC 61850-9-2 sent and received through the network equipment would meet the performance requirements of the message types of IEC 61850.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.47 no.5
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• pp.358-363
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• 2019

If the EOIR equipment mounted on an unmanned aircraft transmits images and receives commands through a data link, there may be delays in data transmission depending on the transmission path of the data and the conditions of the ground equipment or wireless network. This increases the possibility of initial target LOCK-ON failure due to the difference between the time when the received image is viewed and the time when the image is taken. Therefore, this paper proposed a way to use frame indexes to synchronize with images, and to increase the success of target tracking by adding frame indexes to commands from the ground station.

• Journal of Satellite, Information and Communications
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• v.8 no.4
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• pp.111-116
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• 2013

Because LEO (Low Earth Orbit) satellite has very limited contact time between satellite and ground station, all telemetry data generated on satellite are stored in a mass memory and transmitted to the ground during the contact time. There are two downlink modes, real-time mode and playback mode. Only real-time data frames are transmitted to the ground in real-time mode, real-time and playback data frames stored into mass memory are transmitted to the ground in playback mode. In accordance with the data transmission rate, there are two downlink rates, low downlink rate and high downlink rate. This paper briefly introduces downlink interfaces and flight software of a LEO satellite developed in KARI. And it presents the telemetry storage method, real-time and playback downlink management method, and downlink channel and rate control method.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.10B
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• pp.955-963
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• 2009

In this paper, we propose a medium access control(MAC) protocol for reducing the energy efficiency and for improving the transmission efficiency in underwater acoustic sensor networks. In underwater environment, the transmission delay is longer and bandwidth is smaller than terrestrial environment. Considering these points, we propose a new MAC protocol to enhance throughput and to manage efficiently the energy of nodes. The proposed protocol operates as a channel reservation scheme to decrease data collisions, and uses a mechanism to control the hidden node problem and the exposed node problem occurred in ad hoc networks. The proposed protocol consists of the slotted based transmission frame and reduces data collisions between nodes by putting separately the reservation period in the transmission frame. In addition, it is able to solve the hidden node problem and the exposed node problem by reservation information between nodes. We carry out the simulation to evaluate the proposed protocol in terms of the average energy consumption, the ratio of collision, throughput, and the average transmission delay, and compare the proposed protocol to a traditional MAC protocol in the underwater environment. The simulation results show that the proposed protocol outperforms the traditional protocol under a various of network parameters.

• KIPS Transactions on Computer and Communication Systems
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• v.1 no.1
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• pp.29-34
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• 2012

Wireless multicast service can be used for video streaming service to save the network resources by sending the same popular multimedia contents to a group of users at once. For better multimedia streaming multicast service, we propose a quality-aware rate adaptation (QARA) scheme for scalable video multicast in rate adaptive wireless networks. In QARA, transmission rate is determined depending on the content's type and users' channel conditions. First, the base layer is transmitted by a low rate for high reliability. That means we provide basic service quality to all users. On the contrary, the transmission rate for enhancement layer is adapted by using channel condition feedback from a randomly selected node. So, the enhancement layer frames in a multimedia content is sent with various transmission rates. Therefore, each node can be provided with differentiated quality services. Consequently, QARA is capable of serving heterogeneous population of mobile nodes. Moreover, it can utilize network resources more efficiently. Our simulation results show that QARA outperforms utilization of the available transmission rate and reduces the data transmission time.