• Journal of Information Processing Systems
• /
• 제19권6호
• /
• pp.817-829
• /
• 2023

Variable wireless channel is a big challenge for real-time video applications, and the rate adaptation of realtime video streaming becomes a hot topic. Intra-video coding is important for high-quality video communication and industrial video applications. In this paper, we proposed a novel adaptive scheme for real-time video transmission with intra-only coding over a wireless network. The key idea of this scheme is to estimate the instantaneous remaining capacity of the network to adjust the quality of the next several video frames, which not only can keep low queuing delay and ensure video quality, but also can respond to bandwidth changes quickly. We compare our scheme with three different schemes in the video transmission system. The experimental results show that our scheme has higher bandwidth utilization and faster bandwidth change response, while maintaining low queuing delay.

• 한국전자통신학회논문지
• /
• 제14권1호
• /
• pp.49-54
• /
• 2019

음향채널을 주로 사용하는 수중통신환경은 지상통신환경과 달라 통신 서비스를 구축함에 있어 수중환경에 적합하게 전송성능을 분석하는 것이 필요하며, 통신망의 일반적 성능 뿐 아니라 통신 서비스별 전송 대상 트래픽의 전송성능을 분석하여 통신서비스에 적절한 트래픽처리 방안의 강구가 요구된다. 본 연구에서는 수중 MANET(Mobile Ad-hoc Network)에서 비디오 트래픽의 전송 성능을 분석하고 이 결과를 토대로 비디오 트래픽 전송 방안을 제시한다. 본 연구는 NS(Network Simulator)-3에 기반한 컴퓨터 시뮬레이션을 이용하여 수행하며, 전송 성능으로는 처리율, 전송지연, 패킷손실율을 사용한다.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제12권4호
• /
• pp.1854-1868
• /
• 2018

A wireless body-sensor network (WBSN) refers to a network-configured environment in which sensors are placed on both the inside and outside of the human body. The sensors are much smaller and the energy is more constrained when compared to traditional wireless sensor network (WSN) environments. The critical nature of the energy-constraint issue in WBSN environments has led to numerous studies on the reduction of energy consumption of WBSN sensors. The transmission-power-control (TPC) technique adjusts the transmission-power level (TPL) of sensors in the WBSN and reduces the energy consumption that occurs during communications. To elaborate, when transmission sensors and reception sensors are placed in various parts of the human body, the transmission sensors regularly send sensor data to the reception sensors. As the reception sensors receive data from the transmission sensors, real-time measurements of the received signal-strength indication (RSSI), which is the value that indicates the channel status, are taken to determine the TPL that suits the current-channel status. This TPL information is then sent back to the transmission sensors. The transmission sensors adjust their current TPL based on the TPL that they receive from the reception sensors. The initial TPC algorithm made linear or binary adjustments using only the information of the current-channel status. However, because various data in the WBSN environment can be utilized to create a more efficient TPC algorithm, many different types of TPC algorithms that combine human movements or fuse TPC with other algorithms have emerged. This paper defines and discusses the design and development process of an efficient TPC algorithm for WBSNs. We will describe the WBSN characteristics, model, and closed-loop mechanism, followed by an examination of recent TPC studies.

• 한국멀티미디어학회논문지
• /
• 제10권4호
• /
• pp.516-526
• /
• 2007

무선 메쉬 네트워크는 WLAN 기술뿐만 아니라, 센서 네트워크와의 연동을 통해 다양한 분야에 응용할 수 있으며, 유비쿼터스 네트워크 구현을 위한 핵심기술이라 할 수 있다. 그러나 WLAN은 ISM 대역을 전송 주파수 대역으로 사용하기 때문에, 최대 전력이 100mW로 제한된다. 최대 전력이 제한된 상황에서 WLAN기반의 메쉬 네트워크가 비용 효율적인 백본망의 역할을 수행하기 위해서는 장거리 전송을 위한 연구가 필수적이다. 따라서 본 논문에서는 실험 결과를 통해 무선 메쉬 네트워크 단점인 도달거리의 한계를 극복할 수 있는 방안을 제시하였으며 그 효과성을 보였다. 제안한 방법은 다양한 안테나의 적용 및 디바이스 드라이버의 함수 정의와 구현으로 장거리 전송과 전력효율을 높일 수 있었다.

• 방송공학회논문지
• /
• 제9권2호
• /
• pp.119-130
• /
• 2004

We have developed a prototype super-high-definition (SHD) digital cinema distribution system that can store, transmit, and display eight-million-pixel motion pictures that have the image quality of a 35-mm film movie. The system contains a movie server, a real-time decoder, and an SHB projector. Using a Gigabit Ethernet link and TCP/IP, the server transmits JPEG2000 compressed motion picture data streams to the decoder at transmission speeds as high as 300 Mbps. The received data streams are decompressed by the decoder, and then projected onto a screen via the projector. By using an enlarged TCP window, multiple TCP streams, and a shaping function to control the data transmission quantity, we achieved real-time streaming of SHD movie data at about 300 Mbps between Chicago and Los Angeles, a distance of more than 3000 km. We also improved the decoder performance to show movies with Image qualities of 450 Mbps or higher. Since UDP is more suitable than TCP for fast long-distance streaming, we have developed an SHD digital cinema UDP relay system, in which UDP is used for transmission over a fast long-distance network. By using four pairs of server-side-proxy and decoder-side-proxy, 450-Mbps movie data streams could be transmitted.

• 대한전기학회논문지:시스템및제어부문D
• /
• 제53권10호
• /
• pp.720-726
• /
• 2004

The data transmission over MVB(Multifunction Vehicle Bus) of TCN(Train Communication Network) is divided into the periodic transmission phase and the sporadic transmission phase. TCN standard recommends the event-polling method as the message transfer in the sporadic phase. However, since the event-polling method does not use pre-scheduling to the priority of the messages, it is inefficient for the real-time systems. To schedule message transmission, a master node should know the priority of message to be transmitted by a slave node prior to the sporadic phase, but the existing TCN standard does not support any protocol for this. This paper proposes the slave frame bit-stuffing algorithm, with which a master node gets the necessary information for scheduling and includes the simulation results of the event-polling method and the proposed algorithm.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 1997년도 추계학술대회 논문집 학회본부
• /
• pp.584-587
• /
• 1997

In this paper, we present a transmission constraints modeling of carrier relay signal over ATM network. Since teleprotection system, which is used for protecting power transmission lines using telecommunications, has strict transmission delay constraints, it is a important problem to transmit teleprotection signals in future utilities' ATM networks when utilites' communications are integrated. Therefore, we considered the transmission constraints of carrier relay signal over ATM network and the transmission model system.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 1997년도 하계학술대회 논문집 D
• /
• pp.1041-1043
• /
• 1997

When a new transmission line is planned to construct, the system voltage and the conductor size of the transmission line should be decided by both economical and technical point of view. This paper presents a methodology to determine the optimal voltage for upgrading the transmission system voltage of existing the extra high voltage grid network by meeting the requirements of the transmission cost minimization as well as technical constraints of thermal limit and stability limit in the transmission line. As a case study, calculated are optimal voltages versus distance and capacity of a practically applicable transmission line with 4 bundles 2 circuits. By this study 400kV was selected as the next higher voltage for the existing 220kV Libyan grid network.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2001년도 추계학술대회 논문집 전력기술부문
• /
• pp.424-428
• /
• 2001

The methodologies of power transmission pricing are normally divided into two categories such as marginal cost method and embedded cost allocation method. This paper, first, discusses the possible problems that can occur when the marginal cost method is applied to pricing the transmission services. Next, the paper proposes a method to apply the power flow tracing to the transmission network charge. The result of the power flow tracing method is then used in MW-mile method to charge individual loads for the use of transmission network. Effectiveness of the algorithm is verified by computer simulations.

• 산업기술연구
• /
• 제27권B호
• /
• pp.235-243
• /
• 2007

Sensor network is used to obtain sensing data in various area. The interval to sense the events depends on the type of target application and the amounts of data generated by sensor nodes are not constant. Many applications exploit long sensing interval to enhance the life time of network but there are specific applications that requires very short interval to obtain fine-grained, high-precision sensing data. If the number of nodes in the network is increased and the interval to sense data is shortened, the amounts of generated data are greatly increased and this leads to increased amount of packets to transfer to the network. To transfer large amount of packets fast, it is necessary that the delay between successive packet transmissions should be minimized as possible. In Sensor network, since the Operating Systems are worked on the event driven, the Timer Event is used to transfer packets successively. However, since the transferring time of packet completely is varies very much, it is very hard to set appropriate interval. The longer the interval, the higher the delay and the shorter the delay, the larger the fail of transfer request. In this paper, we propose ESTEO which reduces the delay between successive packet transmissions by using SendDone Event which informs that a packet transmission has been completed.In ESTEO, the delay between successive packet transmissions is shortened very much since the transmission of next packet starts at the time when the transmission of previous packet has completed, irrespective of the transmission timee. Therefore ESTEO could provide high packet transmission rate given large amount of packets.