• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.11C
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• pp.1498-1509
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• 2004

In this paper, we evaluate the performance of a noncoherent OOK (On-Off Keying) UWB (Ultra Wide Band) system based on power detection with noise power calibration and noise power windowing for ubiquitous sensor network applications in typical indoor wireless channels. Utilizing noise power calibration and noise power windowing, the current noise information can be initially or adaptively provided to determine suitable detection threshold value for signal demodulation. Simulation results show that the noncoherent OOK UWB system using noise power calibration achieves good BER (Bit Error Rate) performance which is favorably comparable to that of the system using the ideal adaptive threshold, while maintaining simple receiver structure. However, despite the serious loss of the data transmission rate, the performance improvement by noise power windowing is not so remarkable. furthermore, these performance results are similarly maintained in BEE 802.15 Task Group 3a UWB indoor channel model, and it is also revealed that the BER performance can be significantly improved by increasing the pulse repetition rate.

• Journal of Broadcast Engineering
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• v.10 no.3
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• pp.297-312
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• 2005

The multimedia traffic of continuous video and audio data via streaming service accounts for a significant and expanding portion of the Internet traffic. This streaming data delivery is mostly based on RTP with UDP. However, UDP does not support congestion control. For this reason, UDP causes the starvation of congestion controlled TCP traffic which reduces its bandwidth share during overload situation. In this paper, we propose a new TCP-friendly rate control scheme called 'TF-RTP(TCP-Friendly RTP)'. In the congested network state, the TF-RTP exactly estimates the competing TCP's throughput by using the modified parameters. Then, it controls the sending rate of the video streams. Therefore, the TF-RTP adjusts its sending rate to TCP-friendly and fair share with competing TCP traffics. Through the simulation, we prove that the TF-RTP correctly estimates the TCP's throughput and improves the TCP-friendliness and fairness.

• Journal of Broadcast Engineering
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• v.24 no.6
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• pp.1053-1063
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• 2019

Recently, tile-based streaming that transmits one 360 video in several tiles, is actively being studied in order to transmit these 360 video more efficiently. In this paper, for the transmission of high-definition 360 video corresponding to user's viewport in tile-based streaming scenarios, a system of assigning the quality of tiles at each tile by applying the saliency map generated by existing network models is proposed. As a result of usage of Motion-Constrained Tile Set (MCTS) technique to encode each tile independently, the user's viewport was rendered and tested based on Salient360! dataset, streaming 360 video based on the proposed system results in gain to 23% of the user's viewport compared to using the existing high-efficiency video coding (HEVC).

• Proceedings of the Korea Contents Association Conference
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• 2008.05a
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• pp.116-120
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• 2008

Smart Camera provides intelligent vision functionalities which can interpret captured video, extract context-aware information and execute a necessary action in real-timeliness in addition to the functionality of network cameras which transmit the compressed acquired videos through networks. Intelligent vision algorithms demand tremendous computations so that real-time processing of computation of intelligent vision algorithms as well as compression and transmission of videos simultaneously is too much burden for a single CPU. Davinci processor of Texas Instruments is a popular ASSP(Application Specific Standard Product) which has dual core architecture of ARM core and DSP core and provides various I/O interfaces as well as networking interface and video acquiring interface necessary for developing digital video embedded applications. In this paper, we report the results of designing and implementing S/W for Davinci-based smart camera. We implement a face detection as an example of vision application and verify the implementation works well. In the future, for the development of a smart camera with more broad and real-time vision functionalities, it is necessary to study about more efficient vision application S/W architecture and optimization of vision algorithms on DSP core of Davichi processor.

• Journal of Satellite, Information and Communications
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• v.7 no.1
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• pp.65-74
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• 2012

The QoS guarantee for the forward link in satellite communication networks is very important because there are a variety of packets with multiplexing. Especially, the packets are processed depending on the available bandwidth in satellite network changing the wireless channel state in accordance with weather condition. The DVB-S2 increases the transmission efficiency by applying the adaptive coding and modulation (ACM) techniques as a countermeasure of rain attenuations. However, the channel estimation algorithm is required to support the ACM techniques that select the MODCOD values depending on the feedback data transmitted by RCSTs(Return Channel via Satellite Terminal) because satellite communication networks have a long propagation delay. In this paper, we proposed the channel estimation algorithm using rain attenuation values and reference data and the packet scheduling scheme to support the QoS and fairness. As a result of performance evaluation, we showed that proposed algorithm exactly predicts the channel conditions and supports bandwidth fairness to the individual RCST and guarantees QoS for user traffics.

• Journal of KIISE:Computing Practices and Letters
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• v.8 no.5
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• pp.598-606
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• 2002

We suggest a distributed communication and management methodology using PC to PC Query multicasting strategy for efficient management of medical images produced by DICOM(Digital Imaging and Communications in Medicine) Modalities. It is absolutely necessary to reduce strict degradation of PACS system due to large sire of medical images and their very high transport rates. DICOM PC to PC Component is composed of a Service Manager to execute requested queries, a Communication Manager to take charge of file transmission, and a DICOM Manager to manage stored data and system behavior Each Manager itself is a component to search for requested file by interaction or to transmit the file to other PCs. Distributed management and transformation of medical information based on PC to PC Query multicasting methodology will enhance performance of central server and network capacity, reducing overload on both. We organize three major components for system operation. Each component is implemented as Agent. Communication between agents uses XML encoded Agent Communication Language.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.1 no.2
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• pp.81-89
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• 2008

Improved EKF suggests variable path prediction to reduce the event traffic caused by the information sharing among multi-users in networked virtual environment. The three dimensional virtual space is maintained consistently by endless status information exchange among dispersed users, and periodic status transmission brings traffic overhead in network. By using the error between the measured movement trace of dynamic information and the EKF predicted, we propose the method applied to predict the mobile packet of dynamic data which is simultaneously changing. And, the simulation results of DIS dead reckoning algorithms and EKF path prediction is compared here. It followed the specific path and while moving, the proposed method which it proposes predicting with DIS dead reckoning algorithm and to compare to the mobile path of the actual object and it got near it predicts the possibility of knowing it was.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2006.05a
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• pp.95-98
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• 2006

Data collected by sensors in field are transmitted to the base station gathering all of data. Because sensors have to gather data in surroundings and periodically transmit data to the base station, it makes energy consumed much. In this paper, we propose the scheme that is to avoid traffic congestion with achievement of energy efficiency, so collected data is transmitted efficiently. This is to adjust transmission rate differently in case of increasing or decreasing traffic and minimize the energy consumption with setting ideal options up basic CSMA(Carrier Sense Multiple Access) protocol in each sensor. Through the simulation, we find the ideal CSMA options and apply the proposed scheme of traffic control mechanism to them, then show energy efficiency and effective traffic control mechanism.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.19 no.1
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• pp.50-60
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• 2015

A Block-Time-Bounded Time Division Multiple Access (BTB-TDMA) medium access control protocol, which estimates the propagation delay of nodes according to their location and moving velocity information, has been proposed for underwater acoustic networks. BTB-TDMA provides nodes with their transmission schedules by a time block that is a time unit, newly designed for BTB-TDMA. In this paper, we investigate how the receiver collision, that is induced by the asymmetry between node's uplink and downlink propagation delay due to its mobility, affects the performance of BTB-TDMA. To do this, we analytically obtain the collision rate, the channel access delay, and the channel utilization by considering the asymmetry of propagation delay. Then, simulations are extensively performed with respect to the length of a time block by varying the number of nodes, the network range, and the node's velocity. Thus, the simulation results can suggest performance criteria to determine the optimal length of a time block which minimizes the collision rate and concurrently maximizes the channel access delay and the channel utilization.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.15 no.2
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• pp.339-346
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• 2011

In the existing RF communication based WPAN environment, a lowering of battery span and interference problem among sensors occur because the value of output is set and transmitted steadily when the system on sensor is initialized. Therefore, this paper proposes a framework and a transmit method with low power which decreases the electricity consumption by properly controling transmit power of opponent by received signal strength indicator(RSSI) of each sensor. The system proposes a power-lowering method by controling transmit power properly by the transmit intensity of the connected sensor after being affected by the transmit intensity of surrounded sensor. The framework that is proposed in this paper includes data transmit module, transmit power manager module, transmit power searching module, signal transmit module, and signal receiving module.