• Journal of the Institute of Convergence Signal Processing
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• v.8 no.4
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• pp.244-248
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• 2007

In this paper, we propose a novel self-networking and replaceable structure method for the ubiquitous multimedia. As the contents in the ubiquitous multimedia should be realistic and continuously updated in the real-time manner, an efficient scheme of a self-networking and replaceable structure is necessary. In the proposed method, the contents itself connects to the server or corresponding devices and updates itself autonomously. Also, we can reduce the total amount of data transmission comparing to the cases where the whole contents should be downloaded. A Markov chain model is introduced for the proposed structure in order to perform the throughput analysis. The whole mechanism is implemented in the wireless handset and also, various applications of the scheme are discussed.

• Journal of Communications and Networks
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• v.17 no.3
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• pp.275-285
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• 2015

To improve the efficiency of carrier sense multiple access (CSMA)-based medium access control (MAC) protocols, CSMA with collision resolution (CSMA/CR) has been proposed. In the CSMA/CR, a transmitting station can detect a collision by employing additional sensing after the start of a data transmission and then resolve the next collision that might occur by broadcasting a jam signal during a collision detection (CD) period. In this paper, we analyze the delay of a CSMA/CR based on a generic p- persistent CSMA model and obtain the minimum achievable delay of the CSMA/CR by finding the optimal length of the CD period according to the number of contending stations. Through this delay analysis, we also investigate the throughput-delay characteristics of the CSMA/CR protocol according to various parameters. Analysis and simulation results show that the CSMA/CR has a considerably lower delay and its throughput-delay characteristic is significantly improved than the conventional CSMA/CA and wireless CSMA/CD protocols.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2013.10a
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• pp.188-191
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• 2013

In this paper, in order to economize energy inside the vertical-type water treatment plant, a chamber-illumination-LED control board, which operates via nature light or human's touches, is proposed. Moreover, this illumination control process is contrived to be wirelessly monitored in real-rime. In addition, Zigbee communication code is programmed to implement the control board's function of wireless data transmission and automatic LED brightness control. The presented control method contrives brightness to be adjusted in real-time by dimming control, which means nature light changes control, so that the interior energy can realize the maximum energy conservation.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.11A
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• pp.1138-1146
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• 2006

It is very important for the sensor network to save battery capacity. Switching active mode to sleep mode is used for S-MAC protocol and expiring timer before end of the active part is used for T-MAC in order to extend battery life span. We proposed IS-MAC (Improved Sensor MAC) which gives more energy efficiency than S-MAC and T-MAC To improve energy efficiency in sensor network, we used the threshold value in buffer to transmit data packet and proposed the method to reduce the number of control packets which cause extra battery consumption. Based on the analytical results, we found that the proposed IS-MAC protocol shows better performance than conventional MAC protocols.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.1C
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• pp.113-119
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• 2009

The training sequence with the appropriate length for equalization and initial synchronization is necessary before sending the pure data in the burst transmission type DS-UWB system. The length of the training sequence is one of the factors which make throughput decreased. The noble structure with the variable length of the training sequence whose length can be adaptively tailored according to the channel conditions (CM1,CM2,CM3,CM4) in the DS-USB systems is proposed. This structure can increase the throughput without sacrificing the performance than the method with fixed length of training sequence considering the worst case channel conditions. Simulation results under IEEE 802.15.3a channel model show that the proposed scheme can achieve higher throughput than a conventional one with the slight loss of BER performance. And this structure can reduce the computation complexity and power consumption with selecting the short length of the training sequence.

• The Journal of the Korea institute of electronic communication sciences
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• v.7 no.1
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• pp.21-26
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• 2012

This paper presents a real-time image transferring and localization system utilizing HSDPA, a commercial wireless network system. A novel image compression algorithm is developed based on MPEG4 to comply with uploading bandwidth of 130 kbps and QVGA image transmission of 30 fps. Aiming at being embedded in moving vehicles, the proposed system has a small size, low power consumption, and robustness to disturbances. We validate the performance of the system by presenting captured images of transferring video and localization data. Our system can be applied to real-time surround monitoring in moving vehicles or real-time ecology observation in remote places.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37A no.12
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• pp.1065-1075
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• 2012

For the purpose of providing high data rate real-time services, radio transmission technologies (RTT) for ship ad-hoc network (SANET) based on the Recommendation ITU-R 1842-1 are designed. Physical layer parameters of SANET are contrived to meet the requirements of the specification. In order to improve the link reliability for SANET, in this paper, we investigate the performance of the SANET with the multiple antennas, where receive combining (RC), transmit diversity (TD), and beamforming (BF) are employed, respectively. Based on the analysis of the packet error rate (PER) under the highly correlated maritime wireless channel model, we select the efficient multiple antenna schemes for SANET to improve the link reliability. In addition, the optimal MCS levels for the single-carrier (SC) SANET with the bandwidth of 25 kHz, and the multi-carrier (MC) SANET with the bandwidth of 50 kHz and 100 kHz are finalized.

• Journal of the Institute of Convergence Signal Processing
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• v.3 no.1
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• pp.27-32
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• 2002

In this study, we fabricated the advanced telemetry system that transmitting media use radio frequency(RF) for the middle range measurement of the physiological signals and receiving media use optical for electromagnetic interference problem. The telemetry system within a size of 65$\times$125$\times$45mm consists of three parts: RF transmitter, optical receiver and physiological signal processing CMOS one chip. Advantages of proposed telemetry system is wireless middle range(50m) FM transmission, reduce electromagnetic interference to a minimum which enables a comfortable bed-side telemetry system. The monitoring system was designed in the structure of dual-processor for the real time processing. The use of the one channel in our study made it possible the real time wavelet transformation of electrocardiogram data of 360Hz, 16 bits for every 1.42 seconds.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.6 no.1
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• pp.84-97
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• 2012

M2M (Machine-to-Machine) Technology makes it possible to network all kinds of terminal devices and their corresponding enterprise applications. Therefore, several M2M platforms were developed in China in order to collect information from terminal devices dispersed all over the local places through 3G wireless network. However, when enterprise applications try to integrate with M2M platforms, they should be maintained and refactored to adapt the heterogeneous features and properties of M2M platforms. Moreover, syntactical and semantic unification for information sharing among applications and devices are still unsolved because of raw data transmission and the usage of distinguished business vocabularies. In this paper, we propose and develop an M2M Middleware to support agile application integration with M2M platform. This middleware imports the event engine and XML-based syntax to handle the syntactical unification, makes use of Ontology-based semantic mapping to solve the semantic unification and adopts WebService and ETL techniques to sustain multi-pattern interactive approach, in order to agilely make applications integrated with the M2M platform. Now, the M2M Middleware has been applied in the China Telecom M2M platform. The operation results show that applications will cost less time and workload when being integrated with M2M platform.

• Journal of Korea Multimedia Society
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• v.12 no.12
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• pp.1778-1786
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• 2009

Many sensor network applications have been developed for smart home, disaster management, and a wide range of other applications. These applications, however, generally assume a fixed base station as well as fixed sensor nodes. Previous research on sensor networks mainly focused on efficient transmission of data from sensors to fixed sink nodes. Recently there has been active research on mobile sink nodes, sink mobility is one of the most comprehensive trends for information gathering in sensor networks, but the research of an environment where both fixed sink nodes and mobile sinks are present at the same time is rather scarce. This paper proposes a scheme for context-aware by ubiquitous devices with the sink functionality added through fixed sinks under a previously-built, cluster-based multi-hop sensor network environment. To this end, clustering of mobile devices were done based on the fixed sinks of a previously-built sensor network, and by using appropriate fixed sinks, context gathering was made possible. By mathematical comparison with TTDD routing protocol, which was proposed for mobile sinks, it was confirmed that performance increases by average 50% in energy with the number of mobile sinks, and with the number of movements by mobile devices.