• Journal of Internet Computing and Services
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• v.21 no.2
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• pp.99-108
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• 2020

In this paper, we analyze the most suitable RA method among PAMA, DAMA, and RA classified by the multiple access method of satellite communication in the rapidly changing traffic environment according to the emergency and tactical situation. It suggests an alternative to improve the limit of output degradation. Based on the CRDSA protocol selected as the standard of DVB-RCS2 among the current satellite communication methods, CRDSA2R (Contention) maintains an optimal RA channel environment by checking the limitations in an environment where packet volume is rapidly increasing and observing channel load and channel conditions. We propose a Resolution Diversity Slotted ALOHA with Adaptive Random Access.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.20 no.6
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• pp.33-42
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• 2010

With the emergence of increasingly complex networks and diverse user terminals, demand for the next generation IPTV service is rapidly growing. It enables any content to seamlessly be reused on the diverse terminals as well as be broadcasted in real-time through the complex networks. In this paper, a novel security framework is proposed for the real-time and reusable IPTV services. The proposed framework is advantageous over the conventional content protection techniques in easily producing the scalable content with lightweight, perceptual, transcodable, and adjustable security features. It does not only ensure end-to-end security over the entire service range based on a single security mechanism, but also can control a level of security while dynamically transcoding the original content. This approach basically performs selective encryption during and after the compression using scalable video coding. The suitability of the proposed approach is demonstrated through experiments with a practical service scenario. Therefore, it is expected that security technology alone could practically contribute to creating new business opportunities for IPTV services.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.6A
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• pp.555-567
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• 2010

Unlike single-hop systems, multi-hop systems that use relay nodes assign a part of the overall resources to relay communications. If efficient resource allocation schemes are not adopted, this leads to a loss of resources. Moreover, because we may not be able to guarantee high-link performance due to the adjacent-cell interference in relay-based cellular systems, resource efficiency can be severely decreased. In this paper, we propose efficient resource allocation schemes for downlink relay-based networks in 3GPP (3rd Generation Partnership Project) LTE (Long Term Evolution)-Advanced systems. Unlike conventional schemes that have static resource regions for each data link, the proposed schemes dynamically allocate the resources of each link to resource blocks, by considering the channel state and the capacity of each link. We also propose resource overlapping schemes in which two different links overlap at the same resource region, so as to improve cell or user throughput performance. The proposed resource overlapping schemes do not require additional processes such as interference cancellation in users, thank to considering additional interference from resource overlapping in advance.

• Journal of Biosystems Engineering
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• v.7 no.2
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• pp.18-29
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• 1983

A low cost and versatile data acquisition system for the field and laboratory use was developed by using a single board microcomputer. Data acquisition system based on a Z80 microprocessor was built, tested and modified to obtain the present functional system. The microcomputer developed consists of 6 kB ROM, 5 kB RAM, 6-seven segment LED display, 16-Hex. key and 8 command key board. And it interfaces with an 8 channel, 12 bits A/D converter, a microprinter, EPROM programmer for 2716, and RS232C interface to transfer data between the system and HP3000 mini-computer manufactured by Hewlett Packard Co., A software package was also developed, tested, and modified for the system. This package included drivers for the AID converter, LED display, key board, microprinter, EPROM programmer, and RS232c interface. All of these programs were written in 280 assembler language and converted to machine codes using a cross assembler by HP3000 computer to the system during modifying stage by data transferring unit of this system, then the machine language wrote to the EPROM by this EPROM programmer. The results are summarized as follows: 1. Measuring program developed was able to control the measuring intervals, No. of channels used, and No. of data, where the maximum measuring speed was 58.8 microsec. 2. Calibration of the system was performed with triangle wave generated by a function generator. The results of calibration agreed well to the test results. 3. The measured data was able to be written into EPROM, then the EPROM data was compared with original data. It took only 75 sec. for the developed program to write the data of 2 kB the EPROM. 4. For the slow speed measurements, microprinter instead of EPROM programmer proved to be useful. It took about 15 min. for microprinter to write the data of 2 kB. 5. Modified data transferring unit was very effective in communicating between the system and HP3000 computer. The required time for data transferring was only 1~2 min. 6. By using DC/DC converting devices such as 78-series, 79-series. and TL497 IC, this system was modified to convert the only one input power sources to the various powers. The available power sources of the system was DC 7~25 V and 1.8 A.

• The Transactions of the Korea Information Processing Society
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• v.7 no.11S
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• pp.3651-3667
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• 2000

Recently, in the distributed multimedia environments based on internet, as radical growing technologies, the most of researchers focus on both streaming technology and distributed object thchnology, Specially, the studies which are tried to integrate the streaming services on the distributed object technology have been progressing. These technologies are applied to various stream service mamgements and protocols. However, the stream service management mexlels which are being proposed by the existing researches are insufficient for suporting the QoS of stream services. Besides, the existing models have the problems that cannot support the extensibility and the reusability, when the QoS-reiatedfunctions are being developed as a sub-module which is suited on the specific-purpose application services. For solving these problems, in this paper. we suggested a QoS Integrated platform which can extend and reuse using the distributed object technologies, and guarantee the QoS of the stream services. A structure of platform we suggested consists of three components such as User Control Module(UCM), QoS Management Module(QoSM) and Stream Object. Stream Object has Send/Receive operations for transmitting the RTP packets over TCP/IP. User Control ModuleI(UCM) controls Stream Objects via the COREA service objects. QoS Management Modulel(QoSM) has the functions which maintain the QoS of stream service between the UCMs in client and server. As QoS control methexlologies, procedures of resource monitoring, negotiation, and resource adaptation are executed via the interactions among these comiXments mentioned above. For constmcting this QoS integrated platform, we first implemented the modules mentioned above independently, and then, used IDL for defining interfaces among these mexlules so that can support platform independence, interoperability and portability base on COREA. This platform is constructed using OrbixWeb 3.1c following CORBA specification on Solaris 2.5/2.7, Java language, Java, Java Media Framework API 2.0, Mini-SQL1.0.16 and multimedia equipments. As results for verifying this platform functionally, we showed executing results of each module we mentioned above, and a numerical data obtained from QoS control procedures on client and server's GUI, while stream service is executing on our platform.