• Journal of the Institute of Electronics Engineers of Korea TC
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• v.43 no.11 s.353
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• pp.149-158
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• 2006

We proposed a method for improving a performance of TCP downstream between a desktop PC as a fixed host and a PDA as a mobile host in a wired and wireless network based on IEEE 802.11x wireless LAN. With data transmission between these heterogeneous terminals a receiving time during downstream is slower than that during upstream by 20% at maximum. The reason is that their congestion window size will be oscillated due to a significantly lower packet processing rate at receiver compared to a packet sending rate at sender. Thus it will cause to increase the number of control packets to negotiate their window size. To mitigate these allergies, we proposed two distinct methods. First, by increasing a buffer size of a PDA at application layer an internal processing speed of a socket receive buffer of TCP becomes faster and then the window size is more stable. However, a file access time in a PDA is kept nearly constant as the buffer size increases. With the buffer size of 32,768bytes the receiving time is faster by 32% than with that of 512bytes. Second, a delay between packets to be transmitted at sender should be given. With an inter-packet delay of 5ms at sender a resulting receiving time is faster by 7% than without such a delay.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.43 no.2 s.344
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• pp.60-75
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• 2006

The MPEG-21 Multimedia Framework initiative aims to support a wide range of networks and devices in the delivery and consumption of multimedia resources. One of the primary goals of MPEG-21 is universal multimedia access (UMA) through Digital Item Adaptation (DIA), which supports multimedia streaming to heterogeneous devices ensurung the same readability and seamlessness. We pioneer power saving of luminal devices with MPEG-21 DIA, so that the MPEG-21 DIA can also be used to support power saving, even though the framework is not primarily designed for power reduction and only limited power awareness is defined by DIA. We introduce several power-saving techniques conforming to MPEG-21 DIA specifications and show the dependency relation among introduced techniques. We achieve energy savings of up to $66\%$ in hand-held multimedia devices with minor QoS (quality of service) degradation.

• Journal of Korea Multimedia Society
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• v.2 no.1
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• pp.69-79
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• 1999

We have implemented the telecommunication management functions based on TMN (Telecommunications Management Network) architecture that is standardized by ISO/ITU-T. TMN has been developed to manage heterogeneous networks, services and equipment. In this paper, we first analyze the detailed functions of EMS (Element Management System) that performs core functions in the subnetwork management of TMN architecture. We propose an implementation method of EMS for efficient subnetwork management and verify its performance and functionality through detailed implementation and various testing. The proposed EMS consists of EML-Manager module and NML-Agent module. The EML-Manager module controls NEL (Network Element Layer) through the CMIP operations on the managed-objects. The NML-Agent module processes the requests from NMS (Network Management System) in upper layer. We have implemented NMS that performs only the NML-Manager function to test the proposed EMS, and we have used NE-Agent that was designed and implemented by the B-ISDN Lab. of Yeungnam University. The implemented EMS has three management functions: configuration management function, performance management function, and fault management function. We confirmed that the EMS operated normally as we tested the EMS. As further research works, the implementation of NMS with both NML-Manager function and SML-Agent function is required.

• Journal of Navigation and Port Research
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• v.37 no.3
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• pp.275-281
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• 2013

Ship Standard Network was submitted as a common subject of e-navigation by 81th IMO MSC 2005. This agenda was given an official status with strategy planning of e-navigation for Ship Standard Network after approval of WG program of 81th MSC 2006. Nowadays approximately 400 heterogeneous navigation and communication equipments are working on ships at sea. Standardization of ship network is to support exchanging various data efficiently. Among them, 4S network is defined as a wireless communication network between ship to ship and ship to shore which provides unceasing communication channel ship to shore. It has been expected to trigger various services and applications based on 4S network. However, no technologies and products has been appeared at fields yet. but now there's not specific technologies and developing products. In this paper, We developed a 4S multiple media switching server and a ship-land information exchange system to overcome the heterogeneity and provide efficient communication environments.. The performance of the implemented system was verified by TTA(Telecommunications Technology Association) V&V(Verification and Validation).

• The KIPS Transactions:PartC
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• v.17C no.3
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• pp.271-280
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• 2010

For the next generation mobile communication system, diverse wireless network techniques such as beyond 3G LTE, WiMAX/WiBro, and next generation WLAN etc. are proceeding to the form integrated into the All-IP core network. According to this development, Beyond 3G integrated into heterogeneous wireless access technologies must support the vertical handover and network to be used of several radio networks. However, unified management of each network is demanded since it is individually serviced. Therefore, in order to solve this problem this study is introducing the theory of Common Radio Resource Management (CRRM) based on Generic Link Layer (GLL). This study designs the structure and functions to support the vertical handover and propose the vertical handover algorithm of which policy-based and MCDM are composed between LTE and WLAN systems using GLL. Finally, simulation results are presented to show the improved performance over the data throughput, handover success rate, the system service cost and handover attempt number.

• 한국HCI학회:학술대회논문집
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• 2007.02a
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• pp.1051-1056
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• 2007

In current web-based systems, it is generally recognized that one way flow of information from providers to users can cause the static problem of document structure. Therefore, information update frequency and interaction between providers and users are quiet slow. Monopolized information can obstruct the free user's access and heterogeneous format and different protocols also make users difficult to retrieve and to collect information. To resolve these problems, in this study, we introduce the Web 2.0 to move toward the user's participation and share based on the social network and the OAI protocol to improve the free access and the interoperability on bibliographic information for Life Science and then design the bibliographic information network for life science. This network has four main functions such as: 1) Open Repository function that can make up user community for sharing and data exchange. Data such as article, seminar material, research note and research report are considered in design. 2) Open Collection function that can collect and store the metadata on distributed bibliographic information networks, 3) Open Access function that can manage the metadata in the open access environment, and 4) Administration function that can monitor the user activity and statistics and can inspect the registered data.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.48 no.12
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• pp.17-27
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• 2011

Most of the previous mobility management protocols such as IETF MIPv4/6 and its variants standardized by the IETF do not support global seamless handover because they require partially changes of the existing network infrastructure. In this article, we propose a simple mobility management protocol (SMMP) which can support global seamless handover between homogeneous or heterogeneous wireless networks. To do this, the SMMP employs separate location management function as DMMS to support global user and service mobility and the bidirectional tunnels are dynamically constructed to support seamless IP mobility by using the IEEE MIH extension server, which is extended the IEEE 802.21 MIH standards. The detailed architecture and functions of the SMMP have been designed. Finally, the mathematical analysis and the simulation have been done. The performance results show the proposed SMMP outperforms the existing MIPv6 and HMIPv6 in terms of handover latency, packet loss, pear signal noise ratio (PSNR).

• Journal of Broadcast Engineering
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• v.25 no.4
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• pp.560-568
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• 2020

In recent years, as network technology develops, the usage of streaming services by users is increasing. However, the complexity of streaming services is also increasing due to various terminal environments. Even when streaming the same content, it is necessary to re-encode the content according to the type of service. In order to solve the complexity and latency of the streaming service, Moving Picture Experts Group (MPEG) has standardized the Common Media Application Format (CMAF). In addition, as content transmission using a communication network becomes possible, the Republic of Korea's Ultra High Definition (UHD) broadcasting standard has been enacted as a hybrid standard using a broadcasting network and a communication network. The hybrid service enables various services such as transmitting additional information of contents or providing user-customized contents through a communication network. The Republic of Korea's UHD transmission standard utilizes MPEG Media Transport (MMT), and Mobile MMT is an extension of MMT to provide mobile network-specific functions. This paper proposes a method of inserting CMAF contents suitable for various streaming services using signaling messages of MMT and Mobile MMT. In addition, this paper proposes a model for content insertion system in heterogeneous network environment using broadcasting and communication networks, and verifies the validity of the proposed technology by checking the result of content insertion.

• Journal of the Korea Computer Industry Society
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• v.3 no.8
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• pp.963-980
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• 2002

Software reengineering is making various research for solutions against problem of maintain existing systems. Reengineering has a meaning of development of software on exizting systems through the reverse engineering auf forward engineering. Most of the important concepts used in reengineering is composition that is restructuring of the existing objects. Is there a compiler that can compile a program written in a traditional procedural language (like C or Pascal) and generate a Java bytecode, rather than an executable code that runs oかy on the machine it was compiled (such as an a.out file on a Unix machine)\ulcorner This type of compiler may be very handy for today's computing environment of heterogeneous networks. In this paper we present a software system that does this job at the binary-to-binary level. It takes the compiled binary code of a procedural language and translates it into Java bytecode. To do this, we first translate into an assembler code called Jasmin [7] that is a human-readable representation of Java bytecode. Then the Jasmin assembler converts it into real Java bytecode. The system is not a compiler because it does not start at the source level. We believe this kind of translator is even more useful than a compiler because most of the executable code that is available for sharing does not come with source programs. Of course, it works only if the format of the executable binary code is known. This translation process consists of three major stages: (1) analysis stage that identifies the language constructs in the given binary code, (2) initialization stage where variables and objects are located, classified, and initialized, and (3) mapping stage that maps the given binary code into a Jasmin assembler code that is then converted to Java bytecode.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.19 no.9
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• pp.1719-1729
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• 1994

In this paper, an adaptive CAC(Connection Admission Control) method is proposed. The adaptive CAC uses traffic estimates derived from both traffic parameter specified by user and cell flow measurements. Traffic estimation using user-specified parameters is performed at every moment of connection request or connection release by recursive formula which makes real-time calculation possible. Traffic estimation using cell flow measurement is carried out when the number of connected calls does not change during a measurement reflection period-renewal period. The most import ant thing for the traffic estimation using cell flow measurement is the determination of the length of a renewal period to trace a real traffic flow with an allowable time lag and the measurement reflection ratio(MRR) both to reduce the portion of overestimation and to avoid underestimation of real traffic flow. To solve these problems, the adaptive CAC updates renewal period and MRR adaptively according to the number of connections and the elapsed time after last connection or release respectively. Performance analysis for the proposed method is evaluated in several aspects for the cases of both homogeneous and heterogeneous bursty traffic. Numerical examples show the adaptive CAC method has the better performance compared with conventional CAC method based on burst model from the both utilization and QOS point of view.