• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.4B
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• pp.403-410
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• 2004

In general communication system is composed of processor subsystems, I/O processor subsystems and data storage device subsystems those are classified as their functions. In order to improve the data reliability, all subsystems are redundant. Storage device keeps the operational information such as system related information and charging information, and such informations must be stored in non-volatile memory. Flash memory and battery backup memory are commonly used as the non-volatile storage devices. But such kind of memories are expensive per unit capacity and data can't be restored when lost while not being backed up. In this paper we develop a redundant storage device to store a lot of data safely and reliably in communication system. The device consists of micro-controller, FPGA and hard disk It provides many functions those are rebuilding, automatic remapping, host service and remote host service. Also it is designed to provide host service while rebuilding is being done in order not to interrupt the communication services. The developed device can be used instead of expensive storage device like flash memory in various communication systems.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.5C
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• pp.439-444
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• 2010

In this paper, we derive and analyze the channel capacity of the spread spectrum watermarking (SSW) system as an information-theoretic point of view in closed-form approximation formula in order to analyze the effect of the wireless multipath/shadowing channel. It is important to analyze the channel capacity to transmit an additive data through existing wireless channel by the SSW system. From the results, we confirm that the channel capacity of the SSW system can be determined by the HWR, WNR, PN length and host sampling frequency. Also, we verified that the variation of the channel capacity when the SSW system applied to Nakagami-m fading and Log-normal shadowing channel. The results of this paper can be applied to general spread spectrum watermarking system.

• Convergence Security Journal
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• v.8 no.1
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• pp.1-7
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• 2008

The hacking method came to be more complicated, became program ant it was automated. That is hacking trend of recent times. Before, The password crack, catch root authority is trend of hacking which uses the vulnerability of server. Hacker attack network or all of domain not some host. Web application system at hacking technique develops and improve transmitted data through the network shows many vulnerability. The massive data are transmitted through the network without encipherment filtering. It will be able to bring about the neck of a bottle actual condition which is serious in security system because of the network where the user comes to be many it leads and the data which is delivered comes to be many. In this paper, we propose web application system to prevent overload from bottleneck in encipherment system. It can solve security key trust problem in encoding and decoding with public key infrastructure.

• Journal of KIISE
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• v.44 no.11
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• pp.1219-1230
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• 2017

Real-time streaming services over the Internet have increased with the explosive growth of the various mobile platforms, with a focus on smart phones, and the demand for them is growing. In addition, the bandwidth occupied by the streaming services over the Internet had already surpassed 50% in 2010. Because of the shortage of network bandwidth for multimedia services traffic, restrictions on quality and capacity will become more and more serious. CCN is a future Internet architecture that improves how existing host-based Internet architecture handles content-oriented structure, but it is designed for the transmission of general contents and is not suitable for transmitting real-time streaming contents. In this paper, we focus on the inefficient aspects of CCN and propose a hierarchical grade-based scheme for real-time service for a more efficient environment in real-time streaming services. Experiments have shown better performance in terms of bandwidth, network load, and reliability.

• Journal of KIISE:Information Networking
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• v.29 no.3
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• pp.242-252
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• 2002

When a Mobile IP handoff occurs, the packets in flight can be lost because they are tunneled based on out-of-date location information. In this parer, we propose an enhanced handoff protocol that achieves no packet loss during Mobile IP handoff over a wireless LAN. Our handoff protocol predicts the next foreign agent that a mobile host is to visit by using: the information from the data link layer of wireless LAN. After that, when a Mobile IP handoff occult, the current foreign agent forwards the packets destined to a mobile host to the predicted foreign agent which buffers them. This eliminates packet loss and reduces the packet forwarding delay. Our handoff protocol is simulated using the Network Simulator-2 (ns-2) and shows the substantial performance enhancement of TCP with much less overhead up to 6.2 times compared to standard Mobile IP.

• The Transactions of the Korea Information Processing Society
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• v.4 no.3
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• pp.775-791
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• 1997

This paper describes Real-Time Trasport Protocol(RTTP) that procisdes for a ; user cmnnection-oriented sercices with performance fuarantee.Assuming that eral-time network services will be provided,RTTP solves provlems at end-hosts.RTTP has defined a new set of primitives for real-time communication servies based on the analysis of uwer requirements on various applications.Introducing the notion of Abstract Network Layer independent of real networks.RTTP's implementation scheme can be applied to various netwoeks.The study also intriduces an inplemenation strategy, provide prdeictability of protocol processing time,wich should be known a priori for performance guarantee.Intermally,RTTP has a set of QoS translation rules that change a user'w performance requirements to the equivalent network QoS paramenters.RTTP also introuduces a new apportunistic error control mehtod that can trade-off between overhead and error corredtion according to a uwer's requirement on reliability.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.11
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• pp.1-6
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• 2019

Multicast is an efficient method for real-time transmission in many multimedia applications. It is important to recover lost packets and to manage multicast groups according to the network status in order to improve the reliability of multicast transmissions. In this paper, we propose a method that can efficiently recover lost packets in a large multicast group. In the proposed method, we create a recovery cluster (RC) using a multicast domain (MD) for recovery of lost packets. In the conventional methods, clusters send a request message for lost packets to the senders in order to recover the packets lost from many multicast applications. This increases packet delay time and overhead because of the feedback messages and retransmitted packets. In the proposed method, we improve these problems using the RC, which consists of many MDs (which have overlay multicast senders), and many cluster heads (CHs). We divide the message into blocks, and divide each block into many segments for packet recovery using the CHs. When packet loss occurs, all CHs share the segment information and recover the lost segments at the same time. Simulation results show that the proposed method could improve the packet recovery ratio by about 50% compared to the conventional methods.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.6 no.7
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• pp.993-1000
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• 2002

In this paper, we design the CORBA-based Mobile Agent Model (CMAM) which has the capability of the efficient work processing in distributed environment through sensing network traffic and searching the optimal path for migration nodes of mobile agent. In case existing mobile agent model is given various works from user, the network overhead and traffic are increased by increasing of execution module size. Also, if it happens a large quantity of traffics due to migration of nodes according to appointment of the passive host(below node) routing schedule by user, it needs much cost for node search time by traffic. Therefore, in this paper, we design a new mobile agent m()del that assures the reliability of agent's migration through dynamic act on the specific situation according to appointment of the active routing schedule and can minimize agent's work processing time through optimal path search. The proposed model assigns routing schedule of the migration nodes actively using an extended MAFFinder. Also, for decreasing overhead of network by agent's size, it separates the existing mobile agent object by mobile agent including only agent calling module and push agent with work executing module based on distributed object type of CORBA. Also, it reduces the required time for round works of mobile agent through the optimal path search of migration nodes.

• Journal of Internet Computing and Services
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• v.19 no.1
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• pp.37-47
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• 2018

The number of capabilities of Internet of Things (IoT) devices will exponentially grow over the next years. These devices may generate a vast amount of time-constrained data. In the context of IoT, data management should act as a layer between the objects and devices generating the data and the applications accessing the data for analysis purposes and services. In addition, most of IoT services will be content-centric rather than host centric to increase the data availability and the efficiency of data delivery. IoT will enable all the communication devices to be interconnected and make the data generated by or associated with devices or objects globally accessible. Also, fog computing keeps data and computation close to end users at the edge of network, and thus provides a new breed of applications and services to end users with low latency, high bandwidth, and geographically distributed. In this paper, we propose Edge-Fog cloud-based Hierarchical Data Delivery ($EFcHD^2$) method that effectively and reliably delivers IoT data to associated with IoT applications with ensuring time sensitivity. The proposed $EFcHD^2$ method stands on basis of fully decentralized hybrid of Edge and Fog compute cloud model, Edge-Fog cloud, and uses information-centric networking and bloom filters. In addition, it stores the replica of IoT data or the pre-processed feature data by edge node in the appropriate locations of Edge-Fog cloud considering the characteristic of IoT data: locality, size, time sensitivity and popularity. Then, the performance of $EFcHD^2$ method is evaluated through an analytical model, and is compared to fog server-based and Content-Centric Networking (CCN)-based data delivery methods.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2002.11a
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• pp.550-554
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• 2002

In this paper, we design the CORBA-based Mobile-Agent Model (CMAM) which has the capability of the efficient work processing in distributed environment through sensing network traffic and searching the optimal path for migration nodes of mobile agent. In case existing mobile agent model is given various works from user, the network overhead and traffic are increased by increasing of execution module size. Also, if it happens a large quantity of traffics due to migration of nodes according to appointment of the passive host(node) muting schedule by user, it needs much cost for node search time by traffic. Therefore, in this paper, we design a new mobile agent model that assures the reliability of agent's migration through dynamic act on the specific situation according to appointment of the active routing schedule and can minimize agent's work processing time through optimal path search. The proposed model assigns routing schedule of the migration nodes actively using an extended MAFFinder. Also, for decreasing overhead of network by agent's size, it separated by mobile agent including oかy agent calling module and push agent with work executing module based on distributed object type of CORBA. Also, it can reduce the required time for round works of mobile agent through the optimal path search of migration nodes.