• KSII Transactions on Internet and Information Systems (TIIS)
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• v.13 no.7
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• pp.3369-3385
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• 2019

There are various research challenges in vehicular ad hoc networks (VANETs) that need to be focused until an extensive deployment of it becomes conceivable. Design and development of a scalable routing algorithm for VANETs is one of the critical issue due to frequent path disruptions caused by the vehicle's mobility. This study aims to provide a novel road-aware routing protocol for vehicular networks named as Two-level hierarchical Hybrid Road-Aware (THERA) routing for vehicular ad hoc networks. The proposed protocol is designed explicitly for inter-vehicle communication. In THERA, roads are distributed into non-overlapping road segments to reduce the routing overhead. Unlike other protocols, discovery process does not flood the network with packet broadcasts. Instead, THERA uses the concept of Gateway Vehicles (GV) for the discovery process. In addition, a route between source and destination is flexible to changing topology, as THERA only requires road segment ID and destination ID for the communication. Furthermore, Road-Aware routing reduces the traffic congestion, bypasses the single point of failure, and facilitates the network management. Finally yet importantly, this paper also proposes a probabilistical model to estimate a path duration for each road segment using the highway mobility model. The flexibility of the proposed protocol is evaluated by performing extensive simulations in NS3. We have used SUMO simulator to generate real time vehicular traffic on the roads of Gangnam, South Korea. Comparative analysis of the results confirm that routing overhead for maintaining the network topology is smaller than few previously proposed routing algorithms.

• Proceedings of the Korean Information Science Society Conference
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• 2003.10a
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• pp.598-600
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• 2003

이동 Ad Hoc 네트워크는 무선 채널 특성으로 인해 많은 보안상 위협에 노출될 수 있으므로 인증, 무결성, 기밀성 등의 보안 서비스를 제공하기 위한 키 관리 메커니즘이 요구된다. 그런데 Ad Hoc 네트워크는 중앙 집중적인 관리 노드의 부재, 동적인 위상 변화, 통신 자원의 제약 등의 특성을 고려하여 키 관리 메커니즘을 설계하도록 요구하고 있다. 따라서 본 논문에서는 클러스터 기반의 Ad Hoc 네트워크에서 ID 기반의 임계치 암호화 기법을 사용하여 공개키의 사전 분배 가정을 제거함으로써 토폴로지의 확장성과 유연성을 반영하고, 분산적이며 확장성있는 키분배 서비스가 가능하게 하였다. 또한 클러스터간에 교환되는 메시지의 무결성을 보장하기 위한 클러스터 MAC키 협상 방안, 헤드와 클러스터 내 특정 멤버간의 보안 채널 구축 통신하고자 하는 클러스터 멤버 호스트간에 안전하게 세션키를 생성, 분배하는 메커니즘 등을 제안하였다.

• Journal of KIISE:Information Networking
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• v.36 no.5
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• pp.425-436
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• 2009

In recent years, the user demands have increased for multimedia service of high quality over the broadband convergence network. These rising demands for high quality multimedia service led the popularization of various user terminals and large scale display equipments, which needs a variety type of QoS (Quality of Service). In order to support demands for QoS, numerous research projects are in progress both from the perspective of network as well as end system; For example, at the network perspective, QoS guaranteeing by improving of internet performance such as Active Queue Management, while at the end system perspective, SVC (Scalable Video Coding) encoding scheme to guarantee media quality. However, existing AQM algorithms have problems which do not guarantee QoS, because they did not consider the essential characteristics of video encoding schemes. In this paper, it is proposed to solve this problem by deploying the TS- AQM (Temporal Scalability Active Queue Management) which employs the differentiated packet dropping for dependency of the temporal level among the frames, based on SVC encoding characteristics by exploiting the TID (Temporal ID) field of the SVC NAL unit header. The proposed TS-AQM guarantees multimedia service quality through video decoding reliability for SVC streaming service, by differentiated packet dropping when congestion exists.

• Journal of the Korea Society for Simulation
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• v.15 no.1
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• pp.87-95
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• 2006

We need to check into when a security system is newly developed, we against cyber attack which is expected in real network. However it is impossible to check it under the environment of a large-scale distributive network. So it is need to simulate it under the virtual network environment. SSFNet is a event-driven simulator which can be represent a large-scale network. Unfortunately, it doesn't have the module to simulate security functions. In this paper, we added the IDS module to SSFNet. We implement the IDS module by modeling a key functions of Snort. In addition, we developed some useful functions using Java language which can manipulate easily a packet for network simulation. Finally, we performed the simulation to verify the function if our developed IDS and Packets Manipulation. The simulation shows that our expanded SSFNet can be used to further large-scale security system simulator.

• Journal of KIISE:Databases
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• v.32 no.3
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• pp.228-242
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• 2005

The projected clustering seeks to find clusters in different subspaces within a high dimensional dataset. We propose an algorithm to discover near optimal projected clusters without user specified parameters such as the number of output clusters and the average cardinality of subspaces of projected clusters. The objective function of the algorithm computes projected energy, quality, and the number of outliers in each process of clustering. In order to minimize the projected energy and to maximize the quality in clustering, we start to find best subspace of each cluster on the density of input points by comparing standard deviations of the full dimension. The weighting factor for each dimension of the subspace is used to get id of probable error in measuring projected distances. Our extensive experiments show that our algorithm discovers projected clusters accurately and it is scalable to large volume of data sets.

• KIPS Transactions on Software and Data Engineering
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• v.3 no.8
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• pp.293-298
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• 2014

Detecting and understanding the changes between RDF data is crucial in the evolutionary process, synchronization system, and versioning system on the web of data. However, current researches on detecting changes still remain unsatisfactory in that they did neither consider the large scale of RDF data nor accurately produce the RDF deltas. In this paper, we propose a scalable and effective change detection using a MapReduce framework which has been used in many fields to process and analyze large volumes of data. In particular, we focus on the structure-based change detection that adopts a strategy for the comparison of blank nodes in RDF data. To achieve this, we employ a method which is composed of two MapReduce jobs. First job partitions the triples with blank nodes by grouping each triple with the same blank node ID and then computes the incoming path to the blank node. Second job partitions the triples with the same path and matchs blank nodes with the Hungarian method. In experiments, we show that our approach is more accurate and effective than the previous approach.

• Industrial Engineering and Management Systems
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• v.9 no.3
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• pp.285-293
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• 2010

To obtain visible and traceable information from the supply chain, HW/SW standards for the EPC global network, which process electronic product code (EPC) data read from Radio frequency identification (RFID) tags, are regarded as the de facto industry standard. Supply chain participants install information service systems and provide logistics information to partners by following the EPCglobal architecture framework. Although quality of service (QoS) is essential for providing dependable and scalable services as pointed out by Auto-ID Lab, only a few models for the performance analysis of QoS-related work have been developed in the context of EPC information service systems. Specifically, doing so allows alternative design choices to be tested in an easy and cost-effective manner and can highlight potential performance problems in designs long before any construction costs are incurred. Thus, in this study we construct a model of an EPC information service system for the purposes of performance analysis and designing a dependable system. We also develop a set of building blocks for analytical performance models. To illustrate how the model works, we determine the characteristics of an EPC information service system and then select a combination of these proven modeling concepts. We construct a performance model that considers the response time and shows how to derive meaningful performance values. Finally, we compare the analytical results to measurements of the EPC information service system.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.8
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• pp.4077-4091
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• 2017

This paper presents the design of a broadcasting scenario and system for an 8K-resolution content. Due to an 8K content is four times larger than the 4K content in terms of size, many technologies such as content acquisition, video coding, and transmission are required to deal with it. Therefore, high-quality video and audio for 8K (ultra-high definition television) service is not possible to be transmitted only using the current terrestrial broadcasting system. The proposed broadcasting system divides the 8K content into four 4K contents by area, and each area is hierarchically encoded by Scalable High-efficiency Video Coding (SHVC) into three layers: L0, L1, and L2. Every part of the 8K video content divided into areas and hierarchy is independently treated. These parts are transmitted over heterogeneous networks such as digital broadcasting and broadband networks after going through several processes of generating signal messages, encapsulation, and packetization based on MPEG media transport. We propose three methods of generating streams at the sending entity to merge the divided streams into the original content at the receiving entity. First, we design the composition information, which defines the presentation structure for displays. Second, a descriptor for content synchronization is included in the signal message. Finally, we define the rules for generating "packet_id" among the packet header fields and design the transmission scheduler to acquire the divided streams quickly. We implement the 8K broadcasting system by adapting the proposed methods and show that the 8K-resolution contents are stably received and serviced with a low delay.

• Journal of Korea Multimedia Society
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• v.3 no.2
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• pp.148-156
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• 2000

This paper proposed that an MPLS-based VPN using next-generation If switches and appropriate set of traffic engineering algorithms is the best way to implement QoS-capable IP VPNs. While ATM-based solution would not rely scalable the number of connections becomes too large, MPLS-based VPNs’ efficiency could be confirmed network delay time through performance evaluation. And we evaluated the performance about the If VPN based on proposed MPLS, at the result of evaluation. We figured out that delay increased more slowly in case of VPN based on MPLS comparing with the VPN based on ATM which has rapid delay increasement. Therefore we confirm that the VPN based on MPLS has high speed of packet processing and high degree of network efficiency through the performance evaluation.