• Proceedings of the Korean Information Science Society Conference
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• 2005.11a
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• pp.67-69
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• 2005

현재까지의 보안 라우팅 프로토콜은 유무선에 관계 없이 페이로드 부분은 암호화가 되더라도 패킷 헤더의 내용이 평문 형태로 무방비하게 노출되며 라우팅 경로가 안전하게 보장되더라도 악의적인 노드에게 경로가 알려지는 것을 차단 할 수 없다. 또한 유선 환경과는 달리 Ad-hoc 네트워크와 같은 무선 상황에서는 전파의 전방향성 때문에 송수신 범위 내에 있는 노드들이 평문 형태의 라우팅 정보 및 송수신 노드의 정보를 수집하는 것을 방지 할 수 없다. 본 논문에서 제안하는 은닉 라우팅 프로토콜은 한쌍의 노드가 비대칭키 암호화 알고리즘을 통해 공유한 초증가 수열을 통해 송수신 노드를 은닉하면서도 정당한 수신 노드만 자신이 수신 노드임을 알 수 있는 기법을 제공함으로서 악의적인 노드가 라우팅 경로에 대한 정보를 수집하는 것을 원천적으로 차단한다.

• Proceedings of the Korea Information Processing Society Conference
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• 2000.10b
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• pp.1161-1164
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• 2000

손실된 패킷에 대해 재전송이 곤란한 실시간 멀티미디어 전송에서 패킷 손실이 발생하였다면 하이브리드 압축 방식의 시간적, 공간적 의존성 때문에 에러가 한 프레임 내(공간)와 여러 프레임(시간)간에 전파되는 현상을 보인다. 이러한 현상으로 인해 저하된 수신품질을 복구하기 위해 주기적으로 INTRA 모드인 I-프레임을 삽입해야 한다. 본 논문에서는 RTP 기반의 실시간 멀티미디어 전송에서 위와 같은 패킷 손실 이후 에러의 축적 때문에 발생하는 수신측 품질 저하를 복구하기 위한 I-프레임을 단순히 고정 주기적으로 삽입하는 대신 네트워크 상황과 수신측 피드백 정보인 FMB를 이용하여 적응적으로 삽입하는 방법을 제안한다.

• Korean journal of communication and information
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• v.36
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• pp.7-41
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• 2006

This study criticizes the wave of liberalization, privatization, thoughtless and uncontrolled over-competition in the electronic communication networks area. This criticism is based on the 'transport economics' on one side, the 'network neutrality debate' on the other side. Through these standpoints, this study insists that it needs to deal with a social agenda related to the problems such as unplanned and unbalanced development of electronic communication networks, double/tripple-investment in the communication industry, conflicts among network companies and the decline of public values. Also does this study stress on the new ideas in the electronic communication network policy and planning to manage these problems. Electronic communication networks are converging and their borders are blurred. As a result of these flows, the field of information technology, media and contents is faced with radical changes. These changes could be so critical and complicated that nobody can diagnose their multi-level implications. However, the one thing sure is that we should start from the communication networks to think and control a communication system. Therefore, we should discuss and plan the now-and-future of communication infrastructure and its management. we need not only a market mentality but also a socio-cultural mentality. In this respect, this study does insist that it requires the vision of digital democracy and democratic communication ecology to put the steps toward social communication system.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.12 no.5
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• pp.61-66
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• 2012

We propose a traffic information service system for which traffic data are transmitted over vehicle ad-hoc network from neighbor vehicles, and eventually provided to the traffic information center through a few gateway vehicles which are capable of inter-working with the infrastructure network like 3G. The center broadcasts the traffic information through the FM radio. The proposed scheme allows collecting and analyzing traffic status of large areas without incorporating separated monitoring systems, e.g., probe cars and enables to provide accurate traffic information to drivers in timely manner. We also evaluate its performance by ns-3 simulation.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.8
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• pp.1631-1636
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• 2015

With the advance of wireless communication technology in terrestrial area, underwater communication is also evolving very fast from a simple point-to-point transmission to an elaborate networked communications. Underwater acoustic channel has quite different features comparing with the terrestrial radio channel in terms of propagation delay, Doppler shift, multipath, and path loss. Thus, existing technologies developed for terrestrial communication might not work properly in underwater channel. Especially medium access control (MAC) protocols which highly depend on propagation phenomenon should be newly designed for underwater network. CSMA/CA has drawn lots of attention as a candidate of underwater MAC protocol, since it is able to resolve a packet collision and the hidden node problem. However, a received signal could be degraded by the interferences from the nodes locating outside the receiver's propagation radius. In this paper, we study the effects of interference on the CSMA/CA based underwater network. We derived the SNR with the interference using the sonar equation and analyzed the degradation of the RTS/CTS effects. These results are compared with the terrestrial results to understand the differences. Finally we summarized the design considerations in CSMA/CA based underwater network.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.10A
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• pp.784-795
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• 2009

An accurate positioning estimation in the wireless sensor networks (WSN) is very important in which each sensor node is aware of neighbor conditions. The multi-hop positioning estimation technique is considered as one of the suitable techniques for the WSN with many low power devices. However geographical holes, where there is no sensor node, may severely decrease the positioning accuracy so that the positioning error can be beyond the tolerable range. Therefore in this paper, we analyze error factors of DV-hop and hole effect to obtain node's accurate position. The proposed methods include boundary node detection, distance level adjustment, and unreliable anchor elimination. The simulation results show that the proposed method can achieve higher positioning accuracy using the hole detection and enhanced distance calculation methods compared with the conventional DV-hop.

• Knowledge Management Research
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• v.24 no.3
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• pp.195-215
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• 2023

In the telecommunications service industry, until now, it has been possible for Network Operators (NOs) to secure a competitive advantage to increase subscribers and profits through network investment. However, amid a big change to digital economy, network investment fails to lead to increase profits. These days platform companies without holing network infrastructure have a more competitive advantage and take more profits. This makes NOs gradually lose interest in network investment. The purpose of this paper is to find policy measures to promote network investment in digital economy. Specifically, we identify the factors influencing the network investment and promising policy measures energizing the investment, and then analyze their priorities and derive policy implications through Analytic Hierarchy Process (AHP) and Analytic Network Process (ANP). The results of this paper show that market competition is more preferred to public intervention in promoting network investment. However, in order to guarantee and expand the universal access to network, it is necessary to consider expanding the role of the public, focusing on non-economic areas.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.16 no.4
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• pp.31-40
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• 2016

In vehicular ad-hoc networks (VANETs), vehicles sense information on emergency incidents (e.g., accidents, unexpected road conditions, etc.) and propagate this information to following vehicles and a server to share the information. However, this process of emergency message propagation is based on multiple broadcast messages and can lead to broadcast storms. To address this issue, in this work, we use a novel approach to detect the vehicles that are farthest away but within communication range of the transmitting vehicle. Specifically, we discuss a signal-to-noise ratio (SNR)-based linear back-off (SLB) scheme where vehicles implicitly detect their relative locations to the transmitter with respect to the SNR of the received packets. Once the relative locations are detected, nodes that are farther away will set a relatively shorter back-off to prioritize its forwarding process so that other vehicles can suppress their transmissions based on packet overhearing. We evaluate SLB using a realistic simulation environment which consists of a NS-3 VANET simulation environment, a software-based WiFi-IP gateway, and an ITS server operating on a separate machine. Comparisons with other broadcasting-based schemes indicate that SLB successfully propagates emergency messages with latencies and hop counts that is close to the experimental optimal while reducing the number of transmissions by as much as 1/20.

• Journal of Intelligence and Information Systems
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• v.14 no.1
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• pp.117-129
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• 2008

The cost-based scheduling work has been done in both the Operations Research (OR) and Artificial Intelligence (AI) literature. To deal with more realistic problems, AI-based heuristic scheduling approach with non-regular performance measures has been studied. However, there has been little research effort to develop a full inter-job cost propagation algorithm (CPA) for different jobs having multiple downstream and upstream activities. Without such a CPA, decision-making in scheduling heuristics relies upon local, incomplete cost information, resulting in poor schedule performance from the overall cost minimizing objective. For such a purpose, we need two types of CPAs : intra-job CPA and inter-job CPA. Whenever there is a change in cost information of an activity in a job in the process of scheduling, the intra-job CPA updates cost curves of other activities connected through temporal constraints within the same job. The inter-job CPA extends cost propagation into other jobs connected through precedence relationships. By utilizing the cost information provided by CPAs, we propose cost-based scheduling heuristics that attempt to minimize the total schedule cost. This paper develops inter-job CPAs that create and update cost curves of each activity in each search state, and propagate cost information throughout a whole network of temporal constraints. Also we propose various cost-based scheduling heuristics that attempt to minimize the total schedule cost by utilizing the cost propagation algorithm.

• Journal of KIISE:Databases
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• v.35 no.3
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• pp.208-217
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• 2008

Sensors have a function to gather environment-related information operating by small-size battery in sensor networks. The issue related with energy is still an important in spite of the recent advancements in micro-electro-mechanical-system(MEMS) related techology. Generally it is assumed that replacement or rechargement of battery power in sensor is not feasible and a message send operation may spend at least 1000 times battery than a local operation. Thus, there have been several kinds of research efforts to lessen the number of unnecessary messages by maintaining the information of the other neighboring(or all) sensors. In this paper, we propose an index structure based on parent-children relationship to the purpose. Namely, parent node gathers the set of location information and MBA per child. It's named PH and may allow to process the range query with higher accurate and small size information. Through extensive experiments, we show that our index structure has better energy consumption.