Graph-Theoretic Characterization of Nonblo cking Multi-log₂N Multiconnection Networks

車永煥 상지대학교 1994 論文集 Vol.15 No.-

본 논문에서는 다중접속을 지원하는 multi- log₂N 다중접속망의 rearrangeable 넌블럭킹 조건과 strictly 넌블럭킹 조건을 제시하였다. Rearrangeable 넌블럭킹 multi- log₂N 다중접속망을 위한 접속할당은 bipartite multigraph의 edge-coloring 알고리즘으로 해결됨을 보였다. Strictly 넌블럭킹 망의 접속할당을 위해서는 예측[5,6,9]과 달리 흥미롭게도 다중접속에 대한 넌블럭킹 조건들은 일대일접속에 대한 넌블럭킹 조건들과 같음을 보였다. In this paper, both rearrangeable nonblocking condition and strictly nonblocking condition are derived for the multi- log₂N multiconnection networks capable of supporting the multiconnection. It is shown that the edge-coloring algorithm for the bipartite multigraph can be used for the rearrangeable nonblocking connection assignment in the multi- log ₂N muticonnection network. As for the strictly nonblocking connection assignment, a polynomial time algorithm based on SIG(Subconnection-Intersection Graph)-coloring is presented. In contrast to the previous predictions[5,6,9], we show that, interestingly, the general nonblocking condititions for the multiconnection are the same as that for the one-to-one connection.

Routing for Enhancing Source-Location Privacy in Wireless Sensor Networks of Multiple Assets

Tscha, Yeong-Hwan The Korea Institute of Information and Commucation 2009 Journal of communications and networks Vol.11 No.6

In wireless sensor networks, a node that reports information gathered from adjacent assets should relay packets appropriately so that its location context is kept private, and thereby helping ensure the security of the assets that are being monitored. Unfortunately, existing routing methods that counter the local eavesdropping-based tracing deal with a single asset, and most of them suffer from the packet-delivery latency as they prefer to take a separate path of many hops for each packet being sent. In this paper, we propose a routing method, greedy perimeter stateless routing-based source-location privacy with crew size w (GSLP-w), that enhances location privacy of the packet-originating node (i.e., active source) in the presence of multiple assets. GSLP-w is a hybrid method, in which the next-hop node is chosen in one of four modes, namely greedy, random, perimeter, and retreat modes. Random forwarding brings the path diversity, while greedy forwarding refrains from taking an excessively long path and leads to convergence to the destination. Perimeter routing makes detours that avoid the nodes near assets so that they cannot be located by an adversary tracing up the route path. We study the performance of GSLP-w with respect to crew size w (the number of packets being sent per path) and the number of sources. GSLP-w is compared with phantom routing-single path (PR-SP), which is a notable routing method for source-location privacy and our simulation results show that improvements from the point of the ratio of safety period and delivery latency become significant as the number of source nodes increases.

정보통신 : 이동 호스트를 위한 개선된 이동성 관리 및 멀티캐스트 프로토콜

차영환(Tscha Yeong Hwan),성현경(Sung Hyeon Kyeong) 한국정보처리학회 1995 정보처리학회논문지 Vol.2 No.1

By intergrating technologies for portable computers, radio communications, and computer networking, the Land Mobile Computer Network(LMCN) is supposed to overcome the time and space limitation of present computer communication networks. However, because the MHs(mobile hosts) do move any time, the network connectivity is often changed causing temporarily duplicated, lost, or out-of-sequenced message delivery as well as frequent communications for maintainning the network connectivity. Previous works solved the problems through message flooding, used also in multicasting, resulting in high communication cost(i.e., number of communication messages). In this paper, new protocols for efficient mobility management and multicasting are proposed. The protocols define location update, handover, and multicasting procedure of a MH over a hierarchical LMCN architecture. The protocol specification is presented, and it is shown that the communication cost of the new protocols is superior to the existing ones in terms of the communication cost.

무선 센서 네트워크에서의 궤도 기반 콘텐츠 발간 및 구독을 위한 질의 이탈 방지

차영환(Yeong Hwan Tscha) 한국정보과학회 2005 정보과학회논문지 : 정보통신 Vol.32 No.4

This paper is concerned with the query slipping and its prevention for trajectory-based matchmaking service in wireless sensor networks. The problem happens when a query propagating along a subscribe trajectory moves through a publish trajectory without obtaining desired information, even though two trajectories intersect geometrically. There follows resubmission of the query or initiation of another subscribe trajectory. Thus, query slipping results in considerable time delay and in the worst, looping in the trajectory or query flooding the network. We address the problem formally and suggest a solution. First, the area where nodes are distributed is logically partitioned into smaller grids, and a grid-based multicast next-hop selection algorithm is proposed. Our algorithm not only attempts to make the trajectory straight but also considers the nodal density of recipient nodes and the seamless grid-by-grid multicast. We prove that the publishing and subscribing using the algorithm eventually eliminate the possibility of the slipping. It turns out that our algorithm dissipates significantly less power of neighbor nodes, compared to the non grid-based method, as greedy forwarding, and the fixed-sized grid approach, as GAF (Geographical Adaptive Fidelity) 본 논문은 무선 센서 네트워크에 있어서 궤도 기반 매취메이킹 서비스를 위한 질의 이탈 및 이의 방지에 관한 것이다. 이러한 문제는 정보 구독 궤도를 따라 전파되는 질의가 정보 발간 궤도와 기하학적으로는 겹침에도 불구하고 정보를 획득하지 못할 때 발생한다. 이에 따라 질의를 재 제출하거나 새로운 구독 궤도를 시작함으로 인한 시간 지연이 초래되어 최악에는, 궤도내의 루핑이나 네트워크 전체로의 메시지 범람을 야기한다. 이 문제를 정형적으로 다루고 그 해결책을 제시한다. 먼저, 노드들이 존재하는 영역을 논리적으로 작은 그리드들로 분할하고, 그리드 기반 멀티캐스트 다음-홉 선택 알고리즘을 제안한다. 제안 알고리즘은 궤도 설정을 직선형태로 유지하도록 시도함은 물론 수신 노드들의 분포 및 틈새 없는 그리드 단위의 멀티캐스트를 고려한다. 이러한 알고리즘에 의거하여 정보 발간 및 구독을 시행하는 경우 질의 이탈이 궁극적으로 방지됨을 증명한다. 제안 알고리즘이 탐욕적 송출과 같은 비 그리드 기반 알고리즘과 GAF와 같은 고정 크기의 그리드 접근법 보다 이웃 노드들의 전력을 더 적게 소모함을 알 수 있다.

센서 네트워크에서 위치 기밀 수준에 따른 더미 메시지생성

차영환(Yeong Hwan Tscha) 한국전자통신학회 2016 한국전자통신학회 논문지 Vol.11 No.9

센서 네트워크에서 광역 도청에 대응하여 기지국이나 근원지들의 위치 기밀을 유지하기 위해서는 일반적으로 더미 메시지들을 발행해야한다. 이 논문에서는 기지국과 근원지들 간에 통신 경로를 확보하는 한편, 요구되는 기밀 수준을 고려하여 일정 수의 노드들을 아무런 활동도 하지 않는 휴면 상태로 전환하도록 하여 전체 더미 메시지들의 발생을 줄이는 방법을 제안한다. 시뮬레이션을 통해 기지국과 근원지들 간의 경로 설정 성공률과 그들의 위치 기밀 수준을 검증한다. Dummy messages are usually generated for faking in preserving the location privacy of a sink or source against the global eavesdropping in wireless networks. In this paper, we propose a new method in which a certain number of nodes determined by considering the required privacy level are made to transit to the dormant state doing nothing so that the total number of dummy messages is reduced, while the paths from the sink to the sources are ensured. Through simulation we verify the success ratio of path establishments between the sink and a set of sources and the location privacy level of them.

컴퓨터 네트워크 : 이동 호스트들간의 경제성있는 통신을 위한 새로운 루팅 프로토콜

차영환(Tscha Yeong Hwan) 한국정보처리학회 1995 정보처리학회논문지 Vol.2 No.3

This paper is concerned with a routing protocol for cost-effective communications between mobile hosts on computer networks in which mobile hosts can move freely their physical positions. The proposed routing protocol consists of two protocols : one is called location registration protocol performing registration of the location information as the mobile host does move; the other one is called message transfer protocol which actually delivers a message to the destination mobile host. The detailed protocol's operational behavior and major characteristics are presented. And it is shown that out protocols are superior to previous ones, in terms of the communication cost(i.e., number of message) required for routing a message, and are functionally improved ones.

무선망에서의 신호도청에 대응하는 데이터 경로 은닉에 관한 연구

차영환(Yeong-Hwan Tscha) 한국전자통신학회 2020 한국전자통신학회 논문지 Vol.15 No.3

무선망에서 통신 경로상의 노드들은 데이터 전달 시마다 전자기적 신호를 방출하므로 일련의 발생 신호들을 포착하여 분석하면 해당 경로가 노출 및 탐지될 수 있다. 악의적 도청자에 대응하는 방법의 하나로는 특정노드들로 하여금 더미(거짓) 패킷을 생성하도록 하여 마치 데이터 경로상의 노드들처럼 보이도록 하는 것이다. 이 논문에서는 근원지와 도착지 간에 최단 경로를 한 번에 설정하면서 더미 패킷의 과도한 생성을 억제하는 패킷 전송 프로토콜을 제안한다. 시뮬레이션을 통해 통신 경로상의 노드 위치 기밀 수준을 검증한다. Nodes on a data communication path in a wireless network emit electro-magnetic waves whenever they transmit packets; thus, the path can be exposed and identified with capturing and analyzing a sequence of the signals emitted there. One of countermeasures against a malicious eavesdropper is to let certain nodes mimic the nodes on the data path in sending dummy packets. In this paper we propose a packet transfer protocol which establishes the shortest path between source-destination pair a time and restricts heavy generation of dummy packets. We verify the location-privacy of a node on the communication paths through simulation.

사면안정 공법 의사결정을 위한 사면 데이터베이스 시스템 구축

박지해(Ji-Hae Park),이규웅(Kyu-Woong Lee),차영환(Yeong-Hwan Tscha),지영환(Young-Hwan Ji),김기환(Ki-Hwan Kim),황영철(Yeong-Cheol Hwang),이승호(Seung-Ho Lee) 한국지반환경공학회 2008 한국지반환경공학회 학술발표회논문집 Vol.2008 No.-

Strictly Nonblocking Multi-Log₂N Network for Multicast Traffics

차영환 尙志大學校 生産技術硏究所 1999 生産技術論叢 Vol.7 No.-

본 논문에서는 multi-log₂N network 망이 일대다 접속 트래픽에 대해 엄밀하게 (strictly) 넌블럭킹일 충분조건으로 n이 짝수일 때 최소 ??의 log₂N 망들을 병렬 연결하여 구성하여야 함을 보였다. 여기서 N=2ⁿ, ??이며, ??는 χ와 같거나 작은 정수 중 제일 큰 수를 나타낸다. 이와 같이 해당 주제에 대한 미해결 문제를 해결하고, ??인 ?? 망으로의 확장에 대해 다루었다. In this paper, we show that, for even n (respectively, for odd n), a multi-log₂N network is strictly nonblocking for a one-to-many connection traffic if it is designed by vertically stacking, at least, δn /4 + 1 (respectively,δ/2(n-1) + 1 planes of a log₂N network together where N=2ⁿ, ??, and ?? denotes the greatest integer less than or equal to χ. Thus we give answer to open problem left on the subject, and extend the result to a ?? network in which ?? i.e., base 2 is replaced with a positive integer k (>1).

이동 호스트를 위한 효과적인 멀티캐스트 프로토콜

차영환 尙志大學校 生産技術硏究所 1997 生産技術論叢 Vol.- No.1

Multicasting to mobile hosts(MHs) based on broadcasting may result in overloaded unnecessary message even if the number of recipient MHs is relatively small compared with that of nodes in a network. In this paper we propose an improved multicast protocol in which messages are selectively flooded respectively to only the (radio) cells within some distance from the cell where a destination MH resides most recently, so that the number of unnecessary messages carried in multicasting can be reduced. Detailed procedures for the protocol are provided and protocol properties are proven.