• Journal of Korea Multimedia Society
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• v.10 no.1
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• pp.13-25
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• 2007

A cache is used for optimization of query forwarding in the Grid database. To decrease network transmission cost, frequently used data is cached from meta database. Existing cache management method has a unbalanced resource problem, because it doesn't manage replicated data in each node. Also, it increases network cost by cache misses. In the case of data modification, if cache is not updated, queries can be transferred to wrong nodes and it can be occurred others nodes which have same cache. Therefore, it is necessary to solve the problems of existing method that are using unbalanced resource of replica and increasing network cost by cache misses. In this paper, cache management method for query forwarding optimization is proposed. The proposed method manages caches through cache manager. To optimize query forwarding, the cache manager makes caching data from lower loaded replicated node. The query processing cost and the network cost will decrease for the reducing of wrong query forwarding. The performance evaluation shows that proposed method performs better than the existing method.

• Journal of Korea Multimedia Society
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• v.9 no.11
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• pp.1410-1420
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• 2006

In this paper, a replica update propagation method for cost optimization of request forwarding in the Grid database is proposed,. In the Grid database, the data is replicated for performance and availability. In the case of data update, update information is forwarded to the neighbor nodes to synchronize with the others replicated data. There are two kinds of update propagation method that are the query based scheme and the log based scheme. And, only one of them is commonly used. But, because of dynamically changing environment through property of update query and processing condition, strategies that using one propagation method increases transmission cost in dynamic environment. In the proposed method, the three classes are defined from two cost models of query and log based scheme. And, cost functions and update propagation method is designed to select optimized update propagation scheme from these three classes. This paper shows a proposed method has an optimized performance through minimum transmission cost in dynamic processing environment.

• Journal of KIISE:Information Networking
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• v.32 no.4
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• pp.525-534
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• 2005

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 toms 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)

• 한국정보통신설비학회:학술대회논문집
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• 2002.08a
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• pp.242-245
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• 2002

정부는 시내전화 및 지능망서비스(080)에 대하여 2003년 상반기부터 번호이동성 서비스를 제공하도록 규정하고 있다. 번호이동성 서비스는 사업자간에는 경쟁을 활성화시키고 가입자에게는 이용의 편리함을 제공하기 위한 서비스로 서비스 유형으로는 서비스제공자 이동성(Service Provider Portability), 위치이동성(Location Portability) 및 서비스이동성(Service Portability)이 있다. 그리고 서비스 구현방식으로는 크게 교환기 기반 방식(Remote Call Forwarding)과 지능망방식(All Call Query, Query on Release)이 있다. 국내 번호이동성 서비스 적용 방식은 지능망 방식인 QoR 방식으로 결정되었으나 최근의 통신환경의 변화를 감안하여 서비스 도입 초기의 효율적인 서비스 도입을 위한 종합적인 재검토가 이루어지고 있다. 이에 따라 본 논문에서는 QoR 방식의 번호이동성 서비스를 위하여 교환기에서 필요한 필요 기능 및 기술적 문제점들을 교환계위별로 고찰하고자 한다.

• Proceedings of the Korea Information Processing Society Conference
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• 2003.05b
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• pp.1145-1148
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• 2003

본 논문에서는 Ad-hoc 망의 멀티캐스트 라우팅 프로토콜인 ODMRP(On-Demand Multicast Routing Protocol)에서 효율적인 유니캐스트 라우팅 프로토콜을 제안한다. ODMRP는 네트워크 상에서 멀티캐스트그룹의 송신원으로부터 수신원에 이르는 경로상에 있는 노드들을 Fe(Forwarding Group) 노드로 선출하여 이들이 해당 멀티 캐스트그룹에 속하는 패킷을 플러딩 하도록 함으로써 데이터를 전송하는 방안이다. 이러한 ODMRP에서는 어느 한 노드가 유니캐스트 모드로(end-to end) 데이터를 전송해야 하는 경우 경로를 찾기 위해 주기적인 플러딩 과정을 거쳐야 하고 이로 인해 오버헤드가 발생하게 된다. 본 논문에서는 이 문제점을 해결하고자 유니캐스트 모드에서 송신원에서 찾은 경로를 DR 라우팅 테이블에 저장해두고 데이터를 보련 때 DR 라우팅 테이블의 정보를 참조함으로써 수신원에서의 불필요한 컨트롤 패킷(JOIN QUERY, JOIN REPLY)으로 인한 트래픽을 줄일 수 있는 방안을 제안한다. 또한 제안된 방식이 기존의 ODMRP 방식보다 데이터의 전송 시간과 경로를 찾는 시간에 있어 개선되었음을 시뮬레이션을 통해 입증한다.

• Nuclear Engineering and Technology
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• v.54 no.10
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• pp.3587-3594
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• 2022

A distributed high-speed data acquisition and monitoring system for the RF negative ion source at Huazhong University of Science and Technology (HUST) is developed, which consists of data acquisition, data forwarding and data processing. Firstly, the data acquisition modules sample physical signals at high speed and upload the sampling data with corresponding absolute-time labels over UDP, which builds the time correlation among different signals. And a special data packet format is proposed for the data upload, which is convenient for packing or parsing a fixed-length packet, especially when the span of the time labels in a packet crosses an absolute second. The data forwarding modules then receive the UDP messages and distribute their data packets to the real-time display module and the data storage modules by PUB/SUB-pattern message queue of ZeroMQ. As for the data storage, a scheme combining the file server and MySQL database is adopted to increase the storage rate and facilitate the data query. The test results show that the loss rate of the data packets is within the range of 0-5% and the storage rate is higher than 20 Mbps, both acceptable for the HUST RF negative ion source.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.5B
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• pp.253-263
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• 2005

This paper proposed a mobile multicast technique to satisfy end-to-end QoS for various user requirements in mobile network environment. In order to provide seamless mobility, fast handoff technique was applied. By using L2 mobile trigger, it was possible to minimize remarkable amount of packet loss by delay occurred during handoff. To provide efficient multicast, concept of hierarchy was introduced to Xcast++, which results in a creation of HXcast++. HXcast++ optimized transfer path of multicast and reduced expensive multicast maintenance costs caused by frequent handoff. Suggestion of GMA (Group Management Agent) mechanism allows joining to group immediately without waiting IGMP Membership query during handoff. GMA mechanism will minimize the delay for group registration process and the resource usage due to delay of withdrawal process. And also use of buffering & forwarding technique minimized packet loss during generation of multicast tree. IntServ/RSVP was used to provide End-to-End QoS in local domain and DiffServ was used in global domain. To minimize reestablishment of RSVP session delay, extended HXcast++ control messages ware designed to require PATH message. HXcast++ proposed in this thesis is defined as multicast technique to provide end-to-end QoS and also to satisfy various user requirements in mobile network environment.

• Journal of Internet Computing and Services
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• v.6 no.3
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• pp.55-70
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• 2005

In order to provide mobile hosts with multicast service in mobile communication environment, we proposed a multicast mechanism named HXcast++ which is an extended version of the existing Xcast++ with hierarchical architecture, We assured that mobile hosts could get multicast service through an optimal path regardless of their location by making DR(Designated Router) join a group on behalf of the mobile hosts, In this present research we introduced hierarchical architecture in order to reduce the maintenance cost resulting from frequent handoff. We also proposed a GMA (Group Management Agent) based group management mechanism which enables the mobile hosts to join the group without waiting for a new IGMP Membership Query. A fast handoff method with L2 Mobile Trigger was, in this work, employed in order to reduce the amount of the packet loss which occurs as a result of the handoff, We also managed to curtail the packet loss caused by the latency of the group join by using a buffering and forward mechanism.

• Journal of KIISE:Information Networking
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• v.35 no.4
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• pp.251-267
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• 2008

In this paper, we present a distributed topology control algorithm for constructing an optimized topology having a minimal search-time in unstructured peer-to-peer network. According to the proposed algorithm, each node selects the best nodes having higher hit-ratio than other nodes as many as the number being exponentially proportional to the hit-ratio of the node itself, and then it connects to them. The ensemble behavior of the proposed algorithm is very similar to the recrystrallizing phenomenon that is observed in nature. There is a partial order relationship among the hit-ratios of most nodes of constructed topology. Therefore once query message visits a node, it has a higher hit-ratio than the node that was visited last by the message. The query message even sent from freeloader can escape to the node having high hit-ratio by one hop forwarding, and it never revisits any freeloader again. Thus the search can be completed within a limited search time. We also propose the Chain-reactive search scheme using the constructed topology. Such a controlled multicasting reduces the query messages by 43 percent compared to that of the naive Gnutella using broadcasting, while it saves the search time by 94 percent. The search success rate of the proposed scheme is 99 percent.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.5
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• pp.887-898
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• 2009

Conventional routing protocols proposed for wireless sensor networks (WSNs) cannot fully accommodate the characteristics of WSNs. In particular, although it is possible to largely obtain benefits in the solution of energy consumption and global identification problems through applying position information, there are few protocols that actively apply such position information. In the case of geographical and energy aware routing (GEAR) that is a typical algorithm, which uses position information, it does not fully represent the characteristics of WSNs because it is limited to forward query messages and assumed as fixed network environments. The routing protocols proposed in this paper defines the direction of data, which is routed based on the position information of individual and target nodes, in which each node configures its next hop based on this direction and routes signals. Because it performs data-centric routing using position information, it does not require certain global identifications in order to verify individual nodes and is able to avoid unnecessary energy consumption due to the forwarding of packets by defining its direction.