• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.32 no.1B
• /
• pp.53-60
• /
• 2007

We investigate the end-to-end delay bounds in large scale networks with Differentiated services (DiffServ) architecture. It is generally understood that networks with DiffServ architectures, where packets are treated according to the class they belong, can guarantee the end-to-end delay for packets of the highest priority class, only in lightly utilized cases. We focus on tree networks, which are defined to be acyclic connected graphs. We obtain a closed formula for delay bounds for such networks. We show that, in tree networks, the delay bounds exist regardless of the level of network utilization. These bounds are quadratically proportional to the maximum hop counts in heavily utilized networks; and are linearly proportional to the maximum hop counts in lightly utilized networks. Considering that tree networks, especially the Ethernet networks are being accepted more and more for access networks as well as provider networks, we argue that based on these delay bounds DiffServ architecture is able to support real time applications even for a large network. Throughout the paper we use Latency-Rate (LR) server model, with which it has proven that FIFO and Strict Priority are LR servers to each flows in certain conditions.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.34 no.3B
• /
• pp.255-263
• /
• 2009

In this paper, we propose an adaptive beacon scheduling algorithm to control a reception period of actual data according to variation of amount of traffic in IEEE 802.15.4 LR-WPAN(Low Rate-Wireless Personal Area Network) with the cluster-tree topology. If a beacon interval is shortened, the amount of the traffic a node receives can be increased while consumption of the energy can be also increased. In this sense, we can achieve optimal on orgy consumption by controlling the beacon interval when the amount of data to be received is being decreased. The result of simulation using NS-2 shows that the proposed algorithm improves performances in terms of packet loss rate and end-to-end delay compared with algorithm using a fixed beacon interval. For a design of cluster-tree based LR-WPAN managing delay-sensitive services, the proposed algorithm and the associated results can be applied usefully.

• The Journal of the Institute of Internet, Broadcasting and Communication
• /
• v.8 no.5
• /
• pp.173-179
• /
• 2008

An ad hoc network is multi-hop wireledss formed by mobile node without infrastructure. Due to the mobility of nodes in mobile ad hoc networks, the topology of network changes frequently. In this environments, multicast protocols are faced with the challenge of producing multi-hop routes and limitation of bandwidth. We compare the performance of two multicast routing protocols for mobile ad hoc networks - Serial Multiple Disjoint Tree Multicast Routing Protocol (Serial MDTMR) and Adaptive Core Multicast Routing Protocol (ACMRP). The simulator is implemented with GloMoSim.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.20 no.1
• /
• pp.35-43
• /
• 1996

A computer program for automatic deriving the symbolic equations of motion for robots using the programming language MATHEMATICA has been developed. The program, developed based on the Lagrange formalism, is applicable to the closed chain robots as well as the open chain robots. The closed chains are virtually cut open, and the kinematics and dynamics of the virtual open chain robot are analyzed. The constraints are applied to the virtually cut joints. As a result, the spatial closed chain robot can be considered as a tree structured open chain robot with kinematic constraints. The topology of tree structured open chain robot is described by a FATHER array. The FATHER array of a link indicates the link that is connected in the direction of base link. The constraints are represented by Lagrange multipliers. The parallel robot, DELTA, having three-dimensional closed chains is modeled and simulated to illustrate the approach.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.23 no.6
• /
• pp.1538-1545
• /
• 1998

System reliability has been a major concern since the beginning age of the electronic digital computers. One of the modest ways of increasing reliability is to design fault-tolerant system. This paper propose a construction mechanism of fault-tolerant system for the general graph topology. This system has several spare nodes. Up to date, fault-tolerant system design is applied only to loop and tree networks. But they are very limited cases. New algorithm of this paper tried to have a capability which can be applied to any kinds of topologies without such a many restriction. the algorithm consist of several steps : minimal diameter spaning tree extraction step, optimal node decision step, original connectivity restoration step and finally redundancy graph construction step.

• The KIPS Transactions:PartA
• /
• v.15A no.6
• /
• pp.345-350
• /
• 2008

Recently, a HyperStar network HS(2n,n) has been introduced as a new interconnection network of new topology for parallel processing. HyperStar network has properties of hypercube and star graph, further improve the network cost of a hypercube with the same number of nodes. In this paper, we show a construction algorithm of edge-disjoint spanning trees in HyperStar network HS(2n,n). Also, we prove that edge-disjoint spanning tree by the algorithm is optimal.

• Asian-Australasian Journal of Animal Sciences
• /
• v.19 no.10
• /
• pp.1369-1378
• /
• 2006

This is the first study in which genetic variability and relationships of a large number of Japanese chicken breeds were revealed along with those of several foreign breeds by using microsatellite DNA polymorphisms. Twenty-eight breeds (34 populations) of native Japanese chickens and seven foreign breeds or varieties were analyzed. The mean number of alleles per locus, the proportion of the polymorphic loci, and the expected average heterozygosity ranged from 1.75 to 4.70, from 0.55 to 1.00, and from 0.21 to 0.67, respectively. Microsatellite alleles being unique to a particular population were detected in some populations. The $D_A$ genetic distance between populations was obtained from allele frequency for every pair of the populations to construct a neighbor-joining tree. According to the phylogenetic tree, excluding a few exceptions, native Japanese chicken breeds and foreign breeds were clearly separated from each other. Furthermore, the tree topology divided native Japanese chickens into four main classes, which was almost in accordance with the classification based on body morphology; that is, (1) Cochin type, (2) Malay type, (3) layer type, and (4) intermediate type between Malay and layer types. This is the first finding for native Japanese chickens.

• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.44 no.10
• /
• pp.55-63
• /
• 2007

Multicast is an efficient transport mechanism for community communications and MANET is recently regarded as a promising solution for support ubiquitous computing as an underlying network technology. However, it is hard to deploy multicast mechanism into MANET owing to scarce resources in wireless networks and unpredictable changes in network topology. Several multicast mechanisms have been proposed in the literature to overcome the limitations. Especially, overlay multicasting schemes present several advantages over network based multicasting schemes. Yet, the overlay multicasting schemes still introduce redundant data transmissions that waste network bandwidth and battery of relay nodes. As a result the performance of the network is degraded. To reduce the redundancy, we propose an efficient way to construct an overlay structure as a multicast data delivery tree that utilizes a branch node which belongs to the tree. By using network simulation, we show that the proposed scheme presents higher packet delivery ratio and lower transmission cost than previously proposed schemes.

• Journal of information and communication convergence engineering
• /
• v.8 no.2
• /
• pp.212-218
• /
• 2010

In wireless sensor networks (WSNs), both efficient energy management and Quality of Service (QoS) are important issues for some applications. For creating robust networks, real-time services are usually employed to satisfy the QoS requirements. In this paper, we proposed a hierarchical real-time MAC (medium access control) protocol for (m,k)-firm constraint in wireless sensor networks shortly called HRTS-MAC. The proposed HRTS-MAC protocol is based on a dynamic priority assignment by (m,k)-firm constraint. In a tree structure topology, the scheduling algorithm assigns uniform transmitting opportunities to each node. The paper also provides experimental results and comparison of the proposed protocol with E_DBP scheduling algorithm.

• Proceedings of the Korean Information Science Society Conference
• /
• 2006.06d
• /
• pp.40-42
• /
• 2006

무선 센서 네트워크는 제한된 배터리를 갖는 노드로 토폴로지를 구성한다. 이러한 이유 때문에 전체 네트워크의 수명을 극대화하고 라우팅에 에너지 효율성을 고려하여 토폴로지를 구성하는 것이 중요하다. 네트워크 토폴로지는 전송범위에 의해 결정되며 노드의 고정된 전송범위로 인한 에너지 비효율성 문제를 해결하는 방법으로 최적의 전송범위 혹은 MST(Minimum Spanning Tree)기반으로 토폴로지를 구성하는 대안이 있지만 최적의 솔루션은 아니다. 본 논문에서는 단계에 따라 전송범위를 차별화시켜 라우팅을 수행하는 DR(Differential Routing)을 제안하였다. DR은 전송범위에 기반하여 최적의 토폴로지를 구성한다. 그리고 무선 센서 네트워크의 특정한 통신 패턴에 맞게 트리 구성 단계와 데이터 수집 단계의 전송범위를 차별화시켜 전송파워를 조절함으로써 전체 네트워크의 수명 극대화, 파티션 방지, 그리고 에너지 효율성을 향상시킨 알고리즘이다. 실험을 통해 제안한 DR이 최적의 토폴로지를 구성하여 에너지 효율성 측면에서 좋은 성능을 보임을 확인할 수 있었다.