• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.35 no.4A
• /
• pp.394-400
• /
• 2010

Mobile Multi-hop Relaying (MMR) system can provide increased system capacity of wireless access network by coverage extension and enhanced transmission rate within the Base Station (BS) coverage area. The previous researches for the MMR system with a non-transparent mode Relay Station (RS) do not consider channel selection procedure of Mobile Station (MS), co-channel interference and Multi-hop Relay Base Station (MR-BS) coverage and RS coverage ratio in MMR system. In this paper, we investigate the performance of MMR uplink system in multicell environments with various topologies. The performance is presented in terms of call blocking probability, channel utilization, outage probability and system throughput by varying offered load. It is found that, for certain system parameters, the MMR uplink system achieve the maximum system throughput when MR-BS coverage to RS coverage ratio is 7.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.34 no.1B
• /
• pp.16-23
• /
• 2009

This paper investigates how many optimal routes can be established in terms of a given wireless mesh routing metric. Although many of routing metrics have been devised to precisely derive the wireless link quality in mesh, most (if not all) metrics have not been evaluated their optimality along with routing protocols. We consider stateof-the-art routing metrics and a widely accepted routing protocol in order to observe the optimality of established routes varying the number of source nodes. Also, we propose a unidirectional routing to deal with possible link asymmetry feature in wireless links. Through comparative simulation evaluations, we show that the portion of optimally established routes becomes less as the network traffic load increases, regardless of employed metrics, network topologies, and routing protocols.

• Molecules and Cells
• /
• v.19 no.3
• /
• pp.428-435
• /
• 2005

This study was carried out to assess the potential of SSR markers for variety identification by comparing SSR markers and morphological traits in tests of distinctiveness, uniformity, and stability (DUS) of pepper (Capsicum annuum L.) varieties. Twenty-seven SSR markers were polymorphic in 66 pepper varieties, revealing a total of 89 alleles. Average polymorphism information content (PIC) value was 0.529, ranging from 0.03 to 0.877. Cluster analysis of the band patterns separated the varieties into three groups corresponding to varietal types. Morphological trait-based clustering showed some degree of similarity to dendrogram topologies based on the SSR index. However, no significance correlation was found between the SSR and morphological data. SSR markers could be used to complement a DUS test of a candidate variety and to select complimentary varieties by pre-screening existing varieties in the context of protecting new varieties of pepper.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.33 no.7B
• /
• pp.557-566
• /
• 2008

Some types of network nodes such as mobile network node, mobile access point, and ad-hoc network node can be relocated frequently and, by the nature of its usage, are deployed over broad area. In this environment, the network topology is changed constantly since even the manager node as well as the managed nodes can leave or join the management network frequently. The many of existing network management technologies are mostly for small sized and homogeneous networks with static topologies and not proper for the mobile network devices. In this paper, employing peer-to-peer (P2P), the secure group communication techniques, and simple network management protocol (SNMP), we propose a highly secure and available management technique that can be used to manage the mobile network nodes through insecure management network such as the Internet. The proposed technique is implemented to show that it is practically usable.

• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.42 no.9 s.339
• /
• pp.29-40
• /
• 2005

In this paper, we propose a Cluster-based Multicast Routing (CMR) suitable for mobile ad-hoc networks. The main features that our proposed method introduces are the following: a) mobility-based clustering and group based hierarchical structure in order to effectively support stability and scalability, b) group based mesh structure and forwarding tree concepts in order to support the robustness of the mesh topologies which provides limited redundancy and the efficiency of tree forwarding simultaneously, and c) combination of proactive and reactive concepts which provide low route acquisition delay and low overhead. The performance evaluation of the proposed protocol is achieved via modeling and simulation. The corresponding results demonstrate the Proposed multicast protocol's efficiency in terms of packet delivery ratio, scalability, control overhead, end-to-end delay, as a function of mobility, multicast group size, and number of senders.

• The Journal of the Korea institute of electronic communication sciences
• /
• v.12 no.6
• /
• pp.1043-1048
• /
• 2017

Since year 2016, in Korea, the police department started to use drones to patrol violated vehicles on the highway area. They monitor vehicle drivers who use side ways on the highway during traffic congested hours of the season, drunken drivers, or violent drivers. They use the 'Spot Mobility' method which floats the drones for 30 minute period. However, this method is inefficient since it requires manually charging batteries, gathering data, and operate drones with many numbers of policeman. Therefore, in this paper, for the efficient patrol in this purpose, I have suggested an effectively manageable network system consists of many drones as the wireless network nodes and with small numbers of policeman in a wide highway area. To accomplish this, the two topologies of effective drone patrol network systems are designed and simulated in OPNET simulator for performance evaluation.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.21 no.9
• /
• pp.1655-1665
• /
• 2017

Recently data centers are being constructed actively by many cloud service providers, enterprises, research institutes, etc. Generally, they are built on tree topology using ECMP data forwarding scheme for load balancing. In this paper, we examine data center network topologies like tree topology and fat-tree topology, and load balancing technologies like MLAG and ECMP. Then, we propose a scheduling algorithm to efficiently transmit particular files stored on the hosts in the data center to the destination node outside the data center, where fat-tree topology and OpenFlow protocol between infrastructure layer and control layer are used. We run performance analysis by numerical method, and compare the analysis results with those of ECMP. Through the performance comparison, we show the outperformance of the proposed algorithm in terms of throughput and file transfer completion time.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.20 no.5
• /
• pp.410-420
• /
• 2015

This paper provides a comparison of power converter loss and thermal description for voltage source and current source type 5 MW-class medium-voltage topologies of wind turbines. Neutral-point clamped three-level converter is adopted for a voltage source type topology, whereas a two-level converter is employed for current source type topology, considering the popularity in the industry. To match the required voltage level of 4160 V with the same switching device of IGCT as in the voltage source converter, two active switches are connected in series for the case of current source converter. Transient thermal modeling of a four-layer Foster network for heat transfer is done to better estimate the transient junction and case temperature of power semiconductors during various operating conditions in wind turbines. The loss analysis is confirmed through PLECS simulations. Comparison result shows that the VSC-based wind turbine system has higher efficiency than the CSC under the rated operating conditions.

• Journal of Power Electronics
• /
• v.11 no.6
• /
• pp.870-879
• /
• 2011

Regulated peak power tracking (RPPT) systems such as the series structure and the series-parallel structures are commonly used in satellite space power systems. However, these structures process the solar array power or the battery power to the load through two cascaded regulators during one orbit cycle, which reduces the energy transfer efficiency. Also the battery charging time is increased due to placement of converter between the battery and the solar array. In this paper a parallel structure has been proposed which can improve the energy transfer efficiency and the battery charging time for satellite space power RPPT systems. An analogue controller is used to control all of the required functions, such as load voltage regulation and solar array stabilization with maximum power point tracking (MPPT). In order to compare the system efficiency and the battery charging efficiency of the proposed structure with those of a series (conventional) structure and a simplified series-parallel structure, simulations are performed and the results are analyzed using a loss analysis model. The proposed structure charges the battery more quickly when compared to the other two structures. Also the efficiency of the proposed structure has been improved under different modes of solar array operation when compared with the other two structures. To verify the system, experiments are carried out under different modes of solar array operation, including PPT charge, battery discharge, and eclipse and trickle charge.

• ETRI Journal
• /
• v.28 no.3
• /
• pp.329-336
• /
• 2006

This paper investigates the problem of protecting multicast sessions in mesh wavelength-division multiplexing (WDM) networks against single link failures, for example, a fiber cut in optical networks. First, we study the two characteristics of multicast sessions in mesh WDM networks with sparse light splitter configuration. Traditionally, a multicast tree does not contain any circles, and the first characteristic is that a multicast tree has better performance if it contains some circles. Note that a multicast tree has several branches. If a path is added between the leave nodes on different branches, the segment between them on the multicast tree is protected. Based the two characteristics, the survivable multicast sessions routing problem is formulated into an Integer Linear Programming (ILP). Then, a heuristic algorithm, named the adaptive shared segment protection (ASSP) algorithm, is proposed for multicast sessions. The ASSP algorithm need not previously identify the segments for a multicast tree. The segments are determined during the algorithm process. Comparisons are made between the ASSP and two other reported schemes, link disjoint trees (LDT) and shared disjoint paths (SDP), in terms of blocking probability and resource cost on CERNET and USNET topologies. Simulations show that the ASSP algorithm has better performance than other existing schemes.