• The Journal of The Korea Institute of Intelligent Transport Systems
• /
• v.9 no.6
• /
• pp.129-135
• /
• 2010

This paper suggests a multipath establishing scheme for ad hoc networks. Data paths are established by on-demand manner. Multipath are made as a sequence of route control message exchange at route setup process. Multipath can be used as a backup path or load balancing for data exchange. Proposed scheme uses a one-hop pre-search scheme for establishing multipath between source and destination. When a node selects a next node for route reply, the node finds optimal route by exchanging route information with neighbor nodes. Simulation results show that the proposed multipath scheme has better split characteristics among multipath and higher route survivability at the environment where nodes are moving.

• The Journal of the Korea Contents Association
• /
• v.7 no.11
• /
• pp.69-75
• /
• 2007

In this paper, we propose a new distributed processing scheme to support MMORPG (Massively Multiplayer Online Role-Playing Games). But existing distributed game servers have some problems such as hotspot, congestion, server failure problems, and so on. To solve such problems, our proposed scheme begins by splitting the large virtual world into smaller regions, each region handled by a different server. We present a scheme that reduces the bandwidth requirements for both game servers and clients. Also our scheme allows seamless interaction among players residing on areas handled by different servers. We show an excellence of the proposed solution through various experiments.

• 한국전산유체공학회:학술대회논문집
• /
• 1999.11a
• /
• pp.115-126
• /
• 1999

A two-dimensional Navier-Stokes solver using hybrid meshes is parallelized with a domain decompostion method. The focus of this paper is placed on minimizing the amount of effort in parallelizing the serial version of the solver, and this is achieved by adding an additional layer of cells to each decomposed domain. Most subroutines of the serial solver are used without modification, and the information exchange between neighboring domains is achieved using MPI(Message Passing Interface) library. Load balancing among the processors and scheduling of the message passing are implemented to reduce the overhead of parallelization, and the speed-up achieved by parallelization is measured on the transonic invisicd and turbulent flow problems. The parallelization efficiencies of the explicit Runge-Kutta scheme and the implicit point-SGS scheme are compared and the effects of various factors on the results are also studied.

• Proceedings of the Korea Information Processing Society Conference
• /
• 2007.05a
• /
• pp.1283-1285
• /
• 2007

A wireless sensor network is the combination of a large number of deployed sensors over an area. Communication between the sensors is the most important factor for a successful sensor network. It is mandatory that long distance and multi-hop communication will occur between sensors. Generally sensors relay the sensed data of a particular territory to the command center via a base station. For the non uniformed deployment of sensors many sensors may deploy in hostile areas surrounded by full of obstacles or in other condition it may be out of the direct communication range of the base station. It seems a critical problem for routing data to and from those sensors to the base station. This paper proposes a route management scheme using a dynamic load balancing approach based on residual energy of each agent sensors.

• The KIPS Transactions:PartA
• /
• v.19A no.3
• /
• pp.129-138
• /
• 2012

In distributed memory architectures like clusters, each node stores a portion of data. How data is distributed across nodes influences the performance of such systems. The data distribution scheme is the strategy to distribute data across nodes and realize parallel data processing. Due to various reasons such as maintenance, scale up, upgrade, etc., the performance of nodes in a cluster can often become non-identical. In such clusters, data distribution without considering performance cannot efficiently distribute data on nodes. In this paper, we propose a new data distribution scheme based on the number of cores in nodes. We use the number of cores as the performance factor. In our data distribution scheme, each node is allocated an amount of data proportional to the number of cores in it. We implement our data distribution scheme using the Chapel language. To show our data distribution is effective in reducing the execution time of parallel applications, we implement Mandelbrot Set and ${\pi}$-Calculation programs with our data distribution scheme, and compare the execution times on a cluster. Based on experimental results on clusters of 8-core and 16-core nodes, we demonstrate that data distribution based on the number of cores can contribute to a reduction in the execution times of parallel programs on clusters.

• Journal of Power Electronics
• /
• v.8 no.2
• /
• pp.131-140
• /
• 2008

This paper presents a new control approach of DSTATCOM (distribution static compensator) for compensation of reactive power, unbalanced loading and harmonic currents under unbalanced non-sinusoidal ac mains. The control of DSTATCOM is achieved using Adaline based current estimator based on LMS algorithm to maintain source currents real and undistorted. The dc bus voltage of voltage source converter (VSC) working as DSTATCOM is maintained at constant voltage using a proportional-integral (PI) controller. The DSTATCOM system alongwith proposed control scheme is modeled in MATLAB to simulate the behavior of the system. The practical implementation of the DSTATCOM is carried out using dSPACE DS1104 R&D controller having TMS320F240 as a slave DSP. Simulated and implementation results are presented to demonstrate the effectiveness of the DSTATCOM with Adaline based control to meet the severe load perturbations with different types of loads (linear and non-linear) under distorted and unbalanced AC mains.

• Journal of the Korea Society of Computer and Information
• /
• v.18 no.2
• /
• pp.59-68
• /
• 2013

Efficient resource management and hand-over schemes are necessary to maintain consistent QoS because it may be severely defected by some delay and information loss during hand-over in LTE-Advanced networks. This paper proposes a resource management scheme based on the load control to support consistent QoS for heterogeneous services during hand-over in OFDMA based systems. Various multimedia services with different requirements for resource are able to be serviced simultaneously because service continuity can be provided by our proposed scheme. Simulation results show that it provides better performances than the conventional one with the measure of hand-over failure rate and packet loss rate.

• Journal of Communications and Networks
• /
• v.17 no.1
• /
• pp.84-92
• /
• 2015

Multi-hop relay networks have been widely considered as a promising solution to extend the coverage area and to reduce the deployment cost by deploying the relay stations (RSs) in mobile communication systems. Suitable deployment for the RSs is one of the most important features of the demand nodes (DNs) to obtain a high data transmission rate in such systems. Considering a tradeoff among the network throughput, the deployment budget, and the overall coverage of the systems, efficient RS deployment schemes and corresponding algorithms must be developed and designed. A novel cluster-based RS deployment scheme is proposed in this paper to select the appropriate deployment locations for the relay stations from the candidate positions. To make an ideal cluster distribution, the distances between the DNs are calculated when deploying the RSs. We take into account the traffic demands and adopt a uniform cluster concept to reduce the data transmission distances of the DNs. On the basis of the different candidate positions, the proposed scheme makes an adaptive decision for selecting the deployment sites of the RSs. A better network throughput and coverage ratio can be obtained by balancing the network load among the clusters. Simulation results show that the proposed scheme outperforms the previously known schemes in terms of the network throughput and the coverage ratio. Additionally, a suitable deployment budget can be implemented in multi-hop relay networks.

• Journal of KIISE:Information Networking
• /
• v.29 no.2
• /
• pp.165-173
• /
• 2002

In the static channel assignment scheme for cellular mobile computing environment, each cell has a fixed number of channels and supports a service for a user′s request entering to the cell. This scheme has an advantage of simplicity. However, this scheme has a disadvantage that can′t control far hot cell problem. Therefore, to solve this problem, the "channel borrowing" concept is needed. In this paper, we propose a load balancing(channel borrowing, channel reassignment) approach using genetic algorithm. The purposes of using genetic algorithm in this paper are ${\circled1}$ to find early a cell including an available channel and ${\circled2}$ to decrease a number of probings and ${\circled3}$ to migrate to the cell after searching an available channel near upon optimality. To represent effectiveness of the proposed algorithm, we simulated various experiments.

• Journal of Communications and Networks
• /
• v.6 no.3
• /
• pp.216-225
• /
• 2004

In a cellular network, if there are too many data users in a cell, data may suffer long delay, and system's quality-of-service (QoS) will degrade. Some traditional schemes such as dynamic channel-allocation scheme (DCA) will assign more channels to hot (or overloaded) cells through a central control system (CC) and the throughput increase will be upper bounded by the number of new channels assigned to the cell. In mobile-assisted data forwarding (MADF), we add an ad-hoc overlay to the fixed cellular infrastructure and special channels-called forwarding channels- are used to connect mobile units in a hot cell and its surrounding cold cells without going through the hot cell's base station. Thus, mobile units in a hot cell can forward data to other cold cells to achieve load balancing. Most of the forwarding-channel management work in MADF is done by mobile units themselves in order to relieve the load from the CC. The traffic increase in a certain cell will not be upper bounded by the number of forwarding channels. It can be more if the users in hot cell are significantly far away from one another and these users can use the same forwarding channels to forward data to different cold neighboring cells without interference. We find that, in a system using MADF, under a certain delay requirement, the throughput in a certain cell or for the whole net-work can be greatly improved.