• IEMEK Journal of Embedded Systems and Applications
• /
• v.15 no.5
• /
• pp.251-259
• /
• 2020

Ad hoc On-demand Distance Vector (AODV) protocol and its variants employ two important timers, hello and hold timer to keep track of topology changes. Moreover, hold timer is computed by multiplying constant value to hello timer. But, this configuration leads to inaccurate settings of hold timer. To solve this problem, in this paper, we propose a new dynamic adjustment of hello and hold timer scheme by removing dependency between them. A new metric to measure mobility is applied into hello timer, while expected link lifetime does holder timer. Simulation results show a significant reduction in the number of messages, a fact suggesting that it is possible to maintain and in some cases improve the performance of AODV with a minimum amount of messages released into the network.

• Journal of the Korea Computer Industry Society
• /
• v.2 no.9
• /
• pp.1209-1218
• /
• 2001

In this dissertation, we propose a dynamic source routing protocol supporting asymmetric path for mobile ad hoc networks. At present, the existing dynamic source routing protocol supports only symmetric path for routing. However, in fact, there can exist unidirectional links due to asymmetric property of mobile termenals or current wireless environment. Thus, we implement a mobile ad hoc routing protocol supporting asymmetric routing path, which is fit for more general wireless environment. Especially, the proposed protocol uses an improved multipath maintenance method in order to perform rapid route reconfiguration when route error due to mobility is detected.

• Proceedings of the Korea Information Processing Society Conference
• /
• 2003.11b
• /
• pp.899-902
• /
• 2003

무선 환경에서의 실시간 서비스의 확대와 노드의 이동성 증가에 따라 handover 시 발생되는 패킷 손실과 지연으로 인한 실시간 서비스의 중단이 해결해야 할 중요한 문제점이 되고 있다. 본 논문에서는 IETF (Internet Engineering Task Force)의 중요한 마이크로 이동성 프로토콜인 HMIPv6의 기본 동작을 설명하고, 여전히 문제점으로 남아있는 Inter-MAP (Mobility Anchor Point) handover의 성능을 향상시키기 위한 Dynamic MAP Switching handover 알고리듬을 제안한다. 제안한 알고리듬은 인접한 MAP 도메인을 중첩되게 설정하고 Inter-MAP handover가 발생되기 전에 미리 MAP을 switching한다. 따라서 Inter-MAP handover가 발생하지 않도록 함으로써 handover 시 발생하는 데이터의 손실 및 지연을 감소시킬 수 있다. 제안된 알고리듬의 성능 향상은 산술적 분석을 통하여 검증한다.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2014.10a
• /
• pp.54-59
• /
• 2014

The rapid tactical operation and mobility are getting important to recently developed the guided weapon systems. And military wants multi-purposes equipment to carry the war more easily. So military wants to have the equipment that can apply without any distinction about environment. For this reason, the robust design is getting more important now to guarantee survivability of equipment. In this paper, we try to check about structural integrity of Fire Control Unit(FCU) which is one of the guided weapon system using dynamic FEM analysis.

• Proceedings of the Computational Structural Engineering Institute Conference
• /
• 1995.10a
• /
• pp.234-241
• /
• 1995

Offshore structures are exposed to higher probability of collision with ship because of their limited mobility. In general, the consequence of the collision is reported to be relatively small and it is desirable to consider minor collisions in the design stage. It is important to have a comprehensive understanding of the dynamic responses of a tubular, their main member, under collision to design offshore structure against possible accidents. It is needed to estimate the probable extent of damage of a tubular, depth of dent, affected by the time history of impact load in ender to design a tubular strong enough for collision. In this paper, dynamic behaviors of a tubular due to the lateral impact are investigated through the numerical simulations with hydrocode DYNA3D, a three dimensional elasto-plastic large deformation impact contact problem analyzing program.

• The Journal of Information Systems
• /
• v.14 no.3
• /
• pp.48-52
• /
• 2005

The Mobile agent-based distributed systems become obtaining significant popularity as a potential vehicle to allow software components to be executed on heterogeneous environments despite mobility of users and computations. However, as these systems generally force mobile agents to use only common functionalities provided in every execution environment, the agents may not access environment-specific resources. In this paper, we propose a new framework using Aspect Oriented Programming technique to accommodate a variety of static resources as well as dynamic ones whose amount is continually changed at runtime even in the same execution environment. Unlike previous works, this framework divides roles of software developers into three groups to relieve application programmers from the complex and error prone parts of implementing dynamic adaptation and allowing each developer to only concentrate on his own part. Also, the framework enables policy decision makers to apply various adaptation policies to dynamically changing environments for adjusting mobile agents to the change of their resources.

• Proceedings of the KSR Conference
• /
• 2006.11b
• /
• pp.689-694
• /
• 2006

Wireless LAN is getting more popularity and plays a main role in electronic and telecommunication field. Wireless LAN is more convenient than wired LAN when mobility is required, and are sometimes the only feasible choice. Wireless LAN can also pose a significant security risk when not properly installed and maintained. Thus, this paper studies real-time message transmission using existing mobile telecommunication network and describes considerations and procedures when introducing wireless LAN concept and wireless LAN systems. It also studies integrated wired and wireless networking including wireless LAN bridge and AP technology of International Organization for Standardization, and especially real-time dynamic image data transmission in a moving train.

• Journal of Information Processing Systems
• /
• v.20 no.2
• /
• pp.226-238
• /
• 2024

Recently, multi-access edge computing (MEC) has emerged as a promising technology to alleviate the computing burden of vehicular terminals and efficiently facilitate vehicular applications. The vehicle can improve the quality of experience of applications by offloading their tasks to MEC servers. However, channel conditions are time-varying due to channel interference among vehicles, and path loss is time-varying due to the mobility of vehicles. The task arrival of vehicles is also stochastic. Therefore, it is difficult to determine an optimal offloading with resource allocation decision in the dynamic MEC system because offloading is affected by wireless data transmission. In this paper, we study computation offloading with resource allocation in the dynamic MEC system. The objective is to minimize power consumption and maximize throughput while meeting the delay constraints of tasks. Therefore, it allocates resources for local execution and transmission power for offloading. We define the problem as a Markov decision process, and propose an offloading method using deep reinforcement learning named deep deterministic policy gradient. Simulation shows that, compared with existing methods, the proposed method outperforms in terms of throughput and satisfaction of delay constraints.

• Journal of the Institute of Electronics Engineers of Korea CI
• /
• v.46 no.3
• /
• pp.116-122
• /
• 2009

Mobile Wireless Sensor Network is an organized collection of sensor nodes and mobile sink nodes, in which the sensor node transmits the signal to the sink node. In real environment, there are many cases in which sinks have mobility caused by the people, the vehicle and etc. Since all nodes in the sensor networks have limited energy, many researches have been done in order to prolong the lifetime of the entire network. In this paper we propose Dynamic Local Update-based Routing Protocol(D-LURP) that prolong the lifetime of the entire network to efficiently maintain frequent location update of mobile sink static sensor nodes in Mobile WSNs. When the sink node moves out of the local broadcasting area the proposed D-LURP configures dynamically the local update area consisted of the new local broadcasting area and the previous dissemination node(DN) and find the path between the DN and the sink node, instead of processing a new discovering path like LURP. In this way the processing of broadcasting sink node's location information in the entire network will be omitted. and thus less energy will be consumpted. We compare the performances of the proposed scheme and existing Protocols.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2010.10a
• /
• pp.377-380
• /
• 2010

MANET(Mobile Ad-hoc Network) has been proposed as a infrastructure-less network using distributed algorithm for remote environment monitoring and control. The mobility of MANET would make the topology change frequently compared with a static network and a node is resource-constrained. Hence, to improve the routing protocol in MANET, energy efficient routing protocol is required as well as considering the mobility would be needed. In this paper, we extend RODMRP(Resilient Ontology-based Dynamic Multicast Routing Protocol) structure by a modifying the level of cluster. We call this network protocol CACH-RODMRP. Our contribution consists estimating the optimal level of clustering depth with considering node position and reducing the network residual energy. The simulation results of proposal algorithm show that the energy is significantly reduced compared with the previous clustering based routing algorithm for the MANET.