• ETRI Journal
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• v.35 no.1
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• pp.58-68
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• 2013

Five-phase reservation protocol (FPRP) is a contention-based media access control protocol for wireless ad hoc networks. FPRP uses a five-phase reservation process to establish slot assignments based on time division multiple access. It allows a node to reserve only one slot in an information frame. Once a node has reserved a slot, it will cease contending for other slots. As a result, there may be less contending nodes in the remaining slots, so the time slots in an information frame are not fully used by FPRP. To improve time slot utilization, this paper proposes an improved pseudo-Bayesian algorithm, based on which an improved contention access mechanism for FPRP is proposed, in which nodes are allowed to contend for more than one slot in a reservation frame according to a certain probability/priority. Simulation results indicate that the proposed mechanism performs better than FPRP in time slot utilization and hence the network throughput under various scenarios.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.1
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• pp.117-135
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• 2016

Performance enhancement is one of the most important issues in high performance distributed computing systems. In such computing systems, online users submit their jobs anytime and anywhere to a set of dynamic resources. Jobs arrival and processes execution times are stochastic. The performance of a distributed computing system can be improved by using an effective load balancing strategy to redistribute the user tasks among computing resources for efficient utilization. This paper presents a multi-class load balancing strategy that balances different classes of user tasks on multiple heterogeneous computing nodes to minimize the per-class mean response time. For a wide range of system parameters, the performance of the proposed multi-class load balancing strategy is compared with that of the random distribution load balancing, and uniform distribution load balancing strategies using simulation. The results show that, the proposed strategy outperforms the other two studied strategies in terms of average task response time, and average computing nodes utilization.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.9 no.2
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• pp.680-699
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• 2015

The use of web service has been increased rapidly, with an increase in the number of available services, finding the exact service is the challenging task. Service discovery is the most significant job to complete the service discoverers needs. In order to achieve the efficient service discovery, we focus on designing a cluster based service discovery model for service registering and service provisioning among all mobile nodes in a mobile ad hoc network (MANETs). A dynamic backbone of nodes (i.e. cluster heads) that forms a service repository to which MANET nodes can publish their services and/or send their service queries. The designed model is based on storing services with their service description on cluster head nodes that are found in accordance with the proposed cluster head election model. In addition to identifying and analyzing the system parameters for finding the effectiveness of our model, this paper studies the stability analysis of the network, overhead of the cluster, and bandwidth utilization and network traffic is evaluated using analytic derivations and experimental evaluation has been done.

• Journal of the Korea Institute of Military Science and Technology
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• v.24 no.1
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• pp.115-122
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• 2021

In this paper, we propose a dynamic slot allocation scheme to improve the slot utilization rate in tactical multi-hop networks in which the channel condition varies due to node movements. The proposed scheme takes advantage of the fact that nodes that are more than three hops apart can use the same slot simultaneously. The frame is divided into two parts: the control period and the data period. To know the available slot information within two-hop distance, the node exchanges a slot allocation information with one-hop neighbors during the control period. The node can get the information on idle slots that are not used within two-hop distance but assigned already to other nodes that are more than three-hop away. The identified idle slot can be used by the node, which increases the slot utilization rate. The performance analysis results of the proposed scheme show that it increases the slot utilization rate sufficiently despite the overhead of the control period in the multi-hop networks of the future soldier system.

• 제어로봇시스템학회:학술대회논문집
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• 2004.08a
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• pp.777-781
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• 2004

This paper presents an algorithm for multichannel slotted-ring topology medium access protocol (MAC) using in wavelength division multiplexing (WDM) networks. In multichannel ring, there are two main previously proposed architectures: Tunable Transmitter - Fixed Receiver (TTFR) and Fixed Transmitter - Tunable Receivers (FTTR). With TTFR, nodes can only receive packets on a fixed wavelength and can send packets on any wavelengths related to destination of packets. Disadvantage of this architecture is required as many wavelengths as there are nodes in the network. This is clearly a scalability limitation. In contrast, FTTR architecture has advantage that the number of nodes can be much larger than the number of wavelength. Source nodes send packet on a fixed channel (or wavelength) and destination nodes can received packets on any wavelength. If there are fewer wavelengths than there are nodes in the network, the nodes will also have to share all the wavelengths available for transmission. However the fixed wavelength approach of TTFR and FTTR bring low network utilization. Because source node with waiting data have to wait for an incoming empty slot on corresponding wavelength. Therefore this paper presents Tunable Transmitter - Tunable Receiver (TTTR) approach, in which the transmitting node can send a packet over any wavelengths and the receiving node can receive a packet from any wavelengths. Moreover, the self-similar distributed input traffic is used for evaluation of the performance of the proposed algorithm. The self-similar traffic performs better performance over long duration than short duration of the Poison distribution. In order to increase bandwidth efficiency, the Destination Stripping approach is used to mark the slot which has already reached the desired destination as an empty slot immediately at the destination node, so the slot does not need to go back to the source node to be marked as an empty slot as in the Source Stripping approach. MATLAB simulator is used to evaluate performance of FTTR, TTFR, and TTTR over 4 and 16 nodes ring network. From the simulation result, it is clear that the proposed algorithm overcomes higher network utilization and average throughput per node, and reduces the average queuing delay. With future works, mathematical analysis of those algorithms will be the main research topic.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.10
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• pp.5156-5161
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• 2013

In distributed spatial data stream processing, processed tuples of downstream nodes are replicated to the upstream node in order to increase the utilization of distributed nodes and to recover the whole system for the case of system failure. However, while the data input rate increases and multiple downstream nodes share the operation result of the upstream node, the data which stores to output queues as a backup can be lost since the deletion operation delay may be occurred by the delay of the tuple processing of upstream node. In this paper, the adaptive upstream backup scheme based on operation throughput in distributed spatial data stream system is proposed. This method can cut down the average load rate of nodes by efficient spatial operation migration as it processes spatial temporal data stream, and it can minimize the data loss by fluid change of backup mode. The experiments show the proposed approach can prevent data loss and can decrease, on average, 20% of CPU utilization by node monitoring.

• The Transactions of the Korea Information Processing Society
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• v.5 no.10
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• pp.2654-2662
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• 1998

Maximum single bus throughput of standard IEEE 802.6 DQDB(Distributed Queue Dual Bus) is not obtained over 1. Therefore, lots of studies for improving bus throughput have done by QA slot preuse/reuse. We propose three calculation cethods for network's utilization with preuse/reuse scheme based on erasure nodes. One is calculation method by traffic density function, other is calculation method for obtaining maximum throughput. The other is calculation method using probability concept which follows real DQDB operation mechanisms. The calculated throughputs are compared with each others. The results shows some favorite phenomena. The proposed calculation methods can be casily expanded in mumber of nodes or in number of erasure nodes.

• Journal of Digital Convergence
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• v.15 no.2
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• pp.327-334
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• 2017

For enhancing network efficiency, various applications/services like CDN and P2P try to utilize content which have previously been cached somewhere. Content-centric networking (CCN) also utilizes data caching functionality. However, dislike CDN/P2P, CCN implements such a function on network nodes. Then, any intermediated nodes can directly respond to request messages for cached data. Hence, it is essential which content is cached as well as which nodes cache transmitted content. Basically, CCN propose for every nodes on the path from the content publisher of transmitted object to a requester to cache the object. However, such an approach is inefficient considering the utilization of cached objects as well as the storage overhead of each node. Hence, various caching mechanisms are proposed to enhance the storage efficiency of a node. In this paper, we analyze the performance of such mechanisms and compare the characteristics of such mechanisms. Also, we analyze content utilization patterns and apply such pattern to caching mechanisms to analyze the practicalism of the caching mechanisms.

• Journal of Korea Multimedia Society
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• v.18 no.10
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• pp.1225-1230
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• 2015

Mobile Sensor Networks (MSN) is composed of a distributed collection of mobile sensor nodes, each of which has sensing, computation, communication and locomotion capabilities. Since the routing path can be broken when some nodes on the path move to other position, MSN may have a high rate of communication failure. So, MSN has to provide a means for low-cost and low-power routing to support mobility of sensor nodes. In this paper, a limited flooding scheme for routing in MSN is proposed to allow efficient energy utilization without requiring any complicated tasks for path maintenance.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2018.05a
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• pp.649-651
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• 2018

Since the ubiquitous sensor network is not connected to external power source and operated by its own battery, it is required to maximize the network life using the efficient energy utilization. In a conventional hop count based routing protocol, most sensor nodes are designed with a constant transmission power. In this paper, we propose a routing protocol that prolongs the network lifetime by balancing the power consumption among the nodes by controlling the transmit power according to the residual power of the nodes, and compared the performance of the proposed routing protocol through computer simulations.