• ETRI Journal
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• v.28 no.3
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• pp.311-319
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• 2006

This paper presents a terminal-assisted frame-based packet reservation multiple access (TAF-PRMA) protocol, which optimizes random access control between heterogeneous traffic aiming at more efficient voice/data integrated services in dynamic reservation TDMA-based broadband access networks. In order to achieve a differentiated quality-of-service (QoS) guarantee for individual service plus maximal system resource utilization, TAF-PRMA independently controls the random access parameters such as the lengths of the access regions dedicated to respective service traffic and the corresponding permission probabilities, on a frame-by-frame basis. In addition, we have adopted a terminal-assisted random access mechanism where the voice terminal readjusts a global permission probability from the central controller in order to handle the 'fair access' issue resulting from distributed queuing problems inherent in the access network. Our extensive simulation results indicate that TAF-PRMA achieves significant improvements in terms of voice capacity, delay, and fairness over most of the existing medium access control (MAC) schemes for integrated services.

• The Transactions of the Korea Information Processing Society
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• v.6 no.3
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• pp.742-749
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• 1999

This paper proposes the mechanism of cell buffering in the output buffer of ATM switch for the traffic with the different QOS in the ATM environment. The proposed mechanism, VQS(Variable Queue Sharing) can minimize the cell loss ratio(CLR) of bursty traffic through the sharing of CBR queue, VBR queue, ABR queue to maximize the utilization of queue resource. To evaluate VQS performance, we make simulator using Visual Slam 2.0. We compare the CLP and cell average delay of VQS and HOL, QLT_HOL using the bursty traffic patterns.

• Annual Conference of KIPS
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• 2014.11a
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• pp.227-230
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• 2014

LTE 3GPP standard defines several QCI (QoS Class Identifier) classes to provide differential QoS, depending on the requirements of different user applications.These QCI values have been characterized in terms of priority, packet loss and delay budget. In spite of the availability of this robust QoS framework in LTE, there is no such scheduling algorithm that has its working principle based on this framework. The responsibility of fulfilling the user requirements, while satisfying the service class requirements is left upon the cellular service provider and it is an open issue at present. To solve this problem, we have proposed a MAC scheduler, which defines the priority of different users based on their bearer specification and provides desired QoS in terms of the achieved throughput through the resource block allocation based on calculated user priority.

• Natural Product Sciences
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• v.8 no.4
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• pp.144-146
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• 2002

Rhapontica uniflora, Platycodon grandiflorum and Solanum tuberosum extracts affected the recovery of radiation-induced damage at all tested doses $(15.6,\;31.3,\;62.5\;and\;125\;{\mu}g/ml)$. The survival rate of pretreatment with extracts was increased by 2 times more than its compared with untreated cells. All tested extracts protected the growh-delay of normal cells and haematological parameters from their radiation-induced fall. In tested extracts, Solanum tuberosum was significantly superior to Platycodon grandiflorum and Rhapontica uniflora in radio-protection activity.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.24 no.65
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• pp.89-102
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• 2001

In this paper, the aircraft route scheduling consists of two steps; the pairing generation and the aircraft assignment. The pairing generation is heuristic approach how flights construct pairings from and to the main base. The aircraft resource assignment which is to establish a aircraft route schedule is constructed by constraint satisfaction problem technique. ILOG solver and schedule is used to solve this problem. In addition, a aircraft route reschedule process against departure-arrival delay or aircraft maintenance schedule change is added by partial constraints satisfaction problem technique. Also, Gantt chart made by ILOG views is used to show aircraft route schedule results more easily.

• ETRI Journal
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• v.41 no.2
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• pp.207-223
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• 2019

Network function virtualization can significantly improve the flexibility and effectiveness of network appliances via a mapping process called service function chaining. However, the failure of any single virtualized network function causes the breakdown of the entire chain, which results in resource wastage, delays, and significant data loss. Redundancy can be used to protect network appliances; however, when failures occur, it may significantly degrade network efficiency. In addition, it is difficult to efficiently map the primary and backups to optimize the management cost and service reliability without violating the capacity, delay, and reliability constraints, which is referred to as the reliability-aware service chaining mapping problem. In this paper, a mixed integer linear programming formulation is provided to address this problem along with a novel online algorithm that adopts the joint protection redundancy model and novel backup selection scheme. The results show that the proposed algorithm can significantly improve the request acceptance ratio and reduce the consumption of physical resources compared to existing backup algorithms.

• Journal of the Korea Society of Computer and Information
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• v.23 no.12
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• pp.73-80
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• 2018

Certification revocation list(CRL) is needed for excluding compromised, faulty, illegitimate vehicle nodes and preventing the use of compromised cryptographic materials in vehicular communications. It should be distributed to vehicles resource-efficiently and CRL computational load of vehicles should not impact on life-critical applications with delay sensitive nature such as the pre-crash sensing that affords under 50msec latency. However, in the existing scheme, when a vehicle receives CRL, the vehicle calculates linkage values from linkage seeds, which results in heavy computational load. This paper proposes, a new CRL distribution scheme is proposed, which minimizes the time for CRL processing of vehicles. In the proposed scheme, the linkage value calculation procedure is performed by road-side unit(RSU) instead of the vehicle, and then the extracted linkage values are relayed to the vehicle transparently. The simulation results show that the proposed scheme reduces the CRL computational load dramatically, which would minimize impact on life-critical applications' operations with low latency.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.17 no.2
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• pp.450-470
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• 2023

Traditional cloud computing faces some challenges such as huge energy consumption, network delay and single point of failure. Edge computing is a typical distributed processing platform which includes multiple edge servers closer to the users, thus is more robust and can provide real-time computing services. Although outsourcing data to edge servers can bring great convenience, it also brings serious security threats. In order to provide image retrieval while ensuring users' data privacy, a privacy preserving image retrieval scheme in edge environment is proposed. Considering the distributed characteristics of edge computing environment and the requirement for lightweight computing, we present a privacy-preserving image retrieval scheme in edge computing environment, which two or more "honest but curious" servers retrieve the image quickly and accurately without divulging the image content. Compared with other traditional schemes, the scheme consumes less computing resources and has higher computing efficiency, which is more suitable for resource-constrained edge computing environment. Experimental results show the algorithm has high security, retrieval accuracy and efficiency.

• Annual Conference of KIPS
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• 2009.11a
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• pp.527-528
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• 2009

Presuming energy as a crucial resource, several duty cycle based MAC protocol have been proposed for wireless sensor network. However, these protocols have long latency problem for paying more attention on energy efficiency. In this paper, we propose Data Predicted Wakeup Based Duty Cycle MAC (DPW-MAC) for Wireless Sensor Networks for delay sensitive periodic applications in which timely delivery of data is a major concern with the maintenance of duty cycle.

• Annual Conference of KIPS
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• 2022.05a
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• pp.114-116
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• 2022

The advent of the Multi-access Edge Computing (MEC) paradigm allows mobile users to offload resource-intensive and delay-stringent services to nearby servers, thereby significantly enhancing the quality of experience. Due to erratic roaming of mobile users in the network environment, maintaining maximum quality of experience becomes challenging as they move farther away from the serving edge server, particularly due to the increased latency resulting from the extended distance. The services could be migrated, under policies obtained using Deep Reinforcement Learning (DRL) techniques, to an optimal edge server, however, this operation incurs significant costs in terms of service downtime, thereby adversely affecting service quality of experience. Thus, this study addresses the service mobility problem of deciding whether to migrate and where to migrate the service instance for maximized migration benefits and marginal service downtime.