• The Journal of Korean Institute of Communications and Information Sciences
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• v.21 no.3
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• pp.629-642
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• 1996

ATM switch handles the traffic for a wide range of appliations with different QOS(Quality-of-Service) requirements. In ATM switch, the priority control mechanism is needed to improve effectively the required QOS requirements. In this paper, we propose a priority control mechanism using the cell transfer ratio type and discard threshold in order to archive the cell loss probability requirement and the delay requirement of each service class. The service classes of our concern are the service class with high time priority(class 1) and the service class with high loss priority control mechanism, cells for two kind of service classes are stored and processed within one buffer. In case cells are stored in the buffer, cells for class 2 are allocated in the stored and processed within one buffer. In case cells are stored in the buffer, cells for class 2 are allocated in the shole range of the buffer and cells for class 1 are allocated up to discard threshold of the buffer. In case cells in the buffer are transmitted, one cell for class 1 is transmitted whenever the maximum K cells for class 2 are transmitted consecutively. We analyze the time delay and the loss probability for each class of traffic using Markov chain. The results show that the characteristics of the mean cell delay about cells for class 1 becomes better and that of the cell loss probability about cells for class 2 becomes better by selecting properly discard threshold of the buffer and the cell transfer ratio according to the condition of input traffic.

• Journal of Institute of Control, Robotics and Systems
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• v.20 no.6
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• pp.676-688
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• 2014

The IEEE 802.11e EDCA (Enhanced Distributed Channel Access) mechanism has been proposed to improve the QoS (Quality of Service) of various services in WLANs (Wireless Local Area Networks). By differentiating the channel access delay depending on ACs (Access Categories), this mechanism can provide the relative service differentiation among ACs. In this paper, we consider that WLAN is deployed in medical environments to transfer medical traffic and we reveal that the quality of the medical traffic (in particular, ECG signals) is significantly deteriorated even with the service differentiation by IEEE 802.11e EDCA. Also, we analyze the reason for performance degradation and show that IEEE 802.11e EDCA has difficulty in protecting the transmission opportunity of high-priority traffic against low-priority traffic. In order to assure medical-grade QoS, we firstly define the service priority of medical traffic based on their characteristics and requirements, and then we propose the enhanced channel access scheme, referred to as DIFF-CW. The proposed scheme differentiates CW (Contention Window) depending on the service priority and modifies the channel access procedure for low-priority traffic. The simulation results confirm that the DIFF-CW scheme not only assures the QoS of medical traffic but also improves the overall channel utilization.

• The Transactions of the Korea Information Processing Society
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• v.4 no.5
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• pp.1196-1210
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• 1997

Timestamp-Ordering Prltocol among trancaction scheduling alforithms can cause the priority teversion that a transaction with higher priority is processed after the teansaction the trancaction withe lower priority by assigning timestamp to transactions entering system and scheduling them based on the timestamp.To prevent this reversion,we suggest a data priority-based timestamp ordering prioity within the same timestamp group after grouping teansactions into constant time interval based on entering points.To evaluate the performance of this protocol,we compared the performance of this protocol with that of others after constructing the simulation environment with real time database system.We verified that the performance of proposed protocol is supweior to that of timestamp ordering protocol under the comdition of high load and high data conflicts.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.4B
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• pp.153-161
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• 2005

In a multi-channel network based of wavelength division multiplexing (WDM) technology, an efficient protocol is needed in order for the transmitter and receiver to be tuned to the same wavelength during message transmission time. This paper proposes a priority-based reservation protocol that can efficiently support variable-length messages that require different QoS requirements. In this proposed protocol, high-priority nodes can reserve the data channel before low-priority nodes. However, once a node reserves a data channel successfully, it can persistently use the reserved channel till message transmission is finished regardless of the priority of the node. Moreover, the protocol can operate independently of the number of nodes, and any new node can join the network anytime without requiring network re-initialization. The protocol is analyzed with a finite population model and the throughput-delay characteristics are investigated as performance measures.

• The Korean Journal of Franchise Management
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• v.11 no.4
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• pp.45-57
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• 2020

Purpose: The purpose of this study is to determine the importance and priority arising from the relationship between MRO-office supplies franchisor ("franchisor") and franchisees through an in-depth investigation. In particular, with respect to the MRO-Office franchise industry, we would like to make meaningful contributions in the decision-making process by comparing and contrasting factors that affect the importance and priority of communication, conflict, support and satisfaction through AHP analysis. Research design, data, and methodology: After completion of AHP analysis, the study will also identify factors in order of priority and factors of importance between the franchisor and franchisees. Another purpose of this study is to evaluate and propose business relationship strategies between the franchisor and franchisees. Through AHP analysis, this study will facilitate the relationship between the franchisor and franchise, and determine the factors of importance and factors in order of priority. Result: This study evaluates the differences and priorities of the two groups arising from the relationship between the franchisor and the franchisees through AHP analysis after separately analyzing the franchisor. In this study, the franchisees find that communication is the most important factor, then support as the second most important factor between the two groups. In contrast, the franchisor finds that support is the most important factor followed by communication between the two groups. Conclusions: This analysis demonstrates the discrepancy in evaluating important factors from the perspectives of the franchisor and the franchisees. The largest discrepancy between the franchisor and franchisees comes from an information system related to communication factors. This effectively means that the franchisor has an understanding of this inadequate information system on the part of franchisees but this understanding is not deemed an important factor. The franchisees recognize and focus on the need to obtain feedback from the franchisor regarding management improvement as the most important factor rather than the ability of the franchisor to guide them through the franchisees' operations. To this end, the franchisor should be more flexible in dealing with the problem of improving the work required by the franchisees. For this study, a survey was conducted on employees of MRO-office supplies franchisor, franchisees, and employees and completed based on AHP analysis.

• IE interfaces
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• v.19 no.2
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• pp.106-116
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• 2006

In this study, the priority of risk factors in supplying water through water supply pipeline network was evaluated by PROMETHEE and ANP multi-criteria decision analysis. We chose 'corrosion', 'burst' and 'water pollution' in pipe as major reference criteria and selected eight risk factors to evaluate the priority, and then we compared the results of PROMETHEE with those of ANP. We also analyzed the results of the sensitivity analysis by changing the weights and parameters of preference functions in PROMETHEE. We investigated the possibility of integrating two methods by using the results of ANP as the weights of preference function in PROMETHEE. The priority of risk factors for supplying municipal water which is evaluated by this study may provide basic data to establish a contingency plan for accidents, or to establish the specific emergency response procedures.

• Journal of Communications and Networks
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• v.16 no.2
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• pp.193-201
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• 2014

In cognitive radio networks, the packet transmissions of the secondary users (SUs) can be interrupted randomly by the primary users (PUs). That is to say, the PU packets have preemptive priority over the SU packets. In order to enhance the quality of service (QoS) for the SUs, we propose a spectrum access strategy with an ${\alpha}$-Retry policy. A buffer is deployed for the SU packets. An interrupted SU packet will return to the buffer with probability ${\alpha}$ for later retrial, or leave the system with probability (1-${\alpha}$). For mathematical analysis, we build a preemptive priority queue and model the spectrum access strategy with an ${\alpha}$-Retry policy as a two-dimensional discrete-time Markov chain (DTMC).We give the transition probability matrix of the Markov chain and obtain the steady-state distribution. Accordingly, we derive the formulas for the blocked rate, the forced dropping rate, the throughput and the average delay of the SU packets. With numerical results, we show the influence of the retrial probability for the strategy proposed in this paper on different performance measures. Finally, based on the trade-off between different performance measures, we construct a cost function and optimize the retrial probabilities with respect to different system parameters by employing an iterative algorithm.

• Journal of Digital Convergence
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• v.9 no.5
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• pp.141-156
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• 2011

Auditors' subjective opinions m audit activities weaken reliability in audit judgments. This paper suggests fixed quantity models through requirement priority for improving objective evaluation and priorities of requirements in information system audit. The value of requirements was evaluated based on customers' requirements with a premise that they are not in the same level. Furthermore, the audit objective judgments were enhanced to enable fixed quantity of subjective audit by subdividing detailed evaluation index of requirement priority standards into importance of service and function on orderers' perspective, and sectioning cost and schedule on contractors' perspective.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.22 no.1
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• pp.175-182
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• 2018

As Internet of things with a large number of nodes emerges, wireless-power communication networks (WPCN) based on a random access protocol needs to be investigated. In the random access-based WPCN, a terminal accessing later in given random access (RA) slots can harvest more energy before transmission and thus can transmit data with higher power and achieve higher throughput if the access is successful. On the basis of this property, the proposed random access control protocol gives the terminals priority and distinguishes the RA slots according to the priority level, so that a near terminal with access point allows to access preferentially other than a remote terminal. This operation decreases the throughput of near terminal and increases the throughput of remote terminal, and then, the doubly near-far problem in WPCN is resolved and the user fairness is improved. Results show that the proposed random access control improves both channel throughput and user fairness according to the priority level.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.44 no.4
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• pp.17-27
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• 2007

The enhanced distributed channel access (EDCA) of IEEE 802.11e has been standardized for supporting Quality of Service (QoS) in wireless LANs. In the EDCA, support of QoS can be achieved statistically by reducing the probability of medium access for lower priority traffics. In other words, it provides statistical channel access rather than deterministically prioritized access to high priority traffic. Therefore, lower priority traffics affect the performance of higher priority traffics. Consequently, at the high loads, the EDCA does not guarantee the QoS of multimedia applications such as voice and video even though it provides higher priority. In this paper, we propose a simple and effective scheme, called deterministic priority channel access (DPCA), for improving the QoS performance of the EDCA mechanism. In order to provide guaranteed priority channel access to multimedia applications, the proposed scheme uses a busy tone for limiting the transmissions of lower priority traffics when higher priority traffic has data packets to send. Performance of the proposed scheme is investigated by numerical analysis and simulation. Our results show that the proposed scheme outperforms the EDCA in terms of throughput, delay, jitter, and drop under a wide range of contention levels.