• The Journal of Korean Institute of Communications and Information Sciences
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• v.19 no.10
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• pp.2014-2027
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• 1994

A queueing model with two input streams of different service priorities is studied. Specifically, IBP+BP/D/1 with head-of-line priority is analyzed. IBP and BP stand for Interrupted Bernoulli Process and Bernoulli Process respectively. The BP-stream customers have the higher service priority over the IBP-stream customers. An exact analysis of this priority queue is presented to derive the distributions of the state of the system at steady state, the waiting time distributions for each class of customers, and the interdeparture time distributions. The numerical results of the analysis are presented to show how the various parameters of the low and high priority arrival processes affect the performance of the system.

• Journal of Korean Institute of Industrial Engineers
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• v.33 no.4
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• pp.430-438
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• 2007

In the current RFID (Radio Frequency IDentification) middleware systems based on the EPCglobal standard, the tag data received by multiple readers are processed sequentially in FIFO (First In First Out) order. Considering the priority of RFID reader makes the RFID system more flexible and improve the data transaction throughput in the service environment where important tag data with high priority for a specific reader. In this study, we propose a new RFID middleware system architecture supporting priority service with the Buffer Management Component. Our proposals are compliant with the EPCglobal ALE (Application Level Events) standard interface for middleware systems and their clients. To verify the efficiency of this proposed system, simulation is used for evaluation.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.7
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• pp.3446-3464
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• 2017

Backoff mechanism serves as one of the key technologies in the MAC-layer of wireless mobile networks. The traditional Binary Exponential Backoff (BEB) mechanism in IEEE 802.11 Distributed Coordination Function (DCF) and other existing backoff mechanisms poses several performance issues. For instance, the Contention Window (CW) oscillations occur frequently; a low delay QoS guarantee cannot be provided for real-time transmission, and services with different priorities are not differentiated. For these problems, we present a novel Multi-Priority service differentiated and Adaptive Backoff (MPAB) algorithm over IEEE 802.11 DCF for wireless mobile networks in this paper. In this algorithm, the backoff stage is chosen adaptively according to the channel status and traffic priority, and the forwarding and receding transition probability between the adjacent backoff stages for different priority traffic can be controlled and adjusted for demands at any time. We further employ the 2-dimensional Markov chain model to analyze the algorithm, and derive the analytical expressions of the saturation throughput and average medium access delay. Both the accuracy of the expressions and the algorithm performance are verified through simulations. The results show that the performance of the MPAB algorithm can offer a higher throughput and lower delay than the BEB algorithm.

• Journal of Communications and Networks
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• v.13 no.2
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• pp.149-159
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• 2011

In this paper, we study the problem of how to design a medical-grade wireless local area network (WLAN) for healthcare facilities. First, unlike the IEEE 802.11e MAC, which categorizes traffic primarily by their delay constraints, we prioritize medical applications according to their medical urgency. Second, we propose a mechanism that can guarantee absolute priority to each traffic category, which is critical for medical-grade quality of service (QoS), while the conventional 802.11e MAC only provides relative priority to each traffic category. Based on absolute priority, we focus on the performance of real-time patient monitoring applications, and derive the optimal contention window size that can significantly improve the throughput performance. Finally, for proper performance evaluation from a medical viewpoint, we introduce the weighted diagnostic distortion (WDD) as a medical QoS metric to effectively measure the medical diagnosability by extracting the main diagnostic features of medical signal. Our simulation result shows that the proposed mechanism, together with medical categorization using absolute priority, can significantly improve the medical-grade QoS performance over the conventional IEEE 802.11e MAC.

• 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.

• The KIPS Transactions:PartC
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• v.10C no.1
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• pp.45-50
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• 2003

Guaranteed Frame Rate (GFR) service category is one of the most recent ATM service categories. The GFR specification was recently finalized by the ATM Forum and is expected to become an important service category which can efficiently support TCP/IP traffic in ATM network. In GFR switch implementation, it is important to guarantee MCR (minimum cell rate) and improve fairness. In this paper, we propose a new scheduling algorithm for the GFR service. Proposed algorithm provides priority to VC (virtual circuit)s and high Priority given to a VC which has fewer untagged cells in buffer. High priority VCs are serviced before low priority VCs. Proposed algorithm can guarantee MCR and improve fair sharing of the remaining bandwidth between GFR VCs. From computer simulation results, we demonstrate the proposed scheduling algorithm provide much better performance in TCP goodput and fairness than previous schemes.

• Journal of KIBIM
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• v.13 no.4
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• pp.1-12
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• 2023

In Korea, there are many attempts to automate architectural design tasks, focusing on government-led national R&D projects and private operators, in order to enhance global competitiveness and productivity of the building service industry. However, according to a survey of architectural design office practitioners, only 25% (9 out of 37) have used it, suggesting that there are fewer cases of practical use in the field compared to research and investment in automation technology development, and there are discrepancies between automation and technology development items required in the field. In this study, the priority of automation of planning and design work of architectural design office practitioners is derived, and a comparative analysis is conducted with domestic architectural design automation service items based on the priority. A survey was conducted on practitioners of domestic architectural design offices to derive automation priorities for 19 items of architectural planning and design work. Based on the derived priorities, the degree of reflection of the working-level automation needs of domestic services was confirmed by comparing them with the domestic architectural planning and design automation service items. As a result, it was confirmed that domestic architectural planning and design automation services did not properly reflect the priority of planning and design work automation of architectural design office practitioners. This suggests that it is necessary to reflect the priorities derived in this study in technology development in order to increase the cases of practical use of the automation technology in the working environment and improve the productivity of service.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.3B
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• pp.232-238
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• 2006

We propose a novel call admission control scheme which improves the handoff drop and the new call block probabilities of high priority services, minimizing the negative impact on low priority services, in multimedia service cellular networks. This paper proposes three schemes to solve this problem; the packing scheme in which available channels of a cell distributed to each frequency channel are concentrated on one frequency channel and a high transmission rate service is assigned to the frequency channel; the queuing scheme in which the queue is used for high transmission rate calls; and the power reallocation scheme in which the power assigned to calls under service is temporarily reduced and a high transmission rate service is allowed. The simulation results revealed that our scheme improved the drop and the block probabilities of the high priority services compared with the conventional scheme.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.6 no.6
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• pp.1522-1545
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• 2012

Call admission control (CAC) plays an important role in mobile cellular network to guarantee the quality of service (QoS). In this paper, a dynamic hybrid CAC scheme with integrated cutoff priority and handoff queue for mobile cellular network is proposed and some performance metrics are derived. The unique characteristic of the proposed CAC scheme is that it can support any number of service types and that the cutoff thresholds for handoff calls are dynamically adjusted according to the number of service types and service priority index. Moreover, timeouts of handoff calls in queues are also considered in our scheme. By modeling the proposed CAC scheme with a one-dimensional Markov chain (1DMC), some performance metrics are derived, which include new call blocking probability ($P_{nb}$), forced termination probability (PF), average queue length, average waiting time in queue, offered traffic utilization, wireless channel utilization and system performance which is defined as the ratio of channel utilization to Grade of Service (GoS) cost function. In order to validate the correctness of the derived analytical performance metrics, simulation is performed. It is shown that simulation results match closely with the derived analytic results in terms of $P_{nb}$ and PF. And then, to show the advantage of 1DMC modeling for the performance analysis of our proposed CAC scheme, the computing complexity of multi-dimensional Markov chain (MDMC) modeling in performance analysis is analyzed in detail. It is indicated that state-space cardinality, which reflects the computing complexity of MDMC, increases exponentially with the number of service types and total channels in a cell. However, the state-space cardinality of our 1DMC model for performance analysis is unrelated to the number of service types and is determined by total number of channels and queue capacity of the highest priority service in a cell. At last, the performance comparison between our CAC scheme and Mahmoud ASH's scheme is carried out. The results show that our CAC scheme performs well to some extend.

• Journal of the military operations research society of Korea
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• v.30 no.1
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• pp.107-134
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• 2004

Today's Internet is providing a single service which is so-called "best-effort service". Now, multimedia and real-time applications are not only demanding large bandwidth but also requiring high QoS. For this, MPLS and DiffServ technology can be adopted to support more scalability and QoS for data traffic engineering. The DISN(Defense Information Systems Network) supports CBR service for voice traffic and VBR service for data traffic which is best-effort service. We propose how to adopt MPLS and DiffServ technology to support traffic engineering and guarantee QoS in the DISN. A traffic analysis according to prioritized traffic classes is done using OPNET simulation tool for assuring QoS. The result shows that low priority packets are delayed a little bit, but high priority packets are transferred more efficiently than without traffic engineering.gineering.