• Proceedings of the Korean Institute of Communication Sciences Conference
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• 2004.07a
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• pp.95-95
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• 2004

• Journal of IKEEE
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• v.17 no.2
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• pp.96-103
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• 2013

Since multimedia data takes large part of realtime transmission in wireless communication environments such as IEEE 802.11, QoS issues became one of the important problems with network performance. 802.11e MAC provides differentiated services based on priority schemes to solve existing 802.11 MAC problems. The TXOP is an important factor with the priority to improve network performance and QoS because it defines the time duration in which multiple frames can be transferred at one time for each station. In this paper, therefore frame sizes, TXOP Limit, and Priority values in accordance with the number of stations are experimented and derived for best network performance and QoS. Using 802.11e standard parameters, simulation results show the best throughput when the number of stations is 5 and TXOP Limit value is 6.016ms. For fairness, the best result is achieved at 3.008ms of TXOP Limit value and 15-31 of CW(Contention Window) that is lower priority than CW 7-15.

• Journal of Sensor Science and Technology
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• v.22 no.1
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• pp.18-27
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• 2013

Real-time monitoring is one of the prime necessities in a weapon flight test that is required for the efficient and timely collection of large amounts of high-rate sampled data acquired by an event-trigger. The wireless sensor network is a good candidate to resolve this requirement, especially considering the inhospitable environment of a weapon flight test. In this paper, we propose a priority based multi-channel MAC protocol with CSMA/CA over a single radio for a real-time monitoring of a weapon flight test. Multi-channel transmissions of nodes can improve the network performance in wireless sensor networks. Our proposed MAC protocol has two operation modes: Normal mode and Priority Mode. In the normal mode, the node exploits the normal CSMA/CA mechanism. In the priority mode, the node has one of three grades - Class A, B, and C. The node uses a different CSMA/CA mechanism according to its grade that is determined by a signal level. High grade nodes can exploit more channels and lower backoff exponents than low ones, which allow high grade nodes to obtain more transmission opportunities. In addition, it can guarantee successful transmission of important data generated by high grade nodes. Simulation results show that the proposed MAC exhibits excellent performance in an event-triggered real-time application.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.24 no.7B
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• pp.1296-1304
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• 1999

In this paper, we propose an enhanced usage parameter control algorithm, which is one of the preventive traffic control method in ATM networks. Proposed algorithm is based on the cell loss priority bit in the ATM cell header. This algorithm can eliminate the measurement phasing problem in cell conformance testing in ATM networks. Proposed algorithm can minimize the cell loss ratio of high priority cell(CLP = 0) and resolve the burstiness of cells which may be introduced in traffic multiplexing and demultiplexing procedure. For the performance evaluation, we simulate the proposed algorithm with discrete time input traffic model, the results show that the performance of proposed algorithm is better than that of ITU-T usage parameter control algorithm.

• Journal of Korea Multimedia Society
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• v.5 no.3
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• pp.323-330
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• 2002

Recently, the existing embedded real-time operating systems(RTOSs) are being developed in terms of various modified versions in every application fields. Major characteristics and difference of these OSs lie in their distinct development of mechanisms which can be used in various environment and task-scheduling function which can control time-limited contingencies. In this paper, we design and implement round/robin scheduling algorithm based on time-sharing with equal-priority for multiple tasks which are provided preemptive and priority task allocation function in $\mu{C/OS-II}$ version 2.03. We propose the most important event-ready list structure in $\mu{C/OS-II}$; kernel, and provide the running result for multiple tasks with equal priority for the proposed structure.

• The KIPS Transactions:PartA
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• v.17A no.4
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• pp.167-172
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• 2010

This paper proposes a set of runtime test models for priority queues and shows the runtime test results based on the proposed test models for the representative priority queues: the traditional heap, post-order heap, and pairing heap. Among these heaps, the traditional heap is the worst in time complexity analyzed. But, according to our experimental results based on the test models proposed, it is shown that the slowest one is the pairing heap that utilizes pointers and the fastest one is the traditional heap. For the two implicit heaps, these results are in contrary to the fact that the post-order heap is better than the traditional heap in time complexity analyzed.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 1995.04a
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• pp.729-738
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• 1995

We consider a priority-based packet-switching system with three phases of the packet transmission time. Each packet belongs to one of several priority classes, and the packets of each class arrive at a switch in a Poison process. The switch transmits queued packets on a priority basis with three phases of preemption mechanism. Namely, the transmission time of each packet consists of a preemptive-repeat part for the header, a preemptive-resume part for the information field, and a nonpreemptive part for the trailer. By an exact analysis of the associated queueing model, we obtain the Laplace-Stieltjes transform of the distribution function for the delay, i.e., the time from arrival to transmission completion, of a packet for each class. We derive a set of equations that calculates the mean response time for each class recursively. Based on this result, we plot the numerical values of the mean response times for several parameter settings. The probability generating function and the mean for the number of packets of each class present in the system at an arbitrary time are also given.

• Management Science and Financial Engineering
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• v.17 no.1
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• pp.79-94
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• 2011

Team orienteering, an extension of single-competitor orienteering, is the problem of determining multiple paths from a starting node to a finishing node for a given allowed time or distance limit fixed for each of the paths with the objective of maximizing the total collected score. Each path is through a subset of nodes, each of which has an associated score. The team orienteering problem has many applications such as home fuel delivery, college football players recruiting, service technicians scheduling, military operations, etc. Unlike existing optimal and heuristic algorithms often leading to heavy computation, this paper suggests two types of priority rule based heuristics-serial and parallel ones-that are especially suitable for practically large-sized problems. In the proposed heuristics, all nodes are listed in an order using a priority rule and then the paths are constructed according to this order. To show the performances of the heuristics, computational experiments were done on the small-to-medium sized benchmark instances and randomly generated large sized test instances, and the results show that some of the heuristics give reasonable quality solutions within very short computation time.

• Smart Media Journal
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• v.4 no.1
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• pp.25-32
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• 2015

Powering wireless sensors with energy harvested from the environment is coming of age due to the increasing power densities of both storage and harvesting devices and the electronics performing energy efficient energy conversion. In order to maximize the functionality of the wireless sensor network, minimize missing packets, minimize latency and prevent the waste of energy, problems like congestion and inefficient energy usage must be addressed. Many sleep-awake protocols and efficient message priority techniques have been developed to properly manage the energy of the nodes and to minimize congestion. For a WSN that is operating in a strictly energy constrained environment, an energy-efficient transmission strategy is necessary. In this paper, we present a novel transmission priority decision scheme for a heterogeneous body sensor network composed of normal nodes and an energy harvesting node that acts as a cluster head. The energy harvesting node's decision whether or not to clear a normal node for sending is based on a set of metrics which includes the energy harvesting node's remaining energy, the total harvested energy, the type of message in a normal node's queue and finally, the implementation context of the wireless sensor network.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.11
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• pp.4189-4202
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• 2014

In this paper, we propose a priority-based unequal error protection scheme of data partitioned H.264/AVC video with hierarchical quadrature amplitude modulation. In order to map data with higher priority onto the most significant bits of QAM constellation points, a priority sorting method categorizes different data partitions according to the unequal importance factor of encoded video data in one group of pictures by evaluated the average distortion. Then we propose a hierarchical quadrature amplitude modulation arrangement with adaptive constellation distances, which takes into account the unequal importance of encoded video data and the channel status. Simulation results show that the proposed scheme improves the received video quality by about 2 dB in PSNR comparing with the state-of-the-art unequal error protection scheme, and outperforms EEP scheme by up to 5 dB when the average channel SNR is low.