• International Journal of Computer Science & Network Security
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• v.22 no.7
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• pp.13-20
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• 2022

Basically Mobile Ad Hoc Network (MANET) is an autonomous system with the collection of mobile nodes, these nodes are connected to each other by using wireless networks. A mobile ad hoc network poses this quality which makes topology in dynamic manner. As this type of network is Ad Hoc in nature hence it doesn't have fixed infrastructure. If a node wishes to transfer data from source node to a sink node in the network, the data must be passed through intermediate nodes to reach the destination node, hence in this process data packet loss occurs in various MANET protocols. This research study gives a comparison of various Mobile Ad Hoc Network routing protocols like proactive (DSDV) and reactive (AODV, DSR) by using random topology with more intermediate nodes using CBR traffic. Our simulation used 50, 100, and 150 nodes variations to examine the performance of the MANET routing protocols. We compared the performance of DSDV, AODV and DSR, MANET routing protocols with the result of existing protocol using NS-2 environment, on the basis of different performance parameters like Packet Delivery Ratio, average throughput and average end to end delay. Finally we found that our results are better in terms of throughput and packet delivery ratio along with low data loss.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.23 no.4
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• pp.23-28
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• 2023

In a wireless smart utility network communication system, an asynchronous low power MAC is standardized and used according to IEEE 802.15.4e. An asynchronous MAC called RIT (Receiver Initiated Transmission) has a characteristic in which delay time and power consumption are greatly affected by a check-in interval (RIT period). By waking up from sleep every check-in interval and checking whether there is data to be received, power consumption in the receiving end can be drastically reduced, but power consumption in the transmitting end occurs due to an excessive wakeup sequence. If an excessive wake-up sequence is reduced by shortening the check interval, power consumption of the receiving end increases due to too frequent wake-up. In the RIT asynchronous MAC technique, power consumption performance according to traffic load and operation of check-in interval is analyzed and applied to Wi-SUN construction.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.40 no.10
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• pp.59-66
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• 2003

We propose the novel optical burst switching scheme to guarantee a minimum bandwidth for multiple classes. To date, QoS studies on OBS network are capable of differentiating two classes, but have difficulties in providing a minimum bandwidth lot several classes because of lower classes' collision with the highest class bursts in the networks. To solve that problem, in our proposed scheme we assign time zones in a data channel for each class periodically, making one burst have top priority at least its zone. Also, the new burst assembling algorithm, as well as the way of managing data channel, is necessarily proposed to coordinate with the proposed OBS scheme. Through the evaluation, we show that the worst-case end-to-end delay is small enough and the received bandwidth of the lower classes is still assured regardless of the traffic load of the highest class.

• Journal of Korea Multimedia Society
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• v.13 no.6
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• pp.849-864
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• 2010

This paper proposes a multipath routing protocol called cross-layer multipath AODV (CM-AODV) for wireless ad hoc networks, which selects multiple routes on demand based on the signal-to-interference plus noise ratio (SINR) measured at the physical layer. Note that AODV (Ad hoc On-demand Distance Vector) is one of the most popular routing protocols for mobile ad hoc networks. Each time a route request (RREQ) message is forwarded hop by hop, each forwarding node updates the route quality which is defined as the minimum SINR of serialized links in a route and is contained in the RREQ header. While achieving robust packet delivery, the proposed CM-AODV is amenable to immediate implementation using existing technology by neither defining additional packet types nor increasing packet length. Compared to the conventional multipath version of AODV (which is called AOMDV), CM-AODV assigns the construction of multiple paths to the destination node and makes it algorithmically simple, resulting in the improved performance of packet delivery and the less overhead incurred at intermediate nodes. Our performance study shows that CM-AODV significantly outperforms AOMDV in terms of packet delivery ratio and average end-to-end delay, and results in less routing overhead.

• Journal of Communications and Networks
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• v.8 no.2
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• pp.241-252
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• 2006

Traditional service-level agreements (SLAs), defined by average delay or packet loss, often camouflage the instantaneous performance perceived by end-users. We define a set of metrics for service availability to quantify the performance of Internet protocol (IP) backbone networks and capture the impact of routing dynamics on packet forwarding. Given a network topology and its link weights, we propose a novel technique to compute the associated service availability by taking into account transient routing dynamics and operational conditions, such as border gateway protocol (BGP) table size and traffic distributions. Even though there are numerous models for characterizing topologies, none of them provide insights on the expected performance perceived by end customers. Our simulations show that the amount of service disruption experienced by similar networks (i.e., with similar intrinsic properties such as average out-degree or network diameter) could be significantly different, making it imperative to use new metrics for characterizing networks. In the second part of the paper, we derive goodness factors based on service availability viewed from three perspectives: Ingress node (from one node to many destinations), link (traffic traversing a link), and network-wide (across all source-destination pairs). We show how goodness factors can be used in various applications and describe our numerical results.

• International Journal of Precision Engineering and Manufacturing
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• v.2 no.4
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• pp.5-11
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• 2001

Vibration and noise of gears is doc to the transmission error and the vibration exciting force caused by the periodically alternating tooth stiffness. Transmission error is the rotation delay between driving and driven gear caused by manufacturing error, alignment error in assembly and so on. Tooth stiffness changes with the proceeding mesh of teeth. The purpose of this study is to develop how to calculate simultaneously the optimum amounts of tooth profile modification. end relief and crowning by minimizing the vibration exciting force of helical gears. We estimate the vibration exciting force by the meshing analysis of gears. Formulated constraints of this problem consist of contact ratio and strengths of gear teeth such as tooth bending strength, surface durability, and scoring. ADS(Automated Design Synthesis) is used as an optimization tool. We also investigate the relation between the aspect ratio and the optimum values of tooth modification. The proposed method can calculate the optimum amount of tooth modification automatically and is expected to be practically useful to resolve the problem of vibration of helical gears.

• Journal of Korea Multimedia Society
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• v.17 no.12
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• pp.1453-1460
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• 2014

WFQ (Weighted Fair Queuing) provides not only fairness among traffic flows in using bandwidth but also guarantees the Quality of Service (QoS) that individual flow requires, which is why it has been applied to the resource reservation protocol (RSVP)-capable router. The RSVP allocates an enough resource to satisfy both the rate and end-to-end delay requirements of the flow in the condition of no packet loss, and the WFQ scheduler guarantees those QoS requirements with the allocated resource. In practice, however, most QoS-guaranteed services allow a degree of packet loss, especially from 0.1% to 3% for Voice over IP. This paper discovers that the packet loss rate of each traffic flow is determined by only its time-stamp adjustment value, and then enhances the WFQ to provide a differentiated packet loss guarantee under general traffic conditions in terms of both traffic characteristics and QoS requirements. The performance evaluation showed that the proposed WFQ could increase the utilization of bandwidth by 8~11%.

• Journal of Korean Academy of Nursing
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• v.31 no.2
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• pp.279-291
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• 2001

Rapid progress in modern medical technology has made it possible to sustain life and/or delay death using 'heroic' treatments. The availability of life-sustaining treatment brings several issues in end-of-life care such as 'dying with dignity' and an radical increase in health care costs. The use of Advance Directives(AD) have been widely heralded by health care providers, gerontologists, and advocacy groups as means of protecting patients' right to accept or refuse life-sustaining treatment in end-of-life care. The use of AD can not only improve patients' autonomy and quality of life but also bring efficiency in distributing health care resources. The proportion of older persons in Korean population has been increasing. Those 65 years of age or over were about 7 percent of the population. Death and dying is not limited to older persons, but it is more prevalent among them. In conjunction with an aging population and the increasing prevalence of death, the issues of death and dying will become crucial in near future in terms of 'dying with dignity', 'autonomy', and 'self-control'. This paper attempts to explode and establish the concept of advance directives (AD) based on literature review. Data sources are computer searches with the MEDLINE database. Due to the lack of prior study on AD for a Korean cases, studies abroad are reviewed. This paper suggests the need for future study on the possibility of the use of AD in Korea.

• Journal of the Korean Society for Precision Engineering
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• v.17 no.11
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• pp.199-205
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• 2000

The vibration and noise of gears is due to the vibration exciting force caused by the tooth stiffness which changes periodically as the mesh of teeth proceeds and by the transmission error, that is, the rotation delay between driving gear and driven gear caused by manufacturing error and alignment error in assembly and so on. The purpose of this study is to develop how to calculate simultaneously the optimum amounts of tooth profile modification, end relief and crowning by minimizing the vibration exciting force of helical gears. We estimate the vibration exciting force by the mesh analysis of gears. The constraints of this problem consist of contact ratio and strengths of gear teeth such as tooth fillet stress, surface durability and scoring. ADS(Automated Design Synthesis) is used as an optimization tool. And, since the aspect ratio is an important parameter of tooth modification, we investigate the relation between it and the optimum values of tooth modification. The proposed method can calculate the optimum amount of tooth modification automatically and is to be utilized to resolve the problem of vibration of helical gears.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.9
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• pp.3056-3074
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• 2014

Convergecast is probably the most common communication style in wireless sensor networks (WSNs). And linear network coding (LNC) is a promising concept to improve throughput or reliability of convergecast. Most of the existing works have mainly focused on exploiting these benefits without considering its potential adverse effect. In this paper, we argue that LNC may not always benefit convergecast. This viewpoint is discussed within four basic scenarios: LNC-aided and none-LNC convergecast schemes with and without automatic repeat request (ARQ) mechanisms. The most concerned performance metrics, including packet collection rate, energy consumption, energy consumption balance and end-to-end delay, are investigated. Theoretical analyses and simulation results show that the way LNC operates, i.e., conscious overhearing and the prerequisite of successfully decoding, could naturally diminish its advantages in convergecast. And LNC-aided convergecast schemes may even be inferior to none-LNC ones when the wireless link delivery ratio is high enough. The conclusion drawn in this paper casts a new light on how to effectively apply LNC to practical WSNs.