• KIISE Transactions on Computing Practices
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• v.23 no.5
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• pp.328-333
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• 2017

Mobile game apps, which are popular in various mobile devices, tend to be power-hungry and rapidly drain the device's battery. Since a long battery lifetime is a key design requirement of mobile devices, reducing the power consumption of mobile game apps has become an important research topic. In this paper, we investigate the power consumption characteristics of popular mobile games with multiple threads, focusing on the inter-thread. From our power measurement study of popular mobile game apps, we observed that some of these apps have abnormally high-load threads that barely affect the user's gaming experience, despite the high energy consumption. In order to reduce the wasted power from these abnormal threads, we propose a novel technique that detects such abnormal threads during run time and reduces their power consumption without degrading user experience. Our experimental results on an Android smartphone show that the proposed technique can reduce the energy consumption of mobile game apps by up to 58% without any negative impact on the user's gaming experience.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.21 no.11
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• pp.2153-2166
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• 2017

Web apps have a problem that they cause same data to be repetitively retrieved, processed, and displayed when web browsers load different web pages. To resolve the problem, this paper presents and evaluates a new method for restructuring of Java web apps. This approach dynamically analyzes Java web apps from the MVC (Model-View-Controller) architecture point of view and identifies redundant data by using the composite view pattern. Then the input apps are restructured in order not to load the redundant data when users make requests for new pages. This restructuring generates new web apps that conform to the MVC architecture and improve the performance of input web apps. The experimental results showed that when compared to legacy web apps, the restructured apps' response time was reduced on desktop PCs and mobile devices by 38% and 55%, respectively. In addition, case studies using open-source web apps showed the applicability of the proposed approach.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.44 no.3 s.357
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• pp.18-25
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• 2007

In sensor networks, sensor nodes have limited computational capacity, power and memory. Thus energy efficiency is one of the most important requirements. How to extend the lifetime of wireless sensor networks has been widely discussed in recent years. However, one of the most effective approaches to cope with power conservation, network scalability, and load balancing is clustering technique. The function of a cluster head is to collect and route messages of all the nodes within its cluster. Cluster heads must be changed periodically for low energy consumption and load distribution. In this paper, we propose an energy-aware cluster head selection algorithm and Distance Estimation-based distributed Clustering Algorithm (DECA) in wireless sensor networks, which exchanges cluster heads for less energy consumption by distance estimation. Our simulation result shows that DECA can improve the system lifetime of sensor networks up to three times compared to the conventional scheme.

• Journal of information and communication convergence engineering
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• v.4 no.4
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• pp.141-146
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• 2006

In these days, wireless data services are becoming ubiquitous in our daily life because they offers several fundamental benefits including user mobility, rapid installation, flexibility, and scalability. Moreover, the requests for various multimedia services and the Quality of Service (QoS) support have been one of key issues in wireless data communications. Therefore the research relative to Medium Access Control (MAC) has been progressing rapidly. Especially a number of QoS-aware MAC schemes have been introduced to extend the legacy IEEE 802.11 MAC protocol which has not guaranteed any service differentiation. However, none of those schemes fulfill both QoS features and channel efficiency although these support the service differentiation based on priority. Therefore this paper studies a novel MAC scheme, referred to as Enhanced Distributed Coordination Function with Network Adaptation (EDCF-NA), for enhancements of both QoS and medium efficiency. It uses a smart factor denoted by ACK rate and Network Load Threshold (TH). In this paper, we study how the value of TH has effect on MAC performance and how the use of optimal TH pair improves the overall MAC performance in terms of the QoS, channel utilization, collision rate, and fairness. In addition, we evaluate and compare both the performance of EDCF-NA depending on several pairs of TH and the achievement of various MAC protocols through simulations by using Network Simulator-2 (NS-2).

• IEMEK Journal of Embedded Systems and Applications
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• v.10 no.4
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• pp.207-212
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• 2015

Wi-Fi Direct allows battery powered mobile devices to form a wireless ad hoc network. Since one member of the network called Group Owner (GO) takes the role of managing the network, the network lifetime is mainly affected by the energy efficiency of GO. Hence, Wi-Fi Direct defines power saving schemes that allow GO to save the energy by turning off its radio interface during the periods called absence periods. However, the Wi-Fi Direct specification does not specify how to set parameters (denoted by PS parameters) determining the schedule of the absence periods. In this paper, we therefore propose a novel traffic-aware power saving scheme for Wi-Fi Direct networks. In particular, the proposed scheme estimates the application-level traffic load and adaptively tunes the PS parameters according to the estimated value.

• IEIE Transactions on Smart Processing and Computing
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• v.1 no.2
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• pp.106-116
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• 2012

The huge success of location-aware applications has called for the rapid development of an alternative positioning system to the global positioning system (GPS) for indoor localization based on existing technologies, such as 802.11 wireless networks. This paper proposes the Wireless MAC Processor Positioning System (WMPS), which is a localization system running on off-the-shelf 802.11 Access Points and based on the time-of-flight ranging of users' standard terminals. This paper proves through extensive experiments that the propagation delays can be measured with the accuracy required by indoor applications despite the different noise components that can affect the result: latencies of the hardware transreceivers, multipath, ACK jitters and timer quantization. Key to this solution is the choice of the Wireless MAC Processor architecture, which enables a straightforward implementation of the ranging subsystem directly inside the commercial cards without affecting the basic DCF channel access algorithm. In addition to the proposed measurement framework, this study developed a simple and effective localization algorithm that can work without requiring any preliminary calibration or device characterization. Finally, the architecture allows the measurement methodology to be adjusted as a function of the network load or propagation environments at the run time, without requiring any firmware update.

• Journal of Communications and Networks
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• v.16 no.1
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• pp.81-91
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• 2014

This paper proposes hidden-node aware grouping (HAG) algorithm to enhance the performance of institute of electrical and electronics engineers (IEEE) 802.15.4 networks when they undergo either severe collisions or frequent interferences by hidden nodes. According to the degree of measured collisions and interferences, HAG algorithm dynamically transforms IEEE 802.15.4 protocol between a contention algorithm and a contention-limited one. As a way to reduce the degree of contentions, it organizes nodes into some number of groups and assigns each group an exclusive per-group time slot during which only its member nodes compete to grab the channel. To eliminate harmful disruptions by hidden nodes, especially, it identifies hidden nodes by analyzing the received signal powers that each node reports and then places them into distinct groups. For load balancing, finally it flexibly adapts each per-group time according to the periodic average collision rate of each group. This paper also extends a conventional Markov chain model of IEEE 802.15.4 by including the deferment technique and a traffic source to more accurately evaluate the throughput of HAG algorithm under both saturated and unsaturated environments. This mathematical model and corresponding simulations predict with 6%discrepancy that HAG algorithm can improve the performance of the legacy IEEE 802.15.4 protocol, for example, even by 95% in a network that contains two hidden nodes, resulting in creation of three groups.

• Journal of Digital Convergence
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• v.10 no.1
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• pp.349-355
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• 2012

Today, the computing environments is very complex, so researches that endow a system with the self-healing's ability that recognizes problem arising in a target system are being an important issues. However, the existing methodology, the goal for the new requirements for self-healing system developers to model and analyze the constraints that must be greater efforts. Therefore, in this paper are aware of problems detected by the system to solve the problem is the analysis of goal-based scenarios. In addition, there is a pre and post applying a strategy to be dynamically reconfigured to show you how to self-healing. These proposed new requirements for methodology, self-healing reduces the load on the developer's analysis.

• The KIPS Transactions:PartD
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• v.8D no.4
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• pp.439-450
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• 2001

Mobile agent is one of the promising ways of overcoming network load and latency. It is also a new software paradigm including those concepts of client/server, applet/servelet, and code-on-demand. In this paper, a new mobile agent concept with flexible replay scheme is proposed, which can deal with embarrassing situation when replying results should be accomplished in various distributed applications. For example, they are 1) a burden of bulky result, 2) a need of different replay scheme dependent on work type, 3) connection failure to the target node, and 4) a need of fast migration to next node to keep the itinerary. Regarding the source node, there may be another situation that it wants to be aware of whether its wi가 is completed or not. Three kinds of reply schemes are proposed for dealing flexibly with such situations. They are based on priority reply list where nodes to be replied are stored according to their priorities. An experimental supply chain management model using the proposed reply schemes is designed and implemented. It is one of good distributed applications appropriate for our reply schemes, because it requires different reply schemes according to work types and it is important to gather required information in time.

• Korean Journal of Computational Design and Engineering
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• v.10 no.1
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• pp.40-48
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• 2005

A hydraulic hose is an important part of the hydraulic system which transmits power using pressurized fluids. It allows relative motion between components at each end of the hose assembly, and it is much easier to route a hose assembly than it is to bend and install a rigid tubing assembly. Unnecessary loads, which drop the hose's pressure capability and shorten service life, depend on a hose-routing. Therefore, the Hydraulic system designers must be aware to consider unnecessary load does not affect the here. For this consideration in an early stage of the design process, CAD system must support the hose assembly routing design function which is to generate routing path and design fitting angle properly. This paper proposes 2 methods. One is to generate curves that are similar to routing paths of the real hose assembly using the energy minimization method and the optimization method. The other is to design fitting angles that are important design elements of a hose assembly using the Parallel Transport Frame. To implement the proposed methods above, commercial CAD software, CATIA has been integrated with our program.