• Journal of Communications and Networks
• /
• v.3 no.4
• /
• pp.307-316
• /
• 2001

Two hard sub-problems have emerged relating to the use of mobile agents for service management tasks. First, what is their impact on security, and second, how can they receive a flexible capacity to adapt to an open range of different environments on demand, without introducing trio stringent prior assumptions. In this paper, we present work towards solving the second problem, which is of particular interest to management software, because it typically needs to excert fine-grained and therefore particular resource control. We suggest a mechanism that reassembles mobile agents from smaller sub-components during arrival at each hop. The process incorporates patterns of unmutable and mutable sub-components, and is informed by the conditions of each local environment. We discuss different kinds of software adaptation and draw a distinction between static and continuous forms. Our software prototype for dynamic adaptation provides a concept far exchanging environment-dependent implementations of mobile agents during runtime. Dynamic adaptation enhances efficiency of mobile code in terms of bandwidth usage and scalability.

• ETRI Journal
• /
• v.39 no.3
• /
• pp.383-389
• /
• 2017

A small dual-polarized base station antenna with a simple isolation patch is presented. A high isolation is achieved when using a shorted metallic isolation patch. The experimental results indicate that the measured impedance bandwidth of the proposed antenna is 1.72 GHz to 1.89 GHz for small cell systems and that the isolation is more than 30 dB. The proposed antenna exhibits good radiation patterns with a peak gain of 8 dBi.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2018.10a
• /
• pp.429-430
• /
• 2018

The introduction of mobile devices increased the need to apply limitations such as mobile devices' memory, speed, energy, and bandwidth on the designs of searching images. There is a demand to reduce such limitations on searching images on the mobile phone. Hence, this paper proposes a design that adds tags on pictures to manage the images in mobile environment, allowing efficient searches and deletion of duplicate files based on the similarities of the images. The proposed method does not compromise its efficiency by increasing costs; it also reduces the volume of data needed for mobile devices.

• The Journal of the Korea Contents Association
• /
• v.9 no.9
• /
• pp.41-50
• /
• 2009

A conventional middleware system is optimized for wired computing environments. The wireless mobile devices have several disadvantages of low-speed processors, small memory and narrow bandwidth of wireless network. To overcome those problem issues in wireless mobile environments, middleware and many middleware-related applications have to be changed of the small sized components. In this paper, we design a lightweight mobile middleware system called "LightMware" which is optimized for mobile environment and middleware applications

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.16 no.4
• /
• pp.1249-1265
• /
• 2022

Video streaming has become one of the most popular applications for mobile devices. The network bandwidth required for video streaming continues to exponentially increase as video quality increases and the user base grows. Multi-Path TCP (MPTCP), which allows devices to communicate simultaneously through multiple network interfaces, is one of the solutions for providing robust and reliable streaming of such high-definition video. However, mobile video streaming over MPTCP raises new concerns, e.g., power consumption and cellular data usage, since mobile device resources are constrained, and users prefer to minimize such costs. In this work, we propose a mobile video streaming framework over MPTCP (mDASH) to reduce the costs of energy and cellular data usage while preserving feasible streaming quality. Our evaluation results show that by utilizing knowledge about video behavior, mDASH can reduce energy consumption by up to around 20%, and cellular usage by 15% points, with minimal quality degradation.

• The Journal of The Korea Institute of Intelligent Transport Systems
• /
• v.13 no.1
• /
• pp.61-66
• /
• 2014

This paper describes the design, fabrication, and measurement of a compact hexa-band coupling antenna for 4G mobile handset using a small element with two slots. In order to obtain sufficient bandwidth (LTE700, GSM850, GSM900, GSM1800, GSM1900, UMTS) with a Voltage Standing Wave Ratio $(VSWR){\leq}3:1$, two slots are inserted in the small element, and coupling patch is used. The measured result of the fabricated antenna provides 410MHz bandwidth form 0.688 to 1.098GHz and 643 MHz bandwidth form 1.607 to 2.250GHz (${\leq}VSWR 3:1$) with the gain ranging from -0.52 to 4.68 dBi. Also, a good radiation pattern is achieved within the hexa-band (0.698-0.960GHz and 1.710-2.170GHz) range.

• The Transactions of the Korea Information Processing Society
• /
• v.7 no.12
• /
• pp.3923-3932
• /
• 2000

In mobile network, wireless links may be overloaded due to a high concentratioJl of mobile hosts in a given cell. As a result, the required QOS(Quality of Service) cannot be provided to all flows in that cell. So, there exists adaptive applications which can operate with various bandwidth levels. When a wireless link is overloaded, it can adapt by reducing the bandwidths of flows, is referred to as rate adaptation. In this paper, we analyze the performance of existing rate adaptation methods by simulations. The result of simulation experiments shows that average-fair adaptation scheme has very low network overhead but high bandwidth variance of flows, which causes the worse quality of service. We propose a rate adaptation method refined by combining fair adaptation and average-fair adaptation, and shows the refined method can provide lower bandwidth variance of flows by simulations.

• Journal of Korea Multimedia Society
• /
• v.15 no.6
• /
• pp.814-826
• /
• 2012

In this paper, we propose scheduling algorithms for transporting variable-bit-rate video stream using playback buffer level of the clients over wireless communication networks. The proposed algorithms attempt to maximize the utilization of limited bandwidth between the central video server and the clients over a mobile network. Since a video server may serve several video request at the same time, it is important to allocate and utilize network bandwidth to serve them fairly and efficiently. In order to improve the quality of service and real-time performance of individual video playback, the video server attempts to allocate temporarily more network bandwidth to serve a video request with the lower buffer level preferentially. The simulation results prove the fair service and load balancing among the mobile concurrent clients with different buffer levels and hence maximizing the number of frames that are transported successfully to the client prior to their playback times.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.16 no.1 s.92
• /
• pp.84-91
• /
• 2005

In this papers, we study the characteristics of dual band PIFA(Planar Inverted F antenna) for handy phones using H-type silt in the antenna radiators. Slit types on the antenna radiator vary resonance mechanism of the antenna and affect reactance component of impedance for the antenna. Therefore the antennas resonate at the dual band(cellular -band, Korea-PCS band), the bandwidth, input impedance and radiation patterns of the proposed antenna is affected by the silt length on the radiators. In order to demonstrate the validity of the proposed theory, it is implementation the antenna of the 4 types. From results for the experiment of the implementation antenna, -5 dB bandwidth of return loss is content with the allocated bandwidth of Cellular and Korea-PCS system the gains of the antenna is about -8$\~$ - 1 dB, the radiation patterns for x-polarized or y-polarized are omnidirectional pattern. From above the results of this papers, it is conclude mobile phones antenna for handy phones using this papers results.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.9 no.6
• /
• pp.1387-1394
• /
• 2005

In this paper, we propose and the call admission control mechanism that can improve the capacity of the wireless system for the non-uniform traffic load distribution based intelligent information in multiple cellular CDMA environment. The number of mobile stations that can be served simultaneously in a base station is limited by the amount of total interference received in CDMA system. Further, the average number of mobile stations in each cell may not be uniformly distributed. In this paper, considering this factors, the call admission control mechanism using the effective bandwidth concept is adapted to improve the system capacity of non-uniform traffic load distribution based intelligent information. Thus, the bandwidth for a new call can be varied dynamically for reducing the blocking rate of new calls and the dropping rate of handoff calls. The suggested call admission control mechanism is experimented through simulation by dynamically assigning the bandwidth to new and handoff calls. The simulation results show that the proposed call admission control mechanism can accommodate more mobile stations than the other methods in multiple cellular CDMA environment.