Younghwan Lim

Scalable mobile internet servers: selecting useful images from the web for mobile services

Mobile devices can be easily connected to network anywhere today. Therefore, there are many studies on a variety of contents for mobile devices. In order to provide mobile contents for personal computers in a ubiquitous environment. In this paper, the author propose a framework for obtaining Internet contents intended for personal computers on mobile devices. In other words, the primary concern of this paper is to select the best images for optimal performance and convert them into images that can be effectively reproduced on mobile devices. In case contents should be suitable to various platform devices for service, the load of the server is increased. For this, the performance of the server is to be optimized through selecting useful images among the many available images and converting them while considering the display pixel rates (DPR) and the image distribution areas

Enhanced fast handover for mobile IPv6 based on IEEE 802.11 network

In MIPv6, whenever a mobile node changes its attached point, handover process should be followed to inform its home agent and correspondent of the mobile nodes current location. The handover process is decomposed into layer 2 and layer 3 handovers again, and these two handovers are accomplished sequentially, which causes long latency problem. This problem is a critical issue in MIPv6. To make up for this, we propose an enhanced fast handover scheme to reduce the overall latency on handover, revising the fast handover [1]. Especially, several messages in layer 3 are sent in one frame during layer 2 handover. We use cost analysis for the performance evaluation. Compared to MIPv6 handover scheme, the proposed scheme gains 79% improvement while it gains 31% improvement, compared to the fast handover.

Transcoding pattern generation for adaptation of digital items containing multiple media streams in ubiquitous environment

Digital item adaptation (DIA) is one of main parts in MPEG21. The goal of the DIA is to achieve interoperable transparent access to multimedia contents by shielding users from network and terminal installation, management and implementation issues. In general, a digital item consists of multiple discrete or continuous media and adaptation process is to be applied to one of its multiple media. Therefore in the process of adapting the given digital item, the transcoding order of its media has great impact on the adaptation performance because the adaptation process may stop at the point of satisfying a adaptation QoS(Quality of Services). In order to reduce the transcoding time which result in reducing the initial delay time, we propose a pattern based transcoding model for DIA. Because the performance of the model is dependent on the pattern, we also suggest a EPOB based pattern generation method. Finally a sample pattern was suggested based on the experimental results of the method.

Content aware selecting method for reducing the response time of an adaptive mobile web service

One of the particulars to be considered for effective servicing of wireless Internet to mobile terminal is the information of terminal environment. It is because time cost is required in producing mobile contents to suit environment of the connected terminal. In other words, in order to provide mobile web service by considering terminal characteristics, methods to minimize response time and server capacity in accordance with transcoding time in server are required. In this paper, response time to occur in the course of mobile web contents servicing was analyzed and, as a solution for this, Pre-Service method was introduced. Also, this paper suggests two methods in Pre-Service process for selecting optimize content in Cache. One is Device Profile Aware Selection using mobile device information. The other is Content Aware Selection using component information of requested content. Performance level of each method proposed was compared through experiment and the result of analysis was described.

A Real-Time Selection Method of an Acceptable Transcoding Path in a MPEG21 DIA for Mobile Terminals

In order to access the multimedia contents in a server via mobile devices, the contents should be transcoded and streamed into the mobile device according to the system environment and user preferences. In this paper, we propose a method of finding a sequence of multiple unit transcoders called a transcoding path that can be utilized in MPEG21 digital item adaptation for resource adaptation engine based on the theory of a Context Free Grammar.

A method of selecting and transcoding content for mobile web service

A factor to be considered in browsing of an existing web page to a mobile terminal is the difference in hardware environments between average PCs and terminals. It is necessary to service contents effectively in accordance with diverse environmental information of various terminals caused by the rapid development in communication devices. This various terminal information needs much time to generate the content for a server and much capacity to load in the server. Therefore the method to minimize response time and server capacity is required. This paper proposes a CA(Content Aware Selecting) and HCT(Hyperlink Based Content Transcoding) method to provide a more rapid response time according to requirements of various terminals and illustrates the results of test system.

An automatic mobile web generation method from PC web using DFS and W-DFS

This thesis intends to suggest how to produce adaptable contents that can be replayed on a device by extracting web contents in order that an existing web page can be replayed by using a device that can replay multimedia technology such as mobile and TV. To perform a service by using MobileGate system and adaptively converting one HTML page existing on web to a device, a page defined as DIDL in MPEG-21 is used. To use numerous amount of web contents in a device having a limited interface, by extracting a contents through DFS method, Circular Doubly-Linked List is established and served. DIDL of average 18 pages to minimize scroll in one web page is generated and all contents on web can be approached and replayed by only up and down button. In this research, web contents service that can be offered by using PC can be offered from mobile and TV device that are under ubiquitous environment.

Real-Time Creation Method of Personalized Mobile Web Contents for Ubiquitous Contents Access

Although wireless devices are the most suitable device for ubiquitous environment, they have restrictive capacities when using internet services than desktop environments. Therefore this research proposes a wireless internet service method that uses contents-based personalization. The existing websites can easily and promptly access desired news articles and other data through RSS-linked web contents and by the personalization method. The proposed method will make using wireless internet easier while lowering wireless contents production costs. Moreover, personalized mobile web contents that satisfy the preferences of users can be serviced.

An Adaptive PC to Mobile Web Contents Transcoding System Based on MPEG-21 Multimedia Framework

The purpose of this paper is to supply web contents for PC to various multi platform device as PDA or portable device. The conventional studies could not consider these devices, so it created mobile contents beforehand, and then transmitted to the limited mobile device. In this point, the critical problem is to generate mobile contents which are suitable for all kinds of mobile device from PC Web content. This paper propose a service system for transmitting wire web content to various portable device by using MPEG-21 Multimedia Framework. It does not create mobile contents for each device. It just uses DIDL of MEPG-21 as intermediate language to express the structure, resource and description of mobile contents. In DIDL, the multimedia resource is transcoded in off-line previously. The description part is converted in real time as soon as service is requested by end-user. Mobile contents integrate adapted resource with appropriate description and then are transmitted. In addition, this paper proposes the Multi-level caching for reusing mobile contents and describes the result in experiment system.

Evaluation of network blocking algorithm based on ARP spoofing and its application

Sometimes network resources including IP address, MAC address, and hostname could be misused for the weakness of TCP/IP protocol suite and the deficiency of network management. Therefore, there is urgent need to solve the problems from the viewpoint of network management and operation. In this paper, we propose a network network blocking algorithm based on ARP spoofing and evaluate the robustness of this algorithm via various experiments. We have performed several experiments on the gratuitous ARP exchange and IP address conflict detection in order to identify the robustness of the network blocking algorithm under both homogeneous and heterogeneous operating system.