• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.12 no.1
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• pp.17-27
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• 2012

Broadcast-based data dissemination has become a widely accepted approach of communication in the mobile computing environment. However, with a large set of data items, the expected delay of receiving a desired data increases due to the sequential nature of the broadcast channel. This paper explores the issue of designing proper data allocation on multiple broadcast channels to reduce this wait time, and proposes a new data allocation scheme named near optimal data allocation(NODA). The proposed scheme first partitions all data items in K group based on the theoretical lower-bound of the average expected delay to determine data items which each broadcast channel has to broadcast. Then, NODA further partitions each group of data items in B groups using extended dynamic programming algorithm to broadcast data items allocated on the same broadcast channel in different frequencies. The proposed scheme is capable of minimizing the average expected delay time since it can broadcast data items allocated on the same channel reflecting their popularities.

• Journal of Korea Multimedia Society
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• v.16 no.3
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• pp.302-308
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• 2013

In this research, we have explored personal authentication system through multimodal biometrics for mobile computing environment. We have selected face and speaker recognition for the implementation of multimodal biometrics system. For face recognition part, we detect the face with Modified Census Transform (MCT). Detected face is pre-processed through eye detection module based on k-means algorithm. Then we recognize the face with Principal Component Analysis (PCA) algorithm. For speaker recognition part, we extract features using the end-point of voice and the Mel Frequency Cepstral Coefficient (MFCC). Then we verify the speaker through Dynamic Time Warping (DTW) algorithm. Our proposed multimodal biometrics system shows improved verification rate through combining two different biometrics described above. We implement our proposed system based on Android environment using Galaxy S hoppin. Proposed system presents reduced false acceptance ratio (FAR) of 1.8% which shows improvement from single biometrics system using the face and the voice (presents 4.6% and 6.7% respectively).

• Journal of Internet Computing and Services
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• v.6 no.6
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• pp.139-148
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• 2005

The desired level for multimedia services in the mobile web environment, the next generation web environment, is expected to be of PC level quality. And great efforts have been made in the development of hadware technology, communication technology, various kinds of services and standardization to support these services, In the mobile web environment, multimedia contents adaptation services should be available through supporting various kinds of devices, network abilities and users' preferences. It means that due to the variety of both desired devices' hardware specifications, called destinations, and desired QoSes, the QoSes in the destinations are not fixed or defined. If a new user wants to stream multimedia contents in a server through a new kind of terminal device, it should be considered whether the existing transcoders are able to adapt the multimedia contents. However, the existing libraries for multimedia adaptation have heavy transcoder figures which include all adaptive functions in one library, The challenge of universal access is too complex to be solved with these all in one solutions. Therefore, in this paper we propose an application independent multimedia adaptation framework which meets the QoS of new and varied mobile devices. This framework is composed of a group of unit transcoders having only one transcoding function respectively, Instead of heavy transcoders. Also, It includes the transcoder manager supporting the dynamic connections of the unit transcoders in order to satisfy end to end QoS.

• Journal of KIISE:Databases
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• v.34 no.5
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• pp.448-464
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• 2007

Location-Based Services (LBSs) provide results to queries according to the location of the client issuing the query. In LBS, techniques such as caching and prefetching are effective approaches to reducing the data transmission from a server and query response time. However, they can lead to cache inefficiency and network overload due to the client's mobility and query pattern. To solve these drawbacks, we propose a semantic prefetching (SP) scheme using prefetching segment concept and improved cache replacement policies. When a mobile client enters a new service area, called semantic prefetching area, proposed scheme fetches the necessary semantic information from the server in advance. The mobile client maintains the information in its own cache for query processing of location-dependent data (LDD) in mobile computing environment. The performance of the proposed scheme is investigated in relation to various environmental variables, such as the mobility and query pattern of user, the distributions of LDDs and applied cache replacement strategies. Simulation results show that the proposed scheme is more efficient than the well-known existing scheme for range query and nearest neighbor query. In addition, applying the two queries dynamically to query processing improves the performance of the proposed scheme.

• Journal of Internet Computing and Services
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• v.9 no.6
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• pp.63-72
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• 2008

Recent heterogeneous network management researches on information security, however, deal only with simple management using PKI and could not sufficiently address the different kinds of security problems that could arise in a heterogeneous network. Thus, various security requirements should first be satisfied and a security management protocol should first be developed to achieve a secure heterogeneous network. Hence, in this paper, various secure and effective heterogeneous network management that address security issues, which were merely a consideration in existing studies, are proposed. The proposed scheme for the protection of the user privacy is the central object and static middle objects of the process used to mutual authentication, also if communication between users is required 1-out-2 oblivious transfer to communicate by using secret communication, as well as the effectiveness and security conscious approach. Specially The proposed scheme is designed to enhance security and efficiency related to various services required in heterogeneous network, based on the reliable peripheral devices for TTP. Using Mobile device, which has been applied to electronic commerce transactions in existing schemes, this study also proposed an appropriate management scheme that is suitable for a dynamic environment and setting a temporary group to provide various services.

• Journal of the Korea Convergence Society
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• v.9 no.12
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• pp.61-68
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• 2018

As the smartphone and mobile environment develop, the time and space constraints for individual work performance are disappearing. Companies can reduce costs and expand their business quickly through cloud computing. As the use of various cloud expands, the boundaries of users, data, and applications are disappearing. Traditional security approaches based on boundaries (Perimeter) are losing their utility in the cloud environment. This paper describes the limitations of existing network access control (NAC) in a cloud environment and suggests network security technology that complements it. The study explains the SDP and combines SDP(Software Defined Perimeter) to overcome the limitations of NAC, while at the same time explaining its role as a new framework for supporting the cloud environment. The new framework proposed in this paper suggests a software-based network security solution that supports physical and software parts, providing identity-based access control, encrypted segment management, and dynamic policy management, not IP-based.

• The KIPS Transactions:PartD
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• v.13D no.6 s.109
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• pp.839-846
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• 2006

Context-aware adaptive service for overcoming the limitations of wireless devices and maintaining adequate service levels in changing environments is becoming an important issue. However, most existing studies concentrate on an adaptation module on the client, proxy, or server. These existing studies thus suffer from the problem of having the workload concentrated on a single system when the number of users increases md, and as a result, increases the response time to a user's request. Therefore, in this paper the adaptation module is dispersed and arranged over the client, proxy, and server. The module monitors the contort of the system and creates a proposition as to the dispersed adaptation system in which the most adequate system for conducting operations. Through this method faster adaptation work will be made possible even when the numbers of users increase, and more stable system operation is made possible as the workload is divided. In order to evaluate the proposed system, a prototype is constructed and dispersed operations are tested using multimedia based learning content, simulating server overload and compared the response times and system stability with the existing server based adaptation method. The effectiveness of the system is confirmed through this results.