Ohyoung Song

Performance Evaluation of Opportunistic Vertical Handover Considering On–Off Characteristics of VoIP Traffic

Vertical handover is one of the key technologies to support seamless connectivity across multiple wireless communication systems and guarantee quality of service (QoS) for the applications therein. This paper proposes an opportunistic vertical handover scheme for a voice over Internet Protocol (VoIP) connection that makes use of the on-off characteristics of voice traffic by aligning the mutual silence period of the two parties engaged in conversation with the service disruption time that occurs during the vertical handover procedure. From the six-state Brady model, we derive a simplified two-state Markov model in which the characteristics of both the talk-spurt period and the mutual silence period are obtained. We then analyze the performance of the proposed scheme with respect to the handover execution time and the packet loss time. The analysis and simulation results show that the proposed scheme significantly decreases the VoIP packet loss time, whereas the total time required for the vertical handover procedure increases but remains within a tolerable time limit.

Vertical handover based on the prediction of mobility of mobile node

Mobile IPTV is one of the hot applications capitalizing recently advanced wireless communication technologies. This paper proposes a new vertical handover scheme based on the prediction of mobility of mobile node. In contrast with the existing schemes, the proposed approach considers the movement velocity and direction of the MN, and Received Signal Strength (RSS) for accurate prediction of the MNs movement toward a specific access point. Computer simulation reveals that the proposed scheme significantly outperforms the existing scheme in terms of handover success rate and messaging overhead, especially when the velocity of MN is relatively high and the number of APs is large.

Efficient 3G/WLAN interworking techniques for seamless roaming services with location-aware authentication

This paper proposes novel concepts and architectures for location-aware seamless authentication and roaming in the new interworking system between third-generation (3G) mobile networks and wireless local area networks (WLANs) where local mobility movements (micro-mobility) are handled together with global movements (macro-mobility). We introduce location as a key context in secure roaming mechanism for context-aware interworking. The fast secure roaming with location-aware authentication is implemented at an entity called LBS Broker that utilizes the concepts of direction of user and pre-warming zone. We present the interworking techniques with LBS Broker for seamless secure WLAN/3G integration enabling to meet the requirements of the future location-aware service scenarios. Performance evaluation is also presented to demonstrate the effectiveness of the proposed scheme for fast location-aware secure roaming.

An Efficient Design of Security Accelerator for IEEE 802.15.4 Wireless Senor Networks

In this paper, we provide a low cost AES core for ZigBee devices which accelerates the computation of AES algorithms. Also, by embedding the AES core, we present an efficient architecture of security accelerator satisfying the IEEE 802.15.4 specifications. In our experiments, we observed that the AES core and the security accelerator use fewer logic gates and consume lower power than other architectures based on blockwide and folded ones.

Personalized Recommendation System Reflecting User Preference with Context-Awareness for Mobile TV

Mobile TV provides multimedia contents to the user by wireless communication. Here the personalized recommendation system allows the users to easily select the contents wanting to access. In this paper we propose a personalized recommendation scheme which considers the activities of the user at runtime and the information on the environment around the user. It allows efficient operation in mobile device, and interoperability between the TV multimedia metadata and ontology. The accuracy of the proposed scheme is evaluated by an experiment, which reveals a significant improvement compared to the existing schemes.

Balanced Chain-Based Routing Protocol (BCBRP) for Energy Efficient Wireless Sensor Networks

Energy is a critical issue for maintaining the WSNs. In this paper we propose a distributed chain-based routing scheme for energy efficient WSNs. In order to balance the distance between the nodes, the entire area containing the network is partitioned into equal size sub-areas. The nodes in each sub-area are connected into a chain using an algorithm similar to the minimum spanning tree algorithm. The sub-networks comprised of the chains are connected using the bridge nodes. With the proposed scheme, the maximum distance of the between the nodes is reduced and the network life time is increased about 11% and 7% compared to PEGASIS and EBSCR, respectively.

A location-aware secure interworking architecture between 3GPP and WLAN systems

Location-aware computing is widely discussed to be one attractor of the future ubiquitous networks for intelligent home and telematics services. Apart from technical difficulties in providing accurate position information there is also a lack of a clearly defined framework how to create innovative and secure services using location information. In this paper, we identify QoS, interworking and security problems in location-aware computing. We propose a number of concepts and infrastructures for location-aware security services including micro and macro mobility management in ubiquitous home networks and heterogeneous wireless networks. We further explain how the proposed approach can be applied to seamless secure interworking among wireless LANs and 3G, 4G cellular systems. Our approach might be helpful in the discussion for the frameworks especially highlighting evolutionary steps for the next ubiquitous networks.

An Efficient Resource Management Protocol for Handling Small Resource in Wireless Sensor Networks

Wireless sensor nodes with single chips may have insufficient resources for certain applications. We propose a resource management protocol for applications with constrained resources to improve effectiveness by borrowing resources from a resource management server.

An Efficient VoD Scheme Combining Fast Broadcasting with Patching

Today, mobile IPTV provides various multimedia services. Therefore, extensive researches on providing service continuity in the mobile IPTV environment are being conducted. Here reducing the user waiting time under the restriction of limited bandwidth is an important design issue in the video on-demand multicast service. In this paper we propose a scheme reducing the waiting time of a user wanting to start to view the video not from the beginning but from any point. The proposed scheme allows significantly reduced waiting time compared to the existing scheme for varying request rates and number of channels, as verified by computer simulation.

Efficient category-based service discovery on multi-agent platform

Today, multi-agent technologies are widely used for realizing prevalent ubiquitous computing applications, in which service discovery is a critical task for finding a particular service instance. While JADE is a popular system for multi-agent applications, its directory facilitator (DF) used for service discovery employs a sequential search approach, which shows degraded performance when the number of registered services becomes large. This paper proposes a new DF scheme employing the category-based classification and search approach. It greatly reduces the search space and allows accurate matchmaking. The DF implemented with the proposed approach and JADE-DF are compared in terms of query response time and memory space requirement. It demonstrates that the proposed DF allows faster query processing than JADE-DF and requires smaller memory space, especially for a large number of services and queries of multiple parameters.