Kyungshik Lim

Scalable message translation mechanism for the environment of heterogeneous middleware

Various home network middleware such as HAVi, LnCP, LonWorks, and UPnP have been designed. They coexist because one middleware cannot support diverse requests of services and devices. This circumstance creates an interoperability problem among devices based on various types of home network middleware. The Universal Middleware Bridge system is designed and implemented to solve this interoperability problem using a device conversion mechanism and a message translation mechanism among the middleware. These conversion mechanisms make it possible for devices to distinguish and control other devices connected to different middleware networks in the Universal Middleware Bridge system. These mechanisms also easily support new device and middleware by adding some XML files.

A real-time voice service with the adaptive packet loss recovery scheme in the hybrid residential gateway system

This paper presents a real-time voice service with the adaptive packet loss recovery scheme based on the H.323 protocol, which is one of the service functionalities of the hybrid residential gateway system. The proposed scheme analyzes the characteristics of packet losses based on the Gilbert model, and then describes a mechanism that can recover the lost audio packets with the offset redundant data. Using information periodically reported by a receiver, the sender dynamically adjusts the amount and the offset values of redundant data, with a constraint of minimizing the bandwidth consumption of links. Since the wireless environments could be often characterized by frequent and consecutive packet losses, loss recovery mechanisms need to deal with both the random and consecutive packet losses efficiently. To achieve this, the suggested mechanism uses relatively large and discontinuous exponential offset values. To verify the effectiveness of the mechanism, we extended and implemented RTP/RTCP protocols and applications in the hybrid residential gateway system. The experimental results show that our mechanism, with exponential offset, achieves remarkably low complete packet loss rate and adapts dynamically to the fluctuation of the packet loss pattern in the wired and wireless environments.

A Scalable QoS-based inter-domain routing scheme in a high speed wide area network

In this paper we propose a scalable QoS-based inter-domain routing scheme for distributed multimedia applications in a high speed wide area network. The problem of QoS-based routing is formulated as a multicriteria shortest path problem, known as NP-complete [1,2] [W.C. Lee, M.G. Hluchyj, P.A. Humbler, Routing subject to quality of service constraints in integrated communication networks, IEEE Network (July/August 1995) 46-55. Z. Wang, J. Crowcroft, Quality of service routing for supporting multimedia applications, IEEE J. Select. Areas Commun. Special Issues on Multimedia Systems]. Our scheme consists of two phases. In Phase 1, we present a way of mapping the network into a graph that contains a part of the network topology which is neglected completely or partially by existing routing schemes, thus maintaining more accurate topology information. In Phase 2, we develop a heuristic call-by-call algorithm, based on each edges minimum normalized slackness to the QoS requested, for selecting a feasible path efficiently in depth first search (DFS)-like manner on the graph and tailoring to each applications QoS requirements. Note that our routing scheme is one of a few QoS-based hierarchical routing schemes that address explicitly the issue of selecting a path with multiple metrics.

The Conversion of a Device And a Control Message in The Universal Middleware Bridge

This paper describes how the conversion of a device and a control message is accomplished in a UMB. The UMB solves interoperability problems caused by the heterogeneity of several types of home network middleware. To solve the problems, conversion of a device and messages among the middleware is indispensable. Devices can see and control other devices connected to different middlewares in the UMB framework by the mechanism of device and message conversion.

A performance analysis of the reliable multipeer protocol (ReMP) for dynamic multimedia communications

Reliable Multipeer Protocol (ReMP) is a reliable multipeer data transfer protocol, which has been designed to support multimedia group communications. In this paper, we describe ReMP focusing on a reliable data transmission and analyze the performance on the host processing requirements. In addition, ReMP is compared to other reliable multicast protocols. Our numerical results show that ReMP can be more generally used for multimedia group applications, and are acceptable in terms of the performance and the memory requirements.

Efficient stream distribution algorithm for heterogeneous multimedia multicast with link capacity constraint

Abstract In heterogeneous multimedia multicast, a recipient bids for what it wants to receive and the source gains the same amount when a connection is established. The problem of distributing streams for heterogeneous multicast to maximize the sources gain, can be solved using a 0–1 integer programming, known as NP-complete. We consider the problem with constraint on link capacity and propose an efficient stream distribution algorithm, which has better both time and space complexity compared with any existing one. In addition, distributed implementation is straightforward, which is very useful for large networks.

Heuristics for multiway partitioning in hexagonal cellular systems

Given a hexagonal mesh of base stations in cellular systems we consider the problem of finding a cover of disjoint clusters of base stations which generate multiple types of traffic among themselves. The objective is to minimize the total communication cost for the entire system where intercluster communication is more expensive than intracluster communication for each type of traffic. We develop several heuristics based on the techniques of moving or interchanging the boundary nodes between adjacent clusters. The heuristics are compared and shown to behave quite well through experimental tests and analysis.