Vol.4 No.1 March 15, 2008     
Multimedia Modeling and Applications

Editorial (001-001)
        M.K. Denko, E. Shakshuki, and A Koyama

Research Articles:

An Agents Based Middleware for Personalization of Multimedia Service Delivery in SOAs (002-018)  
        R. Aversa, B. Di Martino, N. Mazzocca, and S. Venticinque 
In this paper we present a proxy based middleware that is able to adapt the exploitation of services in SOAs according to the client profile. We focus on the possibility of adapting a multimedia service to the client capabilities by means of a brokering activity and a platform reconfiguration.The platform is composed of several software agents act as proxies, which intercept, process and forward incoming messages to the next agent, till the request is sent to the brokered provider. On the backward path the agents are able to adapt the content of returned responses. Proxies are dynamically created and configured. We describe the design of platform architecture and the personalization mechanisms. We show how a client application can be extended in order to exploit such platform facilities. A prototypal implementation is presented and some preliminary performance results are discussed.

A Rule-based Intelligent Multimedia Streaming Server System (019-041)  
        X.-F. Zhou and K. Ong 
In this paper, a novel multimedia transmission server is designed using rule based expert system technology. It is superior on current media transmission servers because it is more powerful on streaming, flexible on control, and reliable on maintenance. In the proposed expert server, working parameters and management methods are separated from the decision-making procedure and stored in an xml database called knowledge base. The server fires different transmission strategies inside the knowledge base by runtime inference. Thus it can easily adjust transmission parameters under various environments and adopt new developed methods without significantly changing the main body of server codes. In this paper, we not only analyzed the time complexity of inference procedure and the real time characteristics of the server, but also tested the server performance on local area networks. Results showed that the expert system can deliver smooth streams with around 50% deduced throughput oscillations when compared with a single rate control method. The saved 50% bandwidth could be used for supporting more users. When congestion happened, the expert system reacts intelligently and conducts cooperative steps to relocate its resources. At the same time, the congestion related information is recorded and referred for future congestion avoidance. Attractively, these enhanced performances are achieved by taking less than 10% of the CPU time for the execution of the expert server control program.

Mobile Multimedia for Multiuser Environments (042-058)  
        D.C. Doolan, S. Tabirca, and L.T. Yang 
Mobility especially the flexibility given to us by the mobile phone is the future of computing as we know it. No longer are we restricted to sitting at a desk in front of a powerful desktop machine. Mobile technology of today allows users to work, learn and play no matter where they may be. Wireless technology is becoming more and more a standard feature of computing, so much so that it is expected that approximately two billion Bluetooth enabled devices will have been produced by the end of 2007. This paper examines how Bluetooth application development may be simplified for the programmer by use of the Mobile Message Passing Interface (MMPI). It explores a selection of application areas that can benefit from this simplified means of wireless inter-device communication, including: compute intensive tasks, Mobile Learning and Multi-player gaming.

Performance Evaluation of H.264 protocol in Ad hoc Networks (059-070)  
        T.R. Sheltami 
Wireless mobile ad hoc network data transmission between multiple senders and receivers is becoming increasingly important in nowadays networks. There are many applications for sending data from a single source to multiple destinations (e.g. broadcasting) or from multiple senders to multiple receivers (e.g. teleconference). A wireless Mobile Ad hoc Network (MANET) or a multi-hop network is a collection of wireless mobile hosts forming nodes that arbitrarily and randomly change their locations. No centralized administration or infrastructure is supported, and each host communicates via radio packets. Nodes are responsible for establishing and maintaining connections between themselves. Such dynamic topology of MANET leads to several unique design issues that do not exist in other wireless networks. Video transport over ad hoc networks is more challenging than that over other wireless networks. The wireless links in an ad hoc network are not error resilient and can go down frequently because of node mobility, interference, channel fading, and the lack of infrastructure. Moreover, typical video applications may need a higher bandwidth and higher reliability connection than that provided by a single link in current or emerging wireless networks. On the other hand, it is possible to establish multiple paths between a source and a destination. Transporting video over wireless networks is further constrained by: delay limits, power issues and quality of service (QoS) parameters. All of these points should be handled carefully in video transport services. The goal of this research is to calculate the maximum distance, or number of hops, that can be supported in an ad hoc network while maintaining the delay constraints and reasonable quality of service (QoS). In this paper, we will evaluate the performance of H.264 protocol using two routing protocols, mainly: the Neigbhor-Aware Clusterhead (NAC) and the Dynamic Source Routing (DSR) protocols. The simulation results show that it is feasible to have video over ad hoc within an average distance of 6 hops utilizing an average of 5.5 Mbps, however the performance varies from one protocol to another.

Network Adaptive Layered Multicast for Heterogeneous Wireless Networks(071-082)  
        A. Durresi, V. Paruchuri, and L. Barolli
Layered transmission is a promising solution to video multicast over Heterogeneous Wireless Networks. However, since the number of layers is practically limited, noticeable mismatches would occur between the coarse-grained layer subscription levels and the heterogeneous and dynamic rate requirements from the receivers. In this paper, we propose a Network-adaptive Layered Multicast (NALM) approach, that exploits the increasing computing and communications capabilities of wireless devices. We show that by having few multicast nodes (about 10% the number of receivers) to encode and decode the video, an improvement of more than 30% in bandwidth efficiency could be achieved. Furthermore, due to the proximity of such encoding/decoding nodes to the receivers than the source itself, more accurate and faster evaluation of network conditions would be possible leading to faster convergence and further improvement in efficiency.