Maarten Wijnants

Dynamic interactions in physically realistic collaborative virtual environments

This work describes our efforts in creating a general object interaction framework for dynamic collaborative virtual environments. Furthermore, we increase the realism of the interactive world by using a rigid body simulator to calculate all actor and object movements. The main idea behind our interactive platform is to construct a virtual world using only objects that contain their own interaction information. As a result, the object interactions are application independent and only a single scheme is required to handle all interactions in the virtual world. In order to have more dynamic interactions, we also created a new and efficient way for human users to dynamically interact within virtual worlds through their avatar. In particular, we show how inverse kinematics can be used to increase the interaction possibilities and realism in collaborative virtual environments. This results in a higher feeling of presence for connected users and allows for easy, on-the-fly creation of new interactions. For the distribution of both the interactive objects and the dynamic avatar interactions, we keep the network load as low as possible. To demonstrate the effectiveness of our techniques, we incorporate them into an existing CVE framework.

End-to-end QoE Optimization Through Overlay Network Deployment

In this paper an overlay network for end-to-end QoE management is presented. The goal of this infrastructure is QoE optimization by routing around failures in the IP network and optimizing the bandwidth usage on the last mile to the client. The overlay network consists of components that are located both in the core and at the edge of the network. A number of overlay servers perform end-to-end QoS monitoring and maintain an overlay topology, allowing them to route around link failures and congestion. Overlay access components situated at the edge of the network are responsible for determining whether packets are sent to the overlay network, while proxy components manage the bandwidth on the last mile. This paper gives a detailed overview of the end-to-end architecture together with representative experimental results which comprehensively demonstrate the overlay networks ability to optimize the QoE.

Energy aware software evolution for Wireless Sensor Networks

Wireless Sensor Networks (WSNs) are subject to high levels of dynamism arising from changing environmental conditions and application requirements. Reconfiguration allows software functionality to be optimized for current environmental conditions and supports software evolution to meet variable application requirements. Contemporary software modularization approaches for WSNs allow for software evolution at various granularities; from monolithic re-flashing of OS and application functionality, through replacement of complete applications, to the reconfiguration of individual software components. As the nodes that compose a WSN must typically operate for long periods on a single battery charge, estimating the energy cost of software evolution is critical. This paper contributes a generic model for calculating the energy cost of the reconfiguration in WSN. We have embedded this model in the LooCI middleware, resulting in the first energy aware reconfigurable component model for sensor networks. We evaluate our approach using two real-world WSN applications and find that (i.) our model accurately predicts the energy cost of reconfiguration and (ii.) component-based reconfiguration has a high initial cost, but provides energy savings during software evolution.

Managing client bandwidth in the presence of both real-time and non real-time network traffic

Managing client downstream bandwidth is an issue that is rapidly gaining in importance due to the increasing extent to which multimedia content is being exploited in networked applications. Depending on its characteristics, this multimedia content is exchanged in either a real-time or non real-time manner. In this paper, we present the NIProxy, a network intermediary which introduces different types of intelligence in the transportation network in an attempt to improve the Quality of Experience (QoE) provided to users of networked applications. In particular, we concentrate on the NIProxypsilas bandwidth distribution functionality and we report on how support for non realtime network traffic was incorporated through the adoption of buffering as well as rate control techniques. Using representative experimental results, we demonstrate the NIProxypsilas capability to successfully manage client downstream bandwidth in the presence of both real-time and non real-time network traffic. In addition, the presented experimental results are compared to the default scenario in which the NIProxy is not involved, revealing a considerable improvement in the userpsilas QoE in case the NIProxypsilas bandwidth management functionality is leveraged.

The NIProxy: a Flexible Proxy Server Supporting Client Bandwidth Management and Multimedia Service Provision

We present the NIProxy, a flexible network intermediary which aims to improve the Quality of Experience (QoE) of users of networked applications by pushing more intelligence into the network. More specifically, the NIProxy is network- as well as application-aware, meaning it has knowledge of both the transportation network and the application(s) it is serving. This dual awareness is exploited to improve user QoE in two complementary ways. First of all, the NIProxy is capable of dynamically distributing a clients available downstream bandwidth over the different network streams generated by a networked application. Secondly, the NIProxy supports multimedia service provision, meaning it can apply services on multimedia streams on behalf of its clients. An important feature of the NIProxy is that its two QoE-improving mechanisms are not isolated entities but instead can interact with each other. A comprehensive discussion of the NIProxys software architecture is provided and the implementation of an example service, which adds video transcoding functionality to the NIProxy, is described Finally, presented experimental results clearly demonstrate the effectiveness of our approach.

synchronous MediaSharing: social and communal media consumption for geographically dispersed users

Real-time social interaction possibilities are increasingly disappearing from the media consumption process. A decisive contributing factor to this tendency is growing user location disparity. This paper proposes synchronous MediaSharing (sMS), a distributed, purely web-based framework consisting of APIs plus a back-end that enables geographically separated persons to socially consume multimedia content in a synchronized fashion. The sMS service currently resides in a proof-of-concept stage, awaiting qualitative evaluation by means of user experience research methods, yet its underlying network infrastructure as well as the majority of its principal functional components have already been designed, implemented and evaluated. A chief innovation of the system is that its exclusive reliance on open web standards warrants cross-platform support and unlocks seamless content synchronization across the physical and virtual worlds. We outline our vision for the sMS service, motivate the need for such a system, discuss its current implementation, present tentative practical results that confirm the feasibility and validity of our design, and overview the sMS feature roadmap. The sMS functionality has apparent utility in education, training and professional settings, but also in the field of entertainment and the recreational market.

An Eco-friendly Hybrid Urban Computing Network Combining Community-Based Wireless LAN Access and Wireless Sensor Networking

Computer-enhanced smart environments, distributed environmental monitoring, wireless communication, energy conservation and sustainable technologies, ubiquitous access to Internet-located data and services, user mobility and innovation as a tool for service differentiation are all significant contemporary research subjects and societal developments. This position paper presents the design of a hybrid municipal network infrastructure that, to a lesser or greater degree, incorporates aspects from each of these topics by integrating a community-based Wi-Fi access network with Wireless Sensor Network (WSN) functionality. The former component provides free wireless Internet connectivity by harvesting the Internet subscriptions of city inhabitants. To minimize session interruptions for mobile clients, this subsystem incorporates technology that achieves (near-)seamless handover between Wi-Fi access points. The WSN component on the other hand renders it feasible to sense physical properties and to realize the Internet of Things (IoT) paradigm. This in turn scaffolds the development of value-added end-user applications that are consumable through the community-powered access network. The WSN subsystem invests substantially in ecological considerations by means of a green distributed reasoning framework and sensor middleware that collaboratively aim to minimize the networks global energy consumption. Via the discussion of two illustrative applications that are currently being developed as part of a concrete smart city deployment, we offer a taste of the myriad of innovative digital services in an extensive spectrum of application domains that is unlocked by the proposed platform.

An overlay network providing application-aware multimedia services

Real-time streaming of multimedia content is increasingly becoming a crucial part of networked applications. A logical consequence of this evolution is a growing demand for services that can be applied on these multimedia streams. In this paper, we present our overlay network which provides such multimedia services. Although these services are application-aware and can thus exploit application-specific knowledge, the overlay network itself is completely generic. Consequently, multiple applications can take advantage of the overlay network, even concurrently. Furthermore, the overlay network is highly extensible, meaning additional services can be added to it easily. Besides describing the architecture of the software component of our overlay network, we also discuss the implementation of two example multimedia services. The first service mixes multiple audio streams into a single stream to enable lightweight voice communication in a Networked Virtual Environment. The second service applies face detection on a video stream to generate meaningful avatars in a meeting system called iConnect. The experimental results produced by these two services clearly demonstrate that our overlay network is capable of providing valuable services for a wide range of networked multimedia applications.

Exploiting Proxy-Based Transcoding to Increase the User Quality of Experience in Networked Applications

In this work we describe how we extended the functionality of our previously introduced application and network aware proxy system with transcoding capabilities. Based on their compound awareness, our proxies devise a strategy for every connected client that intelligently distributes the clients available bandwidth over the different application data streams. The proxies subsequently put each computed bandwidth allocation strategy into effect by managing and transcoding data streams inside the network before they reach the client. We also present results from the integration of our work into an existing networked virtual environment. These results clearly indicate that our intelligent proxy, enhanced with its novel transcoding functionality, can increase the user quality of experience considerably in networked applications

An optimized adaptive streaming framework for interactive immersive video experiences

This paper describes how optimized streaming strategies, based on MPEG-DASH, can be employed to power a new generation of interactive applications based on immersive video. The latter encompasses ultra-high-resolution, omnidirectional and panoramic video. The goal is to deliver experiences that are made up of multiple videos of short duration, which can be joined at run-time in an order defined through user interactions. Applications of the technology are widespread, ranging from virtual walkthroughs to interactive storytelling, the former of which will be featured in detail. The main technological challenges tackled in this paper are to deliver these experiences in a seamless fashion, at the highest quality level allowed by network conditions and on a wide range of platforms, including the Web. Besides these, the paper focuses on the two-tier software architecture of the proposed framework, as well as a short evaluation to substantiate the validity of the proposed solutions.