Bert Vankeirsbilck

Design and implementation of a hybrid remote display protocol to optimize multimedia experience on thin client devices

In a thin client computing architecture, application processing is delegated to a remote server rather than running the application locally. User input is forwarded to the server, and the rendered images are relayed through a dedicated remote display protocol to the users device. Existing remote display protocols have been successfully optimized for applications with only minor and low-frequent screen updates, such as a spreadsheet or a text editor. However, they are not designed to cope with the fine-grained and complex color patterns of multimedia applications, leading to high bandwidth requirements and an irresponsive user interface. In this article, a hybrid remote display protocol approach is presented. The existing Remote FrameBuffer protocol of Virtual Network Computing (VNC-RFB) protocol is leveraged with a video streaming mode to transport the rendered images of multimedia applications to the client. Dependent on the amount of motion in the images to be presented, the images are relayed to the client either through the VNC-RFB protocol or through video streaming in the H.264 format. The architecture of this hybrid image renderer is presented and the implementation is detailed. Furthermore, the decision heuristic to switch between the VNC-RFB and the streaming mode is discussed. Experimental results clearly show the advantage of the hybrid approach in terms of client CPU and bandwidth requirements.

Cloud-Based Desktop Services for Thin Clients

Cloud computing and ubiquitous network availability have renewed peoples interest in the thin client concept. By executing applications in virtual desktops on cloud servers, users can access any application from any location with any device. For this to be a successful alternative to traditional offline applications, however, researchers must overcome important challenges. The thin client protocol must display audiovisual output fluidly, and the server executing the virtual desktop should have sufficient resources and ideally be close to the users current location to limit network delay. From a service provider viewpoint, cost reduction is also an important issue.

Efficient resource management for virtual desktop cloud computing

In virtual desktop cloud computing, user applications are executed in virtual desktops on remote servers. This offers great advantages in terms of usability and resource utilization; however, handling a large amount of clients in the most efficient manner poses important challenges. Especially deciding how many clients to handle on one server, and where to execute the user applications at each time is important. Assigning too many users to one server leads to customer dissatisfaction, while assigning too little leads to higher investments costs. We study different aspects to optimize the resource usage and customer satisfaction. The results of the paper indicate that the resource utilization can increase with 29% by applying the proposed optimizations. Up to 36.6% energy can be saved when the size of the online server pool is adapted to the system load by putting redundant hosts into sleep mode.

Bandwidth Optimization for Mobile Thin Client Computing through Graphical Update Caching

This paper presents graphical update caching as a mechanism to reduce the network load generated by thin client computing systems. In such system, the user interaction and processing are separated by a network. User input such as keystrokes and mouse clicks are sent to the server over the network and graphical updates are transported the reverse way. The cache proposed in this article is static, meaning that it is composed before the thin client computing session starts and that the cache does not change during the session. Through experiments with an implementation of the cache, we show that graphical update caching effectively reduces the network load generated by thin client computing.

Cross-Layer Optimization of Radio Sleep Intervals to Increase Thin Client Energy Efficiency

Thin client computing trades local processing for network bandwidth consumption by offloading application logic to remote servers. User input and display updates are exchanged between client and server through a thin client protocol. This thin client protocol traffic can lead to a significantly higher power consumption of the radio interface of the wireless device. In this contribution, we present a cross-layer algorithm that exploits thin client protocol layer information to determine intervals where no traffic from the server is expected. During these intervals, the wireless network interface card (WNIC) is instructed to enter the energy conserving sleep mode. Using this algorithm for a remote text editor, WNIC energy consumption reductions of 21-52% can be achieved.

Remote rendering solutions using web technologies

Remote rendering is a well-known solution to the issue of running high-performance applications requiring complex visualizations on less capable hardware/software platforms or when client access to the data source for visualization is undesired or prohibitive in terms of required bandwidth. Visualizing the output of these remote rendering applications is typically achieved through native applications or, when considering a browser environment, through plug-ins. In this paper, several solutions are presented that enable deployment of these applications on standard web browsers, even those from the pre-HTML5 era. The focus in this paper is on two specific use case scenarios, taking into account that the proposed solutions are generic enough to be applied to a range of similar applications. The technologies presented cover the entire range of sub-processes contained in a complete remote rendering solution, such as the establishment of interaction feedback channels and delivery of images as part of the rendering pipeline. Depending on factors such as application requirements, developer preferences, feature availability in the web browser or raw performance figures, a custom solution can be composed from the options discussed in this paper. This is illustrated by applying them to the two aforementioned use cases, each with specific requirements and challenges, and benchmarking these example setups in terms of performance. A comparison of advantages and disadvantages is presented to guide developers in applying the technologies under real-life conditions.

Platform for real-time subjective assessment of interactive multimedia applications

With the advent of cloud computing and remote execution of interactive applications, there is a need for evaluating the Quality of Experience (QoE) and the influence on this QoE of network condition variations, media encoding parameter settings and related optimization algorithms. However, current QoE assessment focuses mainly on audiovisual quality in non-interactive applications, such as video-on-demand services. On the other hand, where experiments aim to quantify interactive quality, the focus is typically targeted at games, using an ad-hoc test setup to assess the impact of network variations on the playing experience. In this paper, we present a novel platform enabling the assessment of a broad range of interactive applications (e.g., thin client remote desktop systems, remotely rendered engineering applications, games). Dynamic reconfiguration of media encoding and decoding is built into the system, to allow dynamic adaptation of the media encoding to the network conditions and the application characteristics. Evaluating the influence of these automatic adaptations is a key asset of our approach. A range of possible use cases is discussed, as well as a performance study of our implementation, showing that the platform we built is capable of highly controllable subjective user assessment. Furthermore, we present results obtained by applying the platform for a subjective evaluation of an interactive multimedia application. Specifically, the influence of visual quality and frame rate on interactive QoE has been assessed for a remotely executed race game.

Characterization of power consumption in thin clients due to protocol data transmission over IEEE 802.11

In thin client computing, applications are executed on a network server instead of on the user terminal. Since the amount of processing at the terminal is reduced, thin clients are potentially energy efficient devices. However, a network connection between client and server is required for the transmission of user input and display updates. The energy needed for this intense network communication might undo or even exceed the power savings achieved by the reduction in client-side processing. In this paper, we present experimental results on power efficiency of the wireless platform on the thin client in case of thin client traffic. The discussion is focused on VNC-RFB, a widespread thin client protocol, over an IEEE 802.11 link in three typical user scenarios. The results indicate that a cross-layer approach between application and wireless link layer could potentially lead to important power savings.

Resource-constrained classification using a cascade of neural network layers

Deep neural networks are the state of the art technique for a wide variety of classification problems. Although deeper networks are able to make more accurate classifications, the value brought by an additional hidden layer diminishes rapidly. Even shallow networks are able to achieve relatively good results on various classification problems. Only for a small subset of the samples do the deeper layers make a significant difference. We describe an architecture in which only the samples that can not be classified with a sufficient confidence by a shallow network have to be processed by the deeper layers. Instead of training a network with one output layer at the end of the network, we train several output layers, one for each hidden layer. When an output layer is sufficiently confident in this result, we stop propagating at this layer and the deeper layers need not be evaluated. The choice of a threshold confidence value allows us to trade-off accuracy and speed.

Towards a multimedia remote viewer for mobile thin clients

Be there a traditional mobile user wanting to connect to a remote multimedia server. In order to allow them to enjoy the same user experience remotely (play, interact, edit, store and share capabilities) as in a traditional fixed LAN environment, several dead-locks are to be dealt with: (1) a heavy and heterogeneous content should be sent through a bandwidth constrained network; (2) the displayed content should be of good quality; (3) user interaction should be processed in real-time and (4) the complexity of the practical solution should not exceed the features of the mobile client in terms of CPU, memory and battery. The present paper takes this challenge and presents a fully operational MPEG-4 BiFS solution.