Scalable video transmission over a network is easily adaptable to different types of mobile experiencing different network conditions. However the transmission of differentiated video packets in an error-prone wireless environment remains problematic. We propose and analyze a cross-layer error control scheme that exploits priority-aware block interleaving (PBI) in the MAC layer for video broadcasting in CDMA2000 systems. The PBI scheme allocates a higher priority to protecting the data which are more critical to the decoding of a video stream, and therefore has more effect on picture quality in the application layer. The use of Reed-Solomon coding in conjunction with PBI in the MAC layer can handle error bursts more effectively if its implementation takes account of underlying error distributions in the physical layer, and differentiates between different types of video packets in the application layer. We also calculate the maximum jitter from the variability of the Reed-Solomon decoding delay and determine the size of jitter buffer needed to prevent interruptions due to buffer underrun. Simulations demonstrate the extent to which we can improve the perceived quality of scalable video.

Demand for 3D visualization is increasing in mobile devices as users have come to expect more realistic immersive experiences. However, limited networking and computing resources on mobile devices remain challenges. A solution is to have a proxy-based framework that offloads the burden of rendering computation from mobile devices to more powerful servers. We present the implementation of a framework for parallel remote rendering using commodity Graphics Processing Units (GPUs) in the proxy servers. Experiments show that this framework substantially improves the performance of rendering computation of 3D video.

The recent development of high-speed data transmission over wireless cellular networks has enabled the delivery of multimedia broadcasting services to mobile users. These services involve a range of interactions among different system components, including the wireless channel, the network, and mobile devices, making it crucial for the service provider to verify the model, design, and behavior of a new service before it is deployed. However, previous studies have largely relied on network simulations or scaled experiments, and there has been little work on the sort of unified framework for quality-of-service (QoS) assessment, which considers the interactions between components, that we propose in this paper. Accurate models of the wireless channel, the network, and the data processing that takes place on an embedded system of a mobile client, are integrated within our framework, and allow us to predict several key system metrics and the quality of the video stream as it is perceived by users. Furthermore, different models of system components can be easily plugged in to extend this framework. As an example application, we analyze the performance of the process of decoding scalable videos on ARM-based mobile embedded systems in CDMA2000 wireless cellular networks.

The recent development of high-speed data transmission over wireless networks enables multimedia broadcasting service to mobile users. Multimedia broadcasting service involves interactions among different system and network components, so it is crucial for the service provider to verify the correctness of system/service model and design, and their behaviors before a new type of service is deployed. However, due to limitations of using network simulations or scaled experimental testbeds, there has been none of research on such verification and simulation framework in 3G broadcasting networks. Therefore, we propose a simulation and analysis framework for multimedia broadcasting service over wireless networks. With concrete modeling of wireless physical channel, network, and data processing on a client device, it enables the prediction of various interesting system parameters and perceived quality of multimedia streams to users. Different models of system and network components can be plugged easily in our simulation framework for further extensions. Using this framework, we analyze the processing performance for decoding scalable videos on mobile devices in CDMA2000 wireless networks.

At the convergence of computer vision, graphics, and multimedia, the emerging 3D video technology promises immersive experiences in a truly seamless environment. However, the requirements of huge network bandwidth and computing resources make it still a big challenge to render 3D video on mobile devices at real-time. In this paper, we present how remote rendering framework can be used to solve the problem. The differences between dynamic 3D video and static graphic models are analyzed. A general proxy-based framework is presented to render 3D video streams on the proxy and transmit the rendered scene to mobile devices over a wireless network. An image-based approach is proposed to enhance 3D interactivity and reduce the interaction delay. Experiments prove that the remote rendering framework can be effectively used for quality 3D video rendering on mobile devices in real time.

Many emerging applications for peer to peer overlays may require nodes to satisfy strict timing deadlines to access a replica of a given object. This includes multimedia and hard realtime applications such as distributed gaming. We formulate the QoS-aware replication problem, the goal of which is to locate the minimum number of replicas to satisfy access time deadlines for all nodes while minimizing storage usage in the overlay. Existing replication schemes cannot be used to solve this problem since they are best-effort only. We show that finding a solution to the QoS-aware object replication in an arbitrary overlay topology is intractable (NP-complete). We then present simple centralized as well as decentralized heuristics for QoS-aware replication, and compare their performance experimentally. In addition, we investigate how these decentralized heuristics effectively works in a real network.

Reducing initial delay of playing time, delay jitter during playing time, and network bandwidth utilization is important for multimedia streaming service. In order to achieve these two goals, our peer-to-peer multimedia caching service exploits the proximity of set of clients and temporal and spatial locality of cached streams on the clients. Peer clients, which are fully connected together, not only receive multimedia streams from a server, but also send cached streams to peer clients like a proxy server upon its request. All information about the peer clients, and video segment they cache, quality of connections, are maintained by a cache service via the publish/subscribe protocols. This paper shows approaches for multimedia streaming, streaming scheduling, pre-fetching and switching streaming clients in the collaborative environment of peer-to-peer clients. Our simulation results show provisioning small initial delay and low jitter during playing time.

In Internet audio applications, delay and delay jitter affect mostly the applications' quality of service. Since packet delays are different and changing over time, the receiver needs to buffer some amount of packets before playout. Therefore, the amount of buffered packets and the timing of playout are very important for the performance of applications. We adopt an autoregressive (AR) model for estimation of packet delay and deploy a robust identification algorithm for adjustment of the parameters of the AR process. In our preliminary experiments, this robust algorithm leads to better performance when the noise is correlated and/or non-stationary, and also it is robust to model uncertainties.