With the rapid development in the areas of mobile manufacturing and multimedia communications, there is an increasing demand for Networked Virtual Environment (NVE) applications, such as Augmented Reality (AR), virtual walk-throughs, and massively multiplayer online games (MMOGs), on hand-held devices. Unfortunately, downloading and rendering a complex 3D scene is very computationally intensive and is not compatible with current mobile hardware specifications nor with available wireless bandwidth. Existing NVE applications deploy client/server based 3D streaming over thin mobile devices, which suffer from single point of failure, latency, and scalability issues. To address these issues, image-based rendering (IBR) and cloud-based 3D streaming have been introduced. The former introduces visual artifacts that reduce, and usually cancel, the realistic behaviors of the Virtual Environment (VE) application, while the latter is considered very expensive to implement. Peer-to-peer (P2P) 3D streaming is promising and affordable, but it has to tackle issues in object discovery and selection as well as content provider strategies. Distributing VE content over a mobile ad-hoc network (MANET) makes the system difficult to update due to the dynamic nature of the mobile clients. In order to tackle these issues, we came up with a novel protocol that combines the pros of both central and distributed approaches. Our proposed hybrid protocol, called OCTET, enables 3D scene streaming over thin devices in a way that can cope with current mobile hardware capabilities and mitigate the challenges of client/server and P2P 3D streaming. In fact, OCTET provides strategies that select, prioritize, and deliver only those objects that contribute to the user’s visible scene. OCTET is implemented using the "ns-2" simulation environment, and extensive experiments have clearly demonstrated significant achievements in mobile resource utilization, throughput, and system scalability.

Demands for multimedia content, one form of digital content, are continuously increasing at a phenomenal pace, as video features are commonly available on personal devices, such as iPod, cell phone, laptop, PDA, and Blackberry. The streaming service poses unique bandwidth and delay challenges to application designers. The size of a typical video content is usually orders of magnitude larger than that of any other type of content, resulting in high demands for bandwidth contribution from the content providers. Even more challenging, the content must be delivered to end hosts in real time to maintain smooth playback, i.e., the content must be transmitted at a satisfactory rate. In this thesis, we present our research towards a high-quality peer-to-peer live streaming system that utilizes network coding, a novel technique that permits coding at every peer, which has proven benefits in file dissemination applications. To ensure the practicality of our work, it is our imperative objective to conduct all experiments under realistic settings.

In large-scale peer-assisted live streaming systems with hundreds of online channels, it becomes critically important to investigate the lifetime pattern of streaming sessions to have a better understanding of peer dynamics. Aiming to improve performance of the P2P streaming systems, the goal of this thesis is twofold: 1) for popular channels, we wish to identify superior peers, that contribute a higher percentage of upload capacities and stay for a longer period of time; 2) for unpopular channels, we seek to explore factors that affect the peer instability. Utilizing more than 130 GB worth of run-time traces from a large-scale real-world live streaming system, UUSee, we conduct a comprehensive and in-depth statistical analysis. Using survival analysis techniques, we discover critical factors that may influence the longevity. Based on the Cox regression models we built, we also discuss several interesting insights from our measurement results.

The integration of heterogeneous access networks is becoming a possible feature of 4G wireless networks. It is challenging to deliver the multimedia services over such integrated networks because of the discrepancy in the bandwidth of different networks. This thesis presents an adaptive approach that combines source rate adaptation and buffering to achieve high quality VBR video streaming with less quality variation over an integrated two-tier network. Statistical information of the residence time in each network or localization information are utilized to anticipate the handoff occurrence. The performance of this approach is analyzed under the CBR case using a Markov reward model. Simulation under the CBR and VBR cases is conducted for different types of network models. The results are compared with a dynamic programming algorithm as well as other naive or intuitive algorithms, and proved to be promising.

In this thesis, we consider error-correction codes for systems which have burst erasure channels, but where the packet delay is constrained. The packet delay itself is the time di erence between the arrival of a source packet at the encoder and the reconstruction of that source packet at the decoder. While such a framework was introduced by Martinian (2004) and his co-authors, several problems remain open. We make three contributions in this thesis. First we develop a rigorous converse proof for the point-to-point case and thus complete the result of Martinian (2004). Our proof technique is also applied to a multicast channel model and new results are obtained. Secondly we study the case when there are multiple parallel links between the encoder and decoder and obtain the capacity in some special cases. Finally we study a setup when there are multiple source streams, each with a di erent delay constraint, and obtain capacity results.

In large-scale peer-assisted live streaming systems with hundreds of online channels, it becomes critically important to investigate the lifetime pattern of streaming sessions to have a better understanding of peer dynamics. Aiming to improve performance of the P2P streaming systems, the goal of this thesis is twofold: 1) for popular channels, we wish to identify superior peers, that contribute a higher percentage of upload capacities and stay for a longer period of time; 2) for unpopular channels, we seek to explore factors that affect the peer instability. Utilizing more than 130 GB worth of run-time traces from a large-scale real-world live streaming system, UUSee, we conduct a comprehensive and in-depth statistical analysis. Using survival analysis techniques, we discover critical factors that may influence the longevity. Based on the Cox regression models we built, we also discuss several interesting insights from our measurement results.

The integration of heterogeneous access networks is becoming a possible feature of 4G wireless networks. It is challenging to deliver the multimedia services over such integrated networks because of the discrepancy in the bandwidth of different networks. This thesis presents an adaptive approach that combines source rate adaptation and buffering to achieve high quality VBR video streaming with less quality variation over an integrated two-tier network. Statistical information of the residence time in each network or localization information are utilized to anticipate the handoff occurrence. The performance of this approach is analyzed under the CBR case using a Markov reward model. Simulation under the CBR and VBR cases is conducted for different types of network models. The results are compared with a dynamic programming algorithm as well as other naive or intuitive algorithms, and proved to be promising.

In this thesis, we consider error-correction codes for systems which have burst erasure channels, but where the packet delay is constrained. The packet delay itself is the time di erence between the arrival of a source packet at the encoder and the reconstruction of that source packet at the decoder. While such a framework was introduced by Martinian (2004) and his co-authors, several problems remain open. We make three contributions in this thesis. First we develop a rigorous converse proof for the point-to-point case and thus complete the result of Martinian (2004). Our proof technique is also applied to a multicast channel model and new results are obtained. Secondly we study the case when there are multiple parallel links between the encoder and decoder and obtain the capacity in some special cases. Finally we study a setup when there are multiple source streams, each with a di erent delay constraint, and obtain capacity results.

Demands for multimedia content, one form of digital content, are continuously increasing at a phenomenal pace, as video features are commonly available on personal devices, such as iPod, cell phone, laptop, PDA, and Blackberry. The streaming service poses unique bandwidth and delay challenges to application designers. The size of a typical video content is usually orders of magnitude larger than that of any other type of content, resulting in high demands for bandwidth contribution from the content providers. Even more challenging, the content must be delivered to end hosts in real time to maintain smooth playback, i.e., the content must be transmitted at a satisfactory rate. In this thesis, we present our research towards a high-quality peer-to-peer live streaming system that utilizes network coding, a novel technique that permits coding at every peer, which has proven benefits in file dissemination applications. To ensure the practicality of our work, it is our imperative objective to conduct all experiments under realistic settings.

With advances in microelectronic and wireless communication technologies, smartphones have computer-like capabilities in terms of computing power and communication bandwidth. They allow users to use advanced applications that used to be run on computers only. Web browsing, email fetching, gaming, social networking, and multimedia streaming are examples of wide-spread smartphone applications. Unsurprisingly, network-related applications are dominant in the realm of smartphones. Users love to be connected while they are mobile. Streaming applications, as a part of network-related applications, are getting increasingly popular. Mobile TV, video on demand, and video sharing are some popular streaming services in the mobile world. Thus, the expected operational time of smartphones is rising rapidly. On the other hand, the enormous growth of smartphone applications and services adds up to a significant increase in complexity in the context of computation and communication needs, and thus there is a growing demand for energy in smartphones. Unlike the exponential growth in computing and communication technologies, the growth in battery technologies is not keeping up with the rapidly growing energy demand of these devices. Therefore, the smartphone's utility has been severely constrained by its limited battery lifetime. It is very important to conserve the smartphone's battery power. Even though hardware components are the actual energy consumers, software applications utilize the hardware components through the operating system. Thus, by making smartphone applications energy-efficient, the battery lifetime can be extended. With this view, this work focuses on two main problems: i) developing an energy testing methodology for smartphone applications, and ii) evaluating the energy cost and designing an energy-friendly downloader for smartphone streaming applications. The detailed contributions of this thesis are as follows: (i) it gives a generalized framework for energy performance testing and shows a detailed flowchart that application developers can easily follow to test their applications; (ii) it evaluates the energy cost of some popular streaming applications showing how the download strategy that an application developer adopts may adversely affect the energy savings; (iii) it develops a model of an energy-friendly downloader for streaming applications and studies the effects of the downloader's parameters regarding energy consumption; and finally, (iv) it gives a mathematical model for the proposed downloader and validates it by means of experiments.