Enhancing the quality of multimedia applications over wireless networks

Wireless networks is the fundamental component of next generation communication networks to provide users ubiquitous access. Due to the flexibility provided by wireless networks, users can access the network-based information and services anytime and anywhere. However, some emerging and popular multimedia applications, like Internet Protocol television (IPTV) and Multimedia Gaming, requiring high bandwidth and small delay, pose challenge for the last-mile wireless access network. Consequently, there is significant amount of research and development efforts in enhancing the performance of multimedia applications over wireless networks. This dissertation makes four important contributions towards that end.;In Chapter 2, we study the various architectures, protocols and standards to support high quality video streaming over broadband mobile networks. We survey the most popular international video coding and compression standard ISO/IEC Moving Picture Experts Group-4 (MPEG-4) or ITU-T H.264. We also survey the next generation broadband mobile LTE (Long Term Evolution) network architecture and key technologies followed by video streaming delivery architectures and network protocols supporting video streaming over broadband mobile networks. Finally, we discuss possible future direction of video streaming in wireless networks.;In Chapter 3, we propose an optimization algorithm to solve the key issue of bitrate switching in next generation HTTP-based adaptive video streaming. Our solution can provide the best possible viewing quality to users without playback interruption, which is reported as the biggest concern of on-line video streaming. The optimization algorithm is based on a specific streaming architecture and it can be easily integrated with other approaches and industry standards. Simulation results show that our optimization algorithm can determine the best video bitrate according to channel condition and buffered streams in local devices to provide viewers the best possible quality with least interruption.;In Chapter 4, we propose a novel architecture and mechanism to delivery high quality video to users that use a wireless mesh access network. The novel mechanism consists of 1) a network route selection scheme which provides paths for multiple video streams with the least interference, called Minimum Interference Route Selection (MIROSE) and 2) an optimization algorithm that determines the compression rates depending on the network condition, called Network State Dependent Video Compression Rate (NSDVCR) algorithm. Simulation results show that our approach can provide significant improvement of video quality measured with Peak Signal-to-noise Ratio (PSNR) compared with standard routing protocols and default compression rates.;In Chapter 5, we present a novel approach to collect multiple categories of data in a resource-limited wireless sensor network. In an advanced wireless sensor network capable of sensing and collecting multiple kinds of data, it is a challenging problem to efficiently and fairly collect various critical information when network has limited resources. We propose an optimization algorithm for the buffer management in the sensor node to provide higher event throughput, and maintain coverage fidelity when network is congested. Our detailed simulation analysis show that our proposed approach has significant performance improvement with respect to event throughput, fairness and the overall "value" of the information collected by the wireless sensor network.;The dissertation proposes and validates a number of novel mechanisms and optimization algorithms to support the most challenging multimedia application namely, video, which has the dual requirements of high-bandwidth and small-delay, in various wireless networks. We first investigate the problem of providing high-quality video streaming in broadband mobile networks. We then enhance the video quality by (1) changing the video encoding and transmission techniques so as to be suitable for the wireless network; (2) designing a novel network architecture and protocol for video streaming; and (3) jointly altering the video compression and the network transport protocol.