Efficient Integration and QoS Management of Video over Wireless Networks

Oregon Health & Science University, Portland OR

Investigators

Abstract

We are currently witnessing an incredible transformation in the way we access information and computing power. With small handheld devices such as personal digital assistants, cellular phones, and palmtop computers, users are taking their computers with them more often than not. Fur- thermore, with the developments in wireless technologies, users are beginning to slowly move away from their dependence on wired access to their information. While this trend is building significant momentum, the types of information that are accessed through these devices is still severely lim- ited by the wireless media. Given the bottle-necks associated with today's power-limited portable devices, the limitation due to channel conditions has not yet been felt by the user; however the strain on the underlying wireless network will only get worse. The goal of the proposed research is the construction of high performance algorithms for tetherless access which consider overall system goals through joint optimization across multiple layers. The objective will be to solve problems which connect the physical layer to the application layer. In the past, a classical approach to wireless communication system design was undertaken { a modular approach loosely based on the Open Systems Interconnection reference stack model. For wired communication networks, such a separation of activities led to functioning systems offering solid performance. However, the deleterious effects of the wireless communications channel force the investigation of all possible methods to improve performance. Thus, to provide the desired fidelity and to transport high-data rate information over the wireless medium, joint optimization across multiple communication layers will be necessary. To focus the research, wireless transport of video via Direct Sequence Code-Division Multiple-Access (DS-CDMA) will be considered. In this project, we propose the research and development of video streaming algorithms that are more suited for wireless transmission using DS-CDMA as an access methodology. There are several reasons why this project is necessary. First, current research onmulti-rate detection and estimation algorithms at the physical layer are not tailored for specific application layer data. Second, many of the video transmission schemes over wireless networks have assumed fixed bit-error rates that are introduced by the wireless transmission. In CDMA systems, the bit-error rate is highly dependent on the channel and the number of active users, both of these processes are time-varying; however, this variability in bit-error rates has not been fully addressed at the application layer. Third, the elasticity ofvideo can be exploited to design efficient algorithms which can take advantage of the shape of video streams as well as time-varying channel conditions to offer desired quality-of-service. This research project has three principle goals: Investigation of efficient multi-rate detection and estimation algorithms for wireless physical media transmission. Investigation of video streaming techniques for wireless networks that use underlying network condition feedback to dynamically adjust the forward error correction used to protect the video data. Investigation of the integration of physical layer media characteristics and higher-level video applications to provide the highest quality-of- service to applications.