Tavarua : a mobile telemedicine system using WWAN striping

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2007.Includes bibliographical references (p. 69-78).Tavarua is a platform designed to support mobile telemedicine systems over wireless wide area networks, WWANs. It utilizes network striping and other complementary techniques to send uni-directional near real time video and audio data streams from a imobile node to a stationary location. The key technical challenge is transmitting high-bandwidth, loss-sensitive data over multiple low-bandwidth, lossy channels. We overcome these challenges using dynamic adjustment of the encoding parameters and a novel video encoding technique (grid encoding) that minimizes the impact of packet losses. Using five WWAN interfaces, our system reliably and consistently transmits audio and diagnostic quality video, with median PSNR values that range from 33.716dB to 36.670dB, with near real-time latencies. We present a study of the characteristic behavior of WWANs, and a description of our system architecture based in part on the lessons gleaned from that study. Through a set of experiments where we transmit video and audio data from a moving vehicle we evaluate the system, focusing on consistency, reliability, and the quality of the audio and video streams. These experiments demonstrate that we can transmit high quality video and audio in varying conditions and even in the presence of hardware failures.by Jennifer Carlisle.S.M

Transport Layer Optimizations for Heterogeneous Wireless Multimedia Networks

The explosive growth of the Internet during the last few years, has been propelled by the TCP/IP protocol suite and the best effort packet forwarding service. However, quality of service (QoS) is far from being a reality especially for multimedia services like video streaming and video conferencing. In the case of wireless and mobile networks, the problem becomes even worse due to the physics of the medium, resulting into further deterioration of the system performance. Goal of this dissertation is the systematic development of comprehensive models that jointly characterize the performance of transport protocols and media delivery in heterogeneous wireless networks. At the core of our novel methodology, is the use of analytical models for driving the design of media transport algorithms, so that the delivery of conversational and non-interactive multimedia data is enhanced in terms of throughput, delay, and jitter. More speciffically, we develop analytical models that characterize the throughput and goodput of the transmission control protocol (TCP) and the transmission friendly rate control (TFRC) protocol, when CBR and VBR multimedia workloads are considered. Subsequently, we enhance the transport protocol models with new parameters that capture the playback buffer performance and the expected video distortion at the receiver. In this way a complete end-to-end model for media streaming is obtained. This model is used as a basis for a new algorithm for rate-distortion optimized mode selection in video streaming appli- cations. As a next step, we extend the developed models for the aforementioned protocols, so that heterogeneous wireless networks can be accommodated. Subsequently, new algorithms are proposed in order to enhance the developed media streaming algorithms when heterogeneous wireless networks are also included. Finally, the aforementioned models and algorithms are extended for the case of concurrent multipath media transport over several hybrid wired/wireless links.Ph.D.Committee Chair: Vijay Madisetti; Committee Member: Raghupathy Sivakumar; Committee Member: Sudhakar Yalamanchili; Committee Member: Umakishore Ramachandran; Committee Member: Yucel Altunbasa

Efficient Passive Clustering and Gateways selection MANETs

Passive clustering does not employ control packets to collect topological information in ad hoc networks. In our proposal, we avoid making frequent changes in cluster architecture due to repeated election and re-election of cluster heads and gateways. Our primary objective has been to make Passive Clustering more practical by employing optimal number of gateways and reduce the number of rebroadcast packets