Road congestion results in a huge waste of time and productivity for millions of people. A possible way to deal with this problem is to have transportation authorities distribute traffic information to drivers, which, in turn, can decide (or be aided by a navigator) to route around congested areas. Such traffic information can be gathered by relying on static sensors placed at specific road locations (e.g., induction loops and video cameras) or by having single vehicles report their location, speed, and travel time. While the former approach has been widely exploited, the latter has come about only more recently; consequently, its potential is less understood. For this reason, in this paper, we study a realistic test case that allows the evaluation of the effectiveness of such a solution. As part of this process, (a) we designed a system that allows vehicles to crowd-source traffic information in an ad hoc manner, allowing them to dynamically reroute based on individually collected traffic information; (b) we implemented a realistic network-mobility simulator that allowed us to evaluate such a model; and (c) we performed a case study that evaluates whether such a decentralized system can help drivers to minimize trip times, which is the main focus of this paper. This study is based on traffic survey data from Portland, OR, and our results indicate that such navigation systems can indeed greatly improve traffic flow. Finally, to test the feasibility of our approach, we implemented our system and ran some real experiments at UCLA's C-Vet test bed.

The great success of P2P systems for the purpose of file-sharing set the path to the next killer application on the Internet, P2P video streaming. Although it solves scalability issues, P2P technology experiences problems of a long start time and churn-induced instability that can greatly affect the user experience. Moreover, technical and business solutions for digital rights management are still under investigation. Great efforts are underway in both academia and industry to solve these problems, whose solution will offer a scalable, affordable, and legal TV-quality-like broadcast of content. In this article, we analyze what is available to the end user in terms of P2P video-streaming products and determine which of these are the most promising for IPTV and content distribution companies. In the following, we offer: (1) A survey of the available architectures. (2) A set of experiments on a popular peer-to-peer system, SopCast. (3) Guidelines for large scale deployment.