Abstract-Citizens develop Wireless Mesh Networks (WMN) in many areas as an alternative or their only way for local interconnection and access to the Internet. This access is often achieved through the use of several shared web proxy gateways. These network infrastructures consist of heterogeneous technologies and combine diverse routing protocols. Network-aware stateof-art proxy selection schemes for WMNs do not work in this heterogeneous environment. We developed a client-side gateway selection mechanism that optimizes the client-gateway selection, agnostic to underlying infrastructure and protocols, requiring no modification of proxies nor the underlying network. The choice is sensitive to network congestion and proxy load, without requiring a minimum number of participating nodes. Extended Vivaldi network coordinates are used to estimate client-proxy network performance. The load of each proxy is estimated passively by collecting the Time-to-First-Byte of HTTP requests, and shared across clients. Our proposal was evaluated experimentally with clients and proxies deployed in guifi.net, the largest community wireless network in the world. Our selection mechanism avoids proxies with heavy load and slow internal network paths, with overhead linear to the number of clients and proxies.
Connected car technology promises to drastically reduce the number of accidents involving vehicles. Nevertheless, this technology requires the vehicle precise location to work. The adoption of Global Positioning System (GPS) as a navigation device imposes limitations to geolocation information under non-line-of-sight conditions. This work introduces the Time Series Dead Reckoning System (TedriS) as a solution for dead reckoning navigation when the GPS fails. TedriS uses Time Series Regression Models (TSRM) and the data from the rear wheel speed sensor of the vehicle to estimate the absolute position. The process to estimate the position is carried out in two phases: training and predicting. In the training phase, a novel technique applies TSRM and stores the relationship between the GPS and the rear wheel speed data; then in the predicting phase, this relationship is used. We analyze TedriS using traces collected at the campus of Federal University of Rio de Janeiro (UFRJ), Brazil, and with indoor experiments with a robot. Results show an accuracy compatible with dead-reckoning navigation state-of-art systems.
Video transmission over IP networks requires appropriate conditions of quality of service, in order to ensure the integrity of the image, which still represents a challenge to be overcome in wireless mesh networks due to traffic capacity limitations inherent to its architecture. In this work we evaluate the performance of high-resolution video over multihop mesh networks and we propose a suitable GOP size for encoding video to be streamed, based on traffic conditions to minimize the loss of quality. Experiments were carried out in a wireless mesh network planned for real testing within a 1500m 2 area of the main UFAM campus, using the IEEE 802.11a and 802.11n network standards.
Video transmission over IP networks requires appropriate conditions of quality of service, in order to ensure the integrity of the image, which still represents a challenge to be overcome in wireless mesh networks due to traffic capacity limitations inherent to its architecture. In this work we evaluate the performance of high-resolution video over multihop mesh networks and we propose a suitable GOP size for encoding video to be streamed, based on traffic conditions to minimize the loss of quality. Experiments were carried out in a wireless mesh network planned for real testing within a 1500m 2 area of the main UFAM campus, using the IEEE 802.11a and 802.11n network standards.
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