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WiFi-based Long Distance (WiLD) networks with links as long as 50–100 km have the potential to provide con-nectivity at substantially lower costs than traditional approaches. However, real-world deployments of such networks yield very poor end-to-end performance. First, the current 802.11 MAC protocol has fundamental shortcomings when used over long(More)
We present the design and evaluation of two forms of power management schemes that reduce the energy consumption of networks. The first is based on putting network components to sleep during idle times, reducing energy consumed in the absence of packets. The second is based on adapting the rate of network operation to the offered workload, reducing the(More)
— Despite the increasing number of WiFi-based Long Distance (WiLD) network deployments, there is a lack of understanding of how WiLD networks perform in practice. In this paper, we perform a systematic study to investigate the commonly cited sources of packet loss induced by the wireless channel and by the 802.11 MAC protocol. The channel induced losses(More)
Very few computer systems that have ever been deployed in rural areas in developing regions have been operational and sustainable in the long term — most such systems have not gone beyond the pilot phase. This paper describes our experiences in deploying and maintaining two rural WiFi-based long-distance networks over the last three years: (a) the Aravind(More)
We consider the problem of efficientMAC design for long-distance WiFi-based mesh networks. In such networks it is common to find long propagation delays, the use of directional antennas, and the presence of inter-link interference. Prior work has shown that these characteristics make traditional CSMA-based MACs a poor choice for long-distance mesh networks(More)
Networked end-systems such as desktops and set-top boxes are often left powered-on, but idle, leading to wasted energy consumption. An alternative would be for these idle systems to enter low-power sleep modes. Unfortunately , today, a sleeping system sees degraded func-tionality: first, a sleeping device loses its network " presence " which is problematic(More)
C omputational devices such as calculators and computers have long been a fixture in the modern classroom—and new, inexpensive wireless devices will only continue this trend. In this issue, we look at innovative applications of technology in the classroom, including using handheld devices to create a collaborative mobile learning environment. Other topics(More)
Software routers can lead us from a network of special-purpose hardware routers to one of general-purpose extensible infrastructure - if, that is, they can scale to high speeds. We identify the challenges in achieving this scalability and propose a solution: a cluster-based router architecture that uses an interconnect of commodity server platforms to build(More)
— We present a network architecture, DTNLite, for reliable message delivery in sensor networks facing problems of high mobility, frequent disconnections and unreliable nodes. It is based on the DTN(Delay Tolerant Networking) architecture and its main features are asynchronous message delivery combined with custody transfer on an overlay network on sensor(More)
Most pedestrian detection approaches that achieve high accuracy and precision rate and that can be used for real-time applications are based on histograms of gradient orientations. Usually multiscale detection is attained by resizing the image several times and by recomputing the image features or using multiple classifiers for different scales. In this(More)