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—Multi-antenna systems can provide greater through-put and range coverage than traditional single antenna systems. A key aspect of exploiting this new physical layer (PHY) is rate adaptation, which consists of finding the best rate for sending data packets. Unlike rate adaptation in single antenna systems, nodes have many choices apart from adapting(More)
—In this paper, we present a collision-free asyn-chronous multi-channel access protocol for Ad Hoc wireless networks using a single transceiver. Our protocol, dubbed AM-MAC for Asynchronous Multi-channel Medium Access Control, targets low-cost and low-power deployments where nodes are equipped with a single transceiver. Other distinguishing features of(More)
—Rate adaptation plays a central role in the efficiency of data transmissions in wireless networks. Due to the complex physical-layer effects of wireless links, including interference, attenuation, and multi-path fading, designing a rate adaptation algorithm that performs well in most scenarios is a challenging problem. We present the Multi-rate Adaptation(More)
We present Chopper, a tool that efficiently explores the vast input space of file system policies to find behaviors that lead to costly performance problems. We focus specifically on block allocation, as unexpected poor layouts can lead to high tail latencies. Our approach utilizes sophisticated statistical methodologies, based on Latin Hypercube Sampling(More)
In science and engineering in general and in computational chemistry in particular, parameter sweeps and optimizations are of high importance. Such parametric modeling jobs are embarrassingly parallel and thus well suited for grid computing. The Nimrod toolkit significantly simplifies the utilization of computational grids for this kind of research by(More)
We consider the problem of verifying the correctness and completeness of the result of a keyword search. We introduce the concept of an authenticated web crawler and present its design and prototype implementation. An authenticated web crawler is a trusted program that computes a specially-crafted signature over the web contents it visits. This signature(More)
We introduce a new topological feature representation for point cloud objects. Specifically, we construct a Stochas-tic Multiresolution Persistent Homology (SMURPH) kernel which represents an object's persistent homology at different resolutions. Under the SMURPH kernel two objects are similar if they have similar number and sizes of " holes " at these(More)