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Full-Text Articles in Physical Sciences and Mathematics
Experimental Evaluation Of Wireless Simulation Assumptions, David Kotz, Calvin Newport, Robert S. Gray, Jason Liu, Yougu Yuan, Chip Elliot
Experimental Evaluation Of Wireless Simulation Assumptions, David Kotz, Calvin Newport, Robert S. Gray, Jason Liu, Yougu Yuan, Chip Elliot
Dartmouth Scholarship
All analytical and simulation research on ad hoc wireless networks must necessarily model radio propagation using simplifying assumptions. We provide a comprehensive review of six assumptions that are still part of many ad hoc network simulation studies, despite increasing awareness of the need to represent more realistic features, including hills, obstacles, link asymmetries, and unpredictable fading. We use an extensive set of measurements from a large outdoor routing experiment to demonstrate the weakness of these assumptions, and show how these assumptions cause simulation results to differ significantly from experimental results. We close with a series of recommendations for researchers, whether …
The Changing Usage Of A Mature Campus-Wide Wireless Network, Tristan Henderson, David Kotz, Ilya Abyzov
The Changing Usage Of A Mature Campus-Wide Wireless Network, Tristan Henderson, David Kotz, Ilya Abyzov
Dartmouth Scholarship
Wireless Local Area Networks (WLANs) are now commonplace on many academic and corporate campuses. As “Wi-Fi” technology becomes ubiquitous, it is increasingly important to understand trends in the usage of these networks. \par This paper analyzes an extensive network trace from a mature 802.11 WLAN, including more than 550 access points and 7000 users over seventeen weeks. We employ several measurement techniques, including syslogs, telephone records, SNMP polling and tcpdump packet sniffing. This is the largest WLAN study to date, and the first to look at a large, mature WLAN and consider geographic mobility. We compare this trace to a …
Design And Implementation Of A Large-Scale Context Fusion Network, Guanling Chen, Ming Li, David Kotz
Design And Implementation Of A Large-Scale Context Fusion Network, Guanling Chen, Ming Li, David Kotz
Dartmouth Scholarship
In this paper we motivate a Context Fusion Network (CFN), an infrastructure model that allows context-aware applications to select distributed data sources and compose them with customized data-fusion operators into a directed acyclic information fusion graph. Such a graph represents how an application computes high-level understandings of its execution context from low-level sensory data. Multiple graphs by different applications inter-connect with each other to form a global graph. A key advantage of a CFN is re-usability, both at code-level and instance-level, facilitated by operator composition. We designed and implemented a distributed CFN system, Solar, which maps the logical operator graph …
A Sensor-Fusion Approach For Meeting Detection, Jue Wang, Guanling Chen, David Kotz
A Sensor-Fusion Approach For Meeting Detection, Jue Wang, Guanling Chen, David Kotz
Dartmouth Scholarship
In this paper we present a context-sensing component that recognizes meetings in a typical office environment. Our prototype detects the meeting start and end by combining outputs from pressure and motion sensors installed on the chairs. We developed a telephone controller application that transfers incoming calls to voice-mail when the user is in a meeting. Our experiments show that it is feasible to detect high-level context changes with “good enough” accuracy, using low-cost, off-the-shelf hardware, and simple algorithms without complex training. We also note the need for better metrics to measure context detection performance, other than just accuracy. We propose …
A Sensor Fusion Approach For Meeting Detection, Jue Wang, Guanling Chen, David Kotz
A Sensor Fusion Approach For Meeting Detection, Jue Wang, Guanling Chen, David Kotz
Dartmouth Scholarship
In this paper we present a context-sensing component that recognizes meetings in a typical office environment. Our prototype detects the meeting start and end by combining outputs from pressure and motion sensors installed on the chairs. We developed a telephone controller application that transfers incoming calls to voice-mail when the user is in a meeting. Our experiments show that it is feasible to detect high-level context changes with ``good enough'' accuracy, using low-cost, off-the-shelf hardware, and simple algorithms without complex training. We also note the need for better metrics to measure context detection performance, other than just accuracy. We propose …
Dependency Management In Distributed Settings (Poster Abstract), Guanling Chen, David Kotz
Dependency Management In Distributed Settings (Poster Abstract), Guanling Chen, David Kotz
Dartmouth Scholarship
Ubiquitous-computing environments are heterogeneous and volatile in nature. Systems that support ubicomp applications must be self-managed, to reduce human intervention. In this paper, we present a general service that helps distributed software components to manage their dependencies. Our service proactively monitors the liveness of components and recovers them according to supplied policies. Our service also tracks the state of components, on behalf of their dependents, and may automatically select components for the dependent to use based on evaluations of customized functions. We believe that our approach is flexible and abstracts away many of the complexities encountered in ubicomp environments. In …
Evaluating Location Predictors With Extensive Wi-Fi Mobility Data, Libo Song, David Kotz, Ravi Jain, Xiaoning He
Evaluating Location Predictors With Extensive Wi-Fi Mobility Data, Libo Song, David Kotz, Ravi Jain, Xiaoning He
Dartmouth Scholarship
Location is an important feature for many applications, and wireless networks can better serve their clients by anticipating client mobility. As a result, many location predictors have been proposed in the literature, though few have been evaluated with empirical evidence. This paper reports on the results of the first extensive empirical evaluation of location predictors, using a two-year trace of the mobility patterns of over 6,000 users on Dartmouth's campus-wide Wi-Fi wireless network. \par We implemented and compared the prediction accuracy of several location predictors drawn from two major families of domain-independent predictors, namely Markov-based and compression-based predictors. We found …