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328
A Measurement Study of Vehicular Internet Access Using
- In Situ Wi-Fi Networks. In 12th ACM MOBICOM Conf
, 2006
"... The impressive penetration of 802.11-based wireless networks in many metropolitan areas around the world offers, for the first time, the opportunity of a “grassroots ” wireless Internet service provided by users who “open up ” their 802.11 (Wi-Fi) access points in a controlled manner to mobile clien ..."
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Cited by 197 (6 self)
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The impressive penetration of 802.11-based wireless networks in many metropolitan areas around the world offers, for the first time, the opportunity of a “grassroots ” wireless Internet service provided by users who “open up ” their 802.11 (Wi-Fi) access points in a controlled manner to mobile clients. While there are many business, legal, and policy issues to be ironed out for this vision to become reality, we are concerned in this paper with an important technical question surrounding such a system: can such an unplanned network service provide reasonable performance to network clients moving in cars at vehicular speeds? To answer this question, we present the results of a measurement study carried out over 290 “drive hours ” over a few cars under typical driving conditions, in and around the Boston metropolitan area (some of our data also comes from a car in Seattle). With a simple caching optimization to speed-up IP address acquisition, we find that for our driving patterns the median duration of linklayer connectivity at vehicular speeds is 13 seconds, the median connection upload bandwidth is 30 KBytes/s, and that the mean duration between successful associations to APs is 75 seconds. We also find that connections are equally probable across a range of urban speeds (up to 60 km/hour in our measurements). Our end-toend TCP upload experiments had a median throughput of about 30 KBytes/s, which is consistent with typical uplink speeds of home broadband links in the US. The median TCP connection is capable of uploading about 216 KBytes of data. Our high-level conclusion is that grassroots Wi-Fi networks are viable for a variety of applications, particularly ones that can tolerate intermittent connectivity. We discuss how our measurement results can improve transport protocols in such networks.
The pothole patrol: Using a mobile sensor network for road surface monitoring
- in ACM MobiSys
, 2008
"... This paper investigates an application of mobile sensing: detecting and reporting the surface conditions of roads. We describe a system and associated algorithms to monitor this important civil infrastructure using a collection of sensor-equipped vehicles. This system, which we call the Pothole Patr ..."
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Cited by 151 (4 self)
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This paper investigates an application of mobile sensing: detecting and reporting the surface conditions of roads. We describe a system and associated algorithms to monitor this important civil infrastructure using a collection of sensor-equipped vehicles. This system, which we call the Pothole Patrol (P 2), uses the inherent mobility of the participating vehicles, opportunistically gathering data from vibration and GPS sensors, and processing the data to assess road surface conditions. We have deployed P 2 on 7 taxis running in the Boston area. Using a simple machine-learning approach, we show that we are able to identify potholes and other severe road surface anomalies from accelerometer data. Via careful selection of training data and signal features, we have been able to build a detector that misidentifies good road segments as having potholes less than 0.2 % of the time. We evaluate our system on data from thousands of kilometers of taxi drives, and show that it can successfully detect a number of real potholes in and around the Boston area. After clustering to further reduce spurious detections, manual inspection of reported potholes shows that over 90 % contain road anomalies in need of repair.
Augmenting Mobile 3G Using WiFi
, 2010
"... We investigate if WiFi access can be used to augment 3G capacity in mobile environments. We first conduct a detailed study of 3G and WiFi access from moving vehicles, in three different cities. We find that the average 3G and WiFi availability across the cities is 87 % and 11%, respectively. WiFi th ..."
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Cited by 150 (5 self)
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We investigate if WiFi access can be used to augment 3G capacity in mobile environments. We first conduct a detailed study of 3G and WiFi access from moving vehicles, in three different cities. We find that the average 3G and WiFi availability across the cities is 87 % and 11%, respectively. WiFi throughput is lower than 3G throughput, and WiFi loss rates are higher. We then design a system, called Wiffler, to augments mobile 3G capacity. It uses two key ideas— leveraging delay tolerance and fast switching—to overcome the poor availability and performance of WiFi. For delay tolerant applications, Wiffler uses a simple model of the environment to predict WiFi connectivity. It uses these predictions to delays transfers to offload more data on WiFi, but only if delaying reduces 3G usage and the transfers can be completed within the application’s tolerance threshold. For applications that are extremely sensitive to delay or loss (e.g., VoIP), Wiffler quickly switches to 3G if WiFi is unable to successfully transmit the packet within a small time window. We implement and deploy Wiffler in our vehicular testbed. Our experiments show that Wiffler significantly reduces 3G usage. For a realistic workload, the reduction is 45 % for a delay tolerance of 60 seconds.
The BikeNet Mobile Sensing System for Cyclist Experience Mapping
- In Proc. of 5th ACM Conf. on Embedded Networked Sensor Systems
, 2007
"... We describe our experiences deploying BikeNet, an extensible mobile sensing system for cyclist experience mapping leveraging opportunistic sensor networking principles and techniques. BikeNet represents a multifaceted sensing system and explores personal, bicycle, and environmental sensing using dyn ..."
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Cited by 147 (13 self)
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We describe our experiences deploying BikeNet, an extensible mobile sensing system for cyclist experience mapping leveraging opportunistic sensor networking principles and techniques. BikeNet represents a multifaceted sensing system and explores personal, bicycle, and environmental sensing using dynamically role-assigned bike area networking based on customized Moteiv Tmote Invent motes and sensor-enabled Nokia N80 mobile phones. We investigate real-time and delay-tolerant uploading of data via a number of sensor access points (SAPs) to a networked repository. Among bicycles that rendezvous en route we explore inter-bicycle networking via data muling. The repository provides a cyclist with data archival, retrieval, and visualization services. BikeNet promotes the social networking of the cycling community through the provision of a web portal that facilitates back end sharing of real-time and archived cycling-related data from the repository. We present: a description and prototype implementation of the system architecture, an evaluation of sensing and inference that quantifies cyclist performance and the cyclist environment; a report on networking performance in an environment characterized by bicycle mobility and human unpredictability; and a description of BikeNet system user interfaces. Visit [4] to see how the BikeNet system visualizes a user’s rides.
VTrack: Accurate, Energy-aware Road Traffic Delay Estimation Using Mobile Phones
"... Traffic delays and congestion are a major source of inefficiency, wasted fuel, and commuter frustration. Measuring and localizing these delays, and routing users around them, is an important step towards reducing the time people spend stuck in traffic. As others have noted, the proliferation of comm ..."
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Cited by 124 (7 self)
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Traffic delays and congestion are a major source of inefficiency, wasted fuel, and commuter frustration. Measuring and localizing these delays, and routing users around them, is an important step towards reducing the time people spend stuck in traffic. As others have noted, the proliferation of commodity smartphones that can provide location estimates using a variety of sensors—GPS, WiFi, and/or cellular triangulation— opens up the attractive possibility of using position samples from drivers ’ phones to monitor traffic delays at a fine spatiotemporal granularity. This paper presents VTrack, a system for travel time estimation using this sensor data that addresses two key challenges: energy consumption and sensor unreliability. While GPS provides highly accurate location estimates, it has several limitations: some phones don’t have GPS at
Cabernet: Vehicular Content Delivery Using WiFi
"... Cabernet is a system for delivering data to and from moving vehicles using open 802.11 (WiFi) access points encountered opportunistically during travel. Using open WiFi access from the road can be challenging. Network connectivity in Cabernet is both fleeting (access points are typically within rang ..."
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Cited by 123 (3 self)
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Cabernet is a system for delivering data to and from moving vehicles using open 802.11 (WiFi) access points encountered opportunistically during travel. Using open WiFi access from the road can be challenging. Network connectivity in Cabernet is both fleeting (access points are typically within range for a few seconds) and intermittent (because the access points do not provide continuous coverage), and suffers from high packet loss rates over the wireless channel. On the positive side, WiFi data transfers, when available, can occur at broadband speeds. In this paper, we introduce two new components for improving open WiFi data delivery to moving vehicles: The first, QuickWiFi, is a streamlined client-side process to establish end-to-end connectivity, reducing mean connection time to less than 400 ms, from over 10 seconds when using standard wireless networking software. The second part, CTP, is a transport protocol that distinguishes congestion on the wired portion of the path from losses over the wireless link, resulting in a 2 × throughput improvement over TCP. To characterize the amount of open WiFi capacity available to vehicular users, we deployed Cabernet on a fleet of 10 taxis in the Boston area. The long-term average transfer rate achieved was approximately 38 Mbytes/hour per car (86 kbit/s), making Cabernet a viable system for a number of non-interactive applications.
Virtual Trip Lines for Distributed Privacy-Preserving Traffic Monitoring
, 2008
"... Automotive traffic monitoring using probe vehicles with Global Positioning System receivers promises significant improvements in cost, coverage, and accuracy. Current approaches, however, raise privacy concerns because they require participants to reveal their positions to an external traffic monito ..."
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Cited by 120 (28 self)
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Automotive traffic monitoring using probe vehicles with Global Positioning System receivers promises significant improvements in cost, coverage, and accuracy. Current approaches, however, raise privacy concerns because they require participants to reveal their positions to an external traffic monitoring server. To address this challenge, we propose a system based on virtual trip lines and an associated cloaking technique. Virtual trip lines are geographic markers that indicate where vehicles should provide location updates. These markers can be placed to avoid particularly privacy sensitive locations. They also allow aggregating and cloaking several location updates based on trip line identifiers, without knowing the actual geographic locations of these trip lines. Thus they facilitate the design of a distributed architecture, where no single entity has a complete knowledge of probe identities and fine-grained location information. We have implemented the system with GPS
The Rise of People-Centric Sensing
"... People-centric sensing is poised to radically change the way we see the world. Technological advances in sensing, computation, storage, and communications will turn the near ubiquitous mobile phone into a global mobile sensing device that enables myriad new personal, social, and public sensing appli ..."
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Cited by 100 (10 self)
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People-centric sensing is poised to radically change the way we see the world. Technological advances in sensing, computation, storage, and communications will turn the near ubiquitous mobile phone into a global mobile sensing device that enables myriad new personal, social, and public sensing applications. People-centric sensing will help drive this trend by enabling a different way to sense, learn, visualize and share information about ourselves, friends, communities, the way we live and the world we live in. Peoplecentric sensing juxtaposes the traditional view of mesh sensor networks where people are passive data consumers that simply interact at the network periphery with physically embedded static sensor webs, with one where people carry mobile sensing elements (i.e., sensor-enabled mobile phones), enabling opportunistic sensing coverage, and thus represent a key architectural component of the system. In this article, we discuss our vision for people-centric sensing, the challenges it brings, and the ongoing development of a number of social sensing applications as part of the MetroSense Project. 1
Vanish: Increasing Data Privacy with Self-Destructing Data
"... Today’s technical and legal landscape presents formidable challenges to personal data privacy. First, our increasing reliance on Web services causes personal data to be cached, copied, and archived by third parties, often without our knowledge or control. Second, the disclosure of private data has b ..."
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Cited by 98 (12 self)
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Today’s technical and legal landscape presents formidable challenges to personal data privacy. First, our increasing reliance on Web services causes personal data to be cached, copied, and archived by third parties, often without our knowledge or control. Second, the disclosure of private data has become commonplace due to carelessness, theft, or legal actions. Our research seeks to protect the privacy of past, archived data — such as copies of emails maintained by an email provider — against accidental, malicious, and legal attacks. Specifically, we wish to ensure that all copies of certain data become unreadable after a userspecified time, without any specific action on the part of a user, and even if an attacker obtains both a cached copy of that data and the user’s cryptographic keys and passwords. This paper presents Vanish, a system that meets this challenge through a novel integration of cryptographic techniques with global-scale, P2P, distributed hash tables (DHTs). We implemented a proof-of-concept Vanish prototype to use both the million-plus-node Vuze Bit-Torrent DHT and the restricted-membership OpenDHT. We evaluate experimentally and analytically the functionality, security, and performance properties of Vanish, demonstrating that it is practical to use and meets the privacy-preserving goals described above. We also describe two applications that we prototyped on Vanish: a Firefox plugin for Gmail and other Web sites and a Vanishing File application. 1
Mobiscopes for human spaces
- IEEE Pervasive Computing
, 2007
"... The proliferation of affordable mobile devices with processing and sensing capabilities, together with the rapid growth in ubiquitous network connectivity, herald an era of Mobiscopes; networked sensing applications that rely on multiple mobile sensors to accomplish global tasks. These distributed s ..."
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Cited by 90 (11 self)
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The proliferation of affordable mobile devices with processing and sensing capabilities, together with the rapid growth in ubiquitous network connectivity, herald an era of Mobiscopes; networked sensing applications that rely on multiple mobile sensors to accomplish global tasks. These distributed sensing systems extend the model of traditional sensor networks, introducing challenges in data management, data integrity, privacy, and network system design. While several applications that fit the above description exist in prior literature, they provide tailored one-time solutions to what essentially is the same set of problems. It is time to work towards a general architecture that identifies common challenges and provides a generalizable methodology for the design of future Mobiscopes. Towards that end, this paper surveys a variety of current and emerging mobile, networked, sensing applications; articulates their common challenges; and provides architectural guidelines and design directions for this important
