6,169 research outputs found
A cloud-assisted design for autonomous driving
No full textThis paper presents Carcel, a cloud-assisted system for autonomous driving. Carcel enables the cloud to have access to sensor data from autonomous vehicles as well as the roadside infrastructure. The cloud assists autonomous vehicles that use this system to avoid obstacles such as pedestrians and other vehicles that may not be directly detected by sensors on the vehicle. Further, Carcel enables vehicles to plan efficient paths that account for unexpected events such as road-work or accidents.
We evaluate a preliminary prototype of Carcel on a state-of-the-art autonomous driving system in an outdoor testbed including an autonomous golf car and six iRobot Create robots. Results show that Carcel reduces the average time vehicles need to detect obstacles such as pedestrians by 4.6x compared to today's systems that do not have access to the cloud.Smart.fmNational Science Foundation (U.S.
Bibliographics for the 983 eprints in the live archives of E-LIS : trends and status report up to 7th July 2004, based on author-self-archiving metadata
No full textThe priority for ideas and philosophy related to "Network Theory" have been traced back and documented by Braun(2004),and credit goes to Karinthy(1929).The IT has empowered to realise it, as the most practical phenomena and it is no more a humour. The OAI (Open Archives Initiatives)and ACIS (Academic Contributor Information System)are progressive in the direction ,which may lead to realise the "Collective Genius" at global level. Focus of present study is on Author-Self-Archiving (A-S-A)Metadata of the 983 Eprints in the Live Archives of the E-LIS (EPrints of Library and Information Science),which were approved till 7th July 2004.The A-S-A Metadata was used for librametric analysis. Self-explanatory bibliographics are illustrated.The highlights include: Conference papers (34%); highest approval, June 2004 (28%); published archives (76%);not refereed (52%); not in public domain (60%); highest self-archiving-author (De Robbio, Antonella).The Nos. of EPrints having single JITA domain specifications were: Theoretical and general aspects of libraries and information(27); Information use and sociology of information(80);Users,literacy and reading(13);Libraries as physical collections(30);Publishing and legal issues(57);Management(13);Industry, profession and education(36);Information sources, supports, channels(113) ; Information treatment for information services, Information functions and techniques (101); Technical services libraries, archives and museums(25); Housing technologies(1); Information technology and library technology(92); and Inter-domainery (395) i.e. having specifications of two or more than two JITA classes
Content-centric network for autonomous driving
No full textThesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2012.Cataloged from PDF version of thesis.Includes bibliographical references (p. 75-79).We introduce CarSpeak, a communication system for autonomous driving. CarSpeak enables a car to query and access sensory information captured by other cars in a manner similar to how it accesses information from its local sensors. CarSpeak adopts a content-centric approach where information objects - i.e., regions along the road - are first class citizens. It names and accesses road regions using a multi-resolution system, which allows it to scale the amount of transmitted data with the available bandwidth. CarSpeak also changes the MAC protocol so that, instead of having nodes contend for the medium, contention is between road regions, and the medium share assigned to any region depends on the number of cars interested in that region. CarSpeak is implemented in a state-of-the-art autonomous driving system and tested on indoor and outdoor hardware testbeds including an autonomous golf car and 10 iRobot Create robots. In comparison with a baseline that directly uses 802.11, CarSpeak reduces the time for navigating around obstacles by 2.4x, and reduces the probability of a collision due to limited visibility by 14 x.by Swarun Suresh Kumar.S.M
Bringing cross-layer MIMO to today's wireless LANs
No full textRecent years have seen major innovations in cross-layer wireless designs. Despite demonstrating significant throughput gains, hardly any of these technologies have made it into real networks. Deploying cross-layer innovations requires adoption from Wi-Fi chip manufacturers. Yet, manufacturers hesitate to undertake major investments without a better understanding of how these designs interact with real networks and applications.
This paper presents the first step towards breaking this stalemate, by enabling the adoption of cross-layer designs in today's networks with commodity Wi-Fi cards and actual applications. We present OpenRF, a cross-layer architecture for managing MIMO signal processing. OpenRF enables access points on the same channel to cancel their interference at each other's clients, while beamforming their signal to their own clients. OpenRF is self-configuring, so that network administrators need not understand MIMO or physical layer techniques.
We patch the iwlwifi driver to support OpenRF on off-the-shelf Intel cards. We deploy OpenRF on a 20-node network, showing how it manages the complex interaction of cross-layer design with a real network stack, TCP, bursty traffic, and real applications. Our results demonstrate an average gain of 1.6x for TCP traffic and a significant reduction in response time for real-time applications, like remote desktop.National Science Foundation (U.S.
A Unified Shell model for Buoyancy-Driven Turbulence
No full textWe construct a unified shell model for stably stratified and convective turbulence. Shell model simulation of stably stratified flow in turbulent regime exhibit Bolgiano-Obukhbov (BO) scaling in which the kinetic energy spectrum varies as . However, simulation of convective turbulence shows Kolmogorov's spectrum. These results are consistent with the direct numerical simulations of Kumar {\em et al.} [Phys. Rev. E {\bf 90}, 023016 (2014)]. We also observe a dual scaling ( and ) for a limited range of parameters in stably stratified flow
LTE radio analytics made easy and accessible
No full textDespite the rapid growth of next-generation cellular networks, researchers and end-users today have limited visibility into the performance and problems of these networks. As LTE deployments move towards femto and pico cells, even operators struggle to fully understand the propagation and interference patterns affecting their service, particularly indoors. This paper introduces LTEye, the first open platform to monitor and analyze LTE radio performance at a fine temporal and spatial granularity. LTEye accesses the LTE PHY layer without requiring private user information or provider support. It provides deep insights into the PHY-layer protocols deployed in these networks. LTEye's analytics enable researchers and policy makers to uncover serious deficiencies in these networks due to inefficient spectrum utilization and inter-cell interference. In addition, LTEye extends synthetic aperture radar (SAR), widely used for radar and backscatter signals, to operate over cellular signals. This enables businesses and end-users to localize mobile users and capture the distribution of LTE performance across spatial locations in their facility. As a result, they can diagnose problems and better plan deployment of repeaters or femto cells. We implement LTEye on USRP software radios, and present empirical insights and analytics from multiple AT&T and Verizon base stations in our locality.National Science Foundation (U.S.
When lorawan frames collide
No full textLoRa, an abbreviation of Long Range, is a Low-Power Wide Area Network (LPWAN) radio technology that has quickly gained popularity as a communications means for the Internet-of-Things (IoT). LoRa is typically used together with the MAC protocol LoRaWAN and operates in the license-free ISM-bands. As such, anyone is allowed to deploy their own LoRaWAN network, provided that they adhere to the LoRaWAN specication and ISM regulations. However, an uncoordinated deployment of LoRaWAN networks may cause neighboring networks to interfere and LoRaWAN frames to collide. In this paper, we present an in-depth investigation of LoRaWAN frame collisions – and the capture eect in particular – through various experiments. Contrary to previous research, we focus on correct reception of data at the application, instead of at the gateway, and we consider multi-gateway, multi-provider, and dense scenarios to obtain insight into collisions within actual networks.Embedded System
Pushing the limits of wireless networks
No full textThesis: Ph. D., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2016.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Cataloged from student-submitted PDF version of thesis.Includes bibliographical references (pages 259-277).Wireless networks are everywhere around us and form a big part of our day-to-day lives. In this dissertation, we address the key challenges and opportunities of modern wireless networks. First, perhaps our biggest expectation from modern wireless networks is faster communication speeds. However, state-of-the-art Wi-Fi networks continue to struggle in crowded environments - airports and hotel lobbies. The core reason is interference - Wi-Fi access points today avoid transmitting at the same time on the same frequency, since they would otherwise interfere with each other. This thesis describes OpenRF, a novel system that enables today's Wi-Fi access points to directly combat this interference and demonstrate significantly faster data-rates for real applications. In addition, it presents MoMIMO, which demonstrates how the natural mobility of mobile users can be used to further mitigate interference. Second, can we use the ubiquitous Wi-Fi infrastructure around us to deliver new services, beyond communication? In particular, this dissertation focuses on indoor positioning, a service that has grabbed the attention of the academia and industry. While GPS has revolutionized outdoor navigation, it does not work indoors. Past work that has explored this problem is either limited in accuracy with errors of several meters, or advocates complete overhaul of the infrastructure with massive antenna-array access points that do not exist on consumer devices. Inspired by radar systems, we present Ubicarse, the first purely-software indoor positioning system for existing Wi-Fi devices that achieves tens of cm in positioning accuracy. Further, we build on this design to develop LTEye, which reveals new insights on how location impacts the performance of commercial AT&T and Verizon LTE cellular networks in the indoor space. Finally, we demonstrate how the tools we develop for indoor positioning open up new connections between wireless networking and robotics, to improve communication and security in multi-robot networks.by Swarun Kumar.Ph. D
Interference alignment by motion
No full textRecent years have witnessed increasing interest in interference alignment which has been demonstrated to deliver gains for wireless networks both analytically and empirically. Typically, interference alignment is achieved by having a MIMO sender precode its transmission to align it at the receiver. In this paper, we show, for the first time, that interference alignment can be achieved via motion, and works even for single-antenna transmitters. Specifically, this alignment can be achieved purely by sliding the receiver's antenna. Interestingly, the amount of antenna displacement is of the order of one inch which makes it practical to incorporate into recent sliding antennas available on the market. We implemented our design on USRPs and demonstrated that it can deliver 1.98× throughput gains over 802.11n in networks with both single-antenna and multi- antenna nodes.National Science Foundation (U.S.
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