1,721,193 research outputs found
A survey of urban vehicular sensing platforms
No full textVehicular sensing where vehicles on the road continuously gather, process, and share location-relevant sensor data (e.g., road condition, traffic flow) is emerging as a new network paradigm for sensor information sharing in urban environments. Recently, smartphones have also received a lot of attention for their potential as portable vehicular urban sensing platforms, as they are equipped with a variety of environment and motion sensors (e.g., audio/video, accelerometer, and GPS) and multiple wireless interfaces (e.g., WiFi, Bluetooth and 2/3G). The ability to take a smartphone on board a vehicle and to complement the sensors of the latter with advanced smartphone capabilities is of immense interest to the industry. In this paper we survey recent vehicular sensor network developments and identify new trends. In particular we review the way sensor information is collected, stored and harvested using inter-vehicular communications (e.g., mobility-assist mobility-assisted dissemination and geographic storage), as well using the infrastructure (e.g., centralized and distributed storage in the wired Internet). The comparative performance of the various sensing schemes is important to us. Thus, we review key results by carefully examining and explaining the evaluation methodology, in the process gaining insight into vehicular sensor network design. Our comparative study confirms that system performance is impacted by a variety of factors such as wireless access methods, mobility, user location, and popularity of the information. (C) 2010 Elsevier B.V. All rights reserved
Design and analysis of fault-tolerant multibus interconnection networks
No full textAbstractIn this paper a new class of fault-tolerant multibus interconnection networks is presented and analyzed. Efficiency and fault tolerance have been the driving forces in the design of these structures. The most common types of faults have been explicitly considered and in particular the jabbering problem has been adequately resolved. The analysis covers the evaluation of capacity, throughput and average delay and it includes faults of one or more channels. The system is shown to be very efficient and to be able to adequately support channel and station faults
Classical control approach to congestion avoidance in ATM high speed networks
No full textIn this paper classical control theory is applied to design a rate-based control law for throttling ABR input rates in high speed ATM networks. At first, a mathematical model for the interaction of ABR-flows with network-queues is developed. Then the control law is designed by following classical Smith's (1959) principle. To implement the resulting EPRCA scheme, a switch architecture consisting of a single FIFO queue per each output link is required. Moreover, network switches do not have to perform any measurement of ABR available bandwidth. Finally, it is theoretically shown that the proposed control algorithm is stable and guarantees full utilization of network links along with max-min fairness in bandwidth allocation
Flow Based Dynamic Load Balancing for Passive Network Monitoring
No full textCluster based packet capturing is a way of overcoming the speed of a slow disk to tap a high-speed network. Most cluster-based architectures, however, do not consider load balancing as an important issue. In order to perform mon itoring at full line speed without losing packets, we accept that the balance among back-end servers must be main tained. Conventional methods rely on fixed or random rout ing where a ”source-destination” address pair is used as a unit for load balancing. Instead of using such a coarse grain unit, we use a flow, a ”source-destination-port” pair. In ad dition, we adaptively balance loads of back-end servers us ing a flow load estimation technique. The proposed meth ods have been validated by performing a trace-based sim ulation. Compared to the existing routing approaches, our method balances load of back-end servers. From a simula tion, we find that for protocols having a transient load with a small variance in flow length, we may use simple meth ods of load balancing such as round-robin, but for those having a persistent load with a large variance, we need to use a flow estimation technique
Optimal Content Prefetching in NDN Vehicle-to-Infrastructure Scenario
Full text linkData replication and in-network storage are two basic principles of the Information Centric Networking (ICN) framework in which caches spread out in the network can be used to store the most popular contents. This work shows how one of the ICN architectures, the Named Data Networking (NDN), with content pre-fetching can maximize the probability that a user retrieves the desired content in a Vehicle-to-Infrastructure scenario. We give an ILP formulation of the problem of optimally distributing content in the network nodes while accounting for the available storage capacity and the available link capacity. The optimization framework is then leveraged to evaluate the impact on content retrievability of topology- and network-related parameters as the number and mobility models of moving users, the size of the content catalog and the location of the available caches. Moreover, we show how the proposed model can be modified to find the minimum storage occupancy to achieve a given content retrievability level. The results obtained from the optimization model are finally validated against a Name Data Networking architecture through simulations in ndnSIM
Vehicular testbeds - Model validation before large scale deployment
No full textVehicular communications are becoming a reality due to the investments by stakeholders like car manufacturers and Public Transport Authorities. The building blocks of the"Vehicle Grid" (radios, Access Points, spectrum, standards, etc.) are coming into place enabling a broad gamut of applications that range from navigation safety, intelligent transport, entertainment and urban sensing. Vehicular protocols and applications, however, must be carefully tested before deployment in the urban grid and introduction to the users. This validation must be carried out progressively in simulation, emulation and small scale testbed environments. In this paper we discuss the important role of the vehicular testbed in validating models and protocols before deployment in large scale scenarios. We illustrate the concept using two case studies that were carried out in the UCLA open vehicular testbed. © 2012 ACADEMY PUBLISHER
Phero-Trail: a Bio-inspired Location Service for Mobile Underwater Sensors
No full textA SEA Swarm (Sensor Equipped Aquatic Swarm) is a collection of mobile underwater sensors that moves as a group with water current and enables 4D (space and time) monitoring of local underwater events such as contaminants and intruders. For prompt alert reporting, mobile sensors routes events to mobile sinks (i.e., autonomous underwater vehicles) via geographic routing that is known to be most efficient under mobility and scarce acoustic bandwidth. In order for a packet to be routed to the destination using geographical routing, it requires to know the location of the destination. This is accomplished by having a location service that returns the location of a requested node. Our goal is to design such location service for SEA Swarm. In this paper, we analyze various design choices to realize an efficient location service in SEA Swarm scenarios. We find that conventional ad hoc network location service protocols cannot be directly used, because the entire swarm moves along water current. We prove that maintaining location information in a 2D plane is a better design choice. Given this, we propose a bio-inspired location service called a Phero-Trail location service protocol. In Phero-Trail, location information is stored in a 2D upper hull of a SEA Swarm, and a mobile sink uses its trajectory (a la a pheromone trail of ants) projected to the 2D hull to maintain location information. This enables mobile sensors to efficiently locate a mobile sink. Our results show that Phero- Trail performs better than existing approaches
APOHN: Subnetwork layering to improve TCP performance over heterogeneous paths
No full textThis paper proposes a novel architecture, named APOHN, designed for data communications over heterogeneous networks. APOHN enables easy implementation of various existing and upcoming performance optimization solutions with the main objective to keep the standardized TCP/IP reference model untouched. APOHN architecture extends ISO/OSI protocol stack model with an additional layer designed for subnetwork communications and optimized with specific physical subnetwork characteristics in mind. TCP/IP flow speedup, subnetwork flow multiplexing and optimized subnetwork communications result in great performance improvements in heterogeneous networks. Moreover, the support of IPsec enables secure communications. APOHN performance is evaluated through simulations using a combined satellite and WLAN network scenario - commonly used in disaster recovery as well as in a variety of military applications. APOHN constitutes an architectural solution competitive with leading architectures such as Performance Enhancement Proxies (PEP) as well as Delay-Tolerant Networking (DTN).12© 2006 IEEE
Multicasting in Myrinet - a high-speed, wormhole-routing network
No full textWormhole-routing networks are emerging as an effective solution for high bandwidth, low latency interconnects in distributed computing and cluster computing applications. An important example (in the local area environment) is the 640 Mb/s crossbar-based Myrinet. A key property of conventional LANs, which is valuable for many distributed applications, is transparent, reliable network level multicast. It is desirable to retain this property also in wormhole LANs. Unfortunately, efficient, reliable multicasting in wormhole LANs is problematic because of the potential for deadlocks. We address the problem of providing transparent, reliable, efficient network level multicasting in the wormhole LAN with special reference to Myrinet. We describe several protocols for achieving deadlock-free, reliable multicasting using restricted routing and fast buffer reservation techniques. Tradeoffs involving complexity and performance of various solutions are discussed, and are illustrated using simulation. Experimental results from a simple multicast implementation for Myrinet are presented
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