Papers by Antonios Skordylis
WCNC 2007 ‚IEEE Wireless Communications & …, 2007
Wireless sensor networks present significant opportunities for fine-grained and continuous monito... more Wireless sensor networks present significant opportunities for fine-grained and continuous monitoring of road traffic, enabling careful city planning, automated road maintenance and accident detection. Users are typically willing to tolerate a small error in car-flow data, in order to reduce the cost of data propagation from the sensor nodes to the gateway nodes, to which users are connected. In this paper, we first examine the relative performance of Fourier-and Wavelet-based algorithms for compressing traffic data locally at the sensor nodes. Using real traffic information from the city of Cambridge (UK), we then demonstrate that car-flow data collected across geographically dispersed sensor nodes exhibit strong spatial and temporal correlations. We then combine lossy Fourier-compression with correlation-based compression to achieve further communication savings within a user-specified error threshold. Two distinct algorithms are proposed, one exploiting same-node temporal correlations and the other spatial correlations across nodes. For a tolerated error of 5-15 cars / 5 min, it is shown that exploitation of temporal correlations yields 14-30% savings relative to Fourier compression alone, whilst use of spatial correlations results in 10-35% savings. Both algorithms are fully distributed and easy to implement in resource-constrained sensor and relay nodes.
ACM MobiHoc, 2008
Ad hoc networks formed by traveling vehicles are envisaged to become a common platform that will ... more Ad hoc networks formed by traveling vehicles are envisaged to become a common platform that will support a wide variety of applications, ranging from road safety to advertising and entertainment. The multitude of vehicular applications calls for routing schemes that satisfy user-defined delay requirements while at the same time maintaining a low level of channel utilization to allow their coexistence. This paper focuses on the development of carry-and-forward schemes that attempt to deliver data from vehicles to fixed infrastructure nodes in an urban setting. The proposed algorithms leverage local or global knowledge of traffic statistics to carefully alternate between the Data Muling and Multihop Forwarding strategies, in order to minimize communication overhead while adhering to delay constraints imposed by the application. We provide an extensive evaluation of our schemes using realistic vehicular traces on a real city map.
Recent developments in sensor network technology have enabled the instrumentation of the physical... more Recent developments in sensor network technology have enabled the instrumentation of the physical world with smart devices for monitoring purposes. A large variety of applications could benefit from the pervasive deployment of inexpensive wireless sensor nodes, ranging from environmental monitoring to emergency detection and response. A significant challenge is to prolong the monitoring operation of sensor nodes by efficiently using their limited energy, bandwidth and computation resources. In this paper, we survey approximate data management techniques for sensor networks that exploit the tolerance of most applications to small inaccuracies in the reported data in order to extend the network lifetime.
The use of general descriptive names, registered names, trademarks, etc. in this publication does... more The use of general descriptive names, registered names, trademarks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use.
The use of general descriptive names, registered names, trademarks, etc. in this publication does... more The use of general descriptive names, registered names, trademarks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use.
Querying of Sensor Data
Learning from Data Streams, 2007
Chapter 6 Querying of Sensor Data Niki Trigoni, Alexandre Guitton, and Antonios Skordylis 6.1 Int... more Chapter 6 Querying of Sensor Data Niki Trigoni, Alexandre Guitton, and Antonios Skordylis 6.1 Introduction Advances in micro-electro-mechanical systems (MEMS) allow sensors, actuators, mini-processors and radio devices to be integrated on smallandinexpensive ...
Poster Abstract: Routing and Processing Multiple Aggregate Queries in Sensor Networks
We present a novel approach to processing continuous aggregate queries in sensor networks, which ... more We present a novel approach to processing continuous aggregate queries in sensor networks, which lifts the as-sumption of tree-based routing. Given a query workload and a special-purpose gateway node where results are ex-pected, the query optimizer exploits ...
Proceedings of the 2009 ACM symposium on …, 2009
Vehicular ad hoc networks (VANETs) are envisaged to become a flexible platform for monitoring roa... more Vehicular ad hoc networks (VANETs) are envisaged to become a flexible platform for monitoring road traffic, which will gradually replace more cumbersome fixed sensor deployments. The efficacy of vehicle-assisted traffic monitoring systems depends on the freshness of traffic data that they can deliver to users, and the bandwidth used to do so. Clearly, high data freshness will allow users to estimate trip times accurately, and to select the fastest route to a destination. Low bandwidth utilization will allow the traffic monitoring application to coexist symbiotically with a wide variety of vehicle-based applications, ranging from road safety to advertising and entertainment.
Efficient Data Propagation in Traffic-Monitoring Vehicular Networks
Intelligent Transportation Systems, …, 2011
ABSTRACT Road congestion and traffic-related pollution have a large negative social and economic ... more ABSTRACT Road congestion and traffic-related pollution have a large negative social and economic impact on several economies worldwide. We believe that investment in the monitoring, distribution, and processing of traffic information should enable better strategic planning and encourage better use of public transport, both of which would help cut pollution and congestion. This paper investigates the problem of efficiently collecting and disseminating traffic information in an urban setting. We formulate the traffic data acquisition problem and explore solutions in the mobile sensor network domain while considering realistic application requirements. By leveraging existing infrastructure such as traveling vehicles in the city, we propose traffic data dissemination schemes that operate on both the routing and the application layer; our schemes are frugal in the use of the wireless medium, rendering our system interoperable with the proliferation of competing applications. We introduce the following two routing algorithms for vehicular networks that aim at minimizing communication and, at the same time, adhering to a delay threshold set by the application: 1) delay-bounded greedy forwarding and 2) delay-bounded minimum-cost forwarding. We propose a framework that jointly optimizes the two key processes associated with monitoring traffic, i.e., data acquisition and data delivery, and provide a thorough experimental evaluation based on realistic vehicular traces on a real city map.
Distributed Computing and Networking, 2008
This paper presents a novel approach to processing continuous aggregate queries in sensor network... more This paper presents a novel approach to processing continuous aggregate queries in sensor networks, which lifts the assumption of tree-based routing. Given a query workload and a special-purpose gateway node where results are expected, the query optimizer exploits query correlations in order to generate an energy-efficient distributed evaluation plan. The proposed optimization algorithms identify common query sub-aggregates, and propose common routing structures to share the sub-aggregates at an early stage. Moreover, they avoid routing sub-aggregates of the same query through long-disjoint paths, thus further reducing the communication cost of result propagation. The proposed algorithms are fully-distributed, and are shown to offer significant communication savings compared to existing tree-based approaches. A thorough experimental evaluation shows the benefits of the proposed techniques for a variety of query workloads and network topologies.
… of the 4th international conference on …, 2006
We present a novel approach to processing continuous aggregate queries in sensor networks, which ... more We present a novel approach to processing continuous aggregate queries in sensor networks, which lifts the assumption of tree-based routing. Given a query workload and a special-purpose gateway node where results are expected, the query optimizer exploits query correlations in order to generate an energy-efficient distributed evaluation plan. The proposed algorithms, named STG and STS, identify common query sub-aggregates, and propose common routing structures to share the sub-aggregates at an early stage. Moreover, they avoid routing sub-aggregates of the same query through long-disjoint paths, thus further reducing the communication cost of result propagation. In this poster, we provide examples to illustrate the functionality and the communication savings of STG and STS compared to the existing tree-based approach.
… of the 2006 ACM CoNEXT conference, 2006
In this work, we investigate the nature of spatio-temporal correlations in an urban traffic scena... more In this work, we investigate the nature of spatio-temporal correlations in an urban traffic scenario, and how they can be exploited to reduce the cost of sensor data propagation to the gateway nodes, where users are connected. We conduct experimental analysis of our proposed algorithms using a real dataset of road traffic data generated in the city of Cambridge.
IEEE CCNC ‚Fifth IEEE Consumer Communications & …, 2008
Road congestion and traffic-related pollution have a large, negative social and economic impact, ... more Road congestion and traffic-related pollution have a large, negative social and economic impact, and we believe many of these problems can be reduced through investment in monitoring, distribution and processing of traffic information. This paper outlines how our on-going work on the TIME project (Transport Information Monitoring Environment) provides a solution, using traffic sensor systems and the design and development of an open and decentralised software framework. We also discuss how we address the privacy and security implications of the increased use of sensors and data processing.
Proceedings of the 9th ACM international …, 2008
Ad hoc networks formed by traveling vehicles are envisaged to become a common platform that will ... more Ad hoc networks formed by traveling vehicles are envisaged to become a common platform that will support a wide variety of applications, ranging from road safety to advertising and entertainment. The multitude of vehicular applications calls for routing schemes that satisfy user-defined delay requirements while at the same time maintaining a low level of channel utilization to allow their coexistence. This paper focuses on the development of carry-and-forward schemes that attempt to deliver data from vehicles to fixed infrastructure nodes in an urban setting. The proposed algorithms leverage local or global knowledge of traffic statistics to carefully alternate between the Data Muling and Multihop Forwarding strategies, in order to minimize communication overhead while adhering to delay constraints imposed by the application. We provide an extensive evaluation of our schemes using realistic vehicular traces on a real city map.
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Papers by Antonios Skordylis