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Park H.,Ewha Womans University | Thomos N.,Ecole Polytechnique Federale de Lausanne | Thomos N.,Distributed Communication Systems | Frossard P.,Ecole Polytechnique Federale de Lausanne
Signal Processing | Year: 2013

This paper considers a framework where data from correlated sources are transmitted with the help of network coding in ad hoc network topologies. The correlated data are encoded independently at sensors and network coding is employed in the intermediate nodes in order to improve the data delivery performance. In such settings, we focus on the problem of reconstructing the sources at decoder when perfect decoding is not possible due to losses or bandwidth variations. We show that the source data similarity can be used at decoder to permit decoding based on a novel and simple approximate decoding scheme. We analyze the influence of the network coding parameters and in particular the size of finite coding fields on the decoding performance. We further determine the optimal field size that maximizes the expected decoding performance as a trade-off between information loss incurred by limiting the resolution of the source data and the error probability in the reconstructed data. Moreover, we show that the performance of the approximate decoding improves when the accuracy of the source model increases even with simple approximate decoding techniques. We provide illustrative examples showing how the proposed algorithm can be deployed in sensor networks and distributed imaging applications. © 2012 Elsevier B.V.

Thomos N.,Ecole Polytechnique Federale de Lausanne | Thomos N.,Signal Processing Laboratory | Thomos N.,Distributed Communication Systems | Frossard P.,Ecole Polytechnique Federale de Lausanne | Frossard P.,Signal Processing Laboratory
IEEE Communications Letters | Year: 2012

In this paper, we propose a novel design for network coding vectors that limits the overhead information. Network coding vectors contain information regarding the operations the packets have undergone in the network nodes. They are used at the decoder side to invert coding operations and recover the data. We propose to reduce the size of this side information with the use of Vandermonde-like generator matrices at the sources. These matrices permit to describe the coding operations performed on packets with only one symbol. We analytically investigate the limitations arising from such design constraints. Interestingly, we find that the feasible generation size is upper bounded by log2 q in Galois field Fq of size q as this is the maximum packet diversity allowed by the employed generator matrices. In addition, we show that network coding nodes should only perform addition operations in order to maintain the properties of the coding vectors. We finally discuss the benefits and limitations of the proposed coding vectors in practical systems. © 2012 IEEE.

Tosic T.,Ecole Polytechnique Federale de Lausanne | Thomos N.,Ecole Polytechnique Federale de Lausanne | Thomos N.,Distributed Communication Systems | Frossard P.,Ecole Polytechnique Federale de Lausanne
Signal Processing | Year: 2013

We investigate the problem of distributed sensors failure detection in networks with a small number of defective sensors, whose measurements differ significantly from the neighbor measurements. We build on the sparse nature of the binary sensor failure signals to propose a novel distributed detection algorithm based on gossip mechanisms and on Group Testing (GT), where the latter has been used so far in centralized detection problems. The new distributed GT algorithm estimates the set of scattered defective sensors with a low complexity distance decoder from a small number of linearly independent binary messages exchanged by the sensors. We first consider networks with one defective sensor and determine the minimal number of linearly independent messages needed for its detection with high probability. We then extend our study to the multiple defective sensors detection by modifying appropriately the message exchange protocol and the decoding procedure. We show that, for small and medium sized networks, the number of messages required for successful detection is actually smaller than the minimal number computed theoretically. Finally, simulations demonstrate that the proposed method outperforms methods based on random walks in terms of both detection performance and convergence rate. © 2012 Elsevier B.V.

Agency: Department of Defense | Branch: Air Force | Program: SBIR | Phase: Phase I | Award Amount: 149.95K | Year: 2014

ABSTRACT: Distributed Communication Systems (DCS) proposes to design and develop a solution for integrating tactical weather sensors with mobile devices for dissemination of the sensor data back to the Air Force Weather enterprise. DCS will evaluate communications methods which include military and commercial satellite communications. Wherever possible, DCS"s solution will leverage existing commercial off the shelf technologies to provide a low-cost, low-risk solution. As part of the evaluation of technologies for this solution, DCS will evaluate the use of Iridium Communications Short Burst Data (SBD) service as a communication method and technology developed for the DeLorme inReach. SBD based devices are lightweight, low-power, and have a robust communication link. DCS will also design and develop a mobile application which complies with the relevant DISA Security Requirement Guides for mobile devices. The mobile application will also make use of supplemental encryption where appropriate to ensure information security. BENEFIT: The technology developed during the proposed Phase I effort has applications to state-of-the-art for low cost supervisory control and data acquisition (SCADA) systems for remote areas outside of the range of traditional communication paths.

Raza S.,Swedish Institute of Computer Science | Shafagh H.,Swedish Institute of Computer Science | Shafagh H.,Distributed Communication Systems | Hewage K.,Uppsala University | And 3 more authors.
IEEE Sensors Journal | Year: 2013

The Internet of Things (IoT) enables a wide range of application scenarios with potentially critical actuating and sensing tasks, e.g., in the e-health domain. For communication at the application layer, resource-constrained devices are expected to employ the constrained application protocol (CoAP) that is currently being standardized at the Internet Engineering Task Force. To protect the transmission of sensitive information, secure CoAP mandates the use of datagram transport layer security (DTLS) as the underlying security protocol for authenticated and confidential communication. DTLS, however, was originally designed for comparably powerful devices that are interconnected via reliable, high-bandwidth links. In this paper, we present Lithe-an integration of DTLS and CoAP for the IoT. With Lithe, we additionally propose a novel DTLS header compression scheme that aims to significantly reduce the energy consumption by leveraging the 6LoWPAN standard. Most importantly, our proposed DTLS header compression scheme does not compromise the end-to-end security properties provided by DTLS. Simultaneously, it considerably reduces the number of transmitted bytes while maintaining DTLS standard compliance. We evaluate our approach based on a DTLS implementation for the Contiki operating system. Our evaluation results show significant gains in terms of packet size, energy consumption, processing time, and network-wide response times when compressed DTLS is enabled. © 2001-2012 IEEE.

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