Wireless Broadcast with Network Coding in Mobile Ad-Hoc Networks: DRAGONCAST

de recherche ISSN 0249-6399 ISRN INRIA/RR–6569–FR+ENG Thème COM INSTITUT NATIONAL DE RECHERCHE EN INFORMATIQUE ET EN AUTOMATIQUE Wireless Broadcast with Network Coding in Mobile Ad-Hoc Networks: DRAGONCAST Song Yean Cho, Cédric Adjih N° 6569 July 2008 Centre de recherche INRIA Paris – Rocquencourt Domaine de Voluceau, Rocquencourt, BP 105, 78153 Le Chesnay Cedex Téléphone : +33 1 39 63 55 11 — Télécopie : +33 1 39 63 53 30 Wireless Broadcast with Network Coding in Mobile Ad-Hoc Networks: DRAGONCAST Song Yean Cho, C´edric Adjih Theme COM — Systemes communicants ´Equipe-Projet Hipercom Rapport de recherche n° 6569 — July 2008 — 23 pages Abstract: Network coding is a recently proposed method for transmitting data, which has been shown to have potential to improve wireless network per- formance. We study network coding for one specific case of multicast, broad- casting, from one source to all nodes of the network. We use network coding as a loss tolerant, energy-efficient, method for broad- cast. Our emphasis is on mobile networks. Our contribution is the proposal of DRAGONCAST, a protocol to perform network coding in such a dynamically evolving environment. It is based on three building blocks: a method to permit real-time decoding of network coding, a method to adjust the network coding transmission rates, and a method for ensuring the termination of the broadcast. The performance and behavior of the method are explored experimentally by simulations; they illustrate the excellent performance of the protocol. Key-words: wireless networks, network coding, broadcasting, multi-hop, min- cut, hypergraph, control Diffusion dans les r´eseaux mobile ad-hoc avec le codage r´eseau: DRAGONCAST R´esum´e : Le codage r´eseau est une m´ethode qui a ´et´e propos´ee r´ecemment, et dont le potentiel pour am´eliorer les performances des r´eseaux sans fil a ´et´e d´emontr´e. Dans ce rapport, nous ´etudions le codage r´eseau pour un cas sp´ecificique de communication multicast, la diffusion, d’une source `a tous les noeuds du r´eseau. Nous utilisons le codage r´eseau comme une m´ethode de diffusion qui est tol´erante aux pertes de messages, et est aussi efficace en ´energie. Notre contri- bution est la proposition de DRAGONCAST, un protocole utilisant le codage r´eseaux dans des environements ´evoluant dynamiquement. Il est bas´e sur trois briques: une m´ethode qui permet le d´ecodage en temps r´eel du codage r´eseau, une m´ethode pour ajuster les d´ebits des retransmissions, et une m´ethode pour garantir la terminaison de la diffusion. La performance et le comportement de la m´ethode sont explor´es exp´erimentalement par des simulations: elles illustrent l’excellente performance du protocole. Mots-cl´es : r´eseaux sans fil, codage de r´eseau, diffusion, multi-sauts, coupe minimale, hypergraphe, contrˆole WNC Broadcast in MANETs: DRAGONCAST 3 Contents 1 Introduction 4 2 Practical Framework for Network Coding 5 2.1 Linear Coding and Random Linear Coding . . . . . . . . . . . . 5 2.2 Decoding, Vector Space, and Rank . . . . . . . . . . . . . . . . . 5 2.3 Rate Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 3 Theoretical Performance of Wireless Network Coding 6 4 Our Approach: DRAGONCAST 7 4.1 Framework for Broadcast with Network Coding . . . . . . . . . . 7 4.2 SEW: Encoding for Real-time Decoding . . . . . . . . . . . . . . 7 4.2.1 Overview of Real-time Decoding . . . . . . . . . . . . . . 7 4.2.2 SEW (Sliding Encoding Window) . . . . . . . . . . . . . . 9 4.3 DRAGON: Rate Selection . . . . . . . . . . . . . . . . . . . . . . 11 4.3.1 Static Heuristic IRON . . . . . . . . . . . . . . . . . . . . 11 4.3.2 Dynamic Heuristic DRAGON . . . . . . . . . . . . . . . . 11 4.4 Termination Protocol . . . . . . . . . . . . . . . . . . . . . . . . . 13 4.5 Proof of convergence of DRAGONCAST . . . . . . . . . . . . . . 13 5 Evaluation Metrics for Experimental Results 15 5.1 Metric for Energy-efficiency . . . . . . . . . . . . . . . . . . . . . 16 5.2 Energy-efficiency reference point for routing . . . . . . . . . . . . 16 5.3 Real-Time Decoding . . . . . . . . . . . . . . . . . . . . . . . . . 17 6 Experimental Results 17 6.1 Real-Time Decoding: Effects of SEW . . . . . . . . . . . . . . . . 17 6.2 Efficiency and Read-Time Decoding . . . . . . . . . . . . . . . . 19 7 Conclusion 21 RR n° 6569 4 Song Yean Cho, C´edric Adjih 1 Introduction The concept of network coding, where intermediate nodes mix information from different flows, was introduced by seminal work from Ahlswede, Cai, Li and Yeung [1]. Since then, a rich literature has flourished for both theoretical and practical aspects. In particular, several results have established network coding as an efficient method to broadcast data to the whole wireless networks (see Lun et al. [6] or Fragouli et al. [16] for instance), when efficiency consists in: minimizing the total number of packet transmissions for broadcasting from the source to all

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