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Title: | Construction and Analysis of Distributed Coding Algorithms for Data Persistence and Data Gathering in Wireless Ad-hoc Networks Konstrukcija i analiza algoritama distribuiranog kodovanja za prikupljanje i očuvanje podataka u bežičnim ad-hok mrežamа Konstrukcija i analiza algoritama distribuiranog kodovanja za prikupljanje i očuvanje podataka u bežičnim ad-hok mrežama |
Authors: | Stefanović Čedomir | Keywords: | distributed coding algorithms, sparse-graph codes, random linear codes;algoritmi za distribuirano kodovanje, kodovi na retkim grafovim, slucajni linearni kodovi | Issue Date: | 24-Oct-2011 | Publisher: | Univerzitet u Novom Sadu, Fakultet tehničkih nauka u Novom Sadu University of Novi Sad, Faculty of Technical Sciences at Novi Sad |
Abstract: | <p>Starting with the rediscovery of low-density parity-check (LDPC) codes, the last<br />decade of coding theory was marked by extensive research and major advances in the field of sparse-graph codes. Low complexity encoding/decoding procedures and close-to-optimal properties of sparse-graph codes spurred their application virtually on all layers of the communication protocol stack.<br />Another important development that occurred recently within coding theory was<br />the introduction of network coding, which reaches the capacity limits of information transfer in multiuser scenarios. Network coding particularly highlighted the potential of simple random linear network codes in various usage scenarios.<br />Among broad variety of applications, the usage of sparse-graph and random linear codes for the efficient packet-level coding for the purposes of efficient data dissemination, distributed data storage and securing data persistence in wireless ad-hoc networks recently attracted a lot of interest. These applications constitute the topic of this thesis. Particularly, the thesis addresses the construction and analysis of simple and efficient coding algorithms in a two specific scenarios of wireless ad-hoc networking.<br />In the first part of thesis, we investigate the distributed sparse-graph coding in<br />decentralized wireless sensor networks (WSNs). We are concerned with WSNs with a flat network topology, where nodes are deployed in remote areas with no access to the external networks and where data gathering is performed only occasionally. Our aim is to develop distributed, robust and stateless sparse-graph coding algorithm that results with distributed data storage, ensures data persistence until the next gathering cycle and allows for the recovery of the whole sensed information by gathering of the encoded data from a random subset of network nodes. Following these objectives, we designed a packet-centric approach to distributed coding. The core idea of the proposed approach is to perform distributed encoding using packets that randomly walk over network, sample and encode sensed data, and finally perform networkwide dispersion of the encoded data. We introduce the the general framework of the proposed scheme and specialize it for several important classes of sparse-graph codes - low-density generator matrix (LDGM) codes, irregular and regular repeat accumulate (IRA and RA) codes, LT and raptor codes. Finally, we assess performance of the scheme for several data gathering strategies.<br />In the second part of the thesis, we expand the proposed packet-centric approach<br />to perform the distributed encoding of random linear codes. Specifically, we analyze the distributed encoding of sparse random linear codes, as our aim is to minimize communication expenses required by the encoding procedure. We further develop the scheme and propose the distributed encoding algorithm called Fireworks, with an aim to exploit the broadcast nature of wireless transmissions. We compare the performance of the packet-centric and Fireworks random linear coding via a simulation study. The third part of the thesis is devoted to efficient infrastructure-to-vehicle (I2V) data dissemination in vehicular ad-hoc networks (VANETs). We consider the scenario where infrastructure nodes (i.e., base stations) periodically distribute traffic-related data to mobile nodes (i.e., vehicles). Our aim is to design a simple and reliable data dissemination scheme, which does not rely on the lengthy/complex acknowledgment, retransmission, handover and content reconciliation procedures. We demonstrate that these goals could be achieved by the usage of fountain codes applied at the application layer. Furthermore, we introduce the importance layers in the disseminated data and demonstrate that the unequal error protection (UEP) fountain codes are well suited for the corresponding set-up, allowing both more reliable and faster retrieval of higher importance layers.</p> <p> Teza se bavi konstrukcijom i analizom distribuiranih kodnih algoritama kodova<br /> na retkim grafovima i slucajnih linearnih kodova, u bežicnim ad-hok mrežama.</p> |
URI: | https://open.uns.ac.rs/handle/123456789/27714 |
Appears in Collections: | FTN Teze/Theses |
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