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Network - Coded Multihop Multicast: Topology and Complexity

In this thesis, we present some novel results on network coding complexity and its relations with the network topology. In particular, the complexity is evaluated in terms of the number of nodes which have to perform coding operations in order to achieve the multicast capacity. Different network topologies and the corresponding complexity are investigated by means of proper simulation algorithms. Both theoretical considerations and simulation guidelines for different networks are presented.
The rest of the thesis is structured as follows. In Chapter 1, we provide an overview on the literature in the field of network coding, by discussing what linear network coding does in order to achieve the multicast capacity. Moreover, we present a brief discussion on graph theory and the main network coding theorem. Finally, we introduce the different definitions of complexity which can be employed for the evaluation. Important theoretical bounds on the minimum number of nodes which have to perform coding operations in order to achieve the network capacity are presented. In Chapter 2 and Chapter 3, we analyze the network coding complexity, defined as the minimum number of coding points, in scenarios where the network topology is defined by a random graph and by pseudo random multihop graph, respectively. This allows to identify topology patterns which require more encoding complexity. In Chapter 4, we propose an analytical framework for network topology characterized by a pseudo random multi-hop graph. Finally, we present and analyze other minimal network topologies with a relatively large number of coding points.

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Introduction Networked systems arise in various communication contexts such as, for instance, phone networks, the public Internet, peer-to-peer networks, ad-hoc wireless networks, and sensor networks. Such systems are becoming central to our daylife. During the last decades, there has been a signicant research eort in the eld of networking. A key aspect in commu- nication networks is related to how information is treated by the nodes of the network. Whether it corresponds to packets in Internet, or voice signals in a phone network, if they originate from heterogeneus sources, they are transported as cars on a transportation net- work of highways or uids through a network of pipes. Independent information streams are typically kept separate. Today, routing, data storage, error control, and generally all network functions operate on the basis of this principle. Network coding is a technique, recently arisen in the eld of information theory, that breaks with this principle. In fact, it has been recently observed that, when dierent information ows should be multicast to destinations, nodes can be allowed not only to forward but also to process them. This can be achieved by recombining several input packets into one or several output packets. At the network layer, for example, intermediate nodes can perform linear combination of independent bitstreams, whereas at the physical layer of optical networks, intermediate nodes can superimpose incoming optical signals. In other words, data streams that are independently produced and consumed do not necessarily need to be kept separate when they are transported throughout the network. There are several ways to combine and later extract independent information. Com- 1

Laurea liv.II (specialistica)

Facoltà: Ingegneria

Autore: Michele Mohorovicich Contatta »

Composta da 94 pagine.

 

Questa tesi ha raggiunto 53 click dal 25/10/2011.

 

Consultata integralmente una volta.

Disponibile in PDF, la consultazione è esclusivamente in formato digitale.