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Network Coding for Large Scale Content Distribution
"... We propose a new scheme for content distribution of large files that is based on network coding. With network coding, each node of the distribution network is able to generate and transmit encoded blocks of information. The randomization introduced by the coding process eases the scheduling of bloc ..."
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Cited by 493 (7 self)
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We propose a new scheme for content distribution of large files that is based on network coding. With network coding, each node of the distribution network is able to generate and transmit encoded blocks of information. The randomization introduced by the coding process eases the scheduling of block propagation, and, thus, makes the distribution more efficient. This is particularly important in large unstructured overlay networks, where the nodes need to make decisions based on local information only. We compare network coding to other schemes that transmit unencoded information (i.e. blocks of the original file) and, also, to schemes in which only the source is allowed to generate and transmit encoded packets. We study the performance of network coding in heterogeneous networks with dynamic node arrival and departure patterns, clustered topologies, and when incentive mechanisms to discourage freeriding are in place. We demonstrate through simulations of scenarios of practical interest that the expected file download time improves by more than 2030 % with network coding compared to coding at the server only and, by more than 23 times compared to sending unencoded information. Moreover, we show that network coding improves the robustness of the system and is able to smoothly handle extreme situations where the server and nodes departure the system.
Networked SlepianWolf: Theory, Algorithms and Scaling Laws
 IEEE Transactions on Information Theory
, 2003
"... Consider a set of correlated sources located at the nodes of a network, and a set of sinks that are the destinations for some of the sources. We consider the minimization of cost functions which are the product of a function of the rate and a function of the path weight. We consider both the data ..."
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Cited by 93 (8 self)
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Consider a set of correlated sources located at the nodes of a network, and a set of sinks that are the destinations for some of the sources. We consider the minimization of cost functions which are the product of a function of the rate and a function of the path weight. We consider both the data gathering scenario, which is relevant in sensor networks, and general tra#c matrices, relevant for general networks. The minimization is achieved by jointly optimizing (a) the transmission structure, which we show consists in general of a superposition of trees from each of the source nodes to its corresponding sink nodes, and (b) the rate allocation across the source nodes, which is done by SlepianWolf coding. We show that the overall minimization can be achieved in two concatenated steps.
Tighter Bounds for Graph Steiner Tree Approximation
 SIAM Journal on Discrete Mathematics
, 2005
"... Abstract. The classical Steiner tree problem in weighted graphs seeks a minimum weight connected subgraph containing a given subset of the vertices (terminals). We present a new polynomialln 3 time heuristic that achieves a bestknown approximation ratio of 1 + ≈ 1.55 for general graphs 2 and best ..."
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Cited by 88 (7 self)
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Abstract. The classical Steiner tree problem in weighted graphs seeks a minimum weight connected subgraph containing a given subset of the vertices (terminals). We present a new polynomialln 3 time heuristic that achieves a bestknown approximation ratio of 1 + ≈ 1.55 for general graphs 2 and bestknown approximation ratios of ≈ 1.28 for both quasibipartite graphs (i.e., where no two nonterminals are adjacent) and complete graphs with edge weights 1 and 2. Our method is considerably simpler and easier to implement than previous approaches. We also prove the first known nontrivial performance bound (1.5 · OPT) for the iterated 1Steiner heuristic of Kahng and Robins in quasibipartite graphs.
Better approximation bounds for the network and Euclidean Steiner tree problems
, 1995
"... The network and Euclidean Steiner tree problems require a shortest tree spanning a given vertex subset within a network G = (V; E; d) and Euclidean plane, respectively. For these problems, we present a series of heuristics finding approximate Steiner tree with performance guarantee coming arbitrary ..."
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Cited by 49 (3 self)
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The network and Euclidean Steiner tree problems require a shortest tree spanning a given vertex subset within a network G = (V; E; d) and Euclidean plane, respectively. For these problems, we present a series of heuristics finding approximate Steiner tree with performance guarantee coming arbitrary close to 1+ln2 1:693 and 1+ln 2 p 3 1:1438, respectively. The best previously known corresponding values are close to 1.746 and 1.1546. Keywords: Combinatorial problems, approximation algorithms, Steiner trees. 1 Introduction Let G = (V; E;d) be a graph with a vertex set V , an edge set E and distance function d : E ! R + . A tree T is called a Steiner tree of S, S ae V , if S is contained in the vertex set of T . Network Steiner Problem (NSP). Given G and S, find the shortest Steiner tree (also called the Steiner minimal tree) of S. This problem is NPcomplete [9], so many approximation algorithms for Steiner minimal trees appeared in the last two decades. The quality of an appr...
Design multicast protocols for noncooperative networks,”
 IEEE INFOCOM.
, 2005
"... AbstractConventionally, most network protocols assume that the network entities who participate in the network activities will always behave as instructed. However, in practice, most network entities are selfish: they will try to maximize their own benefits instead of altruistically contributing t ..."
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Cited by 15 (8 self)
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AbstractConventionally, most network protocols assume that the network entities who participate in the network activities will always behave as instructed. However, in practice, most network entities are selfish: they will try to maximize their own benefits instead of altruistically contributing to the network by following the prescribed protocols. Thus, new protocols should be designed for the noncooperative network that is composed of selfish entities. In this paper, we specifically show how to design truthful multicast protocols for noncooperative networks such that these selfish entities will follow the protocols out of their own interests. By assuming that every entity has a fixed cost for a specific multicast, we give a general framework to decide whether it is possible and how, if possible, to transform an existing multicast protocol to a truthful multicast protocol by designing a proper payment protocol. We then show how the payments to those relay entities are shared fairly among all receivers so that it encourages collaboration among receivers. As running examples, we show how to design truthful multicast protocols for several multicast structures that are currently used in practice. We also conduct extensive simulations to study the relation between the payment and the cost of the multicast structure. Our simulations show that multicast not only saves the total resources, but also benefits the individual receiver even in selfish networks.
Minimizing Communication Cost in Distributed Multiquery Processing
, 2009
"... Increasing prevalence of largescale distributed monitoring and computing environments such as sensor networks, scientific federations, Grids etc., has led to a renewed interest in the area of distributed query processing and optimization. In this paper we address a general, distributed multiquery ..."
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Cited by 8 (0 self)
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Increasing prevalence of largescale distributed monitoring and computing environments such as sensor networks, scientific federations, Grids etc., has led to a renewed interest in the area of distributed query processing and optimization. In this paper we address a general, distributed multiquery processing problem motivated by the need to minimize the communication cost in these environments. Specifically we address the problem of optimally sharing data movement across the communication edges in a distributed communication network given a set of overlapping queries and query plans for them (specifying the operations to be executed). Most of the problem variations of our general problem can be shown to be NPHard by a reduction from the Steiner tree problem. However, we show that the problem can be solved optimally if the communication network is a tree, and present a novel algorithm for finding an optimal data movement plan. For general communication networks, we present efficient approximation algorithms for several variations of the problem. Finally, we present an experimental study over synthetic datasets showing both the need for exploiting the sharing of data movement and the effectiveness of our algorithms at finding such plans.
On the value of a random minimum length Steiner tree
"... Consider a complete graph on n vertices with edge lengths chosen randomly and independently from e.g., an exponential distribution with parameter 1. Fix k vertices and consider the minimal length Steiner tree which contains these vertices. We prove that with high probability the length of this tr ..."
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Cited by 3 (0 self)
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Consider a complete graph on n vertices with edge lengths chosen randomly and independently from e.g., an exponential distribution with parameter 1. Fix k vertices and consider the minimal length Steiner tree which contains these vertices. We prove that with high probability the length of this tree is (k 1) log n n + o( log n n ) when k = const and n !1. 1 Introduction Given an arbitrary weighted graph with a xed set of vertices, the Steiner Tree Problem is the task of nding a minimumcost subtree containing all these vertices. The length of a tree is dened to be the sum of the lengths of the edges, contained by the tree. Steiner trees are very well studied object in the combinatorial optimization literature. The interest is motivated by several practical problems like network design or VLSI design. The minimal Steiner tree problem is well known to be NPcomplete and this separates it from a similar minimal spanning tree problem for which there exists a simple polynomial ti...
A SleepSchedulingBased CrossLayer Design Approach for ApplicationSpecific Wireless Sensor Networks
"... I hereby declare that I am the sole author of this thesis. This is a true copy of the thesis, including any required final revisions, as accepted by my examiners. I understand that my thesis may be made electronically available to the public. ii The pervasiveness and operational autonomy of meshbas ..."
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Cited by 2 (0 self)
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I hereby declare that I am the sole author of this thesis. This is a true copy of the thesis, including any required final revisions, as accepted by my examiners. I understand that my thesis may be made electronically available to the public. ii The pervasiveness and operational autonomy of meshbased wireless sensor networks (WSNs) make them an ideal candidate in offering sustained monitoring functions at reasonable cost over a wide area. To extend the functional lifetime of batteryoperated sensor nodes, stringent sleep scheduling strategies with communication duty cycles running at sub1 % range are expected to be adopted. Although ultralow communication duty cycles can cast a detrimental impact on sensing coverage and network connectivity, its effects can be mitigated with adaptive sleep scheduling, node deployment redundancy and multipath routing within the mesh WSN topology. This work proposes a crosslayer organizational approach based on sleep scheduling, called SenseSleep Trees (SSTrees), that aims to harmonize the various engineering issues and provides a method to extend monitoring capabilities and operational lifetime of meshbased WSNs engaged in widearea surveillance applications. Various practical considerations such as sensing coverage requirements, duty cycling, transmission range assignment, data messaging, and protocol signalling are incorporated to demonstrate and evaluate the feasibility of the proposed design approach.
A provably good global routing algorithm in multilayer IC and MCM layout designs, manuscript
"... Given a multilayer routing area, we consider the global routing problem of selecting a maximum set of nets, such that every net can be routed entirely in one of the given layers without violating the physical capacity constraints. This problem is motivated by applications in multilayer IC and multi ..."
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Cited by 2 (2 self)
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Given a multilayer routing area, we consider the global routing problem of selecting a maximum set of nets, such that every net can be routed entirely in one of the given layers without violating the physical capacity constraints. This problem is motivated by applications in multilayer IC and multichip module (MCM) layout designs. The contribution of this paper is threefold. First, we formulate the problem as an integer linear program (ILP). Second, we modify an algorithm by Garg and Könemann for packing linear programs to obtain an approximation algorithm for the global routing problem. Our algorithm provides solutions guaranteed to be within a certain range of the global optimal solution, and runs in polynomialtime even if all, possibly exponentially many, Steiner trees are considered in the formulation. Finally, we demonstrate that the complexity of our algorithm can be significantly reduced in the case of identical routing layers.
Network Flow Spanners
 In Proceedings of the 7th Latin American Symposium ”LATIN 2006: Theoretical Informatics
"... Abstract. In this paper, motivated by applications of ordinary (distance) spanners in communication networks and to address such issues as bandwidth constraints on network links, link failures, network survivability, etc., we introduce a new notion of flow spanner, where one seeks a spanning subgrap ..."
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Abstract. In this paper, motivated by applications of ordinary (distance) spanners in communication networks and to address such issues as bandwidth constraints on network links, link failures, network survivability, etc., we introduce a new notion of flow spanner, where one seeks a spanning subgraph H = (V, E ′ ) of a graph G = (V, E) which provides a “good ” approximation of the sourcesink flows in G. We formulate several variants of this problem and investigate their complexities. Special attention is given to the version where H is required to be a tree.