Adele A. Rescigno

Efficient Collective Communication in Optical Networks

This paper studies the problems of broadcasting and gossiping in optical networks. In such networks the vast bandwidth available is utilized through wavelength division multiplexing: a single physical optical link can carry several logical signals, provided that they are transmitted on different wavelengths. In this paper we consider both single-hop and multihop optical networks. In single-hop networks the information, once transmitted as light, reaches its destination without being converted to electronic form in between, thus reaching high speed communication. In multihop networks a packet may have to be routed through a few intermediate nodes before reaching its final destination. In both models we give efficient broadcasting and gossiping algorithms, in terms of time and number of wavelengths. We consider both networks with arbitrary topologies and particular networks of practical interest. Several of our algorithms exhibit optimal performances.

Embedding graphs onto the Supercube

In this paper we consider the Supercube, a new interconnection network derived from the hypercube. The Supercube, introduced by A. Sen (1989), has the same diameter and connectivity as a Hypercube but can be realized for any number of nodes, not only powers of 2. We study the Supercubes ability to execute parallel programs, using graph-embedding techniques. We show that complete binary trees and bidimensional meshes (with a side length power of 2) are spanning subgraphs of the Supercube. We then prove that the Supercube is Hamiltonian and, when the number of nodes is not a power of 2, it contains all cycles of length greater than 3 as subgraphs. >

Efficient collective communication in optical networks

This paper studies the problems of broadcasting and gossiping in optical networks. In such networks the vast bandwidth available is utilized through wavelength division multiplexing: a single physical optical link can carry several logical signals, provided that they are transmitted on different wavelengths. In this paper we consider both single-hop and multihop optical networks. In single-hop networks the information, once transmitted as light, reaches its destination without being converted to electronic form in between, thus reaching high speed communication. In multihop networks a packet may have to be routed through a few intermediate nodes before reaching its final destination. In both models we give efficient broadcasting and gossiping algorithms, in terms of time and number of wavelengths. We consider both networks with arbitrary topologies and particular networks of practical interest. Several of our algorithms exhibit optimal performances.

Vertex-disjoint spanning trees of the star network with applications to fault-tolerance and security

Abstract Fault-tolerance and security are desirable properties in communication protocols. In this paper we investigate the use of vertex disjoint spanning trees to obtain efficient, reliable, and secure information distribution protocols in the star network. In the first part of the paper we give an efficient algorithm to construct the optimal number of vertex-disjoint spanning trees of the star networks. Subsequently, we present several communication protocols, based on vertex-disjoint spanning trees, exhibiting various degrees of fault-tolerance and security.

Fault—tolerant hypercube broadcasting via information dispersal

Broadcasting is the process of disseminating a message originated at one node of a network to all other nodes. In this paper, we consider the problem of broadcasting reliably in the hypercube in presence of either transmission or link failures. We propose broadcasting protocols under various assumptions on the communication model. Our broadcasting protocols make use of Rabins Information Dispersal Algorithm.

Fast Gossiping by Short Messages

Gossiping is the process of information diffusion in which each node of a network holds a packet that must be communicated to all other nodes in the network. We consider the problem of gossiping in communication networks under the restriction that communicating nodes can exchange up to a fixed number p of packets at each round. In the first part of the paper we study the extremal case p = 1 and we exactly determine the optimal number of communication rounds to perform gossiping for several classes of graphs, including Hamiltonian graphs and complete k-ary trees. For arbitrary graphs we give asymptotically matching upper and lower bounds. We also study the case of arbitrary p and we exactly determine the optimal number of communication rounds to perform gossiping under this hypothesis for complete graphs, hypercubes, rings, and paths.

Collision-free path coloring with application to minimum-delay gathering in sensor networks

Efficient data gathering is an important challenge in sensor networks. In this paper we address the problem of gathering sensed data to the sink of a sensor network minimizing the time to complete the process. We present optimal time data gathering algorithms for any sensor network topology, in the half-duplex with directional antennas model, when each sensor has one data packet to be gathered and merging of packets is not allowed at intermediate nodes. Our results improve on existing approximation algorithms. We approach the gathering problem by obtaining optimal solutions to a path coloring problem in graphs.

Gathering with Minimum Delay in Tree Sensor Networks

Data gathering is a fundamental operation in wireless sensor networks in which data packets generated at sensor nodes are to be collected at a base station. In this paper we suppose that each sensor is equipped with an half---duplex interface; hence, a node cannot receive and transmit at the same time. Moreover, each node is equipped with omnidirectional antennas allowing the transmission over distance R. The network is a multi-hop wireless network and the time is slotted so that one---hop transmission of one data item consumes one time slot. We model the network with a graph where the vertices represent the nodes and two nodes are connected if they are in the transmission/interference range of each other. Due to interferences a collision happens at a node if two or more of its neighbors try to transmit at the same time. Furthermore we suppose that an intermediate node should forward a message as soon as it receives it. We give an optimal collision free gathering schedule for tree networks whenever each node has at least one data packet to send.

GATHERING WITH MINIMUM COMPLETION TIME IN SENSOR TREE NETWORKS

Data gathering is a fundamental operation in wireless sensor networks in which data packets generated at sensor nodes are to be collected at a base station. In this paper we suppose that each sensor is equipped with an half–duplex interface; hence, a node cannot receive and transmit at the same time. Moreover, each node is equipped with omnidirectional antennas allowing the transmission over distance R. The network is a multi-hop wireless network and the time is slotted so that one–hop transmission of one data item consumes one time slot. We model the network with a graph where the vertices represent the nodes and two nodes are connected if they are in the transmission range of each other. We suppose that the interference range is the same as the transmission range; therefore due to interferences a collision happens at a node if two or more of its neighbors try to transmit at the same time. Furthermore we suppose that an intermediate node should forward a message as soon as it receives it. We give an optimal collision free gathering schedule for tree networks whenever each node has exactly.

A Fast and Effective Heuristic for Discovering Small Target Sets in Social Networks

Given a network represented by a graph