Laura Rosati

On ant routing algorithms in ad hoc networks with critical connectivity

This paper shows a novel self-organizing approach for routing datagrams in ad hoc networks, called Distributed Ant Routing (DAR). This approach belongs to the class of routing algorithms inspired by the behavior of the ant colonies in locating and storing food. The effectiveness of the heuristic algorithm is supported by mathematical proofs and demonstrated by a comparison with the well-known Ad hoc On Demand Distance Vector (AODV) algorithm. The differences and the similarities of the two algorithms have been highlighted. Results obtained by a theoretical analysis and a simulation campaign show that DAR allows obtaining some important advantages that makes it a valuable candidate to operate in ad hoc networks and the same method helps in the selection of the algorithm parameters. Since the approach aims at minimizing complexity in the nodes at the expenses of the optimality of the solution, it results to be particularly suitable in environments where fast communication establishment and minimum signalling overhead are requested. These requirements are typical of ad hoc networks with critical connectivity, as described in the paper. Thus the performance of the proposed algorithm are shown in ad hoc networks with critical connectivity and compared to some existing ad hoc routing algorithms.

Study and Implementation of Switching and Beam-Hopping Tchniques in Satellites with On Board Processing

In this paper we address different downlink dynamic bandwidth allocation (DBA) techniques in a GEO stationary (GEO) satellite communication network. The goal is designing a low complexity system which can adapt to the terminal traffic requests. We investigate a possible way to increase the performance of the system by means of an interaction between on-board switching fabric (SF) and beam hopping (BH). We consider a system where an adaptive process provides uplink DBA, whereas a BH module works as downlink bandwidth allocator. Specifically, the BH module determines the number of carriers to be allocated to each downlink spot-beam on the basis of the traffic queues at the input of the SF. Simulation results show that the interaction between SF and BH is a good candidate to increase the performance of the system, since it allows reducing queue sizes in the satellite.

Jointly Optimal Routing and Resource Allocation in Hybrid Satellite/Terrestrial Networks

In the future hybrid satellite/terrestrial networks, efficient routing at network layer and allocation of resources at link layer will have to be performed in order to satisfy traffic requests and minimizing at the same time the cost of the allocated bandwidth among the heterogeneous network components. This simultaneous routing and resource allocation (SRRA) problem can be specified in the framework of network utility maximization (NUM) theory, according to which each layer of the communication network corresponds to a decomposed subproblem of a global optimization problem, and the interfaces among layers are represented as functions of the optimization variables coordinating the subproblems. These sets of variables are associated by specific restrictions. Since the solution of the SRRA problem directly requires coordination among possibly all sources, thus it is impractical in real networks, we propose a decentralized and distributed solution which is based on the Lagrange dual decomposition method and allows defining a bandwidth-related pricing strategy

Definition and performance evaluation of a request routing algorithm to distribute digital cinema contents

In this work, carried out in the framework of the IST Project EDCINE, we deal with the network distribution of Digital Cinema contents, through a Content Delivery Network, towards theatres. One of the main criticalities of the system is the very large size of the contents to be transferred while respecting the maximum download time requirements. From the operator perspective, this criticality translates into the objective of optimizing the usage of network resources while complying with QoS constraints. The goal of this paper is first to present the network architecture and procedures relevant to the distribution service, and to specifically analyse the problem of service request routing (4-7 routing), whose objective is to select a set of servers to satisfy a content request efficiently. In particular, we focus on the definition of the mathematical model of the problem of minimising the network operational cost of the content distribution. Since some known professional, optimisation tools are not able to find the global optimum even in very simple configurations, we propose a heuristic approach based on the min-plus convolution. Preliminary numerical results show that such an algorithm outperforms the selected professional tools, while maintaining an affordable computation time.

WLC02-3: On Ant Routing Algorithms in Ad-hoc Networks

This paper shows a novel approach for routing datagrams in ad-hoc networks, called distributed ant routing (DAR). This approach belongs to the class of routing algorithms inspired by the behavior of the ant colonies in locating food and storing food. The algorithm aims at minimizing complexity in the nodes and this is achieved at the expenses of the optimality of the derived solution. The work also describes an analytical approach to the problem: The validity of the heuristic approach, ant routing, is supported by mathematical proofs and the same methods helps in the selection of the algorithm parameters. Simulation results are presented at the end to confirm the mathematical calculations.